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  • Chemical Engineering
  • Column liquid chromatography
  • Springer  (1,217)
  • American Association for the Advancement of Science (AAAS)  (5)
  • Elsevier  (1)
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  • 101
    Electronic Resource
    Electronic Resource
    Correlation between the chromatographic poperties of silica phenyl packing materials and the retention behaviour of methylated β-cyclodextrins (1998)
    Springer
    Chromatographia 47 (1998), S. 383-390 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Stationary phase characterization ; Silica packing materials ; Cyclodextrins ; Partially methylated β-cyclodextrins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The chromatographic properties of five columns packed with phenyl-bonded phases were characterized by an approach based on Tanaka's method for column to column comparisons in order to develop an LC analysis of partially methylated β-cyclodextrins. The retention behaviour of β-cyclodextrin, heptakis(2,6-di-O-methyl)-β-cyclodextrin and heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin was examined in order to evaluate the different interactions between phenyl stationary phase and this family of compound. Chromatograms show that the residual silanol activity of the packing materials plays a beneficial role in the partially methylated β-cyclodextrins separation process. It is concluded that knowledge of the interactions involved allows one to make a reasoned choice of the stationary phase in order to obtain the best possible analysis of three different commercial samples of partially methylated β-cyclodextrins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466468
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  • 102
    Electronic Resource
    Electronic Resource
    Rapid determination of ranitidine in human plasma by high-performance liquid chromatography (1998)
    Springer
    Chromatographia 47 (1998), S. 391-395 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ranitidine ; Plasma ; Pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An HPLC method has been developed for the quantification of rantidine in plasma for pharmacokinetic studies. Metoclopramide was used as internal standard. The method uses a simple and rapid sample clean-up procedure involving single-step extraction with organic solvent to extract ranitidine from plasma. After evaporation and reconstitution the samples are chromatographed on a 250 mm×4 mm base-stable reversed-phase column with 0.05 M ammonium acetate-acetonitrile, 75∶25 (v/v) as mobile phase and UV detection at 313 nm. The calibration graph was linear for quantities of ranitidine between 10 and 2000 ng mL−1. Intra- and inter-dayCV did not exceed 11.64%. The quantitation limit was 10 ng mL−1 for human plasma. The applicability of this method for pharmacokinetic studies of ranitidine after oral administration are described. Approximately 90 samples can be processed in 24 h.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466469
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  • 103
    Electronic Resource
    Electronic Resource
    A new validated high-performance liquid chromatographic method for the determination of EGIS-9933 in rat plasma (1998)
    Springer
    Chromatographia 48 (1998), S. 158-162 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; EGIS-9933 ; Solid phase extraction ; Rat plasma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new highly sensitive high-performance liquid chromatographic (HPLC) procedure for determination of EGIS-9933 (a newly developed anxiolytic compound) in rat plasma is described. A gradient, elution method with UV detection at 270 nm has been developed using a mobile phase of a mixture of A: methanol:acetonitrile 1:9 and B:0.5% triethilamine in water, the pH of B was adjusted to 3 with phosphoric acid. Solid phase extraction (SPE) was used for the sample preparation. The calibration was linear in the 10–10000 ng mL−1 concentration range. The limit of quantification was 10 ng mL−1. The bioanalytical method was validated according to internationally accepted criteria for biological samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467535
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  • 104
    Electronic Resource
    Electronic Resource
    Ion-pair HPLC determination of biogenic amines and precursor aminoacids. Application of a method based on simultaneous use of heptanesulphonate and octylamine to some foods (1998)
    Springer
    Chromatographia 48 (1998), S. 763-769 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion-pair chromatography ; Food related-biogenic amines ; Heptanesulphonate ; Octylamine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An ion-pair HPLC method based on the simultaneous use of heptanesulphonate and octylamine has been considered with the aim of optimizing the separation of four food-related biogenic amines (histamine, tyramine, 2-phenylethylamine and tryptamine) and related precursor aminoacids. On changing the eluant pH from 2.70 to 3.20 the capacity factor of precursor aminoacids decreased and those of the biogenic amines increased; pH 3 allowed an optimal separation. An increase of phosphate content, from 6.0 mM to 12.0 mM, shortened the capacity factors. The addition of octylamine to the eluant reduced the peak asymmetry (especially for histamine from 3.20 to 1.69). Some samples of cheese showed a concentration of total amines up to 1284.8 mg L−1; wines and beers showed a very similar total content, ranging from 0.5 mg L−1 to 27.2 mg L−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467645
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  • 105
    Electronic Resource
    Electronic Resource
    Supercritical fluid extraction of bile acids from bovine bile raw materials (1998)
    Springer
    Chromatographia 48 (1998), S. 785-789 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography-mass spectrometry ; Column liquid chromatography ; Supercritical fluid extraction ; Bile acids ; Bovine bile hydrolysates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The use of supercritical fluid extraction (SFE) as an alternative to conventional liquid extraction has been investigated to conventional liquid extraction has been investigated for the isolation of bile acids (cholic acid, deoxycholic acid and chenodeoxycholic acid) from the solid material obtained by bovine bile hydrolysis. Initial studies indicated that bile acids are not soluble in supercritical CO2, consequently the addition of the polar modifier methanol to the CO2 extracting fluid was evaluated. Quantitative recoveries (〉88.5%) were obtained for the bile acids in 20 min with 15% (v/v) methanol in CO2 at 220 atm and 70°C. A comparison of SFE with pyridine extraction was performed on samples of hydrolyzed crude bovine bile. The SFE method yielded recoveries higher than 82.7% compared with conventional liquid extraction. Moreover, SFE minimized sample handling, reduced the consumption of harmful solvents and provided conditions suitable for selective extractions of bile acids from bovine bile raw materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467648
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  • 106
    Electronic Resource
    Electronic Resource
    Enantiomeric resolution of melatonin ligands receptors by liquid chromatography on amylose chiral stationary phases (1998)
    Springer
    Chromatographia 48 (1998), S. 790-796 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral-enantiomeric separation ; Amylose-based chiral phases ; Melatonin analogues ; Tetrahydronaphthalenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Analytical HPLC methods using derivatized amylose chiral stationary phases were developed for the resolution of enantiomers of methoxy an ethyl tetrahydronaphthalenic derivatives, new agonist and antagonist ligands for melatonin receptors. Separation was by normal phase methodology with a mobile phase ofn-hexane-alcohol (methanol, ethanol, 1-propanol or 2-propanol) in various proportions, and a silica-based, amylose tris-(S)-1-phenylethylcarbamate (Chiralpak AS), or tris-3,5-dimethylphenylcarbamate (Chiralpak AD). The mobile phase and the chiral stationary phase were optimized for best resolution. The effects of concentration of alcohol, various aliphatic alcohols in the mobile phase were studied. The effects of substitution were analysed. Baseline separation (Rs〉1.5) was easily obtained in man cases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467649
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  • 107
    Electronic Resource
    Electronic Resource
    Analysis of cannabinoids in fiber hemp plant varieties (Cannabis sativa L.) by high-performance liquid chromatography (1998)
    Springer
    Chromatographia 48 (1998), S. 215-222 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Neutral and acidic cannabinoids ; Fiber hemp plants ; Cannabis accessions and environmental conditions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An analytical procedure was developed for the detection of neutral and acidic cannabinoids in herbal cannabis without the need of any preliminary derivatization. The method was used to assay cannabinoid content of over one hundred fiber hemp samples grown in different Italian localities and harvested at different maturation level degrees during the summer. No interferences were observed due to the vegetal matrix. The influence of genetic factors and environmental conditions on cannabinoid content is discussed; the results may be of interest to enhance potential of fiber hemp in compliance with law enforcement purposes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467674
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  • 108
    Electronic Resource
    Electronic Resource
    An improved analytical method for determination of heterocyclic amines in chicken legs (1998)
    Springer
