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  • Column liquid chromatography  (344)
  • Arctic
  • Springer  (365)
  • American Geophysical Union  (15)
  • Copernicus
  • 2010-2014  (17)
  • 1995-1999  (363)
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  • 1
    Electronic Resource
    Electronic Resource
    Paleolimnological significance of observed distribution patterns of chrysophyte cysts in arctic pond environments (1995)
    Springer
    Journal of paleolimnology 13 (1995), S. 79-83 
    Details
    ISSN: 1573-0417
    Keywords: chrysophytes ; cysts ; Stomatocysts ; diatoms ; periphyton ; Arctic ; Ellesmere Island ; Paleolimnology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract In a survey of 35 high arctic ponds, chrysophycean cysts were relatively more common in moss periphyton and epilithon habitats, than in surface sediment samples. The highest percentages of cysts relative to diatoms were found in the semi-aquatic mosses. Although chrysophytes are generally considered to be planktonic, periphytic taxa may be common in high latitudes. The ratio of diatom frustules to chrysophyte cysts in arctic sediment cores may be tracking different environmental variables than paleolimnologists may intuitively expect based on observations from more temperate regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00678112
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  • 2
    Electronic Resource
    Electronic Resource
    Stratification patterns in Taconite Inlet, Ellesmere Island, N.W.T. (1996)
    Springer
    Journal of paleolimnology 16 (1996), S. 205-215 
    Details
    ISSN: 1573-0417
    Keywords: fjords ; stratification ; meromixis ; paleolimnology ; Arctic ; Ellesmere Island
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract The middle arm of Taconite Inlet shows many features in common with high-Arctic fjords and coastal meromictic lakes. The surface mixed layer is fresh, and a relatively constant 5.5 m deep, indicating a layer of ice of approximately the same thickness blocks communication with the Arctic Ocean. Below the primary halocline to a depth of 85 m, at least partial communication with the Arctic Ocean exists as indicated by the oxygen, salinity and thermal structures. A sill is probably found between 40 and 85 m depth, reducing circulation below it and contributing to the oxycline. For a long but undetermined period prior to the separation of lakes C1, and C2 from the middle arm of Taconite Inlet, the surface water of the inlet was probably strongly brackish to marine suggesting that the entrance to Taconite Inlet was not blocked by an ice shelf at the time of separation. The deep water of these future lakes probably became isolated from the general estuarine circulation and began to develop some of their present limnological features prior to actual separation of the surface waters of the lakes from the inlet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00176936
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  • 3
    Electronic Resource
    Electronic Resource
    The climatic signal in varved sediments from Lake C2, northern Ellesmere Island, Canada (1996)
    Springer
    Journal of paleolimnology 16 (1996), S. 227-238 
    Details
    ISSN: 1573-0417
    Keywords: varves ; paleoclimate ; climate ; hydrology ; Arctic ; Ellesmere Island
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Annually-laminated clastic sediments preserve a high resolution proxy record of paleoclimate, provided that allochthonous sedimentation represents a response to meteorological forcing of watershed sediment transfer. Here, we demonstrate this linkage, and illustrate a calibration process using the most recent 40 years of a varve record from Lake C2 (82°50′ N; 78°00′ W), three years of field measurements, and meteorological data for 1951–92 from nearby AES weather station Alert. Field measurements were used to correlate proxies of the energy available for snowmelt (e.g. air temperature) and daily suspended sediment discharge (SSQ). Our calibration was extended through use of weather data from Alert. Both mean daily air temperature at Echo, and daily SSQ, were well correlated with air temperature at 600 m above Alert, as obtained from the 1200 Z (0800 LST) rawinsonde sounding. Accordingly, we used pooled 1990 and 1992 Alert 600 m data to predict the lagged daily sediment discharge into Lake C2 (adj. r 2=0.43). Daily values were summed each year in order to produce an annual series of predicted sediment transfer to the lake. The original varve chronology was based on eight sediment cores recovered from the deep basin of the lake (〉80 m). Although low-frequency fluctuations of the varve and predicted SSQ series agree, slight tuning of the varve record optimizes the correlation between them. Adjustments were based on examination of weather data for specific years, reexamination of sediment core thin sections, and by aligning fluctuations in the two series which closely matched. Although the original chronology is reasonably well correlated with 600 m temperatures at Alert (for JJA mean, r=0.41, significant at 0.01), the adjusted chronology is both better correlated and contains a more precise climate signal (r=0.54 for July mean, significant at 0.01). This is the first calibrated varve record produced from Arctic lake sediments, and demonstrates that varves from Lake C2 contain a paleoclimatic record. We believe the post-facto manipulations required to produce the adjusted varve chronology are reasonable given the uncertainties inherent in varve counting, and the lack of any independent corroborating chronostratigraphic markers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00176938
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  • 4
    Electronic Resource
    Electronic Resource
    Arctic margin gravity highs: Deeper meaning for sediment depocenters? (1998)
    Springer
    Marine geophysical researches 20 (1998), S. 459-477 
    Details
    ISSN: 1573-0581
    Keywords: Arctic ; continental margin ; gravity anomalies ; mid-plate seismicity ; sediment depocenters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Morphologic, gravity, and seismic reflection/refraction data from ca. 10,000 km of Arctic passive continental margins suggest that the numerous oval free-air gravity anomalies, their +50–150 mGal extrema typically located just landward of shelf breaks, are caused by combinations of rapidly deposited Plio-Pleistocene glacial marine sediment loads, older post-breakup sediments, and perhaps causally related density anomalies (mascons) in the underlying oceanic crust. Dispersed seismicity associated with some gravity highs may reflect ongoing brittle, flexural adjustment to the loads. Multi-channel-seismic-controlled depocenter models for several prominent highs (including the Hornsund gravity high re-examined here) suggest that sediments alone do not suffice to explain the gravity highs, unless depocenter seismic velocities have been significantly underestimated. A flexural backstripping model for the Hornsund anomaly only roughly replicates observed gravity. Subjacent 'mascons', if present below some depocenters, may be caused by (1) anomalous subsidence of initially formed dense/thin crust; (2) depocenter blanketing of early-formed crust, mitigating hydrothermal fracturing and related density reduction; or (3) metastable phase transitions, converting basalt/gabbro to denser phases (Neugebauer–Spohn hypothesis), while cracks close or fill under the increased pressures and temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004775228851
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  • 5
    Electronic Resource
    Electronic Resource
    15N natural abundances and N use by tundra plants (1996)
    Springer
    Oecologia 107 (1996), S. 386-394 
    Details
    ISSN: 1432-1939
    Keywords: Arctic ; 15N abundance ; N cycle ; Nitrate reductase ; Tundra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plant species collected from tundra ecosystems located along a north-south transect from central Alaska to the north coast of Alaska showed large and consistent differences in 15N natural abundances. Foliar δ15N values varied by about 10% among species within each of two moist tussock tundra sites. Differences in 15N contents among species or plant groups were consistent across moist tussock tundra at several other sites and across five other tundra types at a single site. Ericaceous species had the lowest δ15N values, ranging between about −8 to −6‰. Foliar 15N contents increased progressively in birch, willows and sedges to maximum δ15N values of about +2‰ in sedges. Soil 15N contents in tundra ecosystems at our two most intensively studied sites increased with depth and δ15N values were usually higher for soils than for plants. Isotopic fractionations during soil N transformations and possibly during plant N uptake could lead to observed differences in 15N contents among plant species and between plants and soils. Patterns of variation in 15N content among species indicate that tundra plants acquire nitrogen in extremely nutrient-poor environments by competitive partitioning of the overall N pool. Differences in plant N sources, rooting depth, mycorrhizal associations, forms of N taken up, and other factors controlling plant N uptake are possible causes of variations in δ15N values of tundra plant species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00328456
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  • 6
    Electronic Resource
    Electronic Resource
    Flowering phenology in the central highland of Iceland and implications for climatic warming in the Arctic (1998)
    Springer
    Oecologia 114 (1998), S. 43-49 
    Details
    ISSN: 1432-1939
    Keywords: Key words Flowering phenology ; Iceland ; Arctic ; Global warming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The cool and short growing season that characterizes Arctic climates puts severe constraints on life cycles and reproduction in the Arctic flora. The timing of flowering is particularly critical and may affect both breeding system and reproductive success through the heavy penalties associated with later flowering. An 11-year study of 75 species in the central highland of Iceland showed that the onset of flowering varies greatly among years. The number of species in flower by the first week of July was closely correlated with air temperature (degree days above zero) in the preceding 5 weeks, but no correlations were found with degree days in May or with total degree days in the previous growing season. Time of snowmelt, which has widely been regarded as the environmental event initiating growth and flowering in alpine and arctic tundra, only had a significant effect when two exceptionally cold and late summers were included. The species studied, most of which have a wide distribution in the Arctic, are predicted to respond quickly to warmer spring and early summer temperatures. Accelerated phenologies may alter patterns of resource allocation, have implications for pollinators and pollinator-competition, and could increase the size, species richness and intraspecific genetic diversity of the soil seed bank.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050418
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  • 7
    Electronic Resource
    Electronic Resource
    Environmental constraints on the growth, photosynthesis and reproductive development of Dryas octopetala at a high Arctic polar semi-desert, Svalbard (1995)
    Springer
    Oecologia 102 (1995), S. 478-489 
    Details
    ISSN: 1432-1939
    Keywords: Arctic ; Climate change ; Dryas octopetala ; L. ssp. octopetala ; Clonal growth ; Reproductive output
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Opportunities exist in high Arctic polar semidesert communities for colonisation of unvegetated ground by long-lived clonal plants such as Dryas octopetala. This can be achieved by lateral spread of vegetative ramets, or by sexual reproduction and seedling recruitment. The objectives of this study were (1) to determine whether these two means of proliferation show differential sensitivity to contrasting components of the abiotic environment (temperature, soil nutrient and water availability) and (2) to evaluate the potential for D. octopetala to respond to climate change by an increase in cover and biomass in polar semi-desert communities. Factorial environmental manipulations of growing season temperature, soil nutrient and water status were conducted over 3 years at a polar semi-desert community in Svalbard, Norway (78°56.12′N, 11°50.4′E) and both clonal and sexual reproductive performance, together with instantaneous net photosynthesis (Pn), were recorded during the third season (1993). D. octopetala capitalised rapidly on an amelioration in the availability of inorganic nutrients (N, P and K) by an expansion in leaf area and biomass supported by increased Pn per unit leaf weight, and by apparent luxury uptake of nutrients (particularly P). Several facets of sexual reproductive development and seed viability were markedly improved by elevated temperatures or soil nutrient availability. Thus although D. octopetala is a long-lived clonal plant, with many traits characteristic of stress resistance syndrome, it showed considerable phenotypic plasticity in response to environmental manipulations. The results support the hypothesis that clonal growth confers survival potential during unfavourable years, together with the ability to capitalise on nutrient flushes and recycle nutrients internally. Continued investment in sexual reproduction ensures that seed setting is successful during favourable years, even if these occur infrequently. Cimate warming in the high Arctic could thus result in changes in the cover, biomass and the relative significance of clonal versus sexual proliferation of D. octopetala (and thus the genetic diversity of the population) but the long-term responses will probably be constrained by lack of available nutrients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00341360
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  • 8
    Electronic Resource
    Electronic Resource
    Endocrine influences on parental care during a short breeding season: testosterone and male parental care in Lapland longspurs (Calcarius lapponicus) (1999)
    Springer
    Behavioral ecology and sociobiology 45 (1999), S. 360-369 
    Details
    ISSN: 1432-0762
    Keywords: Key wordsCalcarius lapponicus ; Testosterone ; Parental behavior ; Arctic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In males of socially monogamous birds, plasma testosterone (T) typically declines to low levels during the parental phase. Studies on multiple-brooded species indicate that high T may be incompatible with high-quality paternal care. The length of the breeding season may affect the costs and benefits of high T and its effect on paternal care. We studied the effect of experimentally elevated T on paternal care in a single-brooded species with a short breeding season, the Lapland longspur (Calcarius lapponicus). We monitored T levels and parental behavior in 16 males with subcutaneous T implants, 14 males with empty implants, and 14 unimplanted males. We videotaped nests when nestlings were 2–3 days old and again at 4–5 days. T males with 2- to 3-day-old young visited nests and fed young less often than control males, and the mates of the T males compensated with elevated visits and feedings. However, when nestlings were 4–5 days old, T males visited their nests at normal rates – though feeding movements remained below normal – and T females visited and fed at normal rates. Nestling mass and nest success were similar in both groups. Overall, high T suppresses paternal care in Lapland longspur males. The partial improvement of paternal care when nestlings are older, despite high T, may be related to the short 6-week breeding season of this arctic species, and the consequently reduced benefits of sexual behavior late in the breeding season.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002650050572
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  • 9
    Electronic Resource
    Electronic Resource
    Oxidation of acetophenone in a high temperature open-tubular capillary column liquid chromatographic system (1995)
    Springer
    Chromatographia 40 (1995), S. 99-101 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; High temperature open-tubular columns ; Solvent make-up ; Acetophenone oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Acetophnone, a substance stable at room temperature, is readily oxidizes in a high temperature open tubular liquid chromatographic system by the residual oxygen in the mobile phase. The oxidation product is less UV absorptive and detection sensitivity decreases greatly. To prevent the oxidation, through degassing of the mobile phase is necessary.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02274615
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  • 10
    Electronic Resource
    Electronic Resource
    The removal of endotoxins from protein solutions using column packings with aminated poly (γ-methyl L-glutamate) spheres (1995)
    Springer
    Chromatographia 40 (1995), S. 33-38 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Endotoxins ; Lipopolysaccharide ; Aminated poly(γ-methyl L-glutamate) ; Bovine serum albumin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method is described for the selective removal of endotoxins from various protein solutions using columns packed with aminated poly (γ-methyl L-glutamate) (PMLG-NH2) spheres. The PMLG-NH2 adsorbents showed a high adsorbing activity for endotoxins which had an ionic strength of μ=0.05–1.0 and pH 5.0–9.0. The endotoxin-adsorbing capacity per millitre of the wet adsorbent increased from 0.40 to 1.35 mg (E. coli O111: B4 LPS) at μ=0.2 and pH 7.0 while the aminogroup content of the adsorbent increased from 0.8 to 3.5 meq g−1. The PMLG-NH2-3.5 has an amino-group content of 3.5 meq g−1. This column packing selectively adsorbed endotoxins, without loss of the protein, from a γ-globulin or cytochromec solution which contained endotoxins at μ=0.05 and pH 7.0. On the other hand, when bovine serum albumin (BSA) was present in solution with endotoxins, both the endotoxins and the BSA were adsorbed by the column. The BSA-adsorbing activity increased with increasing amino-group content of the adsorbent. However, this undesirable adsorption was suppressed with increasing ionic strength of the buffer. As a result, when the packing which had an amino-group content of 1.5 meg g−1 was used in conditions of μ=0.2 and pH 7.0, the endotoxins were removed from a BSA-containing solution without affecting the recovery of the BSA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02274604
