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  • Column liquid chromatography  (86)
  • photosynthesis  (46)
  • Springer  (132)
  • 2020-2024
  • 1990-1994  (132)
  • 1992  (132)
Collection
Keywords
Publisher
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  • 2020-2024
  • 1990-1994  (132)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Effect of folding and feeding by Cnaphalocrocis medinalis on photosynthesis and transpiration of rice leaves (1992)
    Springer
    Entomologia experimentalis et applicata 63 (1992), S. 101-102 
    Details
    ISSN: 1570-7458
    Keywords: Cnaphalocrosis medinalis ; rice leaffolder ; Oryza sativa ; rice ; photosynthesis ; transpiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00350352
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  • 2
    Electronic Resource
    Electronic Resource
    Assessment of Hg2+ toxicity to a N2-fixing cyanobacterium in long- and short-term experiments (1992)
    Springer
    BioMetals 5 (1992), S. 149-156 
    Details
    ISSN: 1572-8773
    Keywords: Hg2+ toxicity ; cyanobacterium ; Nostoc calcicola ; growth ; photopigments ; nucleic acids ; photosynthesis ; membrane integrity ; nutrient uptake ; enzymes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Toxicological responses of the filamentous N2-fixing cyanobacteriumNostoc calcicola Bréb. towards Hg2+ were studied to enumerate the decisive lethal events. In low-dose, long-term experiments (0.05–0.25 μm Hg2+, 10 days), photoautotrophic growth was severely inhibited with concurrent loss of photosynthetic pigments (phycocyanin〉chlorophyll α〉carotenoids) and nucleic acids. The termination of growth after a day 4 exposure to 0.25 μm Hg2+ has been attributed to the complete inhibition ofin vivo photosynthetic activity in the cyanobacterium (O2 evolution〉14CO2 incorporation). The elevated Hg2+ concentrations irreversibly damaged the cell membrance as observed under light microscopy, and as indicated by the leakage of intracellular electrolytes and phycocyanin. In high-dose, short-term experiments (0.5–20.0 μm Hg2+, up to 6 h), thein vivo activities of selected enzymes (glutamine synthetase 〉 nitrate reductase 〉 nitrogenase) were less inhibited by Hg2+ than the uptake of nutrient ions (NH 4 + 〉NO 3 − 〉PO 4 3− ).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01061321
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  • 3
    Electronic Resource
    Electronic Resource
    Role of pigments on algal communities and photosynthesis (1992)
    Springer
    Aquatic sciences 54 (1992), S. 321-330 
    Details
    ISSN: 1420-9055
    Keywords: Algal pigments ; algal communities ; photosynthesis ; Lake Lugano (Lago di Lugano)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A one-year study of phytoplankton, primary production and related physical and chemical factors was made in a Swiss basin of Lake Lugano (Lago di Lugano). The chlorophylls and 12 carotenoids were analyzed with a TLC technique. The carotenoid monitoring was considered to be particularly interesting, because the role of these pigments in freshwater algae is still very poorly documented by field studies. The dependence of photosynthesis on several factors was statistically evaluated. Evidence was found of light-adaptation phenomena. The variations of photosynthetic activity and efficiency largely depended on the light regime in the few days before the field observations and on the cellular content of chlorophylls and single carotenoids, whose concentrations in their turn were closely linked with light, temperature, average cell size, and with the actual species assemblage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00878144
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  • 4
    Electronic Resource
    Electronic Resource
    High SO2 resistance ofClethra barbinervis established in a smoke-polluted area of Ashio, Tochigi Prefecture, Japan (1992)
    Springer
    Ecological research 7 (1992), S. 363-370 
    Details
    ISSN: 1440-1703
    Keywords: Clethra barbinervis ; interspecific difference ; intraspecific variation ; photosynthesis ; SO2 resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of SO2 on the photosynthesis ofClethra barbinervis collected from a smoke-polluted area near the Ashio copper smelter in Tochigi Prefecture was compared withC. barbinervis collected from a nonpolluted district in Tsukuba, Ibaraki Prefecture andQuercus mongolica var.grosseserrata grown in a nonpolluted field in Nagano Prefecture. The plants were exposed to 0.5–1.5 p.p.m. SO2 for 90 min (short-term) and to 0.3 p.p.m. SO2 for 31–39 days (long-term). TheClethra plants from both sites had a lower intrinsic stomatal conductance and photosynthetic rate thanQuercus plants. Short-and long-term fumigation caused stomatal closure inQuercus plants, but had little effect on the stomatal conductance ofClethra plants. Under short-term fumigation, nonstomatal photosynthetic inhibition per unit of absorbed SO2 was smallest inClethra plants from Ashio. Long-term fumigation caused photosynthetic decline and visible foliar injury toQuercus plants, but had no effect onClethra plants from Ashio. Consequently,Clethra plants from Ashio had a higher photosynthetic rate thanQuercus plants after long-term fumigation. These results suggest thatC. barbinervis populations in the smoke-polluted area of Ashio had evolved high SO2 resistance connected with SO2 detoxification ability in mesophyll cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02347103
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  • 5
    Electronic Resource
    Electronic Resource
    Sequence of the fourth and fifth Photosystem II Type I chlorophyll a/b-binding protein genes of Arabidopsis thaliana and evidence for the presence of a full complement of the extended CAB gene family (1992)
    Springer
    Plant molecular biology 19 (1992), S. 725-733 
    Details
    ISSN: 1573-5028
    Keywords: gene duplication ; photosynthesis ; RFLP ; Southern blots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A second locus (Lhb1B) encoding Photosystem II Type I chlorophyll a/b-binding (CAB) polypeptides was identified in Arabidopsis thaliana. This locus carries two genes in an inverted orientation. The predicted sequences of the polypeptides encoded by these two genes show substantial divergence in their amino termini relative to each other and to the proteins encoded by the three Lhb1 CAB genes previously characterized [10], but little divergence within the predicted primary structure of the mature protein. DNA probes derived from seven additional types of tomato CAB genes, encoding chlorophyll a/b-binding polypeptides of several antenna systems of the photosynthetic apparatus, were tested against A. thaliana. Each of these hybridized in Southern blots to unique DNA fragment(s), demonstrating the existence of each of these different types of CAB genes in the genome of A. thaliana. The number of genes encoding each CAB type in A. thaliana was estimated to be similar to that of tomato.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00027069
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  • 6
    Electronic Resource
    Electronic Resource
    Cloning and sequencing of the petBD operon from the cyanobacterium Synechococcus sp. PCC 7002 (1992)
    Springer
    Plant molecular biology 20 (1992), S. 481-491 
    Details
    ISSN: 1573-5028
    Keywords: photosynthesis ; cytochrome b 6 ; gene regulation ; genome mapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The genes encoding the photosynthetic cytochrome b 6 (petB) and subunit 4 (petD) have been cloned and sequenced from the unicellular, photoheterotrophic, transformable cyanobacterium Synechococcus sp. PCC 7002, formerly designated Agmenellum quadruplicatum. The gene arrangement was found to be similar to that reported in the cyanobacterium Nostoc PCC 7906. The DNA and derived protein sequences were compared to chloroplast and the other cyanobacterial sequences. By pulsed-field electrophoresis, the petBD operon and the petCA operon, encoding the Rieske iron-sulfur protein and cytochrome f, were found to be located on separate, unlinked,Not I-digested DNA fragments. ThepetBD operon was found on the third largest Not I fragment (NC-325) while the petCA operon was found on the second largest Not I fragment (NB-370). These results suggest the two operons are not in proximity. The 1.35 kb transcript was shown to be light-regulated. Transcripts from cells grown under constant illumination showed a decrease in petB transcript levels to undetectable levels within 2 h after the cells were placed in the dark. Upon reillumination, transcript levels rose to three-fold over that seen initially under constant illumination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00040607
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  • 7
    Electronic Resource
    Electronic Resource
    Chlorophyll a/b-binding protein genes are differentially expressed during soybean development (1992)
    Springer
    Plant molecular biology 19 (1992), S. 217-230 
    Details
    ISSN: 1573-5028
    Keywords: chlorophyll a/b-binding protein genes ; Glycine ; LHCP II ; photosynthesis ; soybean ; ribulose-1,5-bisphosphate carboxylase genes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The levels of chlorophyll a/b-binding protein (Cab) gene polysomal poly(A)+ mRNA were quantitated throughout the development of Glycine max L. Cab mRNAs were abundant in young expanding leaves, representing 6.1% of the leaf mRNA population. Lower Cab mRNA levels were present in embryos, stems, and cotyledons of developing seedlings; the lowest levels were found in roots where they accounted for 0.04% of the polysomal poly(A)+ mRNA of this organ. To determine the contribution of different members of the Cab gene family to the Cab mRNA populations, a quantitative S1 nuclease reconstruction assay was developed. Cab3, Cab4, and Cab5 mRNAs were detected in all stages examined during soybean development but their levels underwent differential changes. Cab3 encodes the most abundant Cab mRNA in young leaves, developing embryos, and in Stage VII cotyledons from the developing soybean seedling. The levels of Cab mRNAs were compared to the levels of ribulose-1,5-bisphosphate carboxylase small subunit gene mRNA and differences in their patterns of accumulation were noted. Collectively these data indicate that during soybean embryogenesis developmental control mechanisms supersede light-regulatory signals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00027343
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  • 8
    Electronic Resource
    Electronic Resource
    Dimerization constant and single-channel conductance of Gramicidin in thylakoid membranes (1992)
    Springer
    The journal of membrane biology 126 (1992), S. 265-275 
    Details
    ISSN: 1432-1424
    Keywords: photosynthesis ; thylakoids ; electrochromism ; gramicidin ; conductance ; dimerization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The effect of the pore-forming antibiotic gramicidin on pure lipid membranes is well characterized. We studied its action in protein-rich thylakoid membranes that contain less than 25% (wt/wt) acyl lipids. A transmembrane voltage was induced by flashing light, and its decay was measured and interpreted to yield the distribution of gramicidin over thylakoids, its dimerization constant and its single-channel conductance in this membrane. The distribution of gramicidin over the ensemble of thylakoids was immediately homogeneous when the antibiotic was added under stirring, while it became homogeneous only after 20 min in a stirred suspension that was initially heterogeneous. The dimerization constant, 5×1014 cm2/mol, was about 10 times larger than in pure lipid membranes. This was attributed to the upconcentration of gramicidin in the small fractional area of protein free lipid bilayer and further by a preference of gramicidin for stacked portions of the membrane. The latter bears important consequences with regard to bioenergetic studies with this ionophore. As gramicidin was largely dimerized from a concentration of 1 nm (in the suspension) on, the membrane's conductance then increased linearly as a function of added gramicidin. When the negative surface potential at the thylakoid membrane was screened, the conductance of a single gramicidin dimer agreed well with figures reported for bilayers from neutral lipid (about 0.5 pS at 10 mm NaCl). The modulation of the conductance by the surface potential in spinach versus pea thylakoids and between different preparations is discussed in detail.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00232323
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of drought on chlorophyll fluorescence in potato (Solanum tuberosum L.). II. Relations between plant growth and measurements of fluorescence (1992)
    Springer
    Potato research 35 (1992), S. 35-40 
    Details
    ISSN: 1871-4528
    Keywords: water-stress ; photosynthesis ; yield
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Relations between measurements of the slow kinetics of chlorophyll fluorescence and growth and yield were examined in seven potato genotypes grown either fully irrigated or droughted from the time of plant emergence. Drought reduced total dry matter production and yields and increased tuber dry matter concentration. Drought increased harvest index in cv. Spunta, but decreased it in cv. Pentland Crown. Total dry matter production was correlated with each of constant fluorescence, variable fluorescence and the half life of the decay in variable fluorescence. These correlations were determined largely by the effect of treatment, and did not discriminate effectively between genotypes within a treatment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02357720
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  • 10
    Electronic Resource
    Electronic Resource
    Effects of drought on chlorophyll fluorescence in potato (Solanum tuberosum L.). I. Plant water status and the kinetics of chlorophyll fluorescence (1992)
    Springer
    Potato research 35 (1992), S. 25-34 
    Details
    ISSN: 1871-4528
    Keywords: water-stress ; photosynthesis ; leaf water potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The slow kinetics of chlorophyll fluorescence were examined in seven potato genotypes grown either fully irrigated or droughted from the time of plant emergence. Constant and variable fluorescence (F o andF v respectively) declined with time in plants from both irrigated and droughted treatments, but the decline was greater in droughted than irrigated plants. However, the yield of variable fluorescence (F v/(F o+F v)) was unaffected by the drought treatment. The main effect of drought was upon the quenching of variable fluorescence. Both the half life of the decay of variable fluorescence (q1/2) and the secondary maximum (M) were significantly greater in the droughted plants than in those from the irrigated treatment. Significant differences between genotypes were found forF v/(F o+F v),M andq 1/2. Genotype-by-treatment interactions were non-significant for all the variables examined. Changes in chlorophyll fluorescence transients were not closely related to changes in leaf water potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02357719
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  • 11
    Electronic Resource
    Electronic Resource
    2-Bromoacetyl-6-methoxynaphthalene: A useful fluorescent labelling reagent for HPLC analysis of carboxylic acids (1992)
    Springer
    Chromatographia 33 (1992), S. 13-18 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fatty acids and bile acids ; Fluorogenic precolumn derivatization ; 2-Bromoacetyl-6-methoxynaphthalene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The use of 2-bromoacetyl-6-methoxynaphthalene as a fluorogenic labelling reagent in pre-column derivatization for the HPLC separation of biologically active carboxylic acids (fatty acids and bile acids) has been investigated. The compound reacts (30 min. at 70°C) with carboxylic acids to give fluorescent esters that can be separated by reversedphase HPLC and detected at λ ex. 300 nm, λ em. 460 nm. The experimental conditions for the derivatization and chromatographic separation are discussed. Applications to the determination of valproic acid and chenodeoxycholic acid in pharmaceutical formulations are described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276844
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  • 12
    Electronic Resource
    Electronic Resource
    HPLC method for the simultaneous analysis of valproic acid and other common anticonvulsant drugs in human plasma or serum (1992)
    Springer
    Chromatographia 33 (1992), S. 37-40 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Valproic acid ; Simultaneous determination of anticonvulsants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The derivatizing procedure of Moody et al. [20] for valproic acid has been simplified and applied to the simultaneous HPLC determination of valproic acid (VPA), barbital (B), primidone (PRM), phenobarbital (PB) and carbamazepine (CBZ) in serum or plasma of epileptic patients. The sample is deproteinized with acetonitrile containing esterification agents and an aliquot of the supernatant is heated to 70°C for 15 min with 4-bromophenacyl bromide. The reaction mixture is analysed on a C18 column at ambient temperature, with gradient elution and with detection at 205 nm. The time required for the chromatographic analysis is 13 min; identification is based on retention time and quantification is by peak area determination with an internal standard. The calibration curves show good linearity in the range 6.25 to 100 mg/L. The detection limits at a signal: noise ratio ≥3, ranged from 1 mg/L for B and CBZ to 2–3 mg/L for PRM, PB and VPA. The method described for the simultaneous determination of the five drugs in the same plasma pool, correlated well with isocratic HPLC methods specific for each drug. The simultaneous procedure described allows a reproducible (CVs≤6.5% within run) and rapid (25 min for sample preparation: 13 min for chromatographic run) therapeutic monitoring of patients treated with VPA and two or more antiepileptic drugs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276848