    Chromatographia 48 (1998), S. 223-230 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Heterocyclic amines ; Chicken legs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Several extraction, separation and detection methods for heterocyclic amines (HAs) in chicken legs were evaluated by liquid chromatography. Results showed that the most appropriate extraction method includes the removal of macrosubstances by centrifugation and subsequent purification using a PRS (propylsulfonic acid silica gel) and a C18 cartridge, and the recovery obtained ranged between 51 and 89 %. For HPLC separation, a binary solvent system consisting of acetonitrile and 0.05 M ammonium acetate solution (pH 3.6) with gradient elution with flow rate of 1.0 mL min−1 and detection at 258 nm was used to resolve 16 HAs. With fluorescence nine HAs could be detected by employing a programmable wavelength, and the sensitivity was 100–400 times higher than that by UV detection. The detection limits for UV and fluorescence detection were 0.02≈0.5 ng and 0.05≈3 pg respectively, with a signal-to-noise ratio 3. The presence of HAs in fried chicken legs was also determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467675
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  • 109
    Electronic Resource
    Electronic Resource
    Preparation and characterization ofp-tert-butyl-calix[6]arene-bonded silica gel stationary phase for high-performance liquid chromatography (1998)
    Springer
    Chromatographia 48 (1998), S. 245-250 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Calix[6]arene ; Positional isomers ; PAHs ; Nucleosides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary For the first time calix[6]arene has been chemically combined with silica gel via a longer spacer to prepare calix[6]arene-bonded silica gel stationary phase for high-performance liquid chromatography (HPLC). The separation of positional isomers and polycyclic aromatic hydrocarbons on the calix[6]arene-bonded phase was achieved with methanol-water as mobile phase. Some nucleosides were also separated on the bonded phase. The reversed-phase chromatographic performance of the bonded phase was studied. The results showed that the calix[6]arene-bonded phase was highly hydrophobic. A possible separation mechanism has been proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467678
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  • 110
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    Evidences for temperature-dependent mechanism of host-guest complexation (1998)
    Springer
    Chromatographia 48 (1998), S. 377-382 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Host-guest complexation ; Temperature effects ; Cyclodextrin inclusion complexes ; Polycyclic aromatics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary High-performance liquid chromatography and ultraviolet spectroscopy methods were applied to the studies on the influence of temperature on the complexation of β-cyclodextrin with naphthalene and its derivatives. The strong nonlinearity of Van't Hoff plots suggests, that the retention mechanism of hydrocarbons investigated might be different in high and low temperature region. The total lack of correlation (r=−0.230) between chromatographic data (capacity factors ratio:k PAH/k PAH×CD) and spectrophotometric data (ΔA) at high temperature (60°) as well as a significant correlation (r=0.922) at subambient temperature (15°C) suggest, that the inclusion mechanism starts to be important at low temperature region and the predominant mechanism for chromatographic retention is the formation of an inclusion complexes in the mobile phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467707
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  • 111
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    Extraction of polypropylene additives and their analysis by HPLC (1998)
    Springer
    Chromatographia 48 (1998), S. 491-496 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Polypropylene additives ; Extraction methods ; Antioxidants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The polypropylene additives were extracted by dissolution-precipitation and Soxhlet. The Soxhlet method was adapted for the extraction of phosphorous antioxidants. The RP HPLC method with quaternary gradient elution separated five chemical groups of additives: lower molecular mass di-tert-butyl phenol (D.T.B.P.), hindered amine light stabilizers (Tinuvin 326), hindered phenolic antioxidants (Irganox 1010) and phosphorous antioxidants (Irgafos 168 and Ultranox 626) with their degradation products.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466639
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  • 112
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    Synthesis and characterization of long chain alkyl stationary phases on a silica hydride surface (1998)
    Springer
    Chromatographia 48 (1998), S. 631-636 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Synthesis of new phases ; Evaluation of new phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary C22 and C30 alkyl chains were attached to a silica hydride surface by a hydrosolation reaction. In each case both moieties were successfully bonded by either metal complex catalysis or free radical initiation. Carbon analysis, DRIFT spectra and13C CP-MAS NMR spectra confirm the bonding of the olefin to silica hydride. Conditions for maximum coverage were determined by a simplex procedure. Chromatographic evaluation of these long chain bonded phases was accomplished by separations of several types of mixtures: alkyl substituted benzenes; polycyclic aromatic hydrocarbons; carotenoids, tocopherols; tricyclic antidepressants; and peptides. The C30 column proved significantly better for separating the carotenoid and antidepressant mixtures and somewhat better for the peptide sample.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467592
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  • 113
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    A modified HPLC method for analysis of PSP toxins in algae and shellfish from china (1998)
    Springer
    Chromatographia 48 (1998), S. 671-676 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Paralytic shellfish poisoning (PSP) ; Alexandrium tamarense
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Improvements to an established HPLC method are introduced. The modified method is more efficient for separation and detection of the toxins reponsible for paralytic shellfish poisoning (PSP). The PSP toxin cotent of two strains ofAlexandrium tamarense and approximately forty shellfish samples collected from different locations in China have been analyzed with this HPLC method. Only one shellfish sample, collected from Lianyungang, China, contained PSP toxins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467597
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  • 114
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    Determination of reduced-form glutathione and total glutathione in blood and plasma by high performance liquid chromatography with on-column fluorescence derivatization (1998)
    Springer
    Chromatographia 48 (1998), S. 690-694 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; On-column fluorescence derivatization ; Blood and plasma ; Glutathione ; ortho-Phthalaldehyde
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An on-column fluorometric derivatization method has been developed for the determination of reduced-form glutathione and total glutathione in blood and plasma by high-performance liquid chromatography. Blood hemolysate or diluted plasma was deproteinized with percholoric acid. For total glutathione determination, any oxidized forms of glutathione in samples were converted to reduced-form glutathione with dithiothreitol prior to protein precipitation. Deproteinized samples were injected without pretreatment. Glutathione was fluorescence-derivatized and separated on a C18-bonded vinyl alcohol polymer column withortho-phthalaldehyde in sodium borate buffer-acetonitrile, as mobile phase; theortho-phthalaldehyde-glutathione, fluorescent isoindole adduct is measured by its fluorescence response. Due to the high sensitivity, selectivity reproducibility and the simple HPLC system, the method is particularly suitable for routine assay of numerous or small amounts of samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467600
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  • 115
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    Survey of concentration of polycyclic aromatic hydrocarbons in lake balaton by HPLC with fluorescence detection (1998)
    Springer
    Chromatographia 48 (1998), S. 149-153 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Polycyclic aromatic hydrocarbons ; Lake Balaton ; Water and sediment samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Concentrations of polycyclic aromatic hydrocarbons (PAHs) were determined in water and sediment samples at 15 sites in Lake Balaton during three sampling campaigns in 1996. PAHs were concentrated from water samples by solid phase extraction. Sediment samples were extracted with acetone in an ultrasonic bath then cleaned by solid phase extraction. The total concentration of PAHs ranged from 30–360 ng g−1 and from 170–720 ng L−1 in sediment and water samples, respectively. Spatial and temporal variations of the concentration of PAHs were also investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467532
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  • 116
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    A simple model for RPLC retention and selectivity of imidazole enantiomers using β-cyclodextrin as chiral selector (1998)
    Springer