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  • 11
    Electronic Resource
    Electronic Resource
    Analysis of lignin degradation products by capillary electrophoresis (1995)
    Springer
    Chromatographia 40 (1995), S. 51-57 
    Details
    ISSN: 1612-1112
    Keywords: Column electrophoresis ; Column liquid chromatography ; Phenolic lignin degradation compounds ; Sugar degradation products ; Quantitative analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method for the quantitative analysis of phenolic lignin degradation products by capillary electrophoresis (CE) with on-column UV detection has been developed. The liquid biomass solutions contain low molecular hemicellulosic sugars and phenolic lignin degradation products with various degrees of polymerization. Special attention has been paid to the monomeric phenolic components of lignin degradation fragments, e.g. derivatives of phenolic acids, aldehydes, and alcohols. Uncoated fused silica capillaries and borate-phosphate buffer systems at moderate pH conditions were used in order to separate the compounds of interest. To provide validation of the method, the same samples were analyzed independently by HPLC using gradient elution on a RP-C18 column. As sugar degradation fragment, furan-2-carboxylic acid was detected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02274608
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  • 12
    Electronic Resource
    Electronic Resource
    Liquid chromatography of phenolic compounds in natural water using on-line trace enrichment (1995)
    Springer
    Chromatographia 40 (1995), S. 85-90 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Phenolic compounds ; Ion-pair solid phase extraction ; On-line trace enrichment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Two packing materials, C18 and PLRP-S, are studied for on-line trace enrichment of phenolic compounds in water. Various precolumns of different internal diameter are also tested and the addition of an ion-pair reagent to increase retention and thus, breakthrough volumes of phenolic compounds, is studied. Best results are obtained when a PLRP-S precolumn is coupled on-line with a C18 analytical column and DAD detector. Addition of TBA considerably increases breakthrough volumes. In contrast, when a C18 precolumn is used, breakthrough volumes are lower and it is impossible to determine TCP and PCP, under the experimental conditions used, because of interference of other nonpolar compounds in the samples. The performance of the system is evaluated with river and tap water and the preconcentration of 10 ml of sample in a PLRP-S precolumn involves a linear range between 1 μg 1−1 and 20 μl−1 and limits of determination between 0.5 μg l−1 and 1 μg l−1 are obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02274612
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  • 13
    Electronic Resource
    Electronic Resource
    Screening of water samples for polar organic micropollutants using on-column sample enrichment (1995)
    Springer
    Chromatographia 40 (1995), S. 631-637 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Trace analysis ; Pesticides in tap water ; Aromatic sulphonates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Methodology and instrumentation are described which allow chromatographic screening of water samples under substantially simplified conditions and at reduced cost. A single column is used to accomplish sample extraction, trace enrichment, and separation. The performance of such a system is demonstrated, and the results compared with conventionally used concepts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02315129
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  • 14
    Electronic Resource
    Electronic Resource
    Analysis of pyrithiones by reversed-phase high-performance liquid chromatography (1995)
    Springer
    Chromatographia 40 (1995), S. 669-673 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Transchelation ; Zinc pyrithione and related compounds ; Antidandruff formulations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An analytical procedure has been developed for the determination of zinc pyrithione in antidandruff formulations. Zinc pyrithione was converted into a stable copper complex and then analysed by reversed-phase HPLC. The proposed method allows the separation of the analyte from related pyrithiones and therefore is able to verify the compliance of cosmetic preparations with current legislation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02315135
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  • 15
    Electronic Resource
    Electronic Resource
    Marked differences between acetonitrile/water and methanol/water mobile phase systems on the thermodynamic behavior of benzodiazepines in reversed phase liquid chromatography (1995)
    Springer
    Chromatographia 41 (1995), S. 84-87 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Benzodiazepines ; Solvent effects ; ACN clusters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Two different methods were used to determine the separation factor α at different temperatures and the Gibbs-Helmholtz parameters (Δ(ΔH), Δ(ΔS)) of two adjacent benzodiazepines on a chromatogram were obtained from plots of lnα versus 1/T. We first studied each factor (fraction of water ϕ in the ACN/water mixture and column temperatureT), which controls the retention mechanism, and then we examined the simultaneous variation of all these factors. The changes in Δ(ΔH) and Δ(ΔS) in relation to a volume fraction of water ϕ in an ACN/water mixture were examined. In the ACN/water system, Δ(ΔH) was fairly constant in the acetonitrile region of ϕ≤0.52 and appears to be a roughly linear function of ϕ for ϕ≥0.52. In this system Δ(ΔS) is approximately a parabolic function of ϕ with an optimum at ϕ≅0.52. The retention mechanism of ten benzodiazepines was found to be significantly different in the methanol/water and ACN/water mixtures. The separation optimization of these ten benzodiazepines was then considered. A fraction of water of 0.43 in the ACN/water mixture and a column temperature of 44°C gave the most efficient separation conditions in the ACN/water mixture.
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    URL: http://dx.doi.org/10.1007/BF02274199
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  • 16
    Electronic Resource
    Electronic Resource
    HPLC determination of urinary 2,4- and 2,6-toluendiamines as potential degradation products of polyurethane breast implants (1995)
    Springer
    Chromatographia 41 (1995), S. 661-664 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Polyurethane degradation products ; 2,4- and 2,6-toluendiamine ; Urine analysis ; Breast implants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A reversed-phase HPLC method has been developed for the urinary determination of mutagenic 2,4- and 2,6-toluendiamines. These amines are degradation products of polyurethane, a material used to cover textured silicone breast implants. FMOC-Cl was used as fluorescent derivatising agent in order to obtain a limit of detection of 15 ng/ml in urine. Pre-treatment of urine samples was by liquid/liquid extraction and urine specimens of patients after surgury were analysed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02267801
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  • 17
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    HPLC analysis of flavonoids and phenolic acids and aldehydes inEucalyptus spp. (1995)
    Springer
    Chromatographia 41 (1995), S. 657-660 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Polyphenols ; Flavonoids ; Phenolic acids and aldehydes ; Eucalyptus spp.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Standards of the polyphenols occurring in wood, bark and leaf extracts ofEucalyptus spp. (i.e. flavonoids and phenolic acids and aldehydes) have been analyzed by HPLC using reversed phase columns, gradient elution and diode-array detection. The conditions used are reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02267800
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  • 18
    Electronic Resource
    Electronic Resource
    Polymer encapsulated stationary phases with improved efficiency (1995)
    Springer
    Chromatographia 40 (1995), S. 657-661 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reversed phases ; Polyencapsulated silica ; Polyacrylates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary By copolymerization of silica modified with vinyl groups and acrylic acid esters in suspension highly efficient, polymeric-encapsulated stationary-phases can be prepared. The suspending liquid has to be selected such that the monomers are at least partially adsorbed on the surface and the polymer formed does not precipitate. Under these conditions stationary phases capable of speedy mass transfer can be prepared, where the reduced plate heights are between 2 and 3. The silica surface shielding is optimized so that basic and acidic solutes elute with symmetrical peak.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02315133
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  • 19
    Electronic Resource
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    Determination of D- and L-amino acid residues in peptides with fluorescent chiral tagging reagents by high-performance liquid chromatography (1995)
    Springer
    Chromatographia 40 (1995), S. 645-651 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral resolution of amino acids ; Pre-column derivatization ; Fluorescent chiral tagging reagents ; Stereochemical purity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Derivatization of amino acid enantiomers with fluorescent chiral Edman-type reagents, 4-(3-isothiocyanatopyrrolidin-1-yl)-7-nitro-2,1,3-benzoxadiazole [R(−)- and S(+)-NBD-PyNCS] and 4-(3-isothiocyanatopyrrolidin-1-yl)-7-(N,N-dimethylaminosulfonyl)-2,1,3-benzoxadiazole [R(−)-and S(+)-DBD-PyNCS], yields corresponding diastereomers separable by reversed-phase HPLC on normal achiral columns. The resolved diastereomers were detected fluorometrically at 530 nm with excitation at 490 nm for the NBD-PyNCS derivatives and at 560 nm with excitation at 450 nm for those derived from DBD-PyNCS reagents. This HPLC-derivatization method was used for evaluation of stereochemical purity for some synthetic commercial peptides. The enantioanalysis was reliable down to 0.05% racemization of the amino acid residues and a quantity of 100 μg peptide sample was usually enough for the analysis. Two acid hydrolysis methods, i.e. the standard procedure with constant-boiling hydrochloric acid (HCl) and a rapid vapor-phase procedure with HCl-trifluoroacetic acid (TFA) mixture, were compared. The later was found to be unsuitable owing to increased racemization of the amino acid residues during the hydrolysis. Judging from the results obtained for proline and leucine residues, most of the tested peptides including biologically active peptides, such as neurotensin, [d-Ala2,d-Leu5]-enkepharin and morphine tolerance peptide, possessed stereochemical purities higher than 98%. Influence of structural features of the peptides on the racemization of the amino acid residues was found to be significant.
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    URL: http://dx.doi.org/10.1007/BF02315131
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    HPLC-continuous-flow fast atom bombardment mass spectrometry (HPLC-CFFAB) — a convenient method for the analysis of bile acids in bile and serum (1995)
    Springer
    Chromatographia 40 (1995), S. 674-679 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Mass spectrometric detection ; Fast atom bombardment ionization ; Serum bile acid ; Rat bile
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In order to analyse bile acids in biological matrices, e.g. rat bile and human serum, high performance liquid chromatography (HPLC) was coupled to continuous-flow fast atom bombardment mass spectrometry (CFFAB-MS). A gradient elution system which had already proved to be well suited for the quantitative determination of conjugated bile acids in bile was modified to allow HPLC-CFFAB-MS-coupling. Due to the sensitivity of this coupling method it is possible to obtain more information about the biliary bile acid pattern and species-specific secondary bile acids. Furthermore, we were able to identify obviously unknown bile acid species in rat bile which most likely classify as mono-oxo and di-oxo-taurocholates (MW 513 Da, 511 Da) and mono-oxo-glycocholates (MW 463 Da). In the present study we show that using this system it is possible to determine both conjugated and unconjugated as well as sulfated bile acids, without time consuming group separation and derivatization, from rat bile and human serum. In addition, it is suggested that the method presented here should be considered for use in routine analysis.
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    URL: http://dx.doi.org/10.1007/BF02315136
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    Fluorescence enhancement of dansylamino acids by bovine serum albumin as mobile phase additive in microcolumn liquid chromatography (1995)
    Springer
    Chromatographia 40 (1995), S. 159-162 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fluorescence enhancement ; Bovine serum albumin ; Dansylamino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The effects of acetonitrile and bovine serum albumin (BSA) concentrations on the signal intensity and retention behavior of dansylamino acids have been examined by using γ-cyclodextrin-bonded silica gel as the stationary phase in microcolumn liquid chromatography. Fluorescence intensities of dansylamino acids were enhanced by BSA as a mobile phase additive, e.g., detection limits of dansyl derivatives of L-Ala and L-Phe were improved by a factor of 12–18.
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    URL: http://dx.doi.org/10.1007/BF02272165
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    A statistical study of the correlation between k′ or log k′ and log Pow for a group of benzene and naphthalene derivatives in micellar liquid chromatography using a C-18 column (1995)
    Springer
    Chromatographia 40 (1995), S. 185-192 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Micellar liquid phases ; Octanol-water partition coefficient ; Benzene and naphthalene derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary It is shown that the logarithm of the capacity factor (log k′) for fifteen benzene and naphthalene derivatives in micellar liquid chromatography with forty nine different mobile phases generally correlates better with the logarithm of the octanol-water partition coefficient (log Pow) than the capacity factor (k′). Optimum conditions are established to obtain the best linear correlations of log k′-log Pow.
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    URL: http://dx.doi.org/10.1007/BF02272169
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    Improvement of selectivity of electrochemical detection for the determination of compounds with chloro aromatic rings (1995)
    Springer
    Chromatographia 40 (1995), S. 247-252 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Photolysis ; Electrochemical detection ; Drugs with chlorinated aromatic rings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Pharmaceuticals containing a thiazide ring or chlorinated aromatic ring were investigated with respect to enhanced selectivity in determination. Oxidative electrochemical detection coupled with HPLC was used to study the influence of the pH of the mobile phase under conditions of photolysis. To cover a pH range 3.9–12, the employment of a polymer column stable in alkaline media was necessary. The method offers the great advantage of derivatization without chemicals at low operating potentials, thereby providing high selectivity.
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    URL: http://dx.doi.org/10.1007/BF02290353
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    Separation of structural isomers using cyclodextrin-polymers coated on silica beads (1995)
    Springer
    Chromatographia 40 (1995), S. 296-302 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Structural isomer separation ; Cyclodextrin ; Polymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Several β-cyclodextrin (CD)-bonded stationary phases for high performance liquid chromatography (HPLC) were prepared, based on silica beads coated with a poly(alkylamine), [poly(ethyleneimine)(PEI)]. In order to obtain stationary phases with a high content of CD and maximum accessibility of the CD cavity, the functionalization was carried out after the coating, using the mono-tosyl derivative of CD as the intermediate. The ability of these supports to separate ortho, meta and para isomers of some disubstituted benzene derivatives was examined. The contribution of the amino groups of the polymer and of the CD cavity to the separation process is discussed. The resolution is mainly based on the difference in the stability of the complexes of the various isomers with CD. The influence of the amount of CD on the height of the theoretical plate is also studied.