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  • 13
    Electronic Resource
    Electronic Resource
    Porous polymer packings from vinyl ether derivatives for reversed-phase liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 19-24 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous polymer spherical packings ; Vinyl ether ; Alkali resistance ; No abnormal adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Spherical, porous-polymer particles for column packing in high-performance liquid chromatography were prepared by suspension copolymerization of alkylvinyl ether with triethyleneglycol divinyl ether. The hydrophobicity of the packings was easily adjusted by changing the monomer ratio. The packings showed the usual reversed-phase liquid chromatographic properties, but did not sho abnormal retention, tailing and broadening of peaks and irreversible adsorption of ionic and aromatic substances, owing to the lack of ionic or aromatic groups. In addition, the packings were stable in alkaline solutions because of the relative alkali stability of C−O−C bonds as compared with CO−O and Si−O−C bonds in conventional packings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276845
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  • 14
    Electronic Resource
    Electronic Resource
    Comparison study between indirect photometric and direct conductivity detection for anion exchange chromatography using naphthalenesulfonate derivatives as mobile phases (1992)
    Springer
    Chromatographia 33 (1992), S. 25-31 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Anion exchange ; Indirect photometric and direct conductivity detection ; Naphthalenesulfonate ; Inorganic anions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Indirect photometric and unsuppressed direct conductivity detection modes are examined using naphthalene mono-, di-, and tri-sulfonate as mobile phases for the separation of several anions such as F−, Cl−, NO2 −, Br−, NO3 −, SO4=,I−, and SCN− using a commercial anion exchange column. With all three mobile phases, conductivity detection shows better sensitivities and detection limits than indirect photometry. Conductivity detection is 5 to 16 times more sensitive than indirect photometry for all analytes. Detection limits achieved using these mobile phases are, for example, 0.04 ng and 0.1 ng for chloride ion with conductivity and indirect photometry, respectively. Both detection modes give wide linear ranges extending from at least 100 ppm to the detection limit of each anion which is generally about 0.02 ppm. Sulfur oxide anions such as dithionate and tetrathionate are separated using flow programming with naphthalenetrisulfonate as the mobile phase in less than 20 minutes. With both detection modes, desired chromatographic performance of these three eluents is achieved without pH adjustment of the mobile phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276846
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  • 15
    Electronic Resource
    Electronic Resource
    An enhanced liquid chromatographic method for 5-hydroxymethylfurfural determination in UHT milk (1992)
    Springer
    Chromatographia 33 (1992), S. 45-48 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Heat-treated milk ; Milk quality indicators ; 5-Hydroxymethyl-2-furfuraldehyde
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An enhanced method of HPLC for the determination of 5-Hydroxymethyl-2-furfuraldehyde (HMF) in fluid milk was perfected. Its resolving capacity permitted the specific separation of this compound. The real concentration (μmol/l) of HMF was determined and not the HMF value, as in the colorimetric analysis, where an intermediary coloured compound (HMF-TBA) is utilised. The optimum pH condition (pH=4.0–4.2) for the mobile phase to prevent overlapping between the HMF peak and the peaks of the other compound (α and β) that coeluted with the HMF and also the optimum organic solvent content (3% or 7%) were established. This is a sensitive, quick and safe method for the determination of HMF in fluid milk.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276850
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  • 16
    Electronic Resource
    Electronic Resource
    Ion-pair reversed-phase liquid chromatography of arsenic species on polymeric styrene-divinylbenzene packed columns with an alkaline aqueous mobile phase (1992)
    Springer
    Chromatographia 33 (1992), S. 581-585 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Arsenic compounds ; Polymeric styrene divinylbenzene phase ; Ion-pairing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The resolving power of an ion-pair reversed-phase liquid chromatography method, on a polymeric stationary phase (PRP-1) with an alkaline aqueous mobile phase (pH=9) containing tetrabutylammonium cation as ion-pairing agent, is compared with a traditional ion-pairing system using an octadecyl-modified silica column and a neutral aqueous mobile phase (pH=7.3). This chromatographic system (PRP-1 column) provides a rapid means for the determination of two of the most important arsenic species, arsenobetaine and arsenite. Addition of methanol (5%) to the aqueous mobile phase allows the differentation of arsenobetaine from the system peak when using UV detection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02262252
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  • 17
    Electronic Resource
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    Comparison of provitamin A determination by normal-phase gravity-flow column chromatography and reversed-phase high performance liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 133-137 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gravity-flow column chromatography ; Provitamin A determination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The provitamin A content of some food samples was determined by methods involving MgO: Hyflosupercel gravityflow column chromatography (GFCC) and reversed phase high performance liquid chromatography (HPLC), the quantitation being done by external standardization (HPLC-ES) or internal standardization (HPLC-IS) with Sudan. The results obtained with α- and β-carotene in carrots, β-carotene and β-cryptoxanthin in papaya and β-carotene in tomato and kale agreed well, showing that any of the these techniques can be used, provided the analysis is done under optimum conditions. Good separation of the different provitamins using GFCC depends on the analyst's skill and visual acuity. HPLC-ES required a constant supply of provitamin standards, thus the varying purity of commercially available standards and the high instability of these compounds could pose grave problems. Due to the stability of Sudan, HPLC-IS appeared to be the method of choice although passage of the extract through a MgO: Hyflosupercel minicolumn was required prior to injection to separate chlorophylls, dihydroxy- and polyoxycarotenoids which would otherwise elute with Sudan. Nonconformity of the Sudan structure to those of the provitamins did not effect the quantitative results. The chromatographic separation, identity and quantification of the provitamins could be more easily established by using HPLC-IS, complemented with GFCC.
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    URL: http://dx.doi.org/10.1007/BF02275893
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  • 18
    Electronic Resource
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    Diastereoselective and enantioselective chromatography of the pyrethroid insecticides allethrin and cypermethrin (1992)
    Springer
    Chromatographia 33 (1992), S. 103-112 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gas chromatography ; Chiral separations ; Allethrin ; Cypermethrin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Liquid and gas chromatographic separations of the pyrethroid insecticides allethrin and cypermethrin have been investigated with various achiral and chiral stationary phases. Diastercomeric and enantiomeric selectivity was observed for cypermethrin on a Pirkle-type chiral LC stationary phase, but very strong interactions and therefore long retention times prevented the separation of allethrin on this phase. Trans-allethrin isomers were separated on a chiral β-cyclodextrin RP-HPLC column while cypermethrin showed some difficulties on this phase due to isomerization. Diastereomeric but no enantiomeric selectivity by GC was achieved for cypermethrin with an apolar DB 5 capillary. GC separation of the diastereomers was used to study the selective photodegradation of cypermethrin isomers after forestry applications. Chiral β-cyclodextrin-based GC phases showed some enantioselectivity for cis- and trans-allethrin isomers. A separation of the eight isomers into six partially resolved peaks was achieved by GC with a coupled column consisting of chiral permethylated β-cyclodextrin and DB 1701 as stationary phases. This combination was used to characterize allethrin formulations intended for indoor use and to investigate allethrin products formed by ozonolysis of thin films of the insecticide.
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    URL: http://dx.doi.org/10.1007/BF02275888
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  • 19
    Electronic Resource
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    Estimation of diuretic drugs in biological fluids by HPLC (1992)
    Springer
    Chromatographia 33 (1992), S. 177-185 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Diuretics ; Screening and determination of diuretics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This critical review of different methods proposed for the determination and screening of diuretics is directed mainly, because of its potential application, towards highperformance liquid chromatography.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02275902
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  • 20
    Electronic Resource
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    Peak recognition technique by a computer program copying the human judgement (1992)
    Springer
    Chromatographia 33 (1992), S. 218-224 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Peak ; Pattern recognition ; Prediction interval
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary It is still difficult to determine peaks and peak boundaries properly, though peak recognition is very important for the precision of quantitative data. A new computer program overcomes these problems using a method which is adapted from human judgements. The algorithm was developed for HPLC but can also be used in other fields of analytical chemistry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276186
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  • 21
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    High performance liquid chromatography of raw sugars and polyols using bonded silica gels (1992)
    Springer
    Chromatographia 33 (1992), S. 325-330 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Diol silica gels ; Carbohydrates ; Evaporative light scattering detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Bonded silica columns have been evaluated for their ability to separate carbohydrates and polyols. Mobile phases consisting of dichloromethane/methanol produced the best separations in comparison with the acetonitrile/water mixtures commonly used with amino columns. Of all the bonded phases tested, LiChrospher Diol silica provided the best separations, and selectivities were not very different from those obtained on the most popular system using an amino bonded phase and acetonitrile/water as eluent. In addition, diol columns with a dichloromethane/methanol eluent offer excellent stability with no Schiff’s base formation of reducing sugars. Using an evaporative light scattering detector, low limit detection is obtainable (20 ng of glucose from a column) and gradient elution is quite feasible.
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    URL: http://dx.doi.org/10.1007/BF02275911
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    Retention of some ring-substituted aniline derivatives by porous graphitized carbon. Dependence on physico-chemical parameters (1992)
    Springer
    Chromatographia 33 (1992), S. 356-360 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous graphitized carbon ; Ring-substituted aniline derivatives ; Electronic interactions ; Principal component analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention characteristics of 22 aniline derivatives were determined on a porous, graphitized-carbon column in unbuffered acetonitrile-water and methanol-water mixtures. Each aniline derivative gave symmetrical peaks in each eluent without buffers. Good linear correlations were found between the log k′ and the concentration of the organic component in the eluent. The slope and intercept values differed according to the type of organic modifier and the charcter, number and position of substituents, indicating the different selectivities of methanol and acetonitrile and the good separating power of the column. Multivariate mathematical-statistical calculations proved that the retention of ring-substituted aniline derivatives is mainly governed by electronic parameters and the hydrogen acceptor capacity of substituents.
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    URL: http://dx.doi.org/10.1007/BF02275918
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    Determination of furosine in milk samples by ion-pair reversed phase liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 374-376 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion-pairing ; Furosine ; Pyridosine ; Milk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An ion-pair, reversed-phase, liquid chromatographic procedure using UV detection for quantitation of furosine is described. The standard plot was linear (r〉0.999) over a 5 ng range. An authentic synthesised sample of furosine was used for calibration. Commerical milk samples were analyzed by the described procedure.
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    URL: http://dx.doi.org/10.1007/BF02275921
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    Optimisation of data handling and detection conditions for automated chromatographic assay software (1992)
    Springer
    Chromatographia 33 (1992), S. 361-368 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Automated peak detection ; Discrete Fourier transform ; Frequency acquisition and filtering ; Peak detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The principle of automated chromatographic peak detection and analysis software is summarized, and critical steps are systematically studied. As the only parameter to be entered is the acquisition frequency, evaluation of its effect on software performance is discussed. In the case of relatively noisy chromatograms, it is shown experimentally that numerous points per peak have to be taken, leading to quite fast computer acquisition procedures. The use of discrete Fourier transform filtration techniques can modify peak shapes and a comparative study evaluates the relative errors induced in the shapes and characteristics of the chromatographic profiles. Optimisation of filtering conditions is achieved and it is shown that for a filter position only 2% of the Nyquist frequency no deformation occurs in the chromatographic profile. Detection of the start and finish of chromatographic peaks is optimized according to a simple four step iterative procedure. In the case of simulations, the difference between the values used to simulate peaks and those calculated by the software are less than 1%.
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    URL: http://dx.doi.org/10.1007/BF02275919
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    Simultaneous determination of 5′-deoxy-5-fluorouridine, 5-fluorouracil and its main metabolites in body fluids by HPLC (1992)
    Springer
    Chromatographia 33 (1992), S. 413-417 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fluoropyrimidine drugs ; Pharmacokinetics of doxifluridine ; Chemotherapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A reversed phase high performance liquid chromatographic method has been developed for the simultaneous determination of the pro-drug 5′-deoxy-5-fluorouridine (5′-dFUR), its metabolite 5-fluorouracil (5-FU) and some fluorinated pyrimidines involved in the metabolic activation process of 5-FU. The method has been used to monitor the bioavailability of 5′-dFUR and 5-FU in patients undergoing anticancer chemotherapy. Serum sample treatment involves addition of internal standard (5-bromouracil), protein precipitation with saturated ammonium sulphate solution and liquid-liquid extraction with ethyl acetate-isopropanol (90 ∶ 10 v/v). Urine is simply diluted with mobile phase and injected. The average recovery from serum (at 0.5 μg/mL level) was 95.0%±1.4 for 5′-dFUR and 86.3%±3.5 for 5-FU. A linear response extending over four decades of concentration was observed. Detection limits in the low ng/ mL range were obtained using a 250 μL sample size and a 20 μL injection volume. Within-day and between-day coefficients of variation were below 4 and 10%, respectively.