    Chromatographia 48 (1998), S. 388-394 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Imidazole derivatives ; β-Cyclodextrin ; Enantioselectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Using reversed phase liquid chromatography (RPLC), this paper investigates the enantioselectivity variations, in a series of weak polar R, S-imidazole derivatives, with β-cyclodextrin concentration in the mobile phase over a wide range of column temperatures. These compounds are used for the treatment of onychomycosis. The selectivity data obtained were assessed using a chiral recognition model, based on the formation of complexes between the solute molecule and the cyclodextrin cavity. Gibbs Helmholtz parameters (Δ(ΔH), Δ(ΔS)) between R- and S- enantiomers were determined from the logarithm of the separation factor, α, versus the reciprocal of the temperature plots. The thermodynamic results predicted that the enantioselectivity mechanism was related to both the solute's bulkiness and the asymmetric carbon atom configuration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467709
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  • 117
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    Ion-exchange chromatography with an oxalic acid-α-hydroxyisobutyric acid eluent for the separation and quantitation of rare-earth elements in monazite and xenotime (1998)
    Springer
    Chromatographia 48 (1998), S. 407-414 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion-exchange ; Rare-earth elements ; Monazite ; Xenotime
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An oxalic acid-α-hydroxyisobutyric acid eluent has been used for the separation and determination of rare-earth elements by high-performance ion-exchange chromatography. Fifteen rare-earth elements were separated within less than 25 min on a 150×4.6 mm i.d. column packed with 5-μm sulfonic acid-bonded silica particles by elution with a combined gradient of 0.60–9.0 mM oxalic acid and 19.0–5.0 mM α-hydroxyisobutyric acid at pH 4.6. Detection and quantitation of the separated rare-earth elements was accomplished by visible-absorbance measurements at 600 nm after postcolumn reaction with arsenazo I. The gradient of the two complexing agents was optimized to enable the separation of yttrium(III) without interference from other elements, especially dysprosium(III) and terbium(III). Mass detection limits of the elements were in the range of 2–4 ng. Finally, the chromatographic system was applied to the quantitative analysis of rare-earth elements in monazite and xenotime.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467712
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  • 118
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    Potential of short-column liquid chromatography with tandem mass spectrometric detection for the rapid study of pesticide degradation (1998)
    Springer
    Chromatographia 48 (1998), S. 475-480 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Short-Column LC ; Environmental water samples ; MS-MS detection ; Pesticide degradation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The applicability of solid-phase extraction-LC using two short columns (SPE-LC) and/or single-short-column liquid chromatography (SSC) combined on-line with tandem mass spectrometry (MS) was demonstrated for the rapid study of pesticide degradation. A fast analytical procedure was developed to provide preliminary information concerning experimental conditions, approximate rates of degradation and identity of the degradation products. Surface water samples were spiked at relevant concentration levels with well-known microcontaminants and photolysis was used to transform parent compounds into their degradation products. In general, the strategy was as follows: at 30-min intervals 10-mL samples were on-line enriched, separated by short-column LC and recorded in full-scan MS to obtain information on the disappearance of the parent compound and the appearance of breakdown products. To obtain structural information, product-ion spectra of selected compounds appearing in the full-scan MS chromatogram were recorded; this enabled the identification of several degradation products. Total analysis time of enrichment/separation and detection was about 10–15 min.
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    URL: http://dx.doi.org/10.1007/BF02466637
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  • 119
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    Simultaneous determination of base/neutral and acid herbicides in natural water at the part per trillion level (1998)
    Springer
    Chromatographia 48 (1998), S. 497-505 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; MS detection ; Trace herbicides ; Natural waters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new method for the simultaneous identification and quantification of base/neutral and acidic pesticides at a low nanogram per liter concentration level in natural waters is presented. The method includes enrichment of the compounds by solid phase extraction on graphitized carbon black, followed by sequential elution of the base/neutral and acidic pesticides. Identification and quantification of the compounds is performed with HPLC-ESI-MS. This procedure involves passing 1 L of ground water and 2 L of drinking water samples through a 0.5 g graphitized carbon black (GCB) extraction cartridge. A conventional 4.6-mm-i.d. reversed phase LC C-18 operating with a 1 mL min−1 flow of the mobile phase was used to chromatograph the analytes. A flow of 100 μL min−1 of the column effluent was diverted to the ESI source. The ESI source was operated in positive ion mode for base/neutral pesticides and in negative-ion mode for acid pesticides. For the analyte considered, the response of the mass detector was linearly related to the amount of the analytes injected between 5 and 250 ng. In all cases, recoveries of the analytes were better than 90%. The limit of detection (signal-to-noise ratio=3) of the method for the pesticides considered in drinking water samples was estimated to be about 3–10 ng L−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466640
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  • 120
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    Determination of alkylphenols in water samples by solid-phase extraction on to poly(styrene-divinylbenzene) and quantification by liquid chromatography with UV-detection (1998)
    Springer
    Chromatographia 48 (1998), S. 707-713 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Solid-phase extraction ; Alkylphenols in water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method for determination of alkylphenols in water samples has been developed and validated. The alkylphenols were extracted on to polystyrene solid-phase columns. Six replicates could be processed in parallel in approximately 30 min using home-made equipment. Quantification was performed by reversed-phase liquid chromatography with UV-detection at 278 nm. The method has been validated for determination of 4-n-hexylphenol, 4-tert-octylphenol and nonylphenol in the concentration range 1–100 μg L−1 with 4-n-heptylphenol and/or 4-n-octylphenol as internal standard(s). The repeatability of the method was 1–6%RSD, and the intermediate precision was 1–3%RSD at the 100 μg L−1 level. The accuracy, determined as recovery, was 98–104%. The limit of detection (LOD) was 0.1–0.2 μg L−1 for 1-L water samples. The method has been used for determination of alkylphenols in samples of aquarium water.
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    URL: http://dx.doi.org/10.1007/BF02467603
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  • 121
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    Study of the influence of electronic effects on the retention of substitutedN-benzylideneanilines in normal-phase liquid chromatography (1998)
    Springer
    Chromatographia 47 (1998), S. 164-170 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; N-Benzylideneanilines ; Hierarchical ascending classification ; Correspondence factor analysis ; Electronic effects ; Quantitative structure-retention relationships
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A series of 72 substitutedN-benzylideneanilines (NBA) has been studied by normal-phase liquid chromatography by use of an experimental design based on variation of the composition of mobile phases prepared from heptane and three modifiers, tetrahydrofuran, 1-octanol and ethyl acetate, for each of which the specific interactions are different. Seven mobile phases were defined in the experimental design. The chromatographic data obtained are used to discuss the behavior of NBA by application of complementary chemometric methods—hierarchical ascending classification (HAC) and correspondence factor analysis (CFA). Although solute polarity has the greatest effect on retention, construction of HAC and CFA plots shows that solute behavior is also influenced by second-order electronic effects arising as a result of specific interactions between the solutes and the different modifier solvents. A quantitative structure-retention relationship has been established between Hammett's constants and the solutes projection on the first factorial axis of CFA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466576
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  • 122
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    Interlaboratory study of analysis of phenoxymethylpenicillin by liquid chromatography (1998)
    Springer
    Chromatographia 47 (1998), S. 152-156 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Phenoxymethylpenicillin ; Collaborative study
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A liquid chromatography method for analysis of phenoxymethylpenicillin has been examined in a collaborative study involving 6 laboratories. The method comprised an isocratic part, which is used in the assay. When the isocratic part is combined with gradient elution, the method is suitable for purity control. Five samples of phenoxymethylpenicillin (potassium salts and acid) were analysed. The main component, the most important side product 4-hydroxyphenoxymethyl-penicillin and other impurities were determined. An analysis of variance proved the absence of consistent laboratory bias. Laboratory-sample interaction was not significant. Estimates of the repeatability and reproducibility of the method, expressed as standard deviations (SD) of the result of the determination of phenoxymethylpenicillin, were 0.50 and 0.63 respectively.