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    URL: http://dx.doi.org/10.1007/BF02290360
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    A potential application for large diameter pellicular supports in the reversed phase study of ultra high molecular mass polystyrenes (1995)
    Springer
    Chromatographia 40 (1995), S. 307-312 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reversed phase ; Polystyrene ; Pellicular ; Ultra high molecular mass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Ultra high molecular mass (〉 7 million dalton) polystyrenes are prone to degradation in size exclusion chromatography. In gradient elution reversed phase HPLC they do not elute visibly on small particle size porous supports. However, large diameter C18 pellicular particles were successfully employed for reversed phase study of ultra high molecular mass (15 million dalton) polystyrenes without polymer degradation during elution. Although retention for the lower molecular mass polystyrenes was lower than on small diameter porous particles, the medium high molecular mass polystyrenes (0.5–1 million dalton) showed similar retention. The addition of small diameter porous particles in small quantities, to the large diameter pellicular particles, increased the amount of retention of the low molecular mass polystyrenes without affecting the higher molecular mass polystyrenes.
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    URL: http://dx.doi.org/10.1007/BF02290362
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    High performance liquid chromatographic determination of methyl ethyl ketone in urine as its 3-methyl-2-benzothiazolinone hydrazone derivative (1995)
    Springer
    Chromatographia 40 (1995), S. 336-340 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Methyl ethyl ketone in urine ; Derivatization ; 3-Methyl-2-benzothiazolinone hydrazone ; Comparison with GC-MS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A HPLC method for the determination of methyl ethyl ketone (MEK) in urine after derivatization with 3-methyl-2-benzothiazolinone hydrazone is proposed. The calibration curve for the ketone was linear, ranging between 0.23–10 mg/L, with a detection limit of 0.025 mg/L. The results were compared to those obtained by GC-MS, coupled to the headspace technique. MEK derivatization and the derivative purification processes were verified with respect to the main variables such as reaction temperature, reagent concentration, probable interferences and enrichment phase. The method is simple and reliable and shows a good sensitivity.
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    URL: http://dx.doi.org/10.1007/BF02290366
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    Liquid chromatographic analysis of sulfornamides in foods (1995)
    Springer
    Chromatographia 40 (1995), S. 382-386 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Sulfonamides in foodstuffs ; Honey ; Milk ; Eggs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A procedure for the simultaneous determination of several sulfonamides in different foods, such as honey, milk and eggs is proposed. The analysis is carried out using reversed phase liquid chromatography with spectrophotometric detection. Optimization of the mobile phase led to good separation and a short analysis time when an initial isocratic step with a 3∶97 acetonitrile: water mixture was used for 5 minutes, followed by a linear gradient up to a 40∶60 mixture over 15 min. The proposed method is suitable for routine quality control analysis to ensure the absence of sulfonamides in foods. Recovery studies yielded good results for all food samples because there were no interferences from the matrices.
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    URL: http://dx.doi.org/10.1007/BF02269899
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    Determination of aflatoxins in peanut meal by LC/MS with a particle beam interface (1995)
    Springer
    Chromatographia 40 (1995), S. 411-416 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Particle beam LC/MS interface ; Capillary columns for LC ; Mycotoxins ; Peanut meal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new method for the analysis of aflatoxins in food extracts, based on liquid chromatography/mass spectrometry interfacing, is presented. The chromatographic separation was performed with a reversed phase packed capillary column coupled with a modified particle beam interface capable of handling microliter per minute flow rates. This system allows higher overall sensitivity and easier operation procedures. The method has proved to be particularly suitable for the analysis of the toxins in very complex matrices. The specificity of electron impact ionization allowed positive identification of the aflatoxins with an excellent response linearity for accurate quantitation.
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    URL: http://dx.doi.org/10.1007/BF02269904
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    Retention parameters of some isomeric 2-benzoylbenzoic acids in reversed-phase ion-pair high performance thin-layer and column chromatography (1995)
    Springer
    Chromatographia 40 (1995), S. 453-457 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Thin-layer chromatography ; Reversed phase ; 2-benzoylbenzoic acids ; Anionic and cationic counter ions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The 2-benzoylbenzoic acid series was investigated by reversed-phase, high-performance, thin-layer and column chromatography using various alkylammonium salts and di(2-ethylhexyl)orthophosphoric acid as polar associating reagents. The effects of the individual substituents on retention were quantified by Δlog k′ and ΔRM values. The compounds investigated differing in molecular structure (hydrophilic and hydrophobic substituents) commonly occurring groups in drugs and biologically active substances provide information on molecular interaction in these ion-pair systems. The combined effects on retention of organic modifier and ion-pair reagent concentration were investigated.
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    URL: http://dx.doi.org/10.1007/BF02269912
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    Determination of D- and L-amino acids in biological samples by two-dimensional column liquid chromatography (1995)
    Springer
    Chromatographia 41 (1995), S. 6-14 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Two-dimensional separation ; D- and L-amino acids ; Enantioseperation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A two-dimensional, column liquid chromatographic system is used for the determination of the D- and L-enantiomers of amino acids in biological samples. Separation of the amino acids is first on ion-exchange column by gradient elution with a sodium citratesodium chloride buffer. Enantioseparation is by subsequent injection of 3 μl heart-cuts of the individual amino acids onto a second column with a chiral crown ether stationary phase. Finally, fluorescence detection is after post-column labelling of the amino acids using ano-phthalaldehyde-2-mercaptoethanol reagent solution. The high separation power and selectivity of the system allow processing of complex samples with hardly any additional treatment and the determination of small quantities of D-amino acids in the presence of excess L-form. Applicability of the system is illustrated by the determination of D- and L-aspartate, serine, glutamate and alanine in various complex biological samples, such as protein hydrolysates, urine and biotechnological and food samples. Data are given on detectability, repeatability and linearity.
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    URL: http://dx.doi.org/10.1007/BF02274188
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    Simultaneous determination of preservatives, sweeteners and antioxidants in foods by paired-ion liquid chromatography (1995)
    Springer
    Chromatographia 41 (1995), S. 43-50 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion pair LC ; Sweeteners, preservatives and antioxidants ; Food additive analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A paired-ion, reversed-phase high-performance liquid chromatographic method was developed for the simultaneous determination of sweeteners (dulcin, saccharin-Na and acesulfame-K), preservatives (sodium dehydroacetate, sorbic acid, salicyclic acid, benzoic acid, succinic acid, methyl-para-hydroxybenzoic acid, ethylpara-hydroxybenzoic acid, n-propyl-para-hydroxybenzoic acid, isopropyl-para-hydroxybenzoic acid, n-butyl-para-hydroxybenzoic acid, and isobutyl-para-hydroxybenzoic acid), and antioxidants (3-tertiary-butyl-4-hydroxyanisole and tertiary-butyl-hydroquinone). A mobile phase of acetonitrile-50 mM aqueous α-hydroxy-isobutyric acid solution (pH 4.5) (2.2 ∶ 3.4 or 2.4 ∶ 3.6, v/v) containing 2.5 mM hexadecyltrimethylammonium bromide and a C18 column with a flow rate at 1.0 mL/min and detection at 233 nm were used. This method was found to be very reproducible with detection limits ranged from 0.15 to 3.00 μg. The retention factor (k) of each additive could be affected by concentrations of hexadecyltrimethylammonium bromide and α-hydroxyisobutyric acid, and pH and ratio of mobile phase. The presence of additives in some food samples was determined.
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    URL: http://dx.doi.org/10.1007/BF02274194
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    Prediction of precision from signal and noise measurement in liquid chromatography: Mathematical relationship between integration domain and precision (1995)
    Springer
    Chromatographia 41 (1995), S. 75-83 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Limit of detection ; Precision ; Uncertainty prediction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The precision of integration over noisy instrumental output for quantitative analysis is studied. A probability theory is developed to predict the relative standard deviation (RSD) of integration results over an integration domain from one-point integation (peak height measurement) to entire area integration in HPLC. Common integration modes of horizontal zero line and oblique zero line are taken into account, but no peak overlap is assumed. The question of the analytical superiority of peak height measurement or integration for quantitation is answered. In the HPLC apparatus used, the minimum RSD of measurements is found in the integration domain of ca. ±0.5 σ for analytes [peaks are approximated by the Gaussian signal of width, σ (standard deviation)]. The RSD of integration measurements is also shown to depend on the stochastic properties of back-ground noise (uncorrelated noise and correlated 1/f type noise). The theoretical conclusion is verified by Monte Carlo simulation and HPLC experiments for some aromatic compounds.
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    URL: http://dx.doi.org/10.1007/BF02274198
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    Ion-pair reversed-phase and low-molecular-weight aqueous gel permeation high-performance liquid chromatography methods for the determination of amoxicillin oligomersa (1995)
    Springer
    Chromatographia 41 (1995), S. 651-656 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion-pair and GPC separations ; Amoxicillin oligomers ; β-Lactam ring polymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Polymeric substances formed from concentrated sodium amoxicillin in an aqueous solution have been separated using two high-performance liquid chromatographic methods. We used a C18 reversed-phase column with tetrabutylammonium chloride as an ion-pairing agent with an acetonitrile gradient and a TSKgel G2500PWxl column with water as the solvent for gel permeation chromatography. The separated materials, ranging in size from the monomer to the tetramer, have been characterized by functional-group chemical analysis, while the identification of the piperazine-2,5-dione was done using a pure standard. A greater number of peaks which were also better defined were obtained using the ion-pair reversed-phase method, and open and closed beta-lactam ring polymer forms could be distinguished. Using the gel permeation method, only a few monomer, piperazine-2,5-dione, dimer, trimer and combined amoxicillin trimer and tetramer peaks were obtained with water, although those obtained were quite well defined. The data on the time-course of formation of the oligomers and the amoxicillin degradation product were virtually identical by both methods.
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    URL: http://dx.doi.org/10.1007/BF02267799
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    Signal enhancement by on-column fluorimetric detection in gradient elution of dansyl amino acids in liquid chromatography (1995)
    Springer
    Chromatographia 41 (1995), S. 148-152 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; On-column fluorimetric detection ; Gradient elution ; Dansyl amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Fluorimetric detection in the presence of a stationary phase has been applied to gradient elution of dansyl amino acids in liquid chromatography. A 1.5 mm ID quartz tube packed with the same materials as the separation column was employed for the flow cell. Conventional-size columns were employed. The peak height of analytes increased with increasing retention owing to focusing and environmental effects of the stationary phase, leading to improvements in sensitivity, which was pronounced for analytes eluting late. The lower the gradient, the larger the improvement in sensitivity achieved. Detection limits were improved by a factor of up to 5.1 by fluorimetric detection using the packed flow cell, compared with those achieved using a common empty flow cell.
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    A study of the behaviour of some new column materials in the chromatographic analysis of Cinchona alkaloids (1995)
    Springer
    Chromatographia 41 (1995), S. 153-160 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; LC-MS ; Cinchona alkaloids ; New column packing materials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A major problem in the HPLC analysis of alkaloids is the poor peak shape and consequently low resolution, due to the interactions of the basic alkaloids with the residual acidic silanol groups of most reversed phase materials. The performance of new packing materials specially designed for the separation of basic compounds has been studied using mobile phases without the special additives commonly applied in the analysis of alkaloids. Strongly basic Cinchona alkaloids were used as test compounds. Retention characteristics and selectivities of each material were studied, after mobile phase optimisation for the column. The influence of the major factors (nature and content of the organic modifier, pH value, salt concentration) affecting resolution was studied. The mobile phases were chosen so that they could be used in thermospray LC-MS. The addition of salts to the mobile phase improves separation but in general the modification of the mobile phase gave little change in selectivity. The performance of silicabased C18 material proved superior to the polymer materials tested.
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    Polar cyanobacteria versus green algae for tertiary waste-water treatment in cool climates (1997)
    Springer
    Journal of applied phycology 9 (1997), S. 371-381 
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    ISSN: 1573-5176
    Keywords: Antarctic ; Arctic ; cyanobacteria ; green algae ; mass algal culture ; Phormidium ; temperature ; waste-water treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Forty-nine strains of filamentous, mat-forming cyanobacteria isolated from the Arctic, subarctic and Antarctic environments were screened for their potential use in outdoor waste-water treatment systems designed for cold north-temperate climates. The most promising isolate (strain E18, Phormidium sp. from a high Arctic lake) grew well at low temperatures and formed aggregates (flocs) that could be readily harvested by sedimentation. We evaluated the growth and nutrient uptake abilities of E18 relative to a community of green algae (a Chlorococcalean assemblage, denoted Vc) sampled from a tertiary treatment system in Valcartier, Canada. E18 had superior growth rates below 15°C Canada. (µ = 0.20 d-1 at 10°C under continuous irradiance of 225 µmol photon m-2 s-1) and higher phosphate uptake rates below 10°C (k = 0.050 d-1 at 5°C) relative to Vc (µ=0.087 d-1 at 10°C and k = 0.020 d-1 at 5°C, respectively). The green algal assemblage generally performed better than E18 at high temperatures (at 25°C, µ = 0.39 d-1 and k = 0.34 d-1 for Vc; µ = 0.28 d-1 and k = 0.33 d-1 for E18). However, E18 removed nitrate more efficiently than Vc at most temperatures including 25°C. Polar cyanobacteria such as strain E18 are appropriate species for waste-water treatment in cold climates during spring and autumn. Under warmer summer conditions, fast-growing green algae such as the Vc assemblage are likely to colonize and dominate, but warm-water Phormidium isolates could be used at that time.