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    Total and individual determination of carbamate pesticides by use of an integrated flow-injection/HPLC system (1992)
    Springer
    Chromatographia 33 (1992), S. 449-453 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Flow injection analysis ; Combined flow injection/HPLC ; Carbamate pesticides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An integrated flow injection (FI)/HPLC system for the total and individual determination of carbamate pesticides (propoxur, carbofuran and carbaryl) is proposed. The determination is based on the alkaline hydrolysis of the analytes and subsequent coupling with diazotized sulphanilic acid to yield the monitored dyes with or without a prior separation step by HPLC in a C18 column. The calibration curves obtained are linear in the μg/ml range and r.s.d. values are between 0.5 and 3.7% in all instances. Injection of the sample into the FI manifold allows the total pesticide content in the sample to be screened. The manifold thus acts as a post-column reactor/detector of the chromatograph for samples with high overall carbamate content, which are also injected into the HPLC instrument. The performance was checked with contaminated water samples.
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    URL: http://dx.doi.org/10.1007/BF02262326
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    Evaluation of the enantioselectivity towards β-blocking agents of the α1 glycoprotein type chiral stationary phase: Chiral AGP®glycoprotein type chiral stationary phase: Chiral AGP® (1992)
    Springer
    Chromatographia 33 (1992), S. 454-462 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; α1 glycoprotein ; Enantioseparation ; β-blocking agents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The enantioselectivity of the α1 glycoprotein chiral stationary phase, Chiral AGP® has been evaluated for a number of β-blocking agents. A correlation has been found between the retention behaviour on this stationary phase and the hydrophobicity of the compounds. The separation factor α is higher for compounds that are well retained. Retention, and thus α, are also controlled by pH and the percentage of organic modifier in the mobile phase.
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    Isocratic HPLC separation of aromatic hydrocarbons and fluorine-containing compounds using perfluoroalkyl polymer packings (1992)
    Springer
    Chromatographia 33 (1992), S. 473-477 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Perfluoroalkylated polymer-gel packings ; Aromatic and fluorine-containing compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Porous, perfluoroalkylated polymer-gels for column packings in high-performance liquid chromatography (HPLC) were prepared by suspension polymerization of heptadecafluorodecyl arcylate and ethylene glycol dimethacrylate. The packings showed no abnormal retention for ionic or aromatic compounds, due to the lack of ionic or aromatic groups. In addition, the packings showed no excessive retention for strongly hydrophobic compounds which is often the case with long-chain, alkylated silica gels and polymer gels. This is due to the extremely low surface energy of perfluoroalkyl groups. Therefore, perfluoroalkylated polymer gels enable isocratic HPLC separation of solutes with significantly different hydrophobicity.
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    URL: http://dx.doi.org/10.1007/BF02262330
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    Comments on the paper “correlation between retention in liquid chromatography and the adsorption energy” by J. Kloubek (1992)
    Springer
    Chromatographia 33 (1992), S. 485-486 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous glass ; Surface free energy ; Film pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1007/BF02262332
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    Correlation between retention in liquid chromatography and the adsorption energy (1992)
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    Chromatographia 33 (1992), S. 478-484 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous glass adsorbents ; Surface free energy ; Oriented adsorption of hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The relationship between the specific capacity factor (k/S, where k is the capacity and S is the surface area of the sorbent, in m2) in the liquid chromatography of aromatic hydrocarbons and the adsorption energy (-°GA) has been investigated. The previously published results, based on the calculation of the work of adhesion (WSA) from contact angles, were re-examined and a new hypothesis on interactions at interfaces was employed. Direct proportionality has been found between k/S and-°GA, which allows prediction of the chromatographic behavior of adsorbates on sorbents. The surface free energy components were calculated in order to determine-°GA in terms of the work of adhesion. The dispersion component of the surface free energy of glass was obtained from the adsorption isotherm of n-octane and it was found that the hydrocarbon molecules are adsorbed in an oriented position. The contact angles of liquids on the outer surface of porous solids do not yield reliable values of WSA and of the surface free energy components. A higher intermolecular attraction increases WSA and decreases the contact angle in pores.
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    A high-performance liquid chromatographic method for the analysis of adenosine and some metabolites in the brain tissue of rats (1992)
    Springer
    Chromatographia 34 (1992), S. 563-567 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Adenosine and some metabolites ; Extraction from brain tissue ; Quantitative determination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An analytical procedure has been developed for the assay of adenosine and some metabolites in brain tissue extracts of rats. This paper reports the extraction method, the technique adopted to avoid enzymatic transformations and the chromatographic conditions for the identification and quantitation of these nucleosides and bases. Peaks in the chromatograms of brain tissue extracts were identified by retention times, absorbance ratios of reference compounds and by enzymatic peak-shift.
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    Influence of silica gel surface purity on the coverage density of chemically bonded phases (1992)
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    Chromatographia 34 (1992), S. 573-580 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chemically bonded phases (CBP) ; Surface heterogenity ; Surface purification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The surface chemistry of eight silica-gels with different siliceous matrix structures have been described. The influence of surface impurities on the chemical modification process (coverage density) with monooctadecylsilane has been studied. The surfaces of the adsorbents, before chemical modification, were cleaned by extraction with 20% HCl. Bare and modified materials were characterized using different physico-chemical methods e.g.: SIMS, CP/MAS NMR, porosimetry, pH measurement, elemental analysis and chromatography (GC & HPLC). The presence of trace amounts of different metallic elements creating new adsorption centers on the surfaces of the packings, have been demonstrated. Moreover, it has been shown that washing of silica gel adsorbents increases the coverage density of alkylsilyl ligands and improves the chromatographic properties of prepared packings.
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    Zone electrophoretic sample treatment coupled on-line with column liquid chromatography for the determination of basic and acidic compounds in biological samples (1992)
    Springer
    Chromatographia 34 (1992), S. 581-588 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Zone-electrophoretic sample treatment ; Basic and acidic compounds ; Biological samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A modified valve arrangement for zone-electrophoretic sample treatment (ZEST)-which is coupled on-line with column liquid chromatography — is used to pretreat biological (plasma) samples. Carry-over of plasma proteins depends on the pH of the electrophoresis buffer. The determination of propranolol, metoprolol, cromolyn and salicylic acid demonstrates that both basic and acidic analytes can be isolated from the plasma matrix with high selectivity. Analogous piperazines, with different protein binding properties, were used to study the influence of protein binding on the recovery. It is shown that high protein can cause a decreased recovery.
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    HPLC analysis of the main oxindole alkaloids fromUncaria tomentosa (1992)
    Springer
    Chromatographia 34 (1992), S. 597-600 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Oxindole alkaloids ; Uncaria tomentosa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The main oxindole alkaloids from the root bark ofUncaria tomentosa were separated by reversed phase HPLC with an acetonitrile/methanol/phosphate buffer solvent gradient. UV detection was carried out at 245 nm. The chromatographic parameters for the separation of the alkaloids were optimized by studying the impact of the pH value of the mobile phase and the column temperature on the separation efficiency of the analytical system. The best separation was achieved with a mobile phase pH of 6.6 and a column temperature of 15°C. The method developed is suitable for the qualitative characterisation and quantitative determination of oxindole alkaloids in crudeUncaria tomentosa extracts and phytopharmaceuticals.
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    Indirect stereoselective determination of enantiomers of furprofen in human plasma by high-performance liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 618-620 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Enantiomers of furprofen ; Human plasma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A sensitive and stereoselective liquid chromatographic (HPLC) assay for the S and R enantiomers of furprofen in human plasma has been developed. The assay is based on derivatization with S(−)-1-phenylethylamine with formation of two diastereoisomeric derivatives and on their separation and quantitation using HPLC with uv detection. The method is linear from 25 to 600 ng ml−1 of both enantiomers, with a variation coefficient below 10.8%, and a detection limit of 20 ng ml−1. This procedure is suitable for pharmacokinetic studies.
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    Solute-micelle association constants and correlation of octanol-water coefficients with hydrophobicity for polycyclic aromatic hydrocarbons by micellar chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 627-635 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Micelle-solute association constants ; Polynuclear aromatic hydrocarbons ; Octanol/water partition coefficients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Sodium dodecyl sulphate, hexadecyltrimethylammonium bromide and polyoxyethylene(23) lauryl ether were investigated as mobile phases in the micellar liquid chromatography of polycyclic aromatic hydrocarbons of environmental concern. A wide range of surfactant concentrations were used and the retention parameters and distribution coefficients calculated. The trends in the retention data for the PAHs are discussed and several conclusions are presented concerning the partition coefficients when these surfactants are present in the mobile phase. Comparisons are made between the structural features of the compounds and their capacity factors, and the octanol/water partition coefficients are correlated with hydrophobicity for the PAHs studied.
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    Retention characteristics of chlorinated polycyclic aromatic hydrocarbons in normal phase HPLC. II. Chloro-substituted PAHs (1992)
    Springer
    Chromatographia 34 (1992), S. 115-120 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Normal phase separations ; Chloro-substituted polycyclic aromatic hydrocarbons ; Coupled column system ; Environmental samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention behaviour of chloro-substituted PAHs on several commercial normal bonded phase HPLC columns has been investigated. Chloro-substitution was shown to generally decrease the retention on stationary phases like amino-, diol- and nitrophenylpropyl-modified silica. Dimethylaminosilica exhibited more complex retention characteristics towards chloro-substituted PAHs. On this stationary phase, the position of the chlorine substituents on the aromatic solute seemed to be of greater importance for retention than on the amino-, nitro- and diolsilica. For some chloro-PAHs, the retention was shown to increase with the number of chloro-substitutions, probably due to the large affinity of the electron-rich nitrogen in the stationary phase for the electron deficient π-system of the chloro-PAHs. Chloro-substituted PAHs were strongly retarded on the electron donating 2-(1-pyrenyl)-ethylsilica (PYE) stationary phase. However, the molecular shape of the chloro-derivatives had a large influence on retention, which was considerably decreased for some nonplanar chloro-derivatives of chrysene and benz(a)anthracene. A two-dimensional back-flush HPLC method, consisting of a combination of a nitrophenylsilica column and a PYE column of matched lengths, was shown to be useful for clean-up of chloro-substituted PAHs in environmental samples.
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    A column switching technique for the determination of lidocaine and its metabolites in horse urine (1992)
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    Chromatographia 34 (1992), S. 143-145 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Column switching ; Lidocaine ; Horse urine analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A rapid method is described for the determination of lidocaine and its metabolites in horse urine using a column switching technique and HPLC analysis. This procedure offers a sensitive assay without the need for time consuming extractions.
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    URL: http://dx.doi.org/10.1007/BF02276127
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    Cystine and cysteine analysis as the same phenylthiocarbamyl derivatives by HPLC in protein hydrolyzates (1992)
    Springer
    Chromatographia 34 (1992), S. 132-136 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Cysteine, cystine ; Phenylthiocarbamyl derivatives ; Protein hydrolyzates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new approach is described, and a novel explanation presented, for the high performance liquid chromatographic analysis of cystine and cysteine as their phenylthiocarbamyl derivatives. PTC cystine and cysteine have been eluted with the same retention times and molar responses, most probably due to electrophilic attack of phenylisothiocyanate on cystine resulting in the scission of the disulfide bond yielding two moles of cysteine. Further, total PTC cystine and cysteine have been measured both in model solutions and in standard protein hydrolyzates (lysozyme, bovine albumin, ribonuclease) with the same linearity as the other ineteen amino acids. The reproducibility of the measurements, at the 250–750 pmole level, proved to be 4.1% (Relative Standard Deviation %) or less.
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    Retention behaviour of crown ethers and actinomycin D in reversed-phase HPLC (1992)
    Springer
    Chromatographia 34 (1992), S. 155-158 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Retention ; Crown ethers ; Actinomycin D ; Metal cation complexation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention of crown ethers in reverse-phase HPLC has been determined by their bonding ability with cations present in the eluent. The dependence of retention of crown ethers on cation concentration exhibits an inflection and makes it possible to calculate stability constant for the crown ether-cation complex. It is shown that in 75% MeOH retention of antitumor antibiotic, actinomycin D, depends on [Na+] and not on [K+] at concentrations of K+ from 5×10−7 to 10−1 mol l−1. Hence, actinomycin D may be classified as an ionophore-antibiotic.
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    Liquid chromatographic retention and separation of phenols and related aromatic compounds on reversed phase columns (1992)
    Springer
    Chromatographia 34 (1992), S. 146-154 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Phenolic compounds ; Optimisation of isocratic separations ; River water samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Isocratic column liquid chromatographic systems with UV absorbance detection at 280 nm have been developed for the separation of 29 phenolics and related compounds. The selectivity was investigated on silica-, carbon- and polymer-based separation columns for the separation of phenolic type of components. The effects of various acetonitrile/buffer mixtures, and pH of the mobile phase, and their impact on the retention of the phenols was assessed. Tables of retention times on the four columns for the 29 phenols with two different acetonitrile/buffer mixtures, together with the retention times at three pHs from 6.5 to 2.3 with varying levels of organic modifier on the LiChrospher RP 18 column are presented. As an application, the analysis of real river water samples from the Ebro river is described using a solid phase extraction step prior to injection into the chromatographic system.
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    Microcolumn liquid chromatography on carbon sorbents (1992)
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    Chromatographia 34 (1992), S. 173-176 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carbon packing materials ; Aromatic compound separation ; Eluent effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention volume dependences on the molar volume were found for aromatic compounds using liquid microcolumn chromatography. The contributions of the functional groups in molecules of these compounds to the total retention value were calculated from the capacity factor values. The comparison of capacity factor values for carbon sorbents and octadecyl-silicagel has shown that for several microcolumn separations the carbon sorbent column has a better selectivity and resolution than the octadecyl-silicagel column.