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    Bile acids as stationary phase in liquid chromatography (1998)
    Springer
    Chromatographia 47 (1998), S. 183-188 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Bile acid aggregates as stationary phase ; Enantiomeric separation ; 1,1′-Binaphthyl-2,2′-diyl-hydrogenphosphate enantiomers ; Dansyl amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Bile acids chemically bonded onto aminopropylsilica have been employed as stationary phases in liquid chromatography. Bile acid aggregates were dynamically formed around molecules chemically anchored on the supports when the eluent contained bile salts. The bile salt aggregates achieved the separation of 1,1′-binaphthyl-2,2′-diyl-hydrogenphosphate enantiomers and dansyl amino acids.
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    The chromatographic behavior of arsenic compounds on anion exchange columns with binary organic acids as mobile phases (1998)
    Springer
    Chromatographia 47 (1998), S. 257-263 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion exchange chromatography ; Anion-exchange chromatography ; Arsenic compounds ; Flame atomic absorption detector
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Identification and quantification of arsenic compunds was performed with high- performance liquid chromatography (HPLC) and flame atomic absorption spectrometry (FAAS) as element-specific detector. Arsenous acid, methylarsonic acid, dimethylarsinic acid, arsenic acid, arsenobetaine, and arsenocholine were separated on two anion-exchange columns (Synchropak Q 300 and PRP-X 100) with different binary organic acids as mobile phases. The infleunce of chromatographic parameters, such as pH and the concentration of the mobile phase were investigated. An unusual chromatographic behavior of arsenous acid was observed when tartaric acid was used as mobile phase.
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    URL: http://dx.doi.org/10.1007/BF02466529
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    Retention study on silica gel in high-temperature liquid chromatography (HTLC) (1998)
    Springer
    Chromatographia 47 (1998), S. 278-284 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; High-temperature columns ; Retention behavior ; Column equilibration ; Bilayer formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention volumes (V N) of different kinds of test compound have been measured on silica gel as a function of column temperature (T) in the range 20 to 210°C.n-Heptane and mixtures ofn-heptane and polar modifiers were used as mobile phases. With nC7 and nC7-1,4-dioxane mixtures, there was a good linear relationship between InV N and 1/T for column temperatures above 100 °C. When more polar modifiers such as butanol, ethanol and acetic acid were used, ‘N’-shaped curves were obtained for the plots of InV N against 1/T. Possible explanations of this retention behavior have been proposed on the basis of related studies and common physical chemistry relationships. Column equilibration time after alteration of water content or column temperature is greatly reduced at elevated temperatures. This will benefit the application of LSC on silica gel.
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    Highly selective antibody-mediated extraction of isoproturon from complex matrices (1998)
    Springer
    Chromatographia 47 (1998), S. 453-456 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Affinity chromatography ; Selectivity and capacity ; Isoproturon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary For the analysis of pesticides such as isoproturon in complex matrices the rate determining step is sample preparation. A novel solid-phase extraction system for isoproturon based on antibody mediated extraction has been developed. The isoproturon can be retained while the immuno-extraction column is washed with phosphate buffered saline and eluted using phosphate buffered saline/ethanol at low pH. The column can preconcentrate isoproturon from up to at least 1000 mL water and elute in 1 mL. Quantitative recovery of isoproturon from water, plasma and urine can be obtained and the proposed water assay can detect as low as 50 ng L−1 with a 50 mL sample, or 5 ng L−1 with a 1 L sample.
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    URL: http://dx.doi.org/10.1007/BF02466480
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    Porous copolymer of the methacrylic ester of dihydroxydiphenylmethane diglycidyl ether and divinylbenzene as an HPLC packing (1998)
    Springer
    Chromatographia 47 (1998), S. 509-514 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous copolymers with hydroxyl groups ; Chemical modification of phases ; Selectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Dimethyldichlorosilane has been used to deactivate the hydroxyl groups present in the skeleton of the porous polymer formed from the methacrylic ester ofp, p′-dihydroxydiphenylmethane diglycidyl ether and divinylbenzene. The influence of chemical modification of the copolymer on its chromatographic behavior has been studied. The retention indices of five homologous series and test compounds were calculated to determine the selectivity of the packings.
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    Analysis of anka pigments by liquid chromatography with diode array detection and tandem mass spectrometry (1998)
    Springer
    Chromatographia 47 (1998), S. 529-536 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Thin layer chromatography ; Mass spectrometry detection ; Anka pigments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Anka is withMonascus sp. fermented rice, which shows a purplish red color. On rice grainsMonascus purpureus DSM 1379 synthesized four anka pigments. Through extraction of anka with n-hexane and methanol in succession and through repeated crystallizations from absolute ethanol anka pigments were crystallized into two fractions: organge anka pigments (rubropunctatin and monascorubrin) and yellow anka pigments (monascin and ankaflavin). The treatment of two organge anka pigments with aqueous ammonia solution gave red nitrogen analogues (rubropunctatamine and monascorubramine). The above six pigments were separated into each pigment by two dimensional thin layer chromatography (TLC) or high performance liquid chromatography (HPLC). HPLC-atmospheric pressure chemical ionization-tandem mass spectrometry (HPLC-APCI-MS-MS) and direct probe mass spectrometry (MS) were used to identify these pigments. HPLC-diode array detector (HPLC-DAD) was used to determine UV-VIS spectra of pigments. Pigments were analyzed with HPLC under the following conditions: C18 column, acetonitrile/water (80∶20, v/v), 0.5 mL min−1, 233 nm.
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    Determination of nalbuphine hydrochloride, methylparaben, and propylparaben in nalbuphine hydrochloride injection by high performance liquid chromatography (1998)
    Springer
    Chromatographia 47 (1998), S. 515-522 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; 4,5-Epoxymorphinan ; Nalbuphine hydrochloride injection ; Stability assays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A stability-indicating liquid chromatographic method has been developed for the determination of nalbuphine hydrochloride, methylparaben, and propylparaben in nalbuphine hydrochloride injection. Reversed-phase chromatography was carried out using a mobile phase containing 0.05 % trifuoroacetic acid, acetonitrile, and tetrahydrofuran. Quantitation was achieved with UV detection at 280 nm. Validation data for linearity, accuracy, precision, specificity, and robustness are presented. The chromatographic system resolves nalbuphine from synthetic impurities and degradation products.