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    URL: http://dx.doi.org/10.1023/A:1007987127526
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    Fission of Heton-like Vortices under Sea Ice (1999)
    Springer
    Journal of oceanography 55 (1999), S. 65-78 
    Details
    ISSN: 1573-868X
    Keywords: Fission ; vortices ; heton ; Arctic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Close interactions among vertically stacked pairs of counter-rotating eddies under sea ice were investigated in numerical experiments. The numerical model contains a stratified ocean capped by an ice layer. Under the ice layer, a shallow brine source produces a top cyclone and a submerged anticyclone, while a shallow freshening source generates a top anticyclone and a submerged cyclone. Ice-exerted friction would dissipate the top eddy, leaving the submerged one in lone existence. In this work the winning vorticity is sought from group settings. Arrays of equally spaced salinity sources and sinks, alternate in sign but equal in strength, are employed to produce rows of vertically stacked eddy pairs. Fission occurs when adjacent vortex centers are separated by less than one Rossby radius. This process ejects parcels of density anomalies to the ambient ocean in upper depths. Low salinity anomalies are quickly dispersed into a thin surface layer and are unable to regenerate submerged eddies. High salinity parcels, being difficult to disperse, often maintain or regenerate submerged anticyclones below. Fission is particularly effective if a single row of salinity forcing is used. With multiple rows, fission is active only in the outer rows. The strong interaction among closely packed eddies operates in time scales of tens of days, helping explain the predominance of submerged anticyclones under Arctic sea ice.
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    Sensitivity to stress in the bivalve Macoma balthica from the most northern (Arctic) to the most southern (French) populations: low sensitivity in Arctic populations because of genetic adaptations? (1997)
    Springer
    Hydrobiologia 355 (1997), S. 127-138 
    Details
    ISSN: 1573-5117
    Keywords: Arctic ; adaptation ; copper ; distribution limit ; genetics ; geographic cline ; Macoma balthica ; stress sensitivity ; survival in air
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The stress sensitivity, determined in copper exposureexperiments and in survival in air tests, and thegenetic structure, measured by means of isoenzymeelectrophoresis, were assessed in populations of theBaltic clam Macoma balthica (L.) from itssouthern to its northern distribution limit, in orderto test the hypotheses that near the distributionlimit the clams would be more stress sensitive andwould have a lower genetic variability. Thepopulations in west and north Europe show a stronggenetic resemblance. The populations in the sub-ArcticWhite Sea are genetically slightly different, and showa low stress sensitivity. The populations in theArctic Pechora Sea are genetically very distant fromthe other populations, and show the lowest stresssensitivity. Near the southern distribution limit, inagreement with the hypotheses, genetic variability islow and stress sensitivity high. On the other hand, incontrast to expectation, near the northerndistribution limit, in the populations of the PechoraSea, the genetic variability was higher, thus notreduced, and the stress sensitivity was low comparedto all other populations. Yet, it remains a questionif such is due to gradual physiologicalacclimatization (and ongoing differential selection)or to genetic adaptation.
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    URL: http://dx.doi.org/10.1023/A:1003009524563
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    Boundary-layer ozone depletion as seen in the Norwegian Arctic in spring (1996)
    Springer
    Journal of atmospheric chemistry 23 (1996), S. 301-332 
    Details
    ISSN: 1573-0662
    Keywords: tropospheric ozone ; Arctic ; hydrocarbons ; halogens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Several years of measurements of ozone, hydrocarbons, sulphate and meteorological parameters from Spitsbergen in the Norwegian Arctic are presented. Most of the measurements were taken on the Zeppelin Mountain at an altitude of 474 m a.s.l. The focus is the episodes of ozone depletion in the lower troposphere in spring, which are studied in a climatological way. Episodes of very low ozone concentrations are a common feature on the Zeppelin Mountain in spring. The low ozone episodes were observed from late March to the beginning of June. When the effect of transport direction was subtracted, the frequenty of the low ozone episodes was found to peak in the beginning of May, possibly reflecting the seasonal cycle in the actual depletion process. Analyses based on trajectory calculations show that most of the episodes occurred when the air masses were transported from W-N. Ozone soundings show that the ozone depletion may extend from the surface and up to 3–4 km altitude. The episodes were associated with a cold boundary layer beneath a thermally stable layer, suppressing mixing with the free troposphere. The concentration of several individual hydrocarbons was much lower during episodes of low ozone than for the average conditions. The change in concentration ratio between the hydrocarbons was in qualitative agreement with oxidation of hydrocarbons by Br and Cl atoms rather than by OH radicals.
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    URL: http://dx.doi.org/10.1007/BF00055158
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    The Measurement of Active Chlorine in the Atmosphere by Chemical Amplification (1999)
    Springer
    Journal of atmospheric chemistry 34 (1999), S. 9-20 
    Details
    ISSN: 1573-0662
    Keywords: Arctic ; analytical method ; boundary layer ; bromine oxide ; chemical amplification ; chlorine oxide ; field measurement ; halogens ; ozone depletion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Chemical amplification, CA, a method commonly used for the detection of peroxy radicals, HO2 and RO2, was found to be sensitive towards ClOx (Cl+ClO+OClO) as well. ClOx is reduced by NO to Cl atoms which react with carbon monoxide in the presence of O2. The reaction sequence thus initiated oxidizes CO to CO2 and NO to NO2, with a chain length of 300 ± 60. This allows the atmospheric ClOx content to be measured under ambient conditions with a detection limit of better than 1 ppt. In parallel peroxy radicals are indicated with a chain length of 160 ± 15. Chemical amplification is not specific and does not indicate which radical chain it is seeing. Identification relies solely on plausibility. During the ARCtic Tropospheric Ozone Chemistry (ARCTOC) campaign in spring 1995 and 1996 the CA technique was used at Ny-Ålesund. ClOx at mixing ratios of up to 2 ppt were found in the boundary layer under certain conditions. The low concentrations of ClOx indicate that the arctic boundary ozone depletion is mainly driven by bromine.
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    URL: http://dx.doi.org/10.1023/A:1006208828324
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    Measurements of Photolyzable Halogen Compounds and Bromine Radicals During the Polar Sunrise Experiment 1997 (1999)
    Springer
    Journal of atmospheric chemistry 34 (1999), S. 21-37 
    Details
    ISSN: 1573-0662
    Keywords: Br2 ; HOBr ; BrOx ; Arctic ; ozone depletion ; troposphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract As part of the Polar Sunrise Experiment (PSE) 1997, concentrations of halogen species thought to be involved in ground level Arctic ozone depletion were made at Alert, NWT, Canada (82.5°N, 62.3°W) during the months of March and April, 1997. Measurements were made of photolyzable chlorine (Cl2 and HOCl) and bromine (Br2 and HOBr) using the Photoactive Halogen Detector (PHD), and bromine radicals (BrOx) using a modified radical amplifier. During the sampling period between Julian Day 86 (March 27) and Day 102 (April 12), two ozone depletion episodes occurred, the most notable being on days 96-99, when ozone levels were below detectable limits (≈1 ppbv). Concentrations of BrOx above the 4 pptv detection limit were found for a significant part of the study, both during and outside of depletion events. The highest BrOx concentrations were observed at the end of the depletion event, when the concentration reached 15 pptv. We found substantial amounts of Br2 in the absence of O3, indicating that O3 is not a necessary requirement for production of Br2. There is also Br2 present when winds are from the south, implying local scale (e.g. from the snowpack) production. During the principal O3 depletion event, the HOBr concentration rose to ≈260 pptv, coincident with the BrOx maximum. This implies a steady state HO2 concentration of 6 pptv. During a partial O3 depletion event, we estimate that the flux of Br2 from the surface is about 10 times greater than that for Cl2.
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    URL: http://dx.doi.org/10.1023/A:1006264912394
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    C2-C7 Hydrocarbon Concentrations in Arctic Snowpack Interstitial Air: Potential Presence of Active Br within the Snowpack (1999)
    Springer
    Journal of atmospheric chemistry 34 (1999), S. 55-64 
    Details
    ISSN: 1573-0662
    Keywords: hydrocarbon measurements ; interstitial air ; snow pack ; Arctic ; active bromine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Samples of interstitial air from within the snow pack on an ice floe on the Arctic Ocean were collected during the April 1994 Polar Sunrise Experiment. The concentrations of C2-C7 hydrocarbons are reported for the first time in the snow pack interstitial air. Alkane concentrations tended to be higher than concentrations in free air samples above the snow but very similar to winter measurements at various locations in the Arctic archipelago. However, ethyne concentrations in both interstitial and free air were highly correlated with ozone mixing ratios, consistent with previous demonstrations of the effects of Br atom chemistry. The analysis of total bromine within the snow pack indicate an enrichment in total Br at the interface layer between snow and free troposphere. The mixing ratios of some brominated compounds, such as CHBr3 and CHBr2Cl, are found to be higher in this top layer of snow relative to the boundary layer. Results were inconclusive due to the limited number of samples, but suggest the possible presence of active bromine in the snow pack and also that some differences exist between chemical reactions occurring in interstitial air compared to air in the boundary layer.
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    URL: http://dx.doi.org/10.1023/A:1006289618755
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    A Technique for Estimating Polar Ozone Loss: Results for the Northern 1991/92 Winter Using EASOE Data (1999)
    Springer
    Journal of atmospheric chemistry 34 (1999), S. 365-383 
    Details
    ISSN: 1573-0662
    Keywords: stratospheric ozone ; Arctic ; chemical loss
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract In this paper we describe a technique for estimating chemical ozone loss in the Arctic vortex. Observed ozone and temperature profiles are combined with the model potential vorticity field to produce time series of vortex averaged ozone mixing ratios on chosen isentropic surfaces. Model-derived radiative heating rates and observed vertical gradients of ozone are then used to estimate the change in ozone that would occur due to diabatic descent. Discrepancies with the observed ozone are interpreted as being of chemical origin, assuming that there is negligible horizontal transport or mixing of air into the vortex. The technique is illustrated using ozone sonde measurements collected during the 1991/92 European Arctic Stratospheric Ozone Experiment (EASOE), meteorological analyses from the European Centre for Medium-range Weather Forecasts (ECMWF) and radiative heating rates extracted from the Global Atmospheric Modelling Programme (UGAMP) 3D General Circulation Model. Our results show that there was photochemical ozone destruction inside the Arctic vortex in early 1992 with a loss between 475 K and 550 K (around 20 km) of 0.32±0.15 ppmv in the first 20 days of January, equivalent to a rate of 0.51±0.24%/day (at the 95% confidence level).
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    URL: http://dx.doi.org/10.1023/A:1006273211790
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    Marine Rotifera from a sandy beach at Disko Island, West Greenland, with the description of Encentrum porsildi n. sp. and Notholca angakkoq n. sp. (1998)
    Springer
    Hydrobiologia 386 (1998), S. 153-165 
    Details
    ISSN: 1573-5117
    Keywords: Encentrum n. sp. ; Notholca n. sp. ; taxonomy ; marine ; Greenland ; Arctic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The rotifer fauna from two localities at an Arctic beach at Disko Island was investigated. Five species were found; four are new to Greenland and two of these are new to science. Encentrum graingeri and Proales reinhardti were found in the psammon, and it is suggested that they inhabit the sea-ice during the winter and then shift to inhabit the psammon in the ice-free periods during summer. Encentrum porsildi n. sp. and Notholca angakkoq n. sp. are described. The descriptions are based on detailed SEM-studies of the trophi.
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    Anthropogenic Mercury Deposition to Arctic Lake Sediments (1998)
    Springer
    Water, air & soil pollution 101 (1998), S. 309-321 
    Details
    ISSN: 1573-2932
    Keywords: Arctic ; atmospheric deposition ; contaminants ; lead-210 ; mercury ; sediment ; sewage ; subarctic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The history of atmosheric mercury inputs to remote arctic regions can be measured in lake sediment cores using lead-210 chronology. In this investigation, total mercury deposition is measured in sediments from Imitavik and Annak Lakes on the Belcher Islands in southeastern Hudson Bay, an area in the southern Canadian Arctic with no history of local industrial or agricultural sources of contamination. Both lakes received background and atmospheric inputs of mercury while Annak also received mercury from raw domestic sewage from the Hamlet of Sanikiluaq, a growing Inuit community of about 550 established in the late 1960's. Results from Imitavik show that anthropogenic mercury inputs, apparently transported through the atmosphere, began to appear in the mid-eighteenth century, and continued to the 1990's. Annak had a similar mercury history until the late 1960's when disposal of domestic sewage led to increased sediment and contaminant accumulation. The high input of mercury to Annak confirms that Sanikiluaq residents are exposed to mercury through native food sources.
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    URL: http://dx.doi.org/10.1023/A:1004998417316
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    Functional diversity and community structure of micro-organisms in three arctic soils as determined by sole-carbon-source-utilization (1999)
    Springer
    Biodiversity and conservation 8 (1999), S. 205-221 
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    ISSN: 1572-9710
    Keywords: Arctic ; biodiversity ; community ; micro-organisms ; soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Functional diversities of micro-organisms in arctic soils at three incubation temperatures were assessed using sole-carbon-source-utilization (SCSU). Soil samples were collected from an area of anthropogenic fertilization (mixed Dorset/Thule/Historic site), an area of animal enrichment (bird rock perches), and unaltered tundra (raised beach; control soil site). The micro-organisms were extracted from the soil samples and inoculated into Gram-negative (GN) Biolog plates incubated at 30°C, 10°C, and 4°C. Calculations of the Shannon index, substrate utilization richness, Shannon evenness, and the Jaccard coefficient of similarity were based upon substrate utilization on the Biolog plates. Principal component analysis distinguished microbial communities in enriched soils from unenriched soils. At 10°C and 4°C, Shannon indices of enriched soil microbial communities (10°C: soils influenced by wild animals=4.28, soils influenced by human activities=4.20; 4°C: soils influenced by wild animals=4.15, soils influenced by human activities=4.03) were significantly higher than unenriched soil microbial communities (10°C: 3.66; 4°C: 3.38). Substrate utilization richness and evenness displayed similar trends. Although Jaccard coefficients showed uniformity across the different soil samples, cluster analysis supported patterns demonstrated by PCA. Lower temperatures (4°C and 10°C) yielded greater resolution between soil microbial communities than 30°C based on Biolog colour development patterns.