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    Synthesis of acceptor bonded phases for donor-acceptor liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 177-181 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Synthesis of bonded stationary phases ; Acceptor ligands ; Normal phases ; PAHs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The synthesis of several electron-acceptor stationary phases has been reviewed the materials evaluated for their capacity to separate polyaromatic hydrocarbons (PAHs). Chemically bonded phases were obtained by the same procedure; the organosilane moiety is monofunctional and the HPLC behaviour is compared under identical conditions. Examples of PAHs separations are given.
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    Silanol group effect in C18 bonded phases in HPLC (1992)
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    Chromatographia 34 (1992), S. 182-184 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; C18 bonded phase ; Residual silanol groups ; Metal 5-Br-PADAP complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary If any residual (free) silanol groups remain at the surface of silica gel after bonding treatment, they may affect the retention of solutes since the dissociated groups (≡SiO−) will attract cations. The silanol group effect on the retention of cationic solutes will increase with increasing pH of the mobile phase but the effect will decrease with increasing hydrophobic-ion concentration at the C18 surface because such ions can mask the residual silanol groups. A method for the separation of metal complexes with 2-(5-bromo-2-pyridylazo)-diethylaminephenol (5-Br-PADAP) has been developed. The hydrophobic ion in the MeOH/H2O mobile phase was tetrabutylammonium (TBA).
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    Michael Tswett's columns: Facts and speculations (1992)
    Springer
    Chromatographia 34 (1992), S. 342-346 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; History of chromatography ; Calcium carbonate stationary phase ; Chlorophyll
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Although Michael Tswett is the originator of chromatography, little is known about the performance of his chromatographic systems. His descriptions of the separation of plant pigments are detailed but nevertheless difficult to interprete by today's chromatographic theory. By our own experiments with the system calcium carbonate/benzene it was found that the separation factor of chlorophyll a and b is approx. 1.6 which means that less than 100 theoretical plates are necessary for separation. Tswett's columns with 50 μm particles and 2–3 cm of bed height presumably exceeded this plate number. His separations could have been impaired by mass overload and by a volume flow rate which was two orders of magnitude faster than the optimum.
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    Factors influencing retention and resolution of substituted alkylbenzenes in reversed-phase liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 347-356 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Isomeric substituted alkylbenzenes ; Retention and resolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention data of isomeric xylenes, ethyltoluenes and diethylbenzenes, and of mesitylene, benzene, toluene and ethylbenzene were obtained on a reversedphase column using methanol-water and ethanol-water mobile phases at four different temperatures. This database was used to relate the dependence of solute retention and resolution on the polarity of the mobile phase, solute dipole moment, and column temperature. The additivity of the free energy of the transfer of solute molecules or solute segments from the stationary phase to the mobile phase, was examined for the isomeric compounds. For this, the logarithm of the net retention volume was substituted for the free energy. Deviations from the additivity of free energies indicate that the separation of isomeric substituted alkylbenzenes is governed by their differential interactions with both the polar mobile phase and nonpolar stationary phase. Among the disubstituted alkylbenzenes,ortho-isomers favor the mobile phase more andpara-isomers tend to prefer the stationary phase more. Themeta-isomers are found to follow the additivity rule closely. These trends are amplified as the polarity of the mobile phase is increased indicating that these isomers are resolved better in water-rich mobile phases. These findings are substantiated by analogous results from gas-liquid chromatographic retention data, estimation of dipole moment effects, and examination of the entropic and enthalpic contributions to the net retention volume.
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    Direct determination of Benzo[a]pyrene in oil distillates by on-line two-dimensional HPLC with column switching (1992)
    Springer
    Chromatographia 34 (1992), S. 376-380 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Column switching ; Polycyclic aromatics ; Oil distillates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A selective and sensitive HPLC method for the determination of Benzo[a]pyrene (B[a]p) in oil fractions by means of column switching is described. The diluted oil samples were injected directly onto a silica column with isooctane as eluent. After fast elution of the main part of the sample matrix, the B[a]p containing fraction was transferred on-line to a dinitro-aryl-modified silica column for final separation with isooctane/tetrahydrofuran. A detection limit of 50 ppt B[a]p was found when using fluorescence detection.
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    Gradient high performance liquid chromatography of block copolymers of styrene andt-butyl methacrylate II. Association phenomena in mixtures of block copolymer with polystyrene (1992)
    Springer
    Chromatographia 34 (1992), S. 363-368 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Precipitation chromatography of polymers ; Block copolymers of styrene-butyl methacrylate ; Association phenomena
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Block copolymers of styrene andt-butyl methacrylate can be analysed by methanol/tetrahydrofuran gradients on C18 or phenyl bonded phase columns. On both of these columns, retention increases with styrene content of the samples. At 50°C, the retention of PS or a block copolymer containing 45% styrene was longer on the phenyl than the C18 columns. This indicates the contribution of adsorption to retention on phenyl bonded phase columns. Lowering the temperature from 50 to 30°C caused earlier elution of part of the sample from the phenyl phase. On a C18 phase the same drop in temperature improved the shape of the peak, which also started later than at 50°C. This effect of temperature is generally observed in polymer retention due to an adsorption mechanism, whereas increasing retention with decrease in temperature is characteristic of a precipitation mechanism. The block copolymer investigated contained 15% free polystyrene precursor which could not be separated from the block copolymer under the conditions employed. The addition of 20% PS homopolymer with a molecular weight similar to that of the styrene block in the copolymer showed that the polystyrene eluted together with the block copolymer, whereas the addition of PS homopolymer with a much higher molecular weight caused an extra peak at the expected elution time.
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    Multidentate phenyl-bonded phases in high-performance liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 381-385 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Molecular recognition ; Multidentate phenyl-bonded phases ; PAHs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary New multidentate phenyl-bonded phases (MPBPs) were synthesized and evaluated the chromatographic retention behaviour with polycyclic aromatic hydrocarbons as sample probes in high-performance liquid chromatography. The new MPBPs show different retention characteristics from the previously synthesized MPBP, designated TP. Nevertheless, the results indicate that the retention mechanism is still the same as the TP phase: the size and shape of the solute molecule can be recognized by a cavity-like space formed by the methyl groups and phenyl rings of MPBPs.
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    Comparison and evaluation of HIC columns of different hydrophobicity (1992)
    Springer
    Chromatographia 34 (1992), S. 391-397 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Hydrophobic interaction ; Stationary phases ; Salt effect ; Proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention and selectivity in hydrophobic interaction chromatography (HIC) depend both on the type of stationary phase and on the mobile phase. In the last few years various high performance packing materials and columns have been introduced for HIC resulting in a range of different retentions and selectivity. We have investigated the effect of the stationary phase on the retention of various proteins. The retention of some solutes of different hydrophobicities were measured on three commercial HIC columns (TSK-Phenyl, Synchropack-Propyl, CAA-HIC) under isocratic conditions using water-methanol mixtures as eluent. The log kw values determined according to the literature were devalues determined according to the literature were dependent on the type and structure of the stationary phase and indicated a much less hydrophobic character for these columns than that obtained for reversed phase columns. Gradient separations were then carried out on a standard protein mixture using ammonium sulfate and sodium citrate to change the gradient time. In order to compare the effect of the stationary phase and the two salts investigated apparent capacity factors (kg) were determined and plotted against the gradient time obtained for the three columns in the two eluent system. It was shown that the type of stationary phase had a significant effect on the retention of proteins. In addition, the effect of the mobile phase composition, i.e. salt type, was considerably different on the various stationary phases. In order to exploit the potential of HIC to modulate selectivity for the separation of proteins, the combined effect of the stationary phase and the type of salt should be taken into account.
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    Chromatographic characteristics of porphyrine ether glycerides (1992)
    Springer
    Chromatographia 34 (1992), S. 431-432 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Thin-layer chromatography ; Porphyrine ether glycerides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Efficient TLC and HPLC conditions for the separation of a newly synthesized class of compounds, porphyrine ether glycerides, have been established. Supplementary physico-chemical characteristics are given for this group of solutes.
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    Integrated FIA/HPLC method for preconcentration and determination of transition metal ions (1992)
    Springer
    Chromatographia 34 (1992), S. 445-449 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Flow injection analysis ; Combined methods ; Transition metal ions ; Aqueous samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An automatic method based on the combination of a flow injection (FI) manifold with a liquid chromatograph has been developed for the enrichment and determination of transition metal ions in water samples. Alternatively, the FI configuration can be used as a screening system for the determination of the total concentration of heavy metals. Two-parameter expressions for calibration graphs involving preconcentration time and concentration of the analytes were established for both the FIA and the integrated FIA/HPLC methods. The preconcentration time depends on the concentration level of the analytes in the samples. The method is linear in the range 2–200 ng/ml, with r.s.d. values between 1.5 and 5.0. It has been applied to the determination of copper, lead, zinc, nickel, cobalt, cadmium and manganese in synthetic water samples.
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    Comparison of HPLC and solid phase clean-up methods for identification of PCBs in cod-liver oil by HRGC/MS-SIM technique (1992)
    Springer
    Chromatographia 34 (1992), S. 421-430 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Solid phase extraction ; PCBs in cod-liver oil ; GC/MS identification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A group of non-planar PCBs (IUPAC nos. 28, 52, 101, 118, 138, 153, and 180) was identified in a cod-liver oil product by using high resolution gas chromatography-mass spectrometry (HRGC/MS) in electron impact (EI) and negative chemical ionization (NCI) modes. The cod-liver oil samples were prepared either in a cyano column by high performance liquid chromatography (HPLC) or by a solid phase extraction (SPE) clean-up procedure that included e.g. purified charcoal treatment. The two methods of sample preparation were evaluated on the basis of the detectabilities of the congeners. The GC/MS-SIM method allowed quantitative monitoring of congeners nos. 52, 101, 118, 138, 153, and 180 at low concentration levels. Detection limits were 1.2 pg and 130 fg (m/z 292.00) in EI and NCI modes, respectively. The determination levels in EI and NCI were 1.8 pg and 290 fg in HPLC followed by HRGC/MS and 170 pg and 27 pg in SPE followed by HRGC/MS. The linear range was from 5.0 pg/μl to 1.0 ng/μl and from 1.0 pg/μl to 1.0 ng/μl in EI and NCI modes, respectively. In addition, the co-planar PCBs, PCDDs, and PCDFs were also screened and two of the chlorinated furanes were identified by HRGC/MS-NCI after separation from non-planar PCBs by SPE. In this case the only congeners that could be quantified were 2,3,4,7,8-PCDF and 1,2,3,4,6,7,8-HCDF, the detection limit for them being 740 fg (m/z 351.90) with NCI. SPE allows the separation of the planar and non-planar compounds, but LC separation is more effective for separation of the compounds of interest from the matrix. LC clean-up is easier and faster to perform than SPE clean-up.
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    Separation of stereoisomers of tetramethylcalix[4]arenoctol and derivatives by high-performance liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 453-456 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Calix[4]arenes ; Host-guest chemistry ; Separation of stereoisomers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A high performance liquid chromatographic procedure on 5 μm RP-18 was developed for the separation of the four possible cis-trans isomers of tetramethyl-calix[4]arenoctol, and of their octaacetates, and their octamethyl ethers.
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    HPLC separation of molecular species of intact sphingomyelin, utilizing multivariate design and optimization (1992)
    Springer
    Chromatographia 34 (1992), S. 529-533 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Sphingomyelin ; Molecular species separation ; Experimental design and optimization ; Chemometrics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An improved method has been developed for the separation of molecular species of intact sphingomyelins from natural sources (chicken egg yolk, bovine brain, and bovine milk) by high performance liquid chromatography with light-scattering detection. The method was developed and optimized using a novel multivariate optimization strategy.
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    High-performance liquid chromatography of carbohydrates in enzymic hydrolysate of waste paper (1992)
    Springer
    Chromatographia 34 (1992), S. 534-536 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carbohydrates ; Enzymic hydrolysate ; Waste paper
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Waste paper was pretreated with 5M sulfuric acid at 28°C to give a gel-like solution which was then hydrolyzed with cellulase, purified fromTrichoderma viride, to form carbohydrates. The determination of the carbohydrates was accomplished using an aminopropylbonded silica HPLC column and an RI detector. The detection limits were 20 ppm; xylose, glucose, and cellobiose were the major components. Salts from the buffer solution may affect the activity of cellulase. The analysis of carbohydrates can be performed under acid conditions. HPLC analysis of carbohydrates from enzymatic hydrolysis is reliable and successful.
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    Photosynthetic characteristics of Dunaliella salina (Chlorophyceae, Dunaliellales) in relation to β-carotene content (1992)
    Springer
    Journal of applied phycology 4 (1992), S. 11-15 
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    ISSN: 1573-5176
    Keywords: adaptation ; β-carotene ; Dunaliella salina ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photosynthetic characteristics of Dunaliella salina with high (red form) and low β-carotene (green form) concentrations were studied. D. salina growing in brine saltworks exhibited a high level of β-carotene (15 pg cell−1). The rate of oxygen evolution as a function of irradiance was higher in the red than in the green form (on chlorophyll basis). Photosynthetic inhibition of the green form was observed above 500 µmol m−2 s−1. The red form appeared more resistant to high irradiance and no inhibition in O2 evolution was observed up 2000 µmol m−2 s−1. However, when these results are expressed on a cell number basis the rate of oxygen evolution was significantly higher in the green form. Carbonic anhydrase (CA) activity (total, soluble, membrane bound) was found in red and green forms. CA was higher in the red form on a chlorophyll basis, but lower if expressed on a protein basis. The light dependent rate of oxygen evolution and photoinhibition depends on the concentration of β-carotene in D. salina cells.