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    URL: http://dx.doi.org/10.1007/BF02467488
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    LC phases improve, but not all assays do: Metformin bioanalysis revisited (1998)
    Springer
    Chromatographia 47 (1998), S. 542-546 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Metformin analysis ; Stationary phase variability ; Validation of methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Two assay methods for the antidiabetic metformin, one developed and validated in 1990 and one developed and validated in 1996, are compared. The first method, using an octadecyl phase and an ion pairing agent in the eluent, could not be reproduced some five years later, but another method, using a phenyl phase and no ion pairing agent, could be successfully applied. This paper shows that the retention mechanism of the positively charged analyte is not due to ion-pair formation, as originally assumed, but to interaction with free silanol groups in the LC phase. It is suggested that the number of free silanol groups in octadecyl phases was strongly reduced between 1990 and 1996, whereas for phenyl phases this was not the case. For the second method, validation results on linearity, specificity, accuracy, precision, recovery and stability as well as application of the method to samples from a clinical trial are shown. The validated calibration range is from 20.0 to 2000 ng.mL−1, with accuracy (bias) and precision (coefficient of variation) being below 15% at all levels. Using automated solid-phase extraction for sample preparation, a sample throughput of typically 100 per day can be achieved.
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    URL: http://dx.doi.org/10.1007/BF02467492
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    The use of an optimized RP-HPLC system as a molecular probe in QSPR studies of selected lipid classes (1998)
    Springer
    Chromatographia 47 (1998), S. 643-648 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Quantitative structure retention relationships ; Quantitative structure properties relationships ; Phospholipids ; Molecular probe
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The results of this study show that an optimized RP-HPLC system, in conjunction with molecular mechanics, can be used as a molecular probe to study both configuration and conformation of molecular species of selected phospholipid classes. Specifically, for phosphatidylcholine 18∶0/16∶0, stearic acid is attached to thesn-1 position and palmitic acid is attached to thesn-2 position of the glycerol backbone, for phosphatidylcholine with two monounsaturated fatty acids, the monounsaturated fatty acid attached to thesn-1 position can fold itself backwards on itself, thus allowing van der Waals interaction. Furthermore, it was found in the retention modelling that configurational descriptors alone did not suffice but had to be augmented with conformational descriptors. Nonlinearities were also detected, which could be handled by using a hybrid neural network-PLS regression strategy.
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    Separation of lansoprazole enantiomers in human serum by HPLC (1998)
    Springer
    Chromatographia 47 (1998), S. 171-175 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Lansoprazole ; Enantiomers ; Human serum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new and simple HPLC method is described for the separation and quantitative determination of the (+)-and (−)-enantiomers of lansoprazole. The analytes were extracted from serum as previously described for whole lansoprazole [K. Borner, Chromatographia 45, 450–452 (1997)]. The enantiomers were separated by chromatography on a CHIRAL-AGPR column which contained covalently bound acid α1-glycoprotein as chiral selector. In the pure drug the (−)/(+) ratio was 0.99:1.01. In serum of twelve human volunteers the concentration of the (−)-enantiomer was 3 to 5 times higher than that of the (+)-enantiomer. Both enantiomers differ remarkably in their pharmacokinetics.
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    Determination of eleven priority EPA phenolics at ng L−1 levels by on-line solid-phase extraction and liquid chromatography with UV and electrochemical detection (1998)
    Springer
    Chromatographia 47 (1998), S. 176-182 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Electrochemical detection ; Phenolics in water ; On-line preconcentration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The eleven priority, EPA phenolic pollutants were determined by liquid chromatography followed by two detectors in series; UV and electrochemical. Three different adsorbents, Envi-Carb (a carbon black) and two functionalized polymeric resins, Bond Elut PPL and another synthesized in our laboratory with an ocarboxybenzoyl moiety, were compared for solid-phase extraction (SPE) to detect lower concentrations of the eleven phenolics in natural waters. Higher recoveries were obtained using the functionalized polymeric adsorbents compared with Envi-Carb. When real samples were analysed, the synthetic adsorbent gave lower interference than Bond Elut PPL and phenol was determined at low levels with no humic and fulvic acid inter-ference when Na2SO3 was added. The linearity range for most compounds in tap water was 0.05–20 μg L−1 and the limits of detection were 〈35 ng L−1. Repeatability and reproducibility between days for real samples spiked at 0.1 μg L−1, expressed as relative standard deviation, were 〈8% and 10%, respectively.
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    The use of mobile phase pH and column temperature to reverse the retention order of enantiomers on chiral-AGP® (1998)
    Springer
    Chromatographia 47 (1998), S. 189-196 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Experimental design ; Mosapride ; Reversal of retention order ; Effect of pH and column temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Enantiomeric separation of mosapride and a structurally related compound was performed using chiral chromatography and experimental design. Unique effects of mobile phase pH and column temperature made it possible to control the elution order of the enantiomers when using Chiral-AGP as the solid phase. At a low mobile phase pH (〈6) the (R)-enantiomer of mosapride elutes before the (S)-form whereas the (S)-enantiomer elutes first at a high mobile phase pH (〉6). By using a mobile phase pH around 6, the column temperature could also be used to control the elution order of the enantiomers of mosapride. Similar effects of mobile phase pH and column temperature were obtained for the enantiomers of a structurally related compound, a metabolite (M1). Isocratic chromatographic systems made it possible to determine enantiomeric impurities less than 0.1% in the respective enantiomer of mosapride. The enantiomers of mosapride as well as the enantiomers of M1 could easily be separated simultaneously using Chiral-AGP and a simple gradient elution.
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    HPLC determination of colistin and aminoglycoside antibiotics in feeds by post-column derivatization and fluorescence detection (1998)
    Springer
    Chromatographia 48 (1998), S. 32-36 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Post-column derivatization ; Feeds ; Aminoglycoside antibiotics ; Colistin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Reversed-phase, HPLC methods employing post-column derivatization and fluorescence detection were developed for the determination of the peptide colistin and four aminoglycoside antibiotics in feeds. Extraction of the analytes was by sonication and shaking with dilute hydrochloric acid. Post-column derivatization was performed using orthophtaldialdehyde-2-mercaptoethanol chemistry. Assay of colistin was by using an acetonitrile-aqueous sodium sulphate-triethylammonium phosphate (pH 2.8) eluent. Aminoglycoside antibiotics:amikacin, kanamycin, gentamycin and neomycin were analyzed using a tetrahydrofuran-aqueous sodium sulphate-sodium pentanesulphonate-acetic acid mobile phase. The method was also applied to some pharmaceutical preparations. Preliminary results showed that the method can be adapted for the assay of the above antibiotics in meat and animal serum for residue and pharmacokinetic studies.
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    High-Performance liquid chromatographic separation of enantiomers of unusual amino acids possessing cycloalkane or cycloalkene skeletons on a chiral crown ether containing stationary phase (1998)
    Springer
    Chromatographia 48 (1998), S. 20-26 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Crownpak CR(+) Column ; Cyclic β-Amino Acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Direct reversed-phase high-performance liquid chromatographic methods were developed for the separation and identification of the enantiomers of mono- and bicyclic racemic β-amino acids:cis- andtrans-2-aminocyclopentane-1-carboxylic acids,cis- andtrans-2-aminocyclohexane-1-carboxylic acids,cis- andtrans-2-amino-4-cyclohexene-1-carboxylic acids,diendo- anddiexo-3-aminobicyclo[2.2.1]heptane-2-carboxylic acids anddiendo- anddiexo-3-amino-5-bicyclo[2.2.1]heptene-2-carboxylic acids. Enantioseparation was carried out by the application of a chiral stationary phase, Crownpak CR(+). The conditions of separation were optimized by changing the temperature, the flow rate and the pH of the mobile phase.