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    Determination of vitamin A in pharmaceutical preparations by high-performance liquid chromatography with diode-array detection (1995)
    Springer
    Chromatographia 40 (1995), S. 143-146 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Diode-array detection ; Retinol acetate ; Pharmaceutical preparations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A very simple high-performance liquid chromatographic method for determination of Vitamin A in pharmaceutical preparations without the need for saponification was developed. A reversed-phase (Nova-Pack C18, 4 μm) column was used with a mobile phase of acetonitrile-tetrahydrofuran-water (55∶37∶8) and a flowrate of 1.5 ml/min. Sample treatment only consisted of the extraction of retinol acetate content from capsules or tablets with methanol. Total extraction was achieved by shaking vigorously with the aid of magnetic stirring for three hours at room temperature. No change of solvent is necessary to introduce the sample in the chromatographic system. This method is suitable for routine quantification of Vitamin A.
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    URL: http://dx.doi.org/10.1007/BF02272162
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    Thermodynamic behavior of mixed benzodiazepines by a new liquid chromatographic method (1995)
    Springer
    Chromatographia 40 (1995), S. 193-196 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chemometric methodology ; Elution order ; Simplex optimization ; Benzodiazepines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Using a rapid chemometric methodology to determine the separation factor, α, at different temperatures, Gibbs Helmholtz parameters (Δ (ΔH), Δ (ΔS), Δ (ΔG)) of two adjacent benodiazepines on a chromatogram were obtained from ln α versus T−1 plots. A temperature dependent reversal of the elution order was studied and the mobile phase composition and column temperature were optimized to obtain the best separation. A flow rate of 0.80 ml min−1 with 52.6% methanol in the methanol-water mixture and a column temperature of 48°C gave the most efficient separation of ten benzodiazepines.
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    Mixed-mode liquid chromatography of aliphatic anionic surfactants with a naphthalenetrisulfonate mobile phase (1995)
    Springer
    Chromatographia 40 (1995), S. 237-246 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Mixed mode stationary phases ; Indirect photometric and fluorometric detection ; Conductimetric detection ; Alkyl-sulphates, and sulphonat-phosphates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Separation of three classes of anionic surfactants (alkyl sulfates, alkanesulfonates, and alkyl phosphates) are achieved on a mixed-mode reversed phase (RP) phenyl/-anion exchange column using a naphthalenetrisulfonate (NTS)-acetonitrile (ACN) mobile phase via indirect photometric, indirect fluorometric, direct or indirect conductivity detection. Mixtures of C5−C18 sulfates, C6−C18 sulfonates, and C1−C4 phosphates (mono- and di-ester) can be separated in less than 20, 24, and 20 min respectively. Although hydrophobic effects are more pronounced in mixed-mode chromatography, equivalent-per-equivalent exchange of analysis and eluent ion is still required for sensitive indirect photometric, fluorometric, or conductivity detection. The detection limits of alkyl sulfates and alkanesulfonates are in the range of 3–15 pmoles which are at least an order of magnitude better than suppressed conductivity detection. The determination of surfactants in a variety of real samples is also presented.
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    Enantiomeric separation of D/L-carnitine using HPLC and CZE after derivatization (1995)
    Springer
    Chromatographia 40 (1995), S. 287-295 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Capillary zone electrophoresis ; Enantioseparation ; Carnitine ; Derivatization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Carnitine is an essential component in tissues of animals, higher plants and many microorganisms. Whereas the L-carnitine enantiomer plays an important role in the metabolism of long chain fatty acids, D-carnitine has a considerable toxic influence on biochemical processes. The analytical separation of D-and L-carnitine depends upon derivatization with UV-or fluorescently active substances, e.g. FMOC and (+)/(−)-FLEC. The separation of diastereomeric (+)- and (−)-FLEC carnitine esters was performed successfully with capillary zone electrophoresis (CZE) and HPLC, after optimization of the derivatization process and of the composition and pH of the buffer, using UV- and fluorescence detection. With HPLC separation a detection limit of the carnitine esters of 5 μmol/l when using fluorescence detection was achieved. With both separation systems baseline resolution and short analysis times could be obtained. The enantiomeric FMOC derivatives could be separated using the electrophoretic system and acidic buffers with high concentrations of an osmotic flow modifier together with γ-cyclodextrine as chiral selector. The applicability of the optimized separation conditions are demonstrated in the analysis of agar culture medium inoculated withPseudomonas putida and of pharmaceutical formulations. In all samples very low amounts of D- or L-carnitine could be determined in the presence of the other enantiomeric form. Problems caused by the impurity of the carnitine standards or the derivatization agent (+)/(−)-FLEC are discussed.
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    Retention of fullerenes by octadecyl silica. Correlation with NMR spectra at low temperatures (1995)
    Springer
    Chromatographia 40 (1995), S. 507-512 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fullerenes ; Retention vs NMR spectra ; C18 phases ; Low temperature separations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The temperature effect on the retention of fullerenes in the range 80°C to −70°C in liquid chromatography (LC) has been examined using octadecylsilica stationary phases (ODS). It has been found that the maximum retention temperature lies around −10°C with a highly carbon loaded ODS phase. Solid state CPMAS NMR measurements on the stationary phases indicated that the relaxation time at the 30 ppm methylene signal changes with the temperature and has a minimum relaxation time at the temperature which closely matches the maximum retention temperature observed in chromatography. The interpretation of both NMR spectroscopic and LC chromatographic data are discussed.
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    Derivatisation of DL-amino acids by urethane — Protected α-amino acidN-carboxyanhydrides for separation by LC (1995)
    Springer
    Chromatographia 40 (1995), S. 601-606 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Amino acid analysis ; Chirality ; Diastereoisomers ; Dipeptides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Using a robotic autosampler, free DL-amino acids were derivatized with highly reactive, urethane-protected, L-α-amino acidN-carboxyanhydrides (NACs) with structures: Boc-Phe-NCA, Boc-Asn(Trt)-NCA, Fmoc-Lys(Boc)-NCA, Fmoc-Met-NCA, Fmoc-Ala-NCA, Z-Ala-NCA, Z-Val-NCA and Z-Leu-NCA (Boc=tert-butyloxycarbonyl, Trt=trityl, Fmoc=9-(fluor-enylmethyl)oxycarbonyl, Z=benzyloxycarbonyl). Using sodium borate buffer and acetonitrile solvent, derivatization was complete in 3.5 min at room temperature. By selection of an appropriate reagent, the resulting diastereomeric,N-protected dipeptides were separated on an octylsilica stationary phase using mixtures of sodium acetate buffer and acetonitrile as eluents.
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    High-performance liquid chromatography of dihydroxyacetone as its bis-2,4-dinitrophenylhydrazone derivative (1995)
    Springer
    Chromatographia 41 (1995), S. 61-65 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Dihydroxyacetone ; 2,4-dinitrophenylhydrazine ; Tanning creams
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A rapid and simple HPLC method for the identification and determination of dihydroxyacetone, a tanning agent widely used in a variety of preparations, is presented. The method consists of the analysis of the formulated products after a derivatization reaction which enhances the response and the detection limit of the chromatographic analysis. The characterization and the elucidation of the spacial geometry of the synthesized derivative are described.
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    High performance liquid chromatographic analysis of Patent Blue V in cheese (1995)
    Springer
    Chromatographia 41 (1995), S. 431-434 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Thin-layer chromatography ; Patent Blue V in cheese
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The HPLC method developed for the analysis of the dye Patent Blue V in extracts from cheese is sufficiently sensitive to detect and measure concentrations above 0.1 ppm with a standard deviation of 3%. The extraction procedure described gives a recovery from cheese of about 80%. The method has been applied to commercial samples of cheese and a concentration of the dye of about 0.12 ppm was measured in one case.
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    Modelling and prediction of retention in high-performance liquid chromatography by using neural networks (1995)
    Springer
    Chromatographia 41 (1995), S. 435-444 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Micellar liquid chromatography ; Neural networks ; Retention modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Multi-layer feed-forward neural networks trained with an error back-propagation algorithm have been used to model retention behaviour of liquid chromatography as a function of the composition of the mobile phases. Conventional hydro-organic and micellar mobile phases were considered. Accurate retention modelling and prediction have been achieved using mobile phases defined by two, three and four parameters. With micellar mobile phases, the parameters involved included the concentrations of surfactant and organic modifier, pH and temperature. It is shown that neural networks provide a competitive tool to model varied inherent nonlinear relationships of retention behaviour with respect to the mobile phase parameters. The soft models defined by the weights of the networks are capable of accommodating all types of linear and nonlinear relationships, neural networks being specially useful when the relationships between retention behaviour and the mobile phase parameters are unknown. However, to train neural networks more experimental points than with hard-modelling methods are required, hence the use of the networks is recommended only for those cases where adequate theoretical or empirical models do not exist.
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    Simultaneous assay of four stereoisomers of diltiazem hydrochloride. Application to in vitro chiral inversion studies (1995)
    Springer
    Chromatographia 41 (1995), S. 450-454 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Diltiazem hydrochloride stereoisomers ; Chiralcel OF ; Chiral inversion ; Epimerization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The simultaneous stereospecific assay of four stereoisomers of diltiazem hydrochloride in bulk drug and aqueous solution was developed using HPLC on a Chiralcel OF column. The four isomers were quantitated with good precision by the internal standard method. The chiral inversion of (+)-cis-diltiazem hydrochloride in vitro, stability of its (2S, 3S) configuration in the solid and aqueous states was examined by HPLC. Chiral inversion of (+)-cis-diltiazem hydrochloride was not observed in the solid state, and its (2S, 3S) configuration was stable to heat, humidity and light. Chiral inversion of (+)-cis-diltiazem hydrochloride (2S, 3S) was observed in aqueous solution under UV, but not in aqueous solution stored at 80°C for 5h nor under visible light for 10 h. The (+)-cis-diltiazem hydrochloride (2S, 3S) epimerized to (+)-trans-diltiazem hydrochloride (2R, 3S) with a half-life of 5h in aqueous solution under UV but the reverse chiral inversion of (+)-trans-diltiazem hydrochloride (2R, 3S) to (+)-cis-diltiazem hydrochloride (2S, 3S) was not observed.
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    Detoxification of acetonitrile-water wastes from liquid chromatography (1995)
    Springer
    Chromatographia 41 (1995), S. 488-491 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Acetonitrile disposal ; Acetonitrile hydrolysis ; Degradation kinetics ; Waste solvent management
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Acetonitrile is one of the most frequently used solvents in column liquid chromatography. Because of its toxicity, safe disposal of the waste solvent is essential. Combustion in a hazardous waste plant, if available, is recommended. Otherwise the waste can be degraded in the laboratory to acetic acid and ammonia by treatment with sodium hydroxide. The addition of hydrogen peroxide is not necessary. The waste needs to be diluted to 10% acetonitrile in water in order to prevent the formation of a two-phase system on addition of concentrated sodium hydroxide. This reagent must be added in excess; 2.5 mols of sodium hydroxide per mol of acetonitrile are recommended. It was found that the kinetics are of second order, with an activation energy of 89 kJ mol−1 and a frequency factor of 9×109. Therefore even at room temperature degradation is possible, although a hydrolysis time of approximately 15 days is needed under these conditions. At 80°C, where refluxing is not necessary, hydrolysis is complete after, e.g., 2 h, depending on the amount of sodium hydroxide added.
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    Retention behaviour of metal complexes with 5-sulphoquinoline-8-ol in reversed-phase ion-pair liquid chromatography (1995)
    Springer
    Chromatographia 41 (1995), S. 532-538 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion-pair LC ; 5-Sulphoquinoline-8-ol ; Metal complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The reversed-phase ion-pair liquid chromatographic behaviour of several metal complexes with 5-sulphoquinoline-8-ol (HQS) on an octadecyl-modified silica column was investigated by using a fluorescence detector. The aluminum complex gave two peaks on the chromatograms when eluents containing phosphate buffer were used. The effects of the pH of the eluent, HQS concentration, the nature of anions in the eluent, and the column temperature on the retention behaviour of the aluminum complex are discussed on the basis of the equilibria and the kinetics of the complexation of the aluminum ion with HQS and anions in the eluent. The equilibrium constant for the interconversion reaction between the two Al(III)-HQS species which correspond to the two peaks observed and the second stepwise formation constant for the Zn(II)-HQS complex were evaluated from the HPLC data obtained.
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    Liquid chromatographic determination of aniline and derivatives in environmental waters at nanogram per litre levels using fluorescamine pre-column derivatization (1995)
    Springer
    Chromatographia 41 (1995), S. 568-572 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fluorescamine derivatives ; Aniline and aniline derivatives ; Environmental waters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Fluorescamine (fluram) has been used as a fluorogenic compound for pre-column derivatization of aniline and some derivatives. Anilines were derivatized with fluram in citrate buffer media (pH 5.5) to form pyrrolinones. The highly fluorescence pyrrolinones were isolated and pre-concentrated by solid phase extraction. A reversed phase, Spherisorb RP-8 column and tetrahydrofuran: water:formic acid (42∶56∶2) mobile phase was used for separation. Detection method was by a sensitive fluorimetric method and quantitation was at 395 and 495 nm. The various parameters such as reaction conditions between anilines and fluram, solid phase extraction and chromatographic separation were optimized. Calibrations were linear over the range considered with excellent correlation coefficients (r〉0.999). Relative standard deviations are less than 2.5% and detection limits for aniline,p-toluidine, 4-chloroaniline and 4-bromoaniline were 6, 30, 6 and 8 ng L−1, respectively. This method has been used successfully for the determination of anilines in environmental waters.
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    URL: http://dx.doi.org/10.1007/BF02269721
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    Separation of saponins and determination of quinovic acid 3-O-α-L-rhamnopyranoside fromNauclea diderrichii (de Wild) Merr. Bark by high performance liquid chromatography (1995)
    Springer
    Chromatographia 41 (1995), S. 581-584 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Nauclea diderrichii (de Wild) Merr ; Saponins ; Alkaloid glycoside ; Chrysanthelline A
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A reversed-phase HPLC determination of 11 saponins and an alkaloid glycoside inNauclea diderrichii bark is described. Quantitative analysis of quinovic acid 3-O-α-L-rhamnopyranoside which is one of the main saponins was determined, using Chrysanthelline A as internal standard. The complete separation was achieved in 47 minutes. The method of quantification was validated.