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    Performance of a flat plate, air-lift reactor for the growth of high biomass algal cultures (1992)
    Springer
    Journal of applied phycology 4 (1992), S. 1-9 
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    ISSN: 1573-5176
    Keywords: photobioreactor ; flat plate air-lift reactor ; Chlorella ; Synechococcus ; hydraulic characteristics ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A flat plate, multi-pass air lift reactor (FPALR) for the culture of photosynthetic organisms was constructed from twin wall acrylic sheet and its performance characterised. When operated at an air input of 2.01 min−1 the multi-pass system had a Reynolds number of 5200 indicating fully turbulent flow. Chlorella vulgaris 211/11c was found to have a stationary phase biomass of 1.48 g 1−1 when grown in the flat plate air lift reactor (FPALR) at 100 µmol m−2s−1 compared to 1.11 g 1−1 when cultured in the continually stirred tank reactor (CSTR) at the same PFD (photon flux density). The same organism cultured at 200 µmol m−2s−1 achieved a stationary phase biomass of 1.71 g 1−1 in the FPALR. In contrast, Scenedesmus sp. produced a stationary phase biomass of 2.27 g1−1 and 1.27 g1−1, when cultured at 100 µmol m−2s−1 in the FPALR and the CSTR respectively. The growth rates of both organisms were also higher in the PFALR.
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    pH dependent chlorophyll fluorescence quenching in spinach thylakoids from light treated or dark adapted leaves (1992)
    Springer
    Photosynthesis research 31 (1992), S. 11-19 
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    ISSN: 1573-5079
    Keywords: carotenoid ; chlorophyll fluorescence ; non-photochemical quenching ; pH ; photosynthesis ; zeaxanthin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The pH dependence of maximum chlorophyll fluorescence yield (Fm) was examined in spinach thylakoids in the presence of nigericin to dissipate the transthylakoid pH gradient. 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea (DCMU) was present to eliminate photochemical quenching. Thylakoids were prepared from dark adapted leaves (‘dark’ thylakoids) or preilluminated leaves (‘light’ thylakoids). In the latter there had been approximately 50% conversion of the xanthophyll violaxanthin to zeaxanthin, while no conversion had occurred in the former. In the presence of a reductant such as ascorbate, antimycin A sensitive quenching was observed (half maximal quenching at 5 μM), whose pH dependence differed between the two types of thylakoid. Preillumination of leaves resulted in more quenching at pH values where very little quenching was observed in ‘dark’ thylakoids (pH 5–7.6). This was similar to activation of high-energy-state quenching (qE) observed previously (Rees D, Young A, Noctor G, Britton G and Horton P (1989) FEBS Lett 256: 85–90). Thylakoids isolated from preilluminated DTT treated leaves, that contained no zeaxanthin, behaved like dark thylakoids. A second form of quenching was observed in the presence of ferricyanide, that could be reversed by the addition of ascorbate. This was not antimycin A sensitive and showed the same pH dependence in both types of thylakoid. The former type of quenching, but not the latter, showed similar low temperature fluorescence emission spectra to qE, and was considered to occur by the same mechanism.
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    Light, iron, Sam Granick and the origin of life (1992)
    Springer
    Photosynthesis research 33 (1992), S. 163-170 
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    ISSN: 1573-5079
    Keywords: biosynthetic pathway ; evolution ; free energy ; photochemistry ; photosynthesis ; porphyrin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Living matter is an organized system which requires a continual flux of energy for its survival. As a working assumption, the flux of energy required for the origin of a self-duplicating cell is taken as the power required for the maintenance of a modern cell: 10 mW per g of carbon or some 105 times the output per gram of the sun. Solar photochemistry supplies the energy for the continuing evolution of life and, by continuity, for its origin. The iron oxide-sulfide photosynthetic unit proposed by S. Granick 35 years ago was meant to supply this energy. The evolution of complex organic photosensitizers is rationalized by the Granick hypothesis that biosynthetic pathways recapitulate their evolution. These concepts are discussed in the context of the evolution of photosynthetic systems and the known properties of these pigments.
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    Cultivar differences in leaf photosynthesis of rice bred in Japan (1992)
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    Photosynthesis research 32 (1992), S. 139-146 
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    ISSN: 1573-5079
    Keywords: leaf senescence ; mesophyll conductance ; Oryza sativa L. ; photosynthesis ; specific leaf weight ; stomatal conductance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The grain yield of rice (Oryza sativa L.), as well as of other cereal crops, is limited to a large extent, by the supply of photosynthates produced during grain filling period. In this study, flag leaf photosynthesis (LPS) after heading was compared among 32 cultivars bred during the past century in Japan, to determine if the improvement of LPS has occurred with the breeding advance of high yielding cultivars. Measurement of LPS was made for 5 consecutive years in the paddy field, on the flag leaf of the main stem, at heading (LPS-0), and 2 weeks (LPS-2) and 4 weeks (LPS-4) after heading. LPS decreased with advance of leaf senescence from LPS-0 to LPS-2, and then to LPS-4. However, if nitrogen was top-dressed at the heading time, high LPS-2 was maintained, particularly in the newer cultivars. A significant positive correlation between LPS and the released year of cultivar was found at LPS-2, especially in the nitrogen top-dressed plot, but not at LPS-0 or LPS-4. Cultivar difference in LPS of the senescing leaves were not stable through the different years, whereas LPS-0 was stable over years, suggesting that the LPS in the senescent leaf is susceptible to the environmental variation due to the effects on leaf senescence. Cultivar difference in LPS at any stage was closely associated with mesophyll conductance to CO2, and stomatal conductance was also associated with cultivar difference in such a high LPS as LPS-0 and nitrogen top-dressed LPS-2. Significant correlation between LPS and specific leaf weight was not observed at any stage of the flag leaf.
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    Mechanisms for controlling balance between light input and utilisation in the salt tolerant alga Dunaliella C9AA (1992)
    Springer
    Photosynthesis research 32 (1992), S. 181-191 
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    ISSN: 1573-5079
    Keywords: chlorophyll fluorescence ; Dunaliella ; photosynthesis ; quantum efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The yield of photosynthetic O2 evolution was measured in cultures of Dunaliella C9AA over a range of light intensities, and a range of low temperatures at constant light intensity. Changes in the rate of charge separation at Photosystem I (PS I) and Photosystem II (PS II) were estimated by the parameters ΦPS I and ΦPS II . ΦPS I is calculated on the basis of the proportion of centres in the correct redox state for charge separation to occur, as measured spectrophotometrically. ΦPS II is calculated using chlorophyll fluorescence to estimate the proportion of centres in the correct redox state, and also to estimate limitations in excitation delivery to reaction centres. With both increasing light intensity and decreasing temperature it was found that O2 evolution decreased more than predicted by either ΦPS I or ΦPS II. The results are interpreted as evidence of non-assimilatory electron flow; either linear whole chain, or cyclic around each photosystem.
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    Conjectures and reveries (1992)
    Springer
    Photosynthesis research 33 (1992), S. 171-176 
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    ISSN: 1573-5079
    Keywords: photosynthesis ; origin of life ; clays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The origin of photosynthesis is speculated to have involved carbon dioxide and self-replicating iron-rich clays. The later evolution of photosynthesis is considered to have undergone four distinct phases: (1) The photoreduction of carbon dioxide by ferrous ion to form oxalate and formate. (2) The entry of sulfur into the evolving clay system which led to the formation of acetyl thioesters. The polymerization of the acetyl thioeters led to the formation of quinones. The formation of Fe2S2 and Fe4S4 cores appeared in this phase. (3) The ability to fix nitrogen characterized the third phase. This led to the formation of pyrrole, flavin, nicotinamide, phycobilins, porphyrins and chlorophyll. (4) Finally, phosphate entered the evolving system. The chromophores evolved from ferrous ion through the quinones, carotenoids, phycobilins to chlorophyll. This evolution of chromophores implies that photosynthesis began in the UV and evolved through the blue, yellow, orange into the red. The electron transport chain evolved from ferrous ion through the Fe2S2 and Fe4S4 cores to the hemes.
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    Changes in Photosystem II fluorescence in Chlamydomonas reinhardtii exposed to increasing levels of irradiance in relationship to the photosynthetic response to light (1992)
    Springer
    Photosynthesis research 31 (1992), S. 31-40 
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    ISSN: 1573-5079
    Keywords: Chlamydomonas ; convexity ; chlorophyll a fluorescence ; Photosystem II heterogeneity ; photoinhibition ; photosynthesis ; PS II repair cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of a 60 min exposure to photosynthetic photon flux densities ranging from 300 to 2200 μmol m−2s−1 on the photosynthetic light response curve and on PS II heterogeneity as reflected in chlorophyll a fluorescence were investigated using the unicellular green alga Chlamydomonas reinhardtii. It was established that exposure to high light acts at three different regulatory or inhibitory levels; 1) regulation occurs from 300 to 780 μmol m−2s−1 where total amount of PS II centers and the shape of the light response curve is not significantly changed, 2) a first photoinhibitory range above 780 up to 1600 μmol m−2s−1 where a progressive inhibition of the quantum yield and the rate of bending (convexity) of the light response curve can be related to the loss of QB-reducing centers and 3) a second photoinhibitory range above 1600 μmol m−2s−1 where the rate of light saturated photosynthesis also decreases and convexity reaches zero. This was related to a particularly large decrease in PS IIα centers and a large increase in spill-over in energy to PS I.
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    Species-related differences in the electrophoretic behavior of CP 29 and CP 26: An immunochemical analysis (1992)
    Springer
    Photosynthesis research 34 (1992), S. 249-262 
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    ISSN: 1573-5079
    Keywords: photosynthesis ; light-harvesting chlorophyll-protein complex ; spinach ; maize
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The monomeric chlorophyll-protein complexes, CP 29 and CP 26 seen in the Camm and Green (1980) and Dunahay and Staehelin (1986) green gels do not always migrate in the order of the apparent molecular weight of their apoproteins as determined by denaturing gel electrophoresis. In barley and corn they do, but in spinach they do not. In addition, in some higher plant species these chlorophyll-protein complexes comigrate on green gels causing confusion in the literature. To remedy this situation and circumvent future confusion, we propose that the CP 29 and CP 26 complexes be named according to the relative molecular weight of their apoproteins on denaturing gels. Our proposal is supported by the results obtained from four antibodies used on Western blot samples of whole thylakoids, grana membranes, and PS II preparations from different plants. The higher molecular weight proteins (proposed CP 29's) react strongly to one set of antibodies, and the lower molecular weight proteins (proposed CP 26's) react strongly to a different set. In spinach, CP 26 antibodies react also with CP 29, but the extent of the cross-reactivity depends critically on the gel electrophoresis system used. Accordingly, a lack of antibody reactivity under certain conditions may not indicate two proteins are unrelated, just simply that a particular epitope is no longer accessible following gel electrophoresis with a particular buffer system.
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    Concerning oscillations (1992)
    Springer
    Photosynthesis research 34 (1992), S. 387-395 
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    ISSN: 1573-5079
    Keywords: oscillations ; photosynthesis ; regulation ; phosphate ; down-stream
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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    URL: http://dx.doi.org/10.1007/BF00029813
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    Chloroplast energization and oxidation of P700/plastocyanin in illuminated leaves at reduced levels of CO2 or oxygen (1992)
    Springer
    Photosynthesis research 34 (1992), S. 433-447 
    Details
    ISSN: 1573-5079
    Keywords: chlorophyll fluorescence ; cyclic electron transport ; photorespiration ; photosynthesis ; Photosystem II ; proton gradient
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chlorophyll fluorescence, light scattering, the electrochromic shift P515 and levels of some photosynthetic intermediates were measured in illuminated leaves. Oxygen and CO2 concentrations in the gas phase were varied in order to obtain information on control of Photosystem II activity under conditions such as produced by water stress, when stomatal closure restricts access of CO2 to the photosynthetic apparatus. Light scattering and energy-dependent fluorescence quenching indicated a high level of chloroplast energization under high intensity illumination even when linear electron transport was curtailed in CO2-free air or in 1% oxygen with 35 μll-1 CO2. Calculations of the phosphorylation potential based on measurements of phosphoglycerate, dihydroxyacetone phosphate and NADP revealed ratios of intrathylakoid to extrathylakoid proton concentrations, which were only somewhat higher in air containing 35 μl l-1 CO2 than in CO2-free air or 1% oxygen/35 μl l-1 CO2. Anaerobic conditions prevented appreciable chloroplast energization. Acceptor-limitation of electron flow resulted in a high reduction level of the electron transport chain, which is characterized by decreased oxidation of P700, not only under anaerobic conditions, but also in air, when CO2 was absent, and in 1% oxygen, when the CO2 concentration was reduced to 35 μll-1. Efficient control of electron transport was indicated by the photoaccumulation of P700 + at or close to the CO2 compensation point in air. It is proposed to require the interplay between photorespiratory and photosynthetic electron flows, electron flow to oxygen and cyclic electron flow. The field-indicating electrochromic shift (P515) measured as a rapid absorption decrease on switching the light off followed closely the extent of photoaccumulation of P700 + in the light.
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    Dynamic versus static models for photosynthesis (1992)
    Springer
    Hydrobiologia 238 (1992), S. 189-196 
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    ISSN: 1573-5117
    Keywords: photosynthesis ; phytoplankton ; time scales ; environmental variability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Static P(I) curves relating photosynthesis to the instantaneous light might not be adequate to describe the activity of algal cells in lakes or oceans where mixing can cause a complex pattern of light variation. In recent years experimental results have provided evidence that, subsequent to changes in light, the rate of photosynthesis may be delayed or exhibit complex temporal dynamics. The model DYPHORA (DYnamic model for the PHOtosynthetic Rate of Algae) takes these dynamics into account by introducing two characteristic response times for the biological processes: (1) the effect of light inhibition having a time scale of minutes to a few hours and (2) the time lag of the rate of photosynthesis for increasing light intensities having a time scale of seconds to minutes. The importance of the dynamic relative to the static description of photosynthesis depends on the time scales of the changes in the environment and the biological response, becoming significant when the time scales are comparable.