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    Enantiomeric separation of unusual secondary aromatic amino acids (1998)
    Springer
    Chromatographia 48 (1998), S. 53-58 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gas chromatography ; Enantiomeric separation ; Chiral derivatization ; Unusual secondary aromatic amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary High-performance liquid chromatographic and gas chromatographic methods were developed for the separation of unusual secondary aromatic amino acids. Amino acids containing 1,2,3,4-tetrahydroisoquinoline, 1,2,3,4-tetrahydronorharmane-1-carboxylic acid and 1,2,3,4-tetrahydro-3-carboxy-2-carboline moieties were synthetized in racemic or chiral forms. The high-performance liquid chromatography was carried out either on a teicoplanin-containing chiral stationary phase or on an achiral C18 column. In the latter case the diastereomers of the amino acids formed by precolumn derivatization with the chiral reagents 2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl isothiocyanate or 1-fluoro-2,4-dinitrophenyl-5-L-alanine amide were separated. The gas chromatographic analyses were based on separation on a Chirasil-L-Val column.
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    HPLC analysis of basic organic compounds in a multi-component ion-interaction system: A mechanistic study (1998)
    Springer
    Chromatographia 47 (1998), S. 493-500 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion-interaction chromatography ; Basic organic compounds ; Diamine modifiers ; Retention mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Reversed-phase HPLC separations of basic compounds have been optimized by use of mobile phases containing 1,8-diaminooctane (DAO) as amine modifier and heptanesulfonate as counter-ion. Such studies have demonstrated the high resolution and selectivity of this chromatographic system compared with mobile phases prepared with the more widely used primary amines. With the aim of clarifying the retention mechanism involved, three sets of compounds with different structures and properties were analyzed: sulfamidics and trimethoprim, aromatic diamines and aminophenols, and a standard mixture of lipophilic basic drugs. The conditions investigated were: diaminoalkane modifier concentration, diaminoalkane modifier alkyl-chain length, nature and concentration of the counter-ion, pH of the mobile phase, concentration of the organic modifer, and the nature of the stationary phase as characterized by percentage carbon loading. Analysis of chromatographic behavior as a function of the chromatographic conditions has enabled the proposal of a mechanism of retention of the three classes of compounds.
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    Problems in the analysis of propofol in blood when protein precipitation is used in sample preparation (1998)
    Springer
    Chromatographia 47 (1998), S. 523-528 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Propofol in blood ; Precipitation procedure ; Drug co-precipitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Propofol (2,6-diisopropylphenol) is one of a group of intravenously administered hypnotic agents enabling easy inducement of sleep. Increasingly wider application of this drug in anaesthesiology has led to increasing demands for its precise and reliable analysis in the physiological fluids and tissues of man. The identification of problems in the determination of propofol seems to be essential. This paper deals with difficulties of propofol analysis in blood by HPLC when protein precipitation is used in sample preparation. The data obtained show that introduction of large amounts of fluids (for example electrolytes or blood-substitutes) into the blood, for example during long surgical operations, can significantly influence the results from propofol analysis.
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    High performance liquid chromatography method for the determination of doxycycline in human plasma (1998)
    Springer
    Chromatographia 47 (1998), S. 547-549 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Doxycycline ; Human plasma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A simple, low-cost, sensitive and selective HPLC method was developed for the determination of doxycycline in human plasma. The method has a detection limit of 0.008 μg mL−1 and a limit of quantification of 0.02 μg mL−1. Calibration curves were linear over a large dynamic range, namely within 0.02–5.0 μg mL−1, which allowed accurate determination of doxycycline peak levels in human plasma after administration of 50–200 mg tablets and also the low plasma levels obtained 72 hours after drug administration.
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    Determination of triacylglycerol composition of idiazabal cheese (1998)
    Springer
    Chromatographia 47 (1998), S. 579-586 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Column liquid chromatography ; Ewe's cheese ; Triacylglycerols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Triacylglycerols from Idiazabal cheese fat were analysed by high-performance liquid chromatography (LC) with a non-linear gradient of acetone in acetonitrile and a light-scattering detector. Molecular species of triacylglycerols were predicted by a simple and a multiple linear regression analysis of logk of the LC peaks and molecular variables such as equivalent carbon number of the possible triacylglycerol, chain length and number of double bonds of each fatty acid of the triacylglycerol. Predicted results were confirmed by gas chromatographic analysis of the fatty acids in the LC peaks. The main triacylglycerols of Idiazabal cheese fat contained butyric acid, butyroyl-dipalmitin, butyroyl-myristoyl-palmitin and butyroyl-palmitoyl-olein. The most abundant triacylglycerols were those with even partition numbers of 36, 34 and 38.
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    Rapid determination of carbaryl and 1-naphthol at ppt levels in environmental water samples by automated on-line SPE-LC-DAD-FD (1998)
    Springer
    Chromatographia 47 (1998), S. 596-600 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; On-line trace-enrichment ; Environmental water samples ; Trace carbaryl analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A fully automated method, based on on-line solid phase extraction (SPE) then liquid chromatography with diode-array and fluorescence detection, has been developed for the trace-level determination of carbaryl and 1-naphthol, its primary transformation product, in environmental water samples. By means of rapid enrichment on a 30 mm×4 mm i.d. 10-μm ODS pre-column, using a 10-mL water sample, before LC determination both compounds were recovered satisfactorily from different environmental water samples spiked at various concentrations (0.05–10 μg L−1). Average recoveries were between 93 and 102% with coefficients of variation between 1 and 4%; detection limits as low as 10 and 50 mg L−1 (ppt) were estimated for carbaryl and 1-naphthol, respectively. With this small sample volume, sample throughput was up to 30 samples per day. A carbaryl degradation study was performed by spiking a surface-water sample at 2 μg L−1. After 15 days 80% of the carbaryl was degraded and the presence of 1-naphthol was confirmed by means of its UV spectrum.
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    Isolation and characterization of 3,5,6-trihydroxy-carotenoids from petals ofLilium tigrinum (1998)
    Springer
    Chromatographia 48 (1998), S. 27-31 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Lilium tigrinum ; Carotenoids ; Xanthins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Reinvestigation by HPLC of the petals ofLilium tigrinum and the isolation of some minor compounds is reported. Using HPLC-controlled, preparative-column chromatography, 5,6-diakarpoxanthin (6), 6-epikarpoxanthin (2), 5,6-diacapsokarpoxanthin (8), and 9Z-antheraxanthin (9Z-13) were isolated and characterized. Based on spectroscopic data the absolute configurations of6 and8 were identical with those originating from paprika, thus the 5,6-diakarpoxanthin (6) and 5,6-diacapsokarpoxanthin (8) have the 3S, 5S, 6S configuration and 6-epikarpoxanthin (2) has the 3S, 5R, 6S configuration.
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    URL: http://dx.doi.org/10.1007/BF02467511
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    Chemical removal of humic substances interfering with the on-line solid-phase extraction—Liquid chromatographic determination of polar water pollutants (1998)
    Springer
    Chromatographia 48 (1998), S. 231-236 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; On-line preconcentration ; Humic substances ; Polar pollutants in water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Different methods for removing interference by humic substances in the analysis of polar pollutants have been compared in the analysis of environmental water by solid-phase extraction (SPE) with a chemically modified polymeric resin coupled on-line to liquid chromatography with UV detection. The methods were based on the use of chemical reagents. The best method was found to be addition of sodium sulphite to humic-containing water before SPE. The appropriate amount of sulphite depends on the amount of humic substances dissolved in the sample—for analysis of 50 mL tap and Ebro river water, respectively, 250 μL and 500 μL 10 % Na2SO3 solution had to be added. In both cases, the recovery values after chemical treatment were similar to those when a Milli-Q-quality water standard was analysed.