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    URL: http://dx.doi.org/10.1007/BF02269723
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    Quantitative determination of toxic mono- and non-ortho polychlorinated biphenyls in cod liver oil after selective liquid chromatographic separation (1995)
    Springer
    Chromatographia 41 (1995), S. 585-593 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Column liquid chromatography ; Polychlorinated biphenyls ; Cod liver oil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary By application of a chromatographic column filled with Supelclean ENVI-Carb/Celite and elution with three solvents of different polarity three PCB fractions were obtained. Fraction A contained poly-ortho PCBs, Fraction B mono-ortho PCBs, and Fraction C non-ortho PCBs. The Supelclean ENVI-Carb/Celite column was used in combination with a sample preparation procedure for pre-cleaning of acid-stable chlorinated hydrocarbons such as DDT and its metabolites, HCH isomers, and regulation-relevant PCB congeners. The method was optimized using standard solutions of 55 PCB congeners, 8 chlorinated pesticides and contaminated cod liver oil samples. The influence of traces of remaining matrix on the elution profile of the organochlorine compounds on Supelclean ENVI-Carb/Celite was observed. Quantitation was carried out by GC-ECD with fused silica capillary columns of different polarity.
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    URL: http://dx.doi.org/10.1007/BF02269724
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    High performance liquid chromatography —Electrospray tandem mass spectrometry (HPLC-ESI-MS-MS) for the analysis of heterocyclic aromatic amines (HAA) (1996)
    Springer
    Chromatographia 42 (1996), S. 7-11 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Heterocyclic aromatic amines (HAA) ; Electrospray MS-MS detection ; Selected reaction monitoring (SRM)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Sensitive and selective detection of the sixteen most abundant heterocyclic aromatic amines (HAA) has been achieved by application of high performance liquid chromatography-electrospray tandem mass spectrometry (HPLC-ESI-MS-MS) in combination with selected reaction monitoring (SRM). Detection limits between 0.1 and 50 ng mL−1 were established by use of HAA model solutions.
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    URL: http://dx.doi.org/10.1007/BF02271047
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    The optimization of step-gradient elution conditions in liquid chromatography: Application to pesticide residue analysis using coupled-column reversed-phase LC (1996)
    Springer
    Chromatographia 42 (1996), S. 17-24 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Column switching ; Step-gradient elution ; Optimization ; Trace analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A computer spreadsheet application has been developed for the optimization of step-gradient elution conditions as applied in coupled-column RPLC for online clean-up and separation in the analysis of pesticide residues. The procedure is based on the experimentally determined retention behaviour of the analytes as a function of mobile phase composition. Retention and peak volumes of the analytes eluting under isocratic and one- and/or two-step gradient conditions can be calculated. For a given set of analytes, the spreadsheet systematically calculates the resolution of the least efficiently separated pair of peaks in the space defined by the eluotropic strengths of the mobile phases and the time at which the step-gradient takes place. The performance of the proposed procedure was tested and evaluated for the analysis of nine polar pesticides for which in a previous study adequate conditions had been found by computer-aided chromatogram simulation. the optimum conditions predicted by the procedure were in good agreement with those established experimentally and by simulation. The simultaneous production of data on retention, peak volume and resolution for a group of analytes under selected one- and/or two step-gradient elution conditions makes the calculation procedure highly productive and flexible in searching for and/or adjusting appropriate separation conditions.
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    URL: http://dx.doi.org/10.1007/BF02271049
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    Determination of the specific interaction of disubstituted aromatic compounds on hydrous zirconium oxide-loaded porous polymer resin (1996)
    Springer
    Chromatographia 42 (1996), S. 396-400 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Hydrous zirconium oxide ; Porous polymer resin ; Disubstituted phenols ; ortho-Benzoic acid derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A porous polymer resin loaded with hydrous zirconium oxide (Zr-gel) was evaluated as a stationary phase for the liquid chromatographic separation of disubstituted aromatic compounds. The prepared Zr-gel was used to separate disubstituted phenols andortho-substituted benzoic acid derivatives in reversed-phase mode. The retention time of catechol was greater than those of other disubstituted phenols; this implies that the Zr-gel has specificity for the phenolic hydroxyl group. The retention behavior ofortho-substituted benzoic acid derivatives on the Zr-gel was also evaluated in reversedphase mode using buffer. Phthalic acid was specifically retained in the vicinity of pH 6.0, which has been regarded as the equal adsorbic point. Similar behavior was also observed for salicylic acid, although the retention time of salicylic acid was less than that of phthalic acid. It seems that the specific retention behavior of hydrous zirconium oxide is a result of complexation with ligands such as hydroxyl and carboxyl groups. The results of this study have revealed that the retention mechanism of hydrous zirconium oxide is a combination of ion exchange and interaction based on complexation with ligands.
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    URL: http://dx.doi.org/10.1007/BF02272129
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    HPLC determination of tryptophan enantiomers with photometric, fluorimetric and diode-laser polarimetric detection (1996)
    Springer
    Chromatographia 42 (1996), S. 494-498 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Tryptophan ; Chiral separations ; Diode-laser polarimetric detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The combined utilization of photometric, fluorimetric and polarimetric detection liquid chromatography detectors in series for the identification and quantification of D-tryptophan and L-tryptophan was evaluated. Detection limits of about 1 μg were established with the range of linearity extending to about 100 μg. The relative standard deviation of the D-form and L-form tryptophan were 7.32 and 4.22%, respectively. The amount unknown of tryptophan enantiomers in the different mixtures was determined with an accuracy of 1.58% at the 40 μg injection level.
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    URL: http://dx.doi.org/10.1007/BF02290282
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    Chroamtographic behaviour of un-sulphated and sulphated oligoethyleneglycol nonylphenyl ether surfactants in normal-phase liquid chromatographic systems containing water (1996)
    Springer
    Chromatographia 42 (1996), S. 539-546 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Un-sulphated and sulphated surfactants ; Oligoethyleneglycol nonylphenyl ethers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention behaviour of un-sulphated and sulphated, oligoethyleneglycol nonylphenyl ether, anionic surfactants was investigated in normal-phase LC systems with chemically bonded amino stationary phase in organic mobile phases containing water and cetyl trimethylammonium bromide (CTAB). Addition of water to the mobile phase improves efficiency of separation and linearity of the dependences of logk′ versus number of oxyethylene units in the sulphated oligomers, so that it is possible to describe simultaneous effects of this number and of the concentration of CTAB on retention by a simple equation. In this system, it is possible to separate lower sulphated and un-sulphated oligomers in a single run in 10–15 min under isocratic conditions.
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    URL: http://dx.doi.org/10.1007/BF02290288
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    Identification of vitamin B12 analogues by liquid chromatography with electrothermal atomic absorption detection (1996)
    Springer
    Chromatographia 42 (1996), S. 566-570 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Electrothermal atomic absorption spectrometry ; Vitamin B12 analogues ; Cobalamins and cobalt ; Meat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The coupling of liquid chromatography and electrothermal atomic absorption spectrometry (LC-ETAAS) lowers the detection limit for identification of vitamin B12 analogues. Cobalamins and aqueous cobalt (II) were separated by reversed-phase liquid chromatography using a linear gradient: 26∶74 (v/v) methanol:0.05 M phosphate buffer (pH 4.2) to 50∶50 mixture over 8 min. The vitamins were quantitatively determined in the column effluent by measuring total cobalt by ETAAS. The analysis of meat and liver extracts by LC-ETAAS showed that the matrix did not interfere with the determination of cobalt. Hence, recoveries of cobalt in spiked meat and liver samples were satisfactory.
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    URL: http://dx.doi.org/10.1007/BF02290293
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    High-performance liquid chromatographic determination of meropenem in rat plasma using column-switching (1996)
    Springer
    Chromatographia 42 (1996), S. 405-408 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Meropenem in rat plasma ; Column-switching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The purpose of this study was to develop a columnswitching HPLC method for the determination of meropenem in plasma. This method showed excellent precision and accuracy with good sensitivity and speed. The total analysis time per sample was less than 20 min and the mean coefficients of variation for intra- and inter-assay were less than 4.0%. The method has been successfully applied to plasma samples from rats receiving an intraperitoneal injection of meropenem.
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    URL: http://dx.doi.org/10.1007/BF02272131
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    1,1′-[Ethenylidenebis(sulfonyl)]bis-benzene: A useful pre-chromatographic derivatization reagent for HPLC analysis of thiol drugs (1996)
    Springer
    Chromatographia 42 (1996), S. 515-520 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Thiol drugs ; Pre-chromatographic derivatization ; 1,1′-[ethenylidenebis(sulfonyl)]bis-benzene reagent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The use of 1,1′-[ethenylidenebis(sulfonyl)]bis-benzene as a pre-chromatographic reagent for LC analysis of thiol drugs is proposed. The reagent reacts rapidly (2 min) under mild conditions (pH 7.5, ambient) with thiol drugs and the resulting adducts can be chromatographed under reversed-phase conditions (C-18 column). Excess reagent can be removed from the reaction mixture by simple liquid-liquid extraction with chloroform. The HPLC method using UV detection was successfully applied to the analysis of reduced glutathione (GSH), N-acetylcysteine, N-2-mercaptopropionylglycine and captopril in their commercial formulations.
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    URL: http://dx.doi.org/10.1007/BF02290285
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    Direct enantiomeric HPLC separation of several 2-arylpropionic acids, barbituric acids and benzodiazepines on chiralcel OJ-R chiral stationary phase (1996)
    Springer
    Chromatographia 43 (1996), S. 599-606 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; 2-Arylpropionic acids ; Barbituric acids ; Benzodiazepines ; Cellulose tris(4-methylbenzoate) chiral stationary phase ; Reversed-phase mode ; Chiral recognition mechanisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A newly developed reversed-phase chiral stationary phase, cellulose tris(4-methylbenzoate), known as Chiralcel OJ-R, has been successfully applied to the direct resolution of the enantiomers of several nonsteroidal anti-inflammatory drugs belonging to the profen group. Among the five barbituric acids tested, the chiral resolution of mephobarbital is especially high. The Chiralcel OJ-R column also proved quite efficient for the enantiomeric resolution of a few representatives of the benzodiazepine group. Variations of mobile phase conditions based on acetonitrile and/or methanol were tested. The results obtained are briefly compared with separations performed using a Chiralcel OJ column under normalphase conditions.
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    URL: http://dx.doi.org/10.1007/BF02292974
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    Extraction and identification procedures of polyphenolic compounds and carbohydrates in phillyrea (Phillyrea angustifolia L.) leaves (1996)
    Springer
    Chromatographia 42 (1996), S. 571-577 
    Details
    ISSN: 1612-1112
    Keywords: Liquid-liquid and liquid-solid extractions ; Column liquid chromatography ; Mass spectrometry detection ; Flavonoids inPhillyrea angustifolia leaves
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Liquid-liquid (LLE) and liquid-solid extraction (LSE) procedures were developed to identify polyphenols in phillyrea (Phillyrea angustifolia L.) leaves. The liquidsolid extraction, carried out by using two serial Bond-Elut® CH and Bond-Elut® SAX cartridges allowed the collection of both polyphenols and soluble carbohydrates during a single extraction of leaf. This method seems to be suitable for both phytochemical and physiological study of the species, allowing the identification of two classes of organic compounds which have a central role in the metabolism of phillyrea plants. A method of isolation and concentration of polyphenols for further molecular characterization, using centrifuge chromatography, was also developed. Molecular characterization, carried out by UV-Vis spectrophotometry and mass spectrometry, demonstrated the presence of compounds with interesting biological activity, i.e. flavonoids and oleuropein derivatives. The soluble carbohydrate composition of phillyrea leaves did not substantially differ from that ofOlea europaea L. leaves, except for a higher mannitol/glucose ratio. This carbohydrate distribution may be linked to the evolution pattern of this species which usually grows in severely stressed environments.
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    Simultaneous separation and identification of hashish constituents by coupled liquid chromatography-mass spectrometry (HPLC-MS) (1996)
    Springer
    Chromatographia 43 (1996), S. 129-134 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; On-line liquid chromatography-mass spectrometry ; Neutral and acidic cannabinoids ; Hashish samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This paper reports the use of liquid chromatography for the separation and determination of the major cannabinoids extracted from hashish samples. The direct coupling to the mass spectrometer enables the selective identification both of neutral and acidic cannabinoids. The developed method does not require any preliminary derivatization and should, therefore, be of interest in forensic analysis for simple and unequivocal determination of hashish constituents.
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    URL: http://dx.doi.org/10.1007/BF02292940
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    Effect of solute association on the apparent adsorption isotherm. A model of the separation of non-racemic mixtures of enantiomers in achiral chromatographic systems (1996)
    Springer
    Chromatographia 43 (1996), S. 17-24 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Non-linear adsorption isotherm ; Simulation of chromatographic peak profiles ; Separation of optical isomers ; Non-racemic mixtures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This article discusses the effect of solute association on the apparent adsorption isotherm and on the chromatographic peak profile. The modelling performed has shown that dimerization of a solute in a chromatographic system gives rise to an apparent adsorption isotherm of the non-linear type. This results first of all in peak broadening. Tailing or a fronting can be observed depending on the relative retention of the monomer and the dimer. Secondly, the retention of the solute depends on the amount of sample because of the non-linear character of the adsorption isotherm. As a result, an excess of one of two analytes with absolutely identical adsorption properties i.e. optical isomers, can be separated in such chromatographic systems by considering that the sample contains non-equal amounts of two analytes. The phenomenon is illustrated by simulated chromatograms of the separation of non-racemic mixtures of enantiomers.
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    URL: http://dx.doi.org/10.1007/BF02272816
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    Evaluation of the influence of the base material loaded with hydrous zirconium oxide gel on the retention behavior of disubstituted benzoic acids (1996)
    Springer
    Chromatographia 43 (1996), S. 79-81 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Hydrous zirconium oxide ; Porous polymer resin ; Silica gel ; ortho-Benzoic acid derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Silica gel loaded with hydrous zirconium oxide (Zr-gel-S) has been prepared and the influence of the base material on the retention behavior ofo-phthalic acid on the hydrous zirconium oxide was evaluated. The retention behavior of the acid on the Zr-gel-S was compared with that on Zr-gel-5, the polymer-based Zr-gel. Comparable retention behavior,i.e. maximum retention in the vicinity of pH 6, which has been regarded as the equal adsorbic point, was observed for both types of Zr-gel, although there was a large difference in the retention times. The difference in retention on the two types of Zr-gel could be ascribed to nature of the base material. The results in this experiments showed, however, that the specific behavior at pH 6 was an essential characteristic of hydrous zirconium oxide and was not related to the influence of the base materials.