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    Effects of clay discharges on streams (1992)
    Springer
    Hydrobiologia 248 (1992), S. 215-234 
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    ISSN: 1573-5117
    Keywords: suspended solids ; turbidity ; algae ; photosynthesis ; light ; mining
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Placer gold-mining on the West Coast of the South Island of New Zealand provided a field test-bed for investigating the impacts of fine inorganic suspensoids (clays) on streams not subjected to other abuses. The suspensions of clays (40% between 0.55 and 1 µm in diameter) seeping into the streams from gold mines were colloidally stable. The clay particles attenuated light in the streamwater with near maximum efficiency leading to severe degradation of stream optical quality. Turbidity increased from a median of 2.4 NTU upstream often to 〉 100 NTU (median 15 NTU) downstream. The stream waters, which were strongly-coloured by humic substances, were changed from a dark organge colour to a bright ‘muddy’ appearance downstream of mining, and visual clarity was reduced from a few metres to as low as 0.03 m (median 0.33 m). The clay discharges decreased light penetration into the stream water such that irradiance averaged over a 12 hr photoperiod at the bed (typically about 0.3 m depth in runs at baseflow) fell from about 340 µE m−2 s−1 upstream to as low as 80 µE m−2 s−1 (median 190 µE m−2 s−1) at matched downstream sites. This reduction in light proportionally reduced benthic primary productivity downstream of the mining activity. In turn this reduced benthic algal biomass and lowered the phototrophic content of the epilithon. In spite of their extremely low settling velocities (〈 1 µm s−1) some clay particles were deposited on the stream bed owing to entrapment in the epilithon matrix. This decreased the organic content of the epilithon (from an average of 19% upstream to 8.5% downstream) so reducing its quality as food for invertebrate animals.
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    Photosynthetic performance of deep-water macroalgae (Phaeophyta, Dictyotales) off Bermuda (1992)
    Springer
    Hydrobiologia 231 (1992), S. 93-98 
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    ISSN: 1573-5117
    Keywords: photosynthesis ; macroalgae ; deep-water ; Bermuda ; Dictyotales
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photosynthetic performance and dark respiration rates were determined in situ for abundant macroalgae occurring between 27–49 m depths off Bermuda. Brown algae, particularly members of the order Dictyotales, predominated at all deep-water sites, and Stypopodium zonale was the most abundant species. Species showed net photosynthesis at very low ambient irradiances (〈0.01 maximum Io). Lobophora variegata, a species with a highly decumbent growth form, had low productivity across all irradiances. In contrast, Dictyota spp. (D. bartayresii, D. dichotoma, D. divaricata) and S. zonale had high photosynthetic capacity (ca. 400 µmol O2 gdw−1 h−1), and light saturation was not evidenced at the highest ambient irradiance level (300 µE m−1 s−1) for species with thin, flat thalli. Light-harvesting pigment concentrations reflected tissue-nitrogen levels. C:N atom ratios, except for L. variegata and D. divaricata, were within the ratio for balanced growth. The repeated occurrence and photosynthetic efficiency of these Dictyotalean species in subtropical and tropical deep-water habitats emphasize their successful adaptation to low-light, nutrient-poor environments.
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    Diel periodicity in phytoplankton productivity (1992)
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    Hydrobiologia 238 (1992), S. 1-35 
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    ISSN: 1573-5117
    Keywords: periodicity ; diel ; circadian ; clocks ; photosynthesis ; phytoplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Daily variation in phytoplankton productivity influences the dynamics and linkages between several large scale processes in aquatic ecosystems. As part of an opening address to the 5th International workshop for the Group for Aquatic Productivity (GAP), the daily patterns of variability in photosynthesis for different algal classes was introduced and accompanied by a discussion of the sources of environmental and endogenous regulation of repeating biological oscillations that occur in phytoplankton on timescales of one day. It is suggested that one way to develop a database that serves to sort and predict phytoplankton variability over the day may be to encourage the creation of a ‘temporal library’. Such a library would be comprised of temporally fixed maps of circadian clock-controlled rhythms for individual species, as well as temporally variable maps of diel periodicities that only can be defined for a selected set of environmental conditions.
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    High biomass and production of picoplankton in a Chinese integrated fish culture pond (1992)
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    Hydrobiologia 237 (1992), S. 15-23 
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    ISSN: 1573-5117
    Keywords: picoplankton ; photosynthesis ; primary production ; cyprinids ; fish farm pond
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The phytoplankton dynamics of a Chinese integrated fish culture pond in the suburbs of Shanghai were studied in September and October 1989. The chlorophyll a concentration was high with a range of 62.5–127.3 µg l−1; however, daily net production of phytoplankton was relatively low, with a range of 0.53–1.94 gC m −2 d−1. Of the total phytoplankton biomass, 70–87% was composed of nanoplankton (〈10 µm) and picoplankton, probably because of the selective feeding by phytoplanktivorous carp. In particular, the chlorophyll a concentration of picoplankton was 2.1 – 14.1 mg m −3, and its contribution to total phytoplankton production rate was high (18–68%).
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    Photosynthetic activity of phytoplankton in a high altitude lake (Emerald Lake, Sierra Nevada, California) (1992)
    Springer
    Hydrobiologia 230 (1992), S. 37-48 
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    ISSN: 1573-5117
    Keywords: photosynthesis ; alpine lake ; phytoplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photosynthetic activity by phytoplankton was measured during the ice-free seasons of 1984, 1985 and 1987 using the 14C radioassay in high altitude Emerald Lake (California). Relative quantum yield (αB) and light-saturated chlorophyll-specific carbon uptake (Pm B) were calculated from the relationship of light and photosynthesis fitted to a hyperbolic tangent function. Temporal changes in Pm B showed no regular pattern. Seasonal patterns of αB generally had peaks in the summer and autumn. Phytoplankton biomass (as measured by chlorophyll a) and light-saturated carbon uptake (Pm) had peaks in the summer and autumn which were associated with vertical mixing. Estimates of mean daily carbon production were similar among the three years: 57 mg C m−2 2 d−1 in 1984, 70 mg C m−2 2 d−1 in 1985 and 60 mg C m−2 d−1 in 1987. Primary productivity in Emerald Lake is low compared to other montane lakes of California and similar to high-altitude or high-latitude lakes in other regions.
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    Influence of medium frequency light/dark cycles of equal duration on the photosynthesis and respiration of Chlorella pyrenoidosa (1992)
    Springer
    Hydrobiologia 238 (1992), S. 53-62 
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    ISSN: 1573-5117
    Keywords: light/dark cycles ; photosynthesis ; Chlorella ; diurnal variations ; respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chlorella pyrenoidosa was grown in three continuous cultures each receiving a different light regime during the light period of a diurnal cycle. Hourly samples taken during the light period were subjected to medium frequency light/dark oscillations of equal duration, ranging from 3 to 240 seconds. The oxygen consumption and production of each sample were measured with an oxygen electrode in a small oxygen chamber. Although the light/dark cycles had little overall influence on photosynthetic activity, the microalgae appeared to adapt to the light regime to which they were subjected. Large differences were found between the maximum chlorophyll-specific production rates (P infmax supB ), the chlorophyll-specific production rates (PB) and the respiration rates between the cultures and treated subsamples. Respiration rates increased during the light period, whilst PB either increased, or had a mid light period minimum or maximum. The culture which received an hourly light oscillation during the light period had the highest P infmax supB and lowest respiration rates, and it is suggested that these algae react as in nature, whereas either a sinusoidal or a block light pattern is ‘unnatural’. The latter light regime is commonly used in laboratory studies.
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    The effect of dynamic light regimes on Chlorella II. Minimum quantum requirement and photosynthesis-irradiance parameters (1992)
    Springer
    Hydrobiologia 238 (1992), S. 79-88 
    Details
    ISSN: 1573-5117
    Keywords: dynamic light regime ; photosynthesis ; respiration ; quantum requirement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Comparisons were made of photosynthesis in three light limited cyclostat cultures (LD = 8:16, dilution rate 0.7 d−1) of Chlorella pyrenoidosa, differing only in the dynamics of irradiance supply: as a constant rate, i.e. a block culture; as a sine function of the light period, i.e. a sinusoidal culture; as an 8 h sine function superimposed by an 1 h sine function, i.e. an oscillating culture. The sinusoidal culture had a constant minimum quantum requirement for oxygen evolution (QR) of 10.8 over the photoperiod. The OR of the oscillating culture increased from 24 to 37 during the photoperiod. From changes in α and P max we suggest that: (1) photosynthetic units (PSU) of the block and sinusoidal sulture increased in number; (2) increasingly fewer chlorophyll molecules participated in oxygenic photosynthesis with a decreasing turnover time of the PSU's during an oscillating photoperiod. Values of I k decreased slightly in the block culture, increased slightly in the sinusoidal culture and showed a twofold increase in the oscillating culture. From the ratio of in situ oxygen production (qO2) and P max we infer a balanced equilibrium between photosystem activity and electron transport capacity for the block and sinusoidal culture. We hypothesize that the qO2 values of the oscillating culture underestimated true oxygen production rates due to a nonlinear response at peak light intensities. The results show that a dynamical photoperiod provoked significantly different photosynthetic responses, even though the overall growth rate was unaffected.
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    Epilithic chlorophyll a, photosynthesis, and respiration in control and fertilized reaches of a tundra stream (1992)
    Springer
    Hydrobiologia 240 (1992), S. 121-131 
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    ISSN: 1573-5117
    Keywords: streams ; arctic ; tundra ; epilithon ; photosynthesis ; respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photosynthesis and respiration by the epilithic community on cobble in an arctic tundra stream, were estimated from oxygen production and consumption in short-term (4–12 h), light and dark, chamber incubations. Chlorophyll a was estimated at the end of each incubation by quantitatively removing the epilithon from the cobble. Fertilization of the river with phosphate alone moderately increased epilithic chlorophyll a, photosynthesis, and respiration. Fertilization with ammonium sulfate and phosphate, together, greatly increased each of these variables. Generally, under both control and fertilized conditions, epilithic chlorophyll a concentrations (mg m−2), photosynthesis, and respiration (mg O2 m−2, h−1) were higher in pools than in riffles. Under all conditions, the P/R ratio was consistent at ∼ 1.8 to 2.0. The vigor of epilithic algae in riffles, estimated from assimilation coefficients (mg O2 [mg Chl a]−1 h−1) was greater than the vigor of epilithic algae in pools. However, due to the greater accumulation of epilithic chlorophyll a in pools, total production (and respiration) in pools exceeded that in riffles. The epilithic community removed both ammonium and nitrate from water in chambers. Epilithic material, scoured by high discharge in response to storm events and suspended in the water column, removed ammonium and may have increased nitrate concentrations in bulk river water. However, these changes were small compared to the changes exerted by attached epilithon.
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    Carbon isotope ratio and photosynthetic activity of phytoplankton in the eutrophic Mikawa Bay, Japan (1992)
    Springer
    Ecological research 7 (1992), S. 355-361 
    Details
    ISSN: 1440-1703
    Keywords: carbon isotope ratio ; photosynthesis ; phytoplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Primary production by phytoplankton in the eutrophic Mikawa Bay, Japan, was studied by simultaneous measurements of natural carbon isotope ratio (δ 13C) and short-term carbon uptake rates (13C tracer study) of size-fractionated nannoplankton (〈10 μm) and net plankton (〉10 μm) samples. Short-term photosynthetic rates, which represent the physiological state of algae, were variable regardless of standing stock sizes. Theδ 13C values of particulate organic carbon (POC) in June and July displayed horizontal variations for both the net plankton fraction (−19.8 to −12.7‰) and the nannoplankton fraction (−22.0 to −12.8‰). For both fractions, low concentrations of POC had more negativeδ 13C values (−22 to −18‰). Highδ 13C values for the net plankton were found when POC concentrations were much higher, due to red tide. This suggests that the increase in algal standing crop for the net plankton fraction resulted from accelerated photosynthetic activity. However the nannoplankton fractions with higher POC values have relatively lowδ 13C values.
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    Influence of the mixing regime on algal photosynthetic performance in laboratory scale enclosures (1992)
    Springer
    Hydrobiologia 238 (1992), S. 111-118 
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    ISSN: 1573-5117
    Keywords: mixing regime ; Laboratory Scale Enclosures ; phytoplankton ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The photosynthesis of plankton sampled from the eutrophic Lake Loosdrecht was studied in Laboratory Scale Enclosures (LSEs) with regard to the rate of mixing. First, two LSEs were operated at different mixing rates. No significant differences in photosynthetic performance were found, with the exception of a depressed photosynthesis in the afternoon in the LSE which had a low mixing rate. Secondly, when mixing was stopped, the phytoplankton which stayed in the dark due to the steep light gradient in the LSE responded by changing its maximal photosynthetic capacity. The results show that the filamentous cyanobacteria in the lake can respond rapidly to changes in the depth of the mixed layer by altering their photosynthetic performance.
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    The physiological basis for genetic improvement of oil palm in Malaysia (1992)
    Springer
    Euphytica 60 (1992), S. 179-184 
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    ISSN: 1573-5060
    Keywords: breeding ; Elaeis guineensis ; harvest index ; oil palm ; photosynthesis ; selection progress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Yield of Deli dura oil palms after four generations of selection was 60% greater than that of the unselected base population. Total above-ground dry matter production was increased by selection, apparently through better utilisation of solar radiation. The dry matter requirement for vegetative growth was unchanged, so a greater surplus remained for fruit production in the selected palms. Crossing the dura and pisifera to give the thin-shelled tenera fruit type improved partitioning of dry matter within the fruit, giving a 30% increase in oil yield at the expense of shell, without changing total dry matter production.