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    URL: http://dx.doi.org/10.1007/BF02467676
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    Determination of ketorolac enantiomers in plasma using enantioselective liquid chromatography. Application to pharmacokinetic studies (1998)
    Springer
    Chromatographia 48 (1998), S. 203-208 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ketorolac in plasma ; Enantiomer separation ; Pharmacokinetic studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A direct HPLC method for quantification of the (R) and (S) enantiomers of ketorolac in human plasma for pharmacokinetics studies has been developed. Naproxen sodium [S(+) enantiomer] was used as an internal standard. Plasma samples (1 mL) were vortexed for 30 sec with methyltert-butyl ether, followed by centrifugation at 2000 g for 8 min. The aqueous phase was acidified (pH 1) by adding 1 mL of 2N HCl and back-extracted with 5 mL methyltert-butyl ether. The organic phase was evaporated, and the residue was dissolved in 200 μL of mobile phase. 25 μL were chromatographed on a α1-acid glycoprotein column (Chiral-AGP, 100×4 mm I.D.), using a mobile phase with 8.5% propan-2-ol in phosphate buffer (0.09M NaH2PO4.H2O, 0.01M Na2HPO4, 0.002M Dimethyloctylamine; pH 5.5). Calibration range was 20–20000 ng mL−1 for (R)- and (S)-ketorolac. The LOQ was 5 ng mL−1 for both enantiomers. The sensitivity could be extended to 1 ng mL−1 with the same precison by increasing the injection volume to 100 μL. The method is reproducible, accurate, and stereospecific. The inter-assay and intra-assay CVs were 〈11.40% and 〈9.30% for (R)- and (S)-ketorolac respectively. Under the conditions employed, no racemization was observed.
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    URL: http://dx.doi.org/10.1007/BF02467672
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    Optimisation of mobile phase pH in liquid chromatography. Application to fluorimetric detection of series of quinolones (1998)
    Springer
    Chromatographia 48 (1998), S. 251-257 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Mobile phase optimisation ; Fluorimetric detection ; Quinolones ; Dissociation constants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The dissociation constants of several quinolones in a 7% acetonitrile-water mixture are determined. A model describing the effect of pH on the retention of quinolones by an octadecylsilica stationary phase with a 7% acetonitrile-water mobile phase is proposed. The model uses pH values in the mobile phase instead of pH values in water and takes into account the effect of activity coefficients. Fluorescence of quinolones in the mobile phase is studied, and a chromatographic separation with fluorimetric detection is established. Detection limits for the proposed method range from 3 to 12 μg·L−1.
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    URL: http://dx.doi.org/10.1007/BF02467679
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    Determination of myristicin in rat serum samples using microbore high performance liquid chromatography with column-switching (1998)
    Springer
    Chromatographia 48 (1998), S. 365-368 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Microbore columns ; Column-switching ; Myristicin ; Serum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A microbore high-performance liquid chromatographic method with column-switching was developed for the analysis of myristicin from rat serum without prepurification. Deproteinization, fractionation, concentration and separation of analyte were carried out by appropriate switching of columns and using solvent mixtures. The method showed excellent precision, accuracy and speed with a detection limit of 10 ng mL−1 from 25 μL of serum. The total analysis time per sample was 25 min and the coefficients of variation for intra- and inter-assay were less than 1.8%.
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    URL: http://dx.doi.org/10.1007/BF02467705
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    Electrically driven capillary size exclusion chromatography (1998)
    Springer
    Chromatographia 48 (1998), S. 347-354 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Size exclusion chromatography ; Polystyrene ; Packed capillaries ; Electrochromatography ; Pore flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Electrically driven size exclusion chromatography (ED-SEC) of polystyrenes in packed capillaries using dimethylformamide as solvent is demonstrated. The efficiency and retention behaviour of polystyrenes under pressure and electro drive were investigated. Under pressure drive the plate height (H) increases steadily with increasing linear velocity (u) whereas under electro drive the H-u curves largely coincide and are very flat. At higher velocities the plate heights are about 50% smaller with electro drive than with pressure drive. Calculations show that with increasing ionic strength, the flow through the particles may increase causing a clear diminishing of the elution window.
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    URL: http://dx.doi.org/10.1007/BF02467702
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    Polyfunctional chemically bonded stationary phase for reversed phase high-performance liquid chromatography (1998)
    Springer
    Chromatographia 48 (1998), S. 615-622 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Synthesis of polyfunctional stationary phases ; Quantitative structure-retention relationships, QSRR ; Separation of steroids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Preparation of a chemically-bonded-silica stationary phase (SG-MIX), with different polar and nonpolar functional groups such as hydroxyl (-OH), amino (-NH2), cyano (-CN), phenyl (-Ph), octyl (-C8) and octadecyl (-C18), is described. The characteristics of the prepared packing was done by physicochemical methods such as elemental analysis, FTIR spectroscopy, solid-state nuclear magnetic resonance (NMR), chromatography (GC and HPLC) as well as by analysis of quantitative structure-retention relationships (QSRR). The polyfunctional SG-MIX phase possesses properties of a reversed-phase material modified by specific inputs to retention due to interactions of analytes with polar functionalities on the surface of adsorbent. The new type of packing was successfully used for both analytical and preparative separation of finasteride from its metabolite, N-methylfinasteride.
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    URL: http://dx.doi.org/10.1007/BF02467590
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    Structure-driven retention model for optimization of ternary solvent systems in reversed-phase liquid chromatography (1998)
    Springer
    Chromatographia 48 (1998), S. 607-614 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ternary mobile phase compositions ; Solvation parameter model ; Mixture-design optimization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new approach is presented fro the prediction of retention in reversed-phase liquid chromatography using ternary mobile phase compositions. The solvation parameter model is used to create the system constants that characterize the properties of the mobile and stationary phases in terms of the relative ease of cavity formation, and differences in dispersion, lone pair electron, dipole-type, and hydrogen-bond association interactions for all solvent compasitions employed. A statistical mixture-design approach provides system surfaces and models for the variation of individual system constants as a function of ternary solvent composition. The models for the system surfaces allow the retention factor to be predicted as a function of mobile phase composition for any compound whose descriptor values are known, or can be obtained from estimation rules or determined by experiment. The method is validated using a large literature data base for the retention factor of up to 46 varied aromatic solutes in 72 methonolacetonitrile-water and methonol-tetrahydrofuran-water mobile phase compositions.
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    Convenient and optimized method for sample pre-treatment for the analysis of bile acids in biological matrices (1998)
    Springer
    Chromatographia 48 (1998), S. 681-689 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Thin layer chromatography ; Sample pre-treatment ; Bile salts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The analysis of bile acids in biological matrices, e.g. gall bladder bile and serum, depends on accurate and reproducible sample pre-treatment techniques. The present study compares published and commonly used protocols with a special focus on the analysis of serum bile acids. Since adsorption of bile acids to serum proteins has a dramatic impact on the recovery rate and the reproducibility of the method used, several deproteination procedures were compared. The combination of given protocols made it possible to develop a very sensitive and efficient sample pre-treatment which is well suited for all chromatographic methods for bile acid analysis.