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    URL: http://dx.doi.org/10.1007/BF02272826
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    Normal and reversed-phase HPLC for more complete evaluation of tocopherols, retinols, carotenes and sterols in dairy products (1996)
    Springer
    Chromatographia 43 (1996), S. 89-93 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Sterols, tocopherols, retinols and carotenes ; Dairy products
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary We have previously described a normal-phase HPLC method for the simultaneous determination of α, β, γ and δ tocopherol, thecis andtrans isomers of retinol, and total carotenes in different Italian cheeses and milk. In this paper we describe a reversed-phase HPLC method using solely methanol as the mobile phase for the determination of α-tocopherol, β-+γ-tocopherols, total retinols, cholesterol, β-sitosterol, campesterol and stigmasterol, and α- and β-carotene. The method developed has been applied to some new dairy products such as natural Quark, with olive, basil or banana and to processed cheese with tomato and the results have been compared with the corresponding results obtained by the normal-phase method. The conclusion is that more complete evaluation of the tocopherol, retinol, carotene and sterol content of dairy products, especially when vegetables and fruits are present, is necessary and can be obtained using both the normal- and reversed-phase HPLC methodologies.
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    Determination of pesticides by on-line trace enrichment-reversed-phase liquid chromatography-diode-array detection and confirmation by particle-beam mass spectrometry (1996)
    Springer
    Chromatographia 43 (1996), S. 592-598 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Diode-array detection ; Particle beam mass spectrometric detection ; Pesticides in water ; On-line solid-phase extraction (SPE)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A group of pesticides has been determined by liquid chromatography with diode-array detection (DAD). The coupling of a particle-beam (PB) mass spectrometer to the outlet of the DAD enabled the identities of the pesticides to be confirmed from mass spectra obtained by electron impact ionization. On-line trace enrichment of 200 mL of sample with a PLRP-S precolumn enabled most pesticides to be determined in real samples at levels between 0.2 and 5 μg L−1 and with limits of detection (LOD) between 0.05 and 0.5 μg L−1. In the analysis of real samples, one of the pesticides studied was determined by DAD and its identity was confirmed by comparison of PB mass spectra. The use of PB-MS also enabled the detection of non-target compounds.
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    Comparative study of the use of high-performance liquid chromatography and capillary electrophoresis for determination of phenolic compounds in water samples (1996)
    Springer
    Chromatographia 43 (1996), S. 619-624 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Capillary electrophoresis ; Phenolic compounds ; Water samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A comparative study of high-performance liquid chromatography (HPLC) and capillary zone electrophoresis (CZE) for determination of eleven EPA priority phenols in water samples is discussed. The repeatability, linearity and detection limits of both methods are compared. A solid-phase extraction method using a highly cross-linked styrene-divinylbenzene copolymer sorbent is used for the off-line preconcentration process in order to determine these compounds in water at low levels. Both methods are used to determine phenolic compounds in Ebro river and industrial waste water. Identification was achieved by comparison of the UV spectra corresponding to the different peaks, acquired with a diode-array detector, with those in a spectral library.
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    Polycyclic aromatic hydrocarbons in waste waters and sewage sludge: Extraction and clean-up for HPLC analysis with fluorescence detection (1996)
    Springer
    Chromatographia 43 (1996), S. 135-142 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Polycyclic aromatic hydrocarbons ; Waste waters ; Sewage sludge
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A modified solid-phase extraction technique using sonication of the adsorbent material instead of the elution normally applied has been compared with two conventional liquid-liquid extraction procedures for the determination of the 16 EPA PAHs in municipal waste waters by means of HPLC coupled with fluorescence detection. Liquid-liquid extraction with cyclohexane proved to be the most efficient and simplest procedure. Clean-up of the waste-water extracts was not considered necessary, because of the high chromatographic resolution of the column and the selectivity of the fluorescence detector. Different organic solvents were also compared for ultrasonic extraction of PAHs from sewage sludge. The best results were obtained by use of acetonitrile. Clean-up of sewage-sludge extracts was not found necessary for accurate quantification of the major PAH components with fluorescence detection. The precision of the whole analytical procedure from extraction to the final determination of PAHs was satisfactory for both waste-water and sewage-sludge samples.
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    Optimization of alkali-alkalkine earth cation separation on weak cation-exchangers (1996)
    Springer
    Chromatographia 43 (1996), S. 117-123 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion-exchange chromatography ; Ion-exchange mechanism ; Optimization of alkali and alkaline earth separation ; Crown ether complexing reagents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The elution behavior of alkali and earth alkaline cations has been studied on a newly synthesized weak cationexchanger (WCX). Applying this stationary phase isocratic separation of these cations is possible. The dependence of retention on competing ion concentration is described via a simple model. The influence of crown ethers as well as organic eluent additives on selectivity and peak efficiency is demonstrated. With optimized separation such cations can be determined with detection limits of about 0.5 ppm using a conductivity detector without ion suppression.
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    URL: http://dx.doi.org/10.1007/BF02292938
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    Selectivity of dansyl amino acids in micellar liquid chromatography with an ion-exchange-induced stationary phase (1996)
    Springer
    Chromatographia 43 (1996), S. 143-148 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Micellar liquid chromatography ; Ion-exchange-induced stationary phase ; Dansyl amino acids (Dns-AAs) ; Fluorescence enhancement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention behavior of dansyl amino acids in micellar liquid chromatography has been examined by using ionexchange-induced stationary phases. Several parameters affected the retention of the analytes, including the type and concentration of micellar agent and modifier ion and the concentration of acetonitrile in the mobile phase. The order of elution of dansyl amino acids obtained with the micellar mobile phase was very different from that observed in conventional reversed-phase liquid chromatography. Fluorescence intensities of some dansyl amino acids were enhanced by the micellar mobile phase.
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    URL: http://dx.doi.org/10.1007/BF02292942
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    Optimisation of chiral separation of omeprazole and one of its metabolites on immobilized α1-acid glycoprotein using chemometricsglycoprotein using chemometrics (1997)
    Springer
    Chromatographia 44 (1997), S. 10-18 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Experimental design ; Direct chiral resolution ; Omeprazole ; Hydroxy-omeprazole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A strategy for the optimisation of direct chiral separation of omeprazole and a metabolite, hydroxi-omeprazole, in reversed phase liquid chromatography is described. A factorial design was used, where mobile phase pH, concentration of a mobile phase modifier, ionic strength and column temperature were tested as the variables and enantioselective retention, column efficiency and asymmetry factor as the responses. The experimental results were evaluated with multivariate analyses, which demonstrated that the column temperature and content of mobile phase acetonitrile were by far the most important variables. The enantiomers of omeprazole and one of its metabolites were baseline resolved within 15 minutes. The optimised chromatographic system was used for a separation of the enantiomers of omeprazole and its main metabolite in a patient plasma sample.
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    URL: http://dx.doi.org/10.1007/BF02466509
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  • 82
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    Chemiluminescence determination of tiopronin and its metabolite 2-mercaptopropionic acid in human urine by HPLC coupled with flow injection (1997)
    Springer
    Chromatographia 44 (1997), S. 31-36 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chemiluminescence detection ; Tiopronin ; Thiols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In previous pharmacokinetic studies tiopronin, a drug used for effective treatment of cystinuria and rheumatoid arthritis, and its metabolite 2-mercaptopropionic acid were analysed by conventional liquid chromatography with pre- and post-column derivatization and UV detection. Now a novel HPLC-coupled chemiluminescence-flow-injection analysis (CL-FIA) method has been developed for the determination of tiopronin and 2-mercaptopropionic acid in urine. The method is based on chemiluminescence from a Ce(IV) oxidation system sensitized by quinine, as proposed earlier by this group, and flow-injection analysis. The method, which has the advantages of high sensitivity and selectivity, simple sample treatment and prompt production of results, has also been preliminarily adapted for pharmacokinetic study of tiopronin in urine.
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    URL: http://dx.doi.org/10.1007/BF02466512
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    HPLC analysis of fat-soluble vitamins on standard and narrow bore columns with UV, electrochemical and particle beam MS detection (1997)
    Springer
    Chromatographia 44 (1997), S. 605-612 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; UV and electrochemical detection ; Particle beam-mass spectrometry ; Fat-souble vitamin ; Standard-bore and narrow-bore columns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The application of different detection techniques; UV, electrochemical (ED) and particle beam-mass spectrometry (PB-MS) for the high-performance liquid chromatography analysis of fat-soluble vitamins were studied. Separation of all compounds examined was performed using both C8 standard-bore and narrow-bore columns for UV and MS detection, whereas in the case of HPLC-ED, a C8 standard-bore column only was used. Detector responses were studied in terms of linear range, detection limit and precision. The HPLC methods with UV, PB-MS and electrochemical detection were applied to the assay of vitamins A and E in an infantformula, powdered-milk sample. Recovery studies showed good results both for vitamins A and E, within-run precision being 2–4% for LC-UV and LC-ED techniques. In addition, excellent aggrement between the results obtained with the detection systems explored was found.
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    URL: http://dx.doi.org/10.1007/BF02466663
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  • 84
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    High-performance liquid chromatography of some estrogens on chemically bonded phases (1996)
    Springer
    Chromatographia 43 (1996), S. 551-556 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chemically bonded silica gel ; Mixed solvents ; Steroids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The chromatographic behaviour of 30 estradiol and estrone derivatives has been studied on diol, amino- and cyanopropyl silica gel stationary phases with non-aqueous mobile phases. The slopes of linear relationships between the logarithm of the retention factor and logarithm of the volume fractions of the polar components of the binary eluents have been calculated and are discussed in relation to the characteristics of the solute, eluent and stationary phase. An equation for testing the separation efficiency of stationary phases has been derived.
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    URL: http://dx.doi.org/10.1007/BF02293009
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    Determination of cortisol in guinea pig urine by high performance thin-layer chromatography, high performance liquid chromatography, and thin-layer chromatography/radioimmunoassay (1997)
    Springer
    Chromatographia 44 (1997), S. 50-54 
    Details
    ISSN: 1612-1112
    Keywords: Thin layer chromatography ; Column liquid chromatography ; Radioimmunoassay ; Cortisol ; Guinea pig ; Urine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In order to collect urinary samples from unrestrained guinea pigs, animals were kept in their familiar home cages with wood shavings for bedding. Cortisol was removed from shavings by a simple washing step, and an attempt was made to measure its concentrations by high performance thin-layer chromatography (HPTLC), high performance liquid chromatography (HPLC), or thin layer chromatography/radioimmunoassay (TLC-RIA). After intramuscular administration of 25 mg cortisol, cortisol excretion increased from about 20–30 μg/day to 400–500 μg/day (HPTLC: 531 μg/day, HPLC: 493 μg/day; TLC-RIA: 394 μg/day). Similarly, the treatment of the animals with 20 IU ACTH resulted in an augmented cortisol excretion, with mean values of 294 μg/day (HPTLC), 256 μg/day (HPLC) and 143 μg/day (TLC-RIA), respectively. The present study shows, for the first time, that cortisol excretion in unrestrained laboratory animals can be determined. Whilst the cortisol values measured by HPTLC and HPLC agree, the amounts measured by TLC-RIA were significantly lower. These differences are probably due to the presence of substances in urine or shavings which interfere with the radioimmunological determination. Hence, cortisol should be determined either by HPTLC or HPLC. Beside having a desirable specificity, these methods are more suited than TLC/RIA for steroid analysis since they confer the possibility of measuring additional steroids (e.g. precursors and/or metabolites of cortisol) in a single urine extract. This is especially the case for the HPTLC method since substances can be transformed into fluorescent derivatives.
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    URL: http://dx.doi.org/10.1007/BF02466515
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  • 86
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    Development of a universal Raman detector for microchromatography (1997)
    Springer
    Chromatographia 44 (1997), S. 257-262 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Microchromatography ; Raman spectroscopy ; Deuterated solvents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A detector for microchromatography in which Raman spectroscopy is used to identify the eluted species has been developed. The detector is designed to be applicable to a wide range of compounds without requiring the presence of a chromophore. Its use is illustrated in the analysis of nitro compounds on a 250 μm i.d. column. Raman spectra of each of the compounds could be identified as they passed the detector. The advatages of the use of fully deuterated solvents are demonstrated by the analysis of nitrobenzenes in methanol/water mobile phases. The detection limit for nitrobenzene using the Raman line at 1342 cm−1 was 75ng.
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    URL: http://dx.doi.org/10.1007/BF02466391
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  • 87
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    Development and validation of a stability-indicating HPLC method for the determination of degradation products in dipyridamole injection (1997)
    Springer
    Chromatographia 44 (1997), S. 247-252 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Dipyridamole injection ; Stability studies ; Degradation products
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The development and subsequent validation of an isocratic high-performance liquid chromatographic (HPLC) procedure employing ultraviolet (UV) detection for the determination of degradation products in Dipyridamole Injection is reported. The development of this assay involved the evaluation of several factors including buffer type, ionic strength, pH, organic composition, and column type. The described method is simple, reproducible, accurate, and selective. The precision, relative standard deviation (RSD), amongst five sample preparations for total degradation products was not more than (NMT) 10.2 %, while the individual degradation products were NMT 12.1%. Intermediate precision, as determined from fifteen sample preparations, generated by two Analysts on different HPLC systems over three days, exhibited an RSD for total and individual degradation products of 8.2 % and NMT 27.5 %, respectively. The mean absolute recovery of dipyridamole using the described method is 102.1±1. 9%, (mean±SD, n=12) over the concentration range of 0.03 % to 5.0 % of its label claim of 5 mg mL−1. The limit of detection and limit of quantitation were 0.1 and 0.3 μg mL−1, respectively. The linearity of the peak response was verified with respect to dipyridamole concentration over a range of 0.3 and 50 μg mL−1 (0.03 % to 5.0 % label claim). The Standard and Assay Preparations are stable for up to 48 hours at room temperature. The selectivity was evaluated by subjecting the finished product (Dipyridamole Injection) to thermal, acidic, basic, oxidative and fluorescent radiation stress conditions. No interference in the analysis of degradation products was observed, showing the method is stability-indicating.