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    A differential effect of 3-(3′4′ dichlorophenyl)-1,1 dimethyl urea and atrazine on fluorescence kinetics in chloroplasts (1992)
    Springer
    Photosynthesis research 31 (1992), S. 139-148 
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    ISSN: 1573-5079
    Keywords: Fe ; photosynthesis ; Photosystem II ; variable fluorescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract It was found that DCMU had a differential effect at two concentration ranges on variable fluorescence kinetics in isolated chloroplasts. The increase in fluorescence rate at low concentrations of DCMU was abolished by preincubation of chloroplasts with ferricyanide or formate, treatments which were shown to convert Fe in the PS II reaction center (i.e., the FeQA complex) into a non-oxidizable form, but it was not affected by Tris treatment. Increase in fluorescence kinetics (at the initial linear rate) at high concentrations of DCMU was found to be abolished by Tris treatment but it was only marginally affected by ferricyanide or formate treatments. The effect of Tris could be abolished by addition of hydroquinone-ascorbate, which restored electron flow to the pool of secondary acceptors. Contrary to the effect of DCMU, no such differential concentration dependence of the variable fluorescence kinetics was found for atrazine. The increase in fluorescence kinetics (at the initial linear rate) at a low concentration rate of DCMU is presumably restricted to units which contain an oxidizable Fe in the FeQA complex. Increase in fluorescence kinetics (at the initial linear rate) at high DCMU concentration is probably related to the effect of DCMU at the QB site.
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    Physiological effects of sublethal atrazine on barley chloroplast thylakoid membranes (1992)
    Springer
    Photosynthesis research 32 (1992), S. 1-10 
    Details
    ISSN: 1573-5079
    Keywords: chlorophyll a/b ratio ; chlorophyll-proteins ; electron transport ; herbicide ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study was conducted to more clearly define the physiological effects of PS II herbicides on chloroplast thylakoid membrane activity and composition. Barley (Hordeum vulgare L. cv Boone) was grown in hydroponic culture at 20°C in a growth chamber with a light intensity of 500 μmole photons m-2 s-1. Atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine), a Photosystem II herbicide, was supplied continuously via the roots to 7-day-old plants. Atrazine concentrations greater than 0.07 ppm (0.32 μM) were associated with decreased leaf chlorophyll (chl), lowered chl a/b ratio, inhibition of chloroplast electron transport, and plant death within 1 to 2 weeks. Atrazine at 0.07 ppm was defined as sublethal because no toxic effects were observed. Sublethal atrazine induced a decrease in chl a/b ratio with no effect on leaf chl content. Photosynthetic electron transport was either unaffected in fully expanded leaves or slightly stimulated in expanding leaves by treatment of intact plants with 0.07 ppm atrazine. The major effect of sublethal atrazine was on the chl-protein complex composition. Sublethal atrazine increased the level of the Photosystem II light-harvesting complex (LHC-II) and lowered the level of the CP1a Photosystem I complex relative to controls. The numbers of Photosystem II and Photosystem I reaction centers and cytochrome b 6/f complexes per unit chl were not affected by sublethal atrazine. The overall result was an atrazine-induced redistribution of light-harvesting chl from Photosystem I to Photosystem II with no effect on the number of thylakoid membrane-protein complexes associated with electron transport.
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    Simultaneous photoreduction and photooxidation of cytochrome b-559 in Photosystem II treated with carbonylcyanide-m-chlorophenylhydrazone (1992)
    Springer
    Photosynthesis research 33 (1992), S. 203-212 
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    ISSN: 1573-5079
    Keywords: Cytochrome b-559 ; ADRY agent ; electron transport ; photosynthesis ; QA ; QB ; reaction center
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The possibility of a Photosystem II (PS II) cyclic electron flow via Cyt b-559 catalyzed by carbonylcyanide m-chlorophenylhydrazone (CCCP) was further examined by studying the effects of the PS II electron acceptor 2,6-dichloro-p-benzoquinone (DCBQ) on the light-induced changes of the redox states of Cyt b-559. Addition to barley thylakoids of micromolar concentrations of DCBQ completely inhibited the changes of the absorbance difference corresponding to the photoreduction of Cyt b-559 observed either in the presence of 10 μM ferricyanide or after Cyt b-559 photooxidation in the presence of 2 μM CCCP. In CCCP-treated thylakoids, the concentration of photooxidized Cyt b-559 decreased as the irradiance of actinic light increased from 2 to 80 W m-2 but remained close to the maximal concentration (0.53 photooxidized Cyt b-559 per photoactive Photosystem II) in the presence of 50 μM DCBQ. The stimulation of Cyt b-559 photooxidation in parallel with the inhibition of its photoreduction caused by DCBQ demonstrate that the extent of the light-induced changes of the redox state of Cyt b-559 in the presence of CCCP is determined by the difference between the rates of photooxidation and photoreduction of Cyt b-559 occuring simultaneously in a cyclic electron flow around PS II. We also observed that the Photosystem I electron acceptor methyl viologen (MV) at a concentration of 1 mM barely affected the rate and extent of the light-induced redox changes of Cyt b-559 in the presence of either FeCN or CCCP. Under similar experimental conditions, MV strongly quenched Chl-a fluorescence, suggesting that Cyt b-559 is reduced directly on the reducing side of Photosystem II.
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    Thermoluminescence study of the in vivo effects of bicarbonate depletion and acetate/formate presence in the two algae Chlamydobotrys stellata and Chlamydomonas reinhardtii (1992)
    Springer
    Photosynthesis research 34 (1992), S. 279-285 
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    ISSN: 1573-5079
    Keywords: acetate ; bicarbonate effect ; CO2-depletion ; electron transport ; formate ; photosynthesis ; thermoluminescence ; Chlamydobotrys stellata ; Chlamydomonas reinhardtii
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We investigated the influence of CO2/HCO3 −-depletion and of the presence of acetate and formate on the in vivo photosynthetic electron transport in the two green algae Chlamydobotrys stellata and Chlamydomonas reinhardtii by means of thermoluminescence technique and mathematical glow curve analysis. The main effects of the removal of CO2 from the algal cultures was: (1) A shift of the glow curve peak position to lower temperatures resulting from a decrease of the B band and an increase of the Q band. (2) Treatment of CO2-deficient Chl. stellata with DCMU yielded two thermoluminescence bands in the Q band region peaking at around +12°C and +5°C; in case of Chl. reinhardtii DCMU treatment induced only one band with an emission maximum at +5°C. The presence of acetate or formate in CO2-depleted algal cultures lowered the intensities of all of the individual TL bands but that of a HT band (TL+37). The effects of CO2-depletion and of the presence of anions were fully reversible.
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    URL: http://dx.doi.org/10.1007/BF00033445
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    Second-site mutation at M43 (Asn→Asp) compensates for the loss of two acidic residues in the QB site of the reaction center (1992)
    Springer
    Photosynthesis research 32 (1992), S. 147-153 
    Details
    ISSN: 1573-5079
    Keywords: electron transfer ; proton transfer ; photosynthesis ; quinone ; reaction center ; site-specific mutagenesis ; suppressor mutations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two acidic residues, L212Glu and L213Asp, in the QB binding sites of the photosynthetic reaction centers of Rhodobacter capsulatus and Rhodobacter sphaeroides are thought to play central roles in the transfer of protons to the quinone anion(s) generated by photoinduced electron transfer. We constructed the site-specific double mutant L212Ala-L213Ala in R. capsulatus, that is incapable of growth under photosynthetic conditions. A photocompetent derivative of that strain has been isolated that carries the original L212Ala-L213Ala double mutation and a second-site suppressor mutation at residue M43 (Asn→Asp), outside of the QB binding site, that is solely responsible for restoring the photosynthetic phenotype. The Asp,Asn combination of residues at the L213 and M43 positions is conserved in the five species of photosynthetic bacteria whose reaction center sequences are known. In R. capsulatus and R. sphaeroides, the pair is L213Asp-M43Asn. But, the reaction centers of Rhodopseudomonas viridis, Rhodospirillum rubrum and Chloroflexus aurantiacus reverse the combination to L213Asn-M43Asp. In this respect, the QB site of the suppressor strain resembles that of the latter three species in that it couples an uncharged residue at L213 with an acidic residue at M43. These reaction centers, in which L213 is an amide, must employ an alternative proton transfer pathway. The observation that the M43Asn→Asp mutation in R. capsulatus compensates for the loss of both acidic residues at L212 and L213 suggests that M43Asp is involved in a new proton transfer route in this species that resembles the one normally used in reaction centers of Rps. virddis, Rsp. rubrum and C. aurantiacus.
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    URL: http://dx.doi.org/10.1007/BF00035949
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    Remarks on mixotrophic and autotrophic carbon nutrition of Vitis plantlets cultured in vitro (1992)
    Springer
    Plant cell, tissue and organ culture 31 (1992), S. 239-244 
    Details
    ISSN: 1573-5044
    Keywords: Vitis ; grapevine ; in vitro culture ; photomixotropy ; photosynthesis ; respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two Vitis species were cultured in vitro under photoautrophic (sucrose-free culture medium) and photomixotrophic (sucrose 15 g l-1) conditions during the period following microcutting rooting (day 34 to day 120). Several parameters were measured at the end of the culture: growth, plant dry weight, carbohydrate uptake from the medium and rates of photosynthesis and dark respiration. The two species behaved very differently. Under photoautotrophic conditions, dark respiration, net photosynthesis and daily CO2 fixation were higher in Vitis vinifera than in Vitis rupestris. Culture under mixotrophic conditions caused increase in growth, respiration and photosynthesis in Vitis rupestris. In contrast, photosynthesis decreased in Vitis vinifera under the same conditions.
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    URL: http://dx.doi.org/10.1007/BF00036230
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  • 86
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    Effect on leaf photosynthetic rate by leaf blast for rice cultivars with different types and levels of resistance (1992)
    Springer
    Euphytica 66 (1992), S. 81-87 
    Details
    ISSN: 1573-5060
    Keywords: leaf blast ; Oryza sativa ; photosynthesis ; Pyricularia oryzae ; rice ; tolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effect of an inoculation with Pyricularia oryzae (isolate P06-6) on net leaf photosynthetic rate of rice (Oryza sativa) was studied with four cultivars. Measurements were taken on the sixth leaf of the main culm of plants in the early tillering stage. On cultivars CO39, IR50 and IR64 a susceptible infection type developed, but a clear difference in relative infection efficiency of the cultivars was observed. The highest number of lesions developed on leaves of CO39, whereas the lowest number was found on leaves of IR64. For all three cultivars the effect of a single lesion on the reduction in net leaf photosynthetic rate was found to be equal to a reduction in leaf area of three times the area occupied by the visible lesion. On IR68, a cultivar with complete resistance, brown specks of pinpoint size appeared without any effect on net leaf photosynthetic rate.
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    URL: http://dx.doi.org/10.1007/BF00023511
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  • 87
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    How various factors influence the CO2/O2 specificity of ribulose-1,5-bisphosphate carboxylase/oxygenase (1992)
    Springer
    Photosynthesis research 31 (1992), S. 157-164 
    Details
    ISSN: 1573-5079
    Keywords: Chlamydomonas reinhardtii ; chloroplast mutations ; enzyme catalysis ; photorespiration ; photosynthesis ; protein engineering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Temperature, activating metal ions, and amino-acid substitutions are known to influence the CO2/O2 specificity of the chloroplast enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase. However, an understanding of the physical basis for enzyme specificity has been elusive. We have shown that the temperature dependence of CO2/O2 specificity can be attributed to a difference between the free energies of activation for the carboxylation and oxygenation partial reactions. The reaction between the 2,3-enediolate of ribulose 1,5-bisphosphate and O2 has a higher free energy of activation than the corresponding reaction of this substrate with CO2. Thus, oxygenation is more responsive to temperature than carboxylation. We have proposed possible transition-state structures for the carboxylation and oxygenation partial reactions based upon the chemical natures of these two reactions within the active site. Electrostatic forces that stabilize the transition state of the carboxylation reaction will also inevitably stabilize the transition state of the oxygenation reaction, indicating that oxygenase activity may be unavoidable. Furthermore, the reduction in CO2/O2 specificity that is observed when activator Mg2+ is replaced by Mn2+ may be due to Mg2+ being more effective in neutralizing the negative charge of the carboxylation transition state, whereas Mn2+ is a transition-metal ion that can overcome the triplet character of O2 to promote the oxygenation reaction.
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    URL: http://dx.doi.org/10.1007/BF00028792
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  • 88
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    Dark inhibition of ribulose-1,5-bisphosphate carboxylase/oxygenase in legumes: A biosystematic study (1992)
    Springer
    Photosynthesis research 32 (1992), S. 37-44 
    Details
    ISSN: 1573-5079
    Keywords: photosynthesis ; 2-carboxyarabinitol 1-phosphate ; Fabaceae ; genetic variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 2-carboxyarabinitol 1-phosphate (CA 1-P) is a naturally occurring inhibitor of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). Members of the Fabaceae exhibit a particularly wide range in the extent of CA 1-P accumulation during darkness and include Phaseolus vulgaris, whose dark/light regulation of Rubisco activity is principally achieved by synthesis/degradation of CA 1-P. An extensive survey of the degree of dark inhibition of Rubisco was undertaken for the subfamily Papilionoideae to elucidate evolutionary patterns in the occurrence of this regulatory mechanism. Seventy-five species from 21 tribes were examined. Dark inhibition of Rubisco was found in ancestral tribes such as the Sophoreae, but was substantially reduced or absent in representative species of three more recently evolved tribes, Cicereae, Hedysareae and Vicieae. We conclude that regulation of Rubisco by CA 1-P is neither of recent origin nor of restricted distribution among the Papilionoideae. On the contrary, it becomes lost or less pronounced only in a minority of the more evolutionarily advanced species in this important subfamily.