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    URL: http://dx.doi.org/10.1007/BF02467599
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    Optimisation of chiral separation of omeprazole and one of its metabolites on immobilized α1-acid glycoprotein using chemometricsglycoprotein using chemometrics (1997)
    Springer
    Chromatographia 44 (1997), S. 10-18 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Experimental design ; Direct chiral resolution ; Omeprazole ; Hydroxy-omeprazole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A strategy for the optimisation of direct chiral separation of omeprazole and a metabolite, hydroxi-omeprazole, in reversed phase liquid chromatography is described. A factorial design was used, where mobile phase pH, concentration of a mobile phase modifier, ionic strength and column temperature were tested as the variables and enantioselective retention, column efficiency and asymmetry factor as the responses. The experimental results were evaluated with multivariate analyses, which demonstrated that the column temperature and content of mobile phase acetonitrile were by far the most important variables. The enantiomers of omeprazole and one of its metabolites were baseline resolved within 15 minutes. The optimised chromatographic system was used for a separation of the enantiomers of omeprazole and its main metabolite in a patient plasma sample.
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    Chemiluminescence determination of tiopronin and its metabolite 2-mercaptopropionic acid in human urine by HPLC coupled with flow injection (1997)
    Springer
    Chromatographia 44 (1997), S. 31-36 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chemiluminescence detection ; Tiopronin ; Thiols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In previous pharmacokinetic studies tiopronin, a drug used for effective treatment of cystinuria and rheumatoid arthritis, and its metabolite 2-mercaptopropionic acid were analysed by conventional liquid chromatography with pre- and post-column derivatization and UV detection. Now a novel HPLC-coupled chemiluminescence-flow-injection analysis (CL-FIA) method has been developed for the determination of tiopronin and 2-mercaptopropionic acid in urine. The method is based on chemiluminescence from a Ce(IV) oxidation system sensitized by quinine, as proposed earlier by this group, and flow-injection analysis. The method, which has the advantages of high sensitivity and selectivity, simple sample treatment and prompt production of results, has also been preliminarily adapted for pharmacokinetic study of tiopronin in urine.
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    URL: http://dx.doi.org/10.1007/BF02466512
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    HPLC analysis of fat-soluble vitamins on standard and narrow bore columns with UV, electrochemical and particle beam MS detection (1997)
    Springer
    Chromatographia 44 (1997), S. 605-612 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; UV and electrochemical detection ; Particle beam-mass spectrometry ; Fat-souble vitamin ; Standard-bore and narrow-bore columns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The application of different detection techniques; UV, electrochemical (ED) and particle beam-mass spectrometry (PB-MS) for the high-performance liquid chromatography analysis of fat-soluble vitamins were studied. Separation of all compounds examined was performed using both C8 standard-bore and narrow-bore columns for UV and MS detection, whereas in the case of HPLC-ED, a C8 standard-bore column only was used. Detector responses were studied in terms of linear range, detection limit and precision. The HPLC methods with UV, PB-MS and electrochemical detection were applied to the assay of vitamins A and E in an infantformula, powdered-milk sample. Recovery studies showed good results both for vitamins A and E, within-run precision being 2–4% for LC-UV and LC-ED techniques. In addition, excellent aggrement between the results obtained with the detection systems explored was found.
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    URL: http://dx.doi.org/10.1007/BF02466663
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    Determination of cortisol in guinea pig urine by high performance thin-layer chromatography, high performance liquid chromatography, and thin-layer chromatography/radioimmunoassay (1997)
    Springer
    Chromatographia 44 (1997), S. 50-54 
    Details
    ISSN: 1612-1112
    Keywords: Thin layer chromatography ; Column liquid chromatography ; Radioimmunoassay ; Cortisol ; Guinea pig ; Urine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In order to collect urinary samples from unrestrained guinea pigs, animals were kept in their familiar home cages with wood shavings for bedding. Cortisol was removed from shavings by a simple washing step, and an attempt was made to measure its concentrations by high performance thin-layer chromatography (HPTLC), high performance liquid chromatography (HPLC), or thin layer chromatography/radioimmunoassay (TLC-RIA). After intramuscular administration of 25 mg cortisol, cortisol excretion increased from about 20–30 μg/day to 400–500 μg/day (HPTLC: 531 μg/day, HPLC: 493 μg/day; TLC-RIA: 394 μg/day). Similarly, the treatment of the animals with 20 IU ACTH resulted in an augmented cortisol excretion, with mean values of 294 μg/day (HPTLC), 256 μg/day (HPLC) and 143 μg/day (TLC-RIA), respectively. The present study shows, for the first time, that cortisol excretion in unrestrained laboratory animals can be determined. Whilst the cortisol values measured by HPTLC and HPLC agree, the amounts measured by TLC-RIA were significantly lower. These differences are probably due to the presence of substances in urine or shavings which interfere with the radioimmunological determination. Hence, cortisol should be determined either by HPTLC or HPLC. Beside having a desirable specificity, these methods are more suited than TLC/RIA for steroid analysis since they confer the possibility of measuring additional steroids (e.g. precursors and/or metabolites of cortisol) in a single urine extract. This is especially the case for the HPTLC method since substances can be transformed into fluorescent derivatives.
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    Development of a universal Raman detector for microchromatography (1997)
    Springer
    Chromatographia 44 (1997), S. 257-262 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Microchromatography ; Raman spectroscopy ; Deuterated solvents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A detector for microchromatography in which Raman spectroscopy is used to identify the eluted species has been developed. The detector is designed to be applicable to a wide range of compounds without requiring the presence of a chromophore. Its use is illustrated in the analysis of nitro compounds on a 250 μm i.d. column. Raman spectra of each of the compounds could be identified as they passed the detector. The advatages of the use of fully deuterated solvents are demonstrated by the analysis of nitrobenzenes in methanol/water mobile phases. The detection limit for nitrobenzene using the Raman line at 1342 cm−1 was 75ng.
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    Development and validation of a stability-indicating HPLC method for the determination of degradation products in dipyridamole injection (1997)
    Springer
    Chromatographia 44 (1997), S. 247-252 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Dipyridamole injection ; Stability studies ; Degradation products
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The development and subsequent validation of an isocratic high-performance liquid chromatographic (HPLC) procedure employing ultraviolet (UV) detection for the determination of degradation products in Dipyridamole Injection is reported. The development of this assay involved the evaluation of several factors including buffer type, ionic strength, pH, organic composition, and column type. The described method is simple, reproducible, accurate, and selective. The precision, relative standard deviation (RSD), amongst five sample preparations for total degradation products was not more than (NMT) 10.2 %, while the individual degradation products were NMT 12.1%. Intermediate precision, as determined from fifteen sample preparations, generated by two Analysts on different HPLC systems over three days, exhibited an RSD for total and individual degradation products of 8.2 % and NMT 27.5 %, respectively. The mean absolute recovery of dipyridamole using the described method is 102.1±1. 9%, (mean±SD, n=12) over the concentration range of 0.03 % to 5.0 % of its label claim of 5 mg mL−1. The limit of detection and limit of quantitation were 0.1 and 0.3 μg mL−1, respectively. The linearity of the peak response was verified with respect to dipyridamole concentration over a range of 0.3 and 50 μg mL−1 (0.03 % to 5.0 % label claim). The Standard and Assay Preparations are stable for up to 48 hours at room temperature. The selectivity was evaluated by subjecting the finished product (Dipyridamole Injection) to thermal, acidic, basic, oxidative and fluorescent radiation stress conditions. No interference in the analysis of degradation products was observed, showing the method is stability-indicating.
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    A weak cation-exchange phase for the separation of biogenic amines by open tubular liquid chromatography (1997)
    Springer
    Chromatographia 44 (1997), S. 295-302 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Open tubular columns ; Weak cation-exchange stationary phase ; Biogenic amines ; LIF detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The preparation and performance of a weak cation-