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    URL: http://dx.doi.org/10.1007/BF02466389
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    A weak cation-exchange phase for the separation of biogenic amines by open tubular liquid chromatography (1997)
    Springer
    Chromatographia 44 (1997), S. 295-302 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Open tubular columns ; Weak cation-exchange stationary phase ; Biogenic amines ; LIF detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The preparation and performance of a weak cation-exchange stationary phase for Open Tubular Liquid Chromatography (OT-LC) was investigated. The stationary phase was prepared in 5.4 μm I.D. fused silica capillaries byin situ photopolymerization of a mixture of silicon acrylate and acrylic acid. The influence of pH, counter ion concentration and organic modifier concentration of the mobile phase on the retention was studied with catecholamines as test solutes using LIF detection. Other biological amines like amino acids, small peptides and nucleic acid derivatives could be separated on this stationary phase as well. The kinetic performance of the stationary phase was studied with several cations and neutral solutes.
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    URL: http://dx.doi.org/10.1007/BF02466398
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    Quantitative analysis of mebeverine in dosage forms by HPLC (1997)
    Springer
    Chromatographia 44 (1997), S. 427-430 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Mebeverine in dosage forms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A simple and rapid, high performance liquid chromatographic (HPLC) procedure for determination of mebeverine in dosage forms (tablet and liquid) is described. Reversed-Phase chromatography was carried out using a mobile phase containing 0.05 M ammonium acetate buffer and acetonitrile, [(45%, v/v) pH 5.2] with UV-detection (263 nm). Replicate regression analyses of three standard plots in the concentration range of 0.5–10 mcg mL−1 obtained on three different days gave a correlation coefficient 〉0.9995 and the coefficient of variation of the slopes 〈2.2%. The assay was precise within day and between days as indicated by ANOVA test. The recoveries from 10 replicate tablets of two commercial mebeverine brands and liquid were in order 99.3, 100.5 and 100.1% of the label amount and their coefficient of variations were 1.41, 0.89 and 0.69%, respectively. The limit of quantitation of mebeverine was 5 ng mL−1.
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    URL: http://dx.doi.org/10.1007/BF02466322
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    Synthesis of new stable aliphatic isothiocyanate-based chiral derivatizing agent and application to indirect separation of chiral amino and thiol compounds (1997)
    Springer
    Chromatographia 44 (1997), S. 465-472 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Indirect separation ; Chiral derivatization ; Stable CDA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new chiral derivatizing agent (CDA) (1S, 2S) N-[(2-isothiocyanato)-cyclohexyl)-pivalinoyl amide ((S,S)-PDITC) is described. The CDA is available from 1,2-diamino cyclohexane (DACH) via a straightforward synthesis in both the (R,R) and (S,S)-configuration and can serve as a highly selective, stable reagent for the indirect resolution of chiral primary and secondary amines, amino acids and thiol compounds. The resulting diastereomeric thioureas and dithiocarbamates can be separated by simple RP-HPLC as demonstrated with a number of pharmaceutically important examples of amines and amino alcohol-type drugs. The latter diastereomers are compared with the well-established GITC derivatized compounds. The separation factors (α) of the diastereomeric thioureas range between 1.03 and 2.08 and were usually higher than those of the GITC derivatives. The chemical stability of the PDITC derivatives is excellent due to the absence of hydrolyzable ester groups— considered an advantage compared to GITC derivatives.
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    URL: http://dx.doi.org/10.1007/BF02466738
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    Synthesis and characterization of titania based stationary phases using the silanization/hydrosilation method (1997)
    Springer
    Chromatographia 44 (1997), S. 538-544 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Octadecyl titania ; Hydride surface ; Hydrosilation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The silanization/hydrosilation bonding method is tested on both a laboratory synthesized and commercial titania. The laboratory titania made by the sol-gel process shows evidence of residual organic material that is removed by an initial acid hydolysis followed by bonding of the hydride (triethoxysilane) under acidic conditions. DRIFT and solid state CP-MAS NMR studies are used to confirm the formation of the hydride layer on the titania and the success of the hydrosilation process for attaching an organic moiety (1-octadecene) to the surface. Chromatographic testing, primarily on the commercial titania based C-18 phase, indicates good reverse phase properties and few residual OH groups, either Ti−OH or Si−OH, as determined by the symmetrical peak shapes obtained for anilines and alkylphenylamines using mobile phases with no buffers or masking agents in the aqueous component.
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    URL: http://dx.doi.org/10.1007/BF02466748
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    Application of SPE for the HPLC analysis of taxanes fromTaxus cell cultures (1998)
    Springer
    Chromatographia 47 (1998), S. 25-34 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Solid Phase Extraction ; RP-HPLC gradient analysis ; Taxus Cell Cultures ; Taxol and Taxanes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Solid phase extraction (SPE) methods are studied for the sample pretreatment for HPLC analysis ofTaxus cell suspension cultures. Various types of SPE materials were tested for the extraction of both the taxane standards and samples of various origin. Comparison between the different cartridges and the different elution solvents are made in terms of extraction recovery and sample clean-up. Selective elution of the taxanes is achieved by a gradient elution scheme.
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    URL: http://dx.doi.org/10.1007/BF02466782
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    Ionic strength dependence of heavy metal tartrate complex stabilities (1998)
    Springer
    Chromatographia 47 (1998), S. 77-80 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion chromatography ; Stability constants ; Ionic strength ; Heavy metals ; Tartaric acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Ion chromatography and potentiometry were used for the determination of the stability constants Pb, Zn, Co, Ni, Mn tartrate complexes at different ionic strengths. An extrapolation function based on the Debye-Hückel equation was applied to obtain the thermodynamic stability constants.
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    URL: http://dx.doi.org/10.1007/BF02466789
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    Development of an Ion-pair HPLC method for the determination of 2,4- and 2,6-toluendiamine in human plasma (1998)
    Springer
    Chromatographia 47 (1998), S. 84-88 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion-pair LC ; Plasma ; 2,4-Toluendiamine ; 2,6-Toluendiamine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An ion-pair HPLC method is presented for the determination in plasma of 2,4- and 2,6-toluendiamine (TDA), known carcinogens. The chromatographic conditions consisted in isocratic elution on a reversed phase C18 column with 5 mM octanesulfonic acid in methanol-water, 45∶55, as mobile phase. UV detection was performed at 235 nm. Samples were analyzed after a simple single step liquid-liquid extraction and the method was validated by measurement of precision (interassay and intraassay), sensitivity, specificity, linearity, and recovery. The detection limit for both TDAs in plasma was 20 ng mL−1. The correlation coefficients based on the intrassay calibration curve were 0.998 and 0.997 for 2,6- and 2,4-TDA, respectively. The intraassay accuracy, expressed in terms of recovery, was found to be up to 89.91% and 97.05% for 2,6- and 2,4-TDA, respectively.
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    URL: http://dx.doi.org/10.1007/BF02466791
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    Direct resolution of a new antifungal agent, voriconazole (UK-109,496) and its potential impurities, by use of coupled achiral-chiral high-performance liquid chromatography (1998)
    Springer
    Chromatographia 47 (1998), S. 649-654 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Enantiomer separation ; Voriconazole (UK-109,496) ; Effect of organic mobile-phase modifier
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Coupled achiral-chiral high-performance liquid chromatography (HPLC) with an achiral amino-based column coupled with a chiral amylose-based column has been used for qualitative and quantitative determination of the potential chiral and achiral impurities of Voriconazole (UK-109,496), a new antifungal agent with two stereogenic centres. The effect of the organic mobile-phase modifier, ethanol, was studied. The assay response was linearly dependent on concentration over the range 1.2–40.4 μg for Voriconazole and 2.5–104.0 ng for the impurities. The limit of detection was 2.5 ng for each analyte.
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    URL: http://dx.doi.org/10.1007/BF02467448
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    Separation of inorganic anions and cations on titania by use of acetic acid-sodium acetate and bicine-sodium hydroxide buffers (1998)
    Springer
    Chromatographia 47 (1998), S. 655-658 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion chromatography ; Titania packings ; Inorganic anions and cations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The ion-exchange retention behavior of titania synthesized in our laboratory was investigated by ion chromatography of inorganic anions and cations. Dilute acetic acid-sodium acetate and bicine-sodium hydroxide buffers were used as mobile phases with no use of suppresor. We observed that the titania, although poor at separating monovalent anions expcept nitrite ion in this experiment, was both an anion and a cation exchanger, and selectively retained fluoride and carbonate ions. We concluded that because of its specific retention properties there were possibilites of using this amphoteric exchanger for simultaneous analysis of anions and cations, and of using it as a selective packing material for ion chromatography.
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    Retention behavior of morphine and its metabolites on a porous graphitic carbon column (1998)
    Springer
    Chromatographia 47 (1998), S. 667-672 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous graphitic carbon ; Optimization ; Morphine and metabolites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The chromatographic behaviour of a series of morphine-based opiates has been investigated using a porous graphitic carbon packing material at acid and alkaline pH. The effects of mobile phase pH, mobile phase organic percentage, column temperature and ionpairing agents were studied. All six opiates were separated within a close retention window despite large differences in measured lipophilicities of the individual opiates. The retention order was not related to the log P values of the opiates and strong retention of the fully ionised compounds was observed, particularly those with acidic functional groups. The effect of pH on the retention of the compounds indicated that the degree of ionisation of the individual compounds was important in the separation mechanism, suggesting that hydrophobic interactions were present in addition to the polar retentive effects observed above. The strong retention of the ionised glucuronide and sulphate conjugates of morphine is a particularly useful feature of the porous graphitic carbon packing material which has general applicability to the analysis of polar or ionised drug metabolites.
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    URL: http://dx.doi.org/10.1007/BF02467451
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    Application of micropellicular poly-styrene/divinylbenzene stationary phases for high-performance reversed-phase liquid chromatography electrospray-mass spectrometry of proteins and peptides (1997)
    Springer
    Chromatographia 44 (1997), S. 438-448 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Electrospray ionization mass spectrometry ; Micropellicular poly-styrene/divinylbenzene ; Peptides and proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Short columns packed with highly crosslinked 2.3 μm poly-styrene/divinylbenzene (PS/DVB) particles were used for rapid and efficient separation of proteins and peptides by reversed-phase high-performance liquid chromatography at elevated temperatures. Enhancement of the diffusivities of the sample components at elevated temperatures together with the short diffusion pathlength with the micropellicular polymeric stationary phases were responsible for high efficiency, high speed of analysis, and short column regeneration times. Underivatized PS/DVB beads as well as PS/DVB microspheres which have been modified with polyvinylalcohol or octadecyl chains on the surface were synthesized, employed, and compared to HY-TACH-C18, a commercially available micropellicular octadecyl-silica stationary phase, for the separation of proteins, octapeptides and tryptic protein digests. Highest performance was obtained with the silica- and PS/DVB-based octadecyl stationary phases, which exhibited similar column efficiencies but different selectivities for proteins and peptides. The minimum detectability at 214 nm and the maximum loading capacity for ribonuclease A using analytical 30×4.6 mm I.D. columns were 10 ng (0.6 pmol) and 1 μg, respectively. Finally, reversed-phase HPLC with a 60×2 mm I.D. narrow-bore column packed with micropellicular octadecyl PS/DVB was coupled successfully to electrospray mass spectrometry at a flow-rate of 0.15 mL min−1 and on-line full-scan mass spectra for molecular mass determination and identification of proteins in the lower picomol range were obtained.
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    URL: http://dx.doi.org/10.1007/BF02466324
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    Simultaneous determination of parathion and metabolites in serum by HPLC with column switching (1997)
    Springer
    Chromatographia 44 (1997), S. 473-476 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Column-switching ; Parathion, and metabolites in serum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new high-performance liquid chromatographic method with column-switching has been developed for the simultaneous determination of parathion and its metabolites such asp-nitrophenol and paraoxon in serum. Serum samples were injected onto a precolumn packed with LiChroprep RP-8 after simple dilution with 20% phosphoric acid. Polar plasma components were washed with 0.02 M phosphate buffer (pH 3.0). After valve switching, the concentrated compounds were eluted in back-flush mode and separated on a Ultracarb ODS 30 column with a gradient of acetonitrile −0.01 M phosphate buffer (pH 3.0) as mobile phase. The method showed excellent precision, accuracy and speed with detection limit of 0.1 μg mL−1. Total analysis time per sample was 〈40 min and coefficients of variation for intra-and inter-assay were 〈4.5%.
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    URL: http://dx.doi.org/10.1007/BF02466739
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  • 100
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    Comparison of GC-MS and HPLC for overcoming matrix interferences in the analysis of PAHs in smoked food (1997)
    Springer
    Chromatographia 44 (1997), S. 497-504 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Gas chromatography-mass spectrometry ; Column liquid chromatography ; Polycyclic aromatic hydrocarbons ; Food analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Several separation and detection methods for polycyclic aromatic hydrocarbons (PAHs) in smoked chicken by GC and HPLC were compared. With HPLC and a gradient solvent system, all 16 PAHs could be simultaneously separated and detected by fluorescence with seven settings of programmable wavelength (excitation/emission). The presence of impurities in smoked chicken could interfere with the subsequent identification and quantification of PAHs by HPLC. With GC and a temperature programming method, all 16 PAHs could be separated and the PAHs in the chicken sample could be detected with an ion-trap mass spectrometer even in the presence of fat-or PAH-like impurities. Nine PAHs were identified by the former method while fourteen PAHs were identified by the latter method. The retention times by HPLC were shorter than those by GC, also, the former had better separation for most PAHs than the latter.
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    URL: http://dx.doi.org/10.1007/BF02466743
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