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    URL: http://dx.doi.org/10.1007/BF00028796
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    Photosystem I cyclic electron transport: Measurement of ferredoxin-plastoquinone reductase activity (1992)
    Springer
    Photosynthesis research 34 (1992), S. 409-418 
    Details
    ISSN: 1573-5079
    Keywords: PS I cyclic electron transport ; ferredoxin-plastoquinone reductase ; antimycin ; ferredoxin-NADP reductase ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Absorbance changes of ferredoxin measured at 463 nm in isolated thylakoids were shown to arise from the activity of the enzyme ferredoxin-plastoquinone reductase (FQR) in cyclic electron transport. Under anaerobic conditions in the presence of DCMU and an appropriate concentration of reduced ferredoxin, a light-induced absorbance decrease due to further reduction of Fd was assigned to the oxidation of the other components in the cyclic pathway, primarily plastoquinone. When the light was turned off, Fd was reoxidised and this gave a direct quantitative measurement of the rate of cyclic electron transport due to the activity of FQR. This activity was sensitive to the classical inhibitor of cyclic electron transport, antimycin, and also to J820 and DBMIB. Antimycin had no effect on Fd reduction although this was inhibited by stigmatellin. This provides further evidence that there is a quinone reduction site outside the cytochrome bf complex. The effect of inhibitors of ferredoxin-NADP+ reductase and experiments involving the modification of ferredoxin suggest that there may be some role for the reductase as a component of FQR. Contrary to expectations, NADPH2 inhibited FQR activity; ATP and ADP had no effect.
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    URL: http://dx.doi.org/10.1007/BF00029815
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    A photoacoustic study of water infiltrated leaves (1992)
    Springer
    Photosynthesis research 33 (1992), S. 37-50 
    Details
    ISSN: 1573-5079
    Keywords: energy storage ; photosynthesis ; induction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photoacoustic measurements of photosynthetic energy storage were conducted on water infiltrated pea and sugar maple leaves. The samples were vacuum infiltrated with pure water or with a suitable buffer. The use of such methodology permitted an accurate determination of the energy storage parameter at low modulation frequencies, where in non-infiltrated leaves oxygen evolution dominates the photoacoustic signal and does not allow energy storage measurements. Differences between infiltration media were not essential, however the use of pure water as infiltration medium sometimes caused instability of the measured energy storage, particularly at longer experimental time. Values of energy storage in individual samples ranged mostly between 0.2 to 0.35. Measured as a function of the modulation frequency, energy storage was found to be constant from about 10 to 200 Hz for pea leaves. In sugar maple leaves, the energy storage slightly increased between 100 and 500 Hz. Obtaining an accurate value for energy storage also allowed an accurate estimation of the O2 evolution contribution to the photoacoustic signal of an unfiltrated leaf. In a maple leaf its frequency dependence showed only the effect of diffusion in the entire frequency range (10–500 Hz). Energy storage transients were observed after long periods (ca. 1/4-2 hrs) of dark adaptation upon the transition to light. In this case the initial energy storage was roughly about 1/2 that of the steady state value indicating strong PS I activity, while PS II was transiently incompetent. Energy-storage increased during illumination in a way to correspond to photosynthetic induction events as previously measured by fluorescence and O2 evolution. Transients in energy storage were also found following high light to low light transitions (i.e., switch off of the saturating background light), that paralleled similar transients in oxygen evolution, showing initial transient inactivation followed by progressive reactivation of PS II.
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    URL: http://dx.doi.org/10.1007/BF00032981
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    On the relationship between the quantum yield of Photosystem II electron transport, as determined by chlorophyll fluorescence and the quantum yield of CO2-dependent O2 evolution (1992)
    Springer
    Photosynthesis research 33 (1992), S. 51-62 
    Details
    ISSN: 1573-5079
    Keywords: chlorophyll fluorescence ; quantum yield ; quenching ; photosynthesis ; Photosystem II
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We tested the two empirical models of the relationship between chlorophyll fluorescence and photosynthesis, previously published by Weis E and Berry JA 1987 (Biochim Biophys Acta 894: 198–208) and Genty B et al. 1989 (Biochim Biophys Acta 990: 87–92). These were applied to data from different species representing different states of light acclimation, to species with C3 or C4 photosynthesis, and to wild-type and a chlorophyll b-less chlorina mutant of barley. Photosynthesis measured as CO2-saturated O2 evolution and modulated fluorescence were simultaneously monitored over a range of photon flux densities. The quantum yields of O2 evolution (ØO2) were based on absorbed photons, and the fluorescence parameters for photochemical (qp) and non-photochemical (qN) quenching, as well as the ratio of variable fluorescence to maximum fluorescence during steady-state illumination (F'v/F'm), were determined. In accordance with the Weis and Berry model, most plants studied exhibited an approximately linear relationship between ØO2/qp (i.e., the yield of O2 evolution by open Photosystem II reaction centres) and qN, except for wild-type barley that showed a non-linear relationship. In contrast to the linear relationship reported by Genty et al. for qp×F'v/F'm (i.e., the quantum yield of Photosystem II electron transport) and ØCO2, we found a non-linear relationship between qp×F'v/F'm and ØO2 for all plants, except for the chlorina mutant of barley, which showed a largely linear relationship. The curvilinearity of wild-type barley deviated somewhat from that of other species tested. The non-linear part of the relationship was confined to low, limiting photon flux densities, whereas at higher light levels the relationship was linear. Photoinhibition did not change the overall shape of the relationship between qp×F'v/F'm and ØO2 except that the maximum values of the quantum yields of Photosystem II electron transport and photosynthetic O2 evolution decreased in proportion to the degree of photoinhibition. This implies that the quantum yield of Photosystem II electron transport under high light conditions may be similar for photoinhibited and non-inhibited plants. Based on our experimental results and theoretical analyses of photochemical and non-photochemical fluoresce quenching processes, we conclude that both models, although not universal for all plants, provide useful means for the prediction of photosynthesis from fluorescence parameters. However, we also discuss that conditions which alter one or more of the rate constants that determine the various fluorescence parameters, as well as differential light penetration in assays for oxygen evolution and fluorescence emission, may have direct effect on the relationships of the two models.
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    URL: http://dx.doi.org/10.1007/BF00032982
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    HPLC separation of catecholamines after derivatization with 9-fluorenylmethyl chloroformate (1992)
    Springer
    Chromatographia 33 (1992), S. 83-86 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Pre-derivatization ; Catecholamines ; 9-fluorenylmethyl chloroformate (FMOC-Cl)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Optimum conditions for the separation of 9-fluorenylmethyl chloroformate derivatized catecholamines by HPLC are described; three catecholamines (noradrenaline, adrenaline and dopamine) and an internal standard (epinine) were separated in less than 20 minutes under isocratic conditions. This method is 17 to 350 times more sensitive than electrochemical detection, depending on the test compounds. It has been applied to the analysis of catecholamines in urine. The sample was extracted by a metal-loaded silica prior to separation.
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    URL: http://dx.doi.org/10.1007/BF02276857
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    Preparation and determination of manganese(III) chlorophylls by reversed-phase high performance liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 567-570 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chlorophylls ; Manganese(III) chlorophylls
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Manganese chlorophylls have been synthesized by refluxing a mixture of pheophytins dissolved in acetone and manganese(II) acetate anhydride dissolved in glacial acetic acid. A good separation of manganese(III) chlorophylls has been attained by RP-HPLC using chemically bonded C18 silica as a stationary phase and methanol with 3% acetic acid as a mobile phase. An accurate and rapid HPLC method is described for the simultaneous determination of manganese(III) chlorophyll-a [Mn(III)-chl-a] and manganese(III) chlorophyll-b [Mn(III)-chl-b]. Tailing arising from dissociation of acetate ions is improved by addition of sodium acetate (5×10−3 M) to the mobile phase (acetone: methanol=90∶10, vol/vol). The analytical values obtained by the HPLC method are very close to the calculated contents in all samples, but those obtained by spectrophotometry are high because of the interferences from overlapping of absorption bands. In the proposed HPLC method the calibration graphs of Mn(III)-chl-a and Mn(III)-chl-b are linear in the concentration range 0–20 μg cm−3 with relative standard deviations (n=10) of 3.46% and 4.54%, respectively.
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    URL: http://dx.doi.org/10.1007/BF02262249
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    Liquid chromatographic separation of the anomers and isomers of 2′-deoxyuridine (1992)
    Springer
    Chromatographia 33 (1992), S. 571-574 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; 2′-Deoxyuridine ; Anomer separation ; Isomer separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A liquid chromatographic assay method was developed to separate 2′-deoxyuridine from its anomer and pentopyranosyl isomers. The influence of the pH of the mobile phase, the type of organic modifier and the column temperature on the chromatographic parameters was systematically investigated. Using a Hypersil C18 (5 μm) column at 10°C, the following mobile phase was found suitable: tetrahydrofuran −0.2 M potassium phosphate buffer pH 4.0-water (0.1∶5∶94.9, v/v).
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    Controlled-porosity glasses as alternative adsorbents to silica gel for HPLC (1992)
    Springer
    Chromatographia 33 (1992), S. 122-126 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Controlled-porosity glasses ; Correlation between silica and porous glass ; Hydrocarbons separations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The paper deals with the use of controlled-porosity glasses (CPGs) as adsorbents for HPLC. The physicochemical and chromatographic properties of small-pore CPGs are compared to the analogous properties of silica gels. The results show good correlation between them and suggest the possibility of application of CPGs as adsorbents for liquid chromatography.
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    URL: http://dx.doi.org/10.1007/BF02275891
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    Retention, enantioselectivity and enantiomeric elution order of propranolol and its ester derivatives on an alpha1-acid glycoprotein-bonded column (1992)
    Springer
    Chromatographia 33 (1992), S. 127-132 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral separation ; Alpha 1-acid glycoprotein-bonded column ; Propranolol ; Propranolol ester derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention, enantionselectivity and enantiomeric elution order of racemic propranolol (PP) and its ester derivatives (O-acetyl,-propionyl,-butyrul and-valeryl PP) on an α1-acid glycoprotein (AGP)-bonded column have been investigated by changing eluent composition (eluent pH, buffer concentration, type and content of organic modifier). The retention of these cationic solutes, PP and its ester derivatives, was influenced by eluent pH, ionic strength and organic modifier content. The enantioselectivity was dependent on eluent pH and type of organic modifier. Reversal of the enantiomeric elution order of ester derivatives of PP (O-propionyl-butyryl) and-valeryl PP) occurred around eluent pH 6–7. These results suggst that chiral recognition or binding properties may be altered by the change in eluent composition, espeically eluent pH and type of organic modifier.
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    The development and validation of a solid phase extraction/HPLC method for the determination of aflatoxins in groundnut meal (1992)
    Springer
    Chromatographia 33 (1992), S. 208-212 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Solid phase extraction ; Validation ; Aflatoxins in groundnut meal ; CB method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The efficiency of an analytical method for the determination of aflatoxins in groundnut meal has been statistically examined. The procedure consists of a phenyl bonded phase (PH) clean-up of an acetone: water (85∶15) extract followed by HPLC quantification. Average recoveries from spiked groundnut meal extracts were calculated to be 101.3% and 101.8%, with limits of detection of 7.4 and 2.62 μg/kg for aflatoxins-B1 and-B2 respectively. Higher recoveries of aflatoxin-B1 from naturally contaminated samples were recorded using the proposed procedure than those recorded using the official AOAC (CB) method although the precisions of the two methods were not found to differ at the 5% significance level. Similar recoveries of aflatoxin-B2 were recorded for both methods but the proposed procedure was found to be more precise. The proposed PH-HPLC method was far less time consuming and more economical on solvents than the CB procedure.
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    URL: http://dx.doi.org/10.1007/BF02276184
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    Preparation of octadecyl modified column gels using heat-treated silicas and their retention behaviour in high-performance liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 203-207 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Octadecyl modified silica ; Hexamethyldisilazane treated silica ; Calcination ; Heat-treated silica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The effect of silanol groups on three types of octadecylmodified column gels using heat-treated silicas by calcination has been studied by high-performance liquid chromatography. After heat-treating at 180°C, 500°C and 950°C, the silicas treated with octadecyldimethylchlorosilane were used for the measurement of physical and chemical analysis. From elemental carbon analysis data, the reactive silanol group concentrations, αOH(s), were determined to be 2.0 in the 180°C treated silica, 2.1 in the 500°C treated silica and 1.6 in the 950°C treated silica, respectively (original silica: mean pore diameter 116 Å, specific surface area 298 m2/g, pore volume 1.22 ml/g, particle size 5.0 μm). The separation factors, α, of pyridine versus phenol were measured to be 0.79 on 180°C treated silica, 0.91 on 500°C treated silica and 1.98 on 950°C treated silica, using acetonitrile-water mixtures as the eluent. And then, on the basis of the physico-chemical and chromatographic data, the three types of octadecyl modified column gels using heat-treated silicas by calcination have been compared.
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    URL: http://dx.doi.org/10.1007/BF02276183
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    Determination of chloride in biological fluids as pentafluorobenzylchloride by reversed-phase high-performance liquid chromatography and UV detection (1992)
    Springer
    Chromatographia 33 (1992), S. 317-320 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; UV detection ; Pentafluorobenzyl chloride by UV detection ; Chloride in biological fluids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A reversed-phase high-performance liquid chromatographic method for the determination of chloride in plasma, urine, saliva, sweat and aqueous solution is described. Chloride, in solution in aqueous acetone, is converted by means of pentafluorobenzyl bromide into pentafluorobenzyl chloride. This derivative is separated on a ODS-5 μm reversed-phase column using isocratic elution with acctonitrile/water, 50/50, v/v, at a flow rate of 2.0 ml/min, and detected by a UV detector at 264 nm. The method is rapid, accurate and sufficiently sensitive for the determination of chloride in less than 10 μl sample volume of a biological fluid.
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    URL: http://dx.doi.org/10.1007/BF02275909
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    Liquid chromatography of carbon clusters (1992)
    Springer
    Chromatographia 33 (1992), S. 344-346 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Charge-transfer chromatography ; Carbon clusters ; Fullerenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A comparison of three binary mobile phases in LC separation of C60 and C70 fullerences on chemically bonded 2,4-dinitroanilinopropyl (DNAP) stationary phase was carried out, n-Hexane-benzene has been found to be the best mobile phase for efficient separation of the all-carbon molecules permitting high loads in preparative LC.
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    URL: http://dx.doi.org/10.1007/BF02275915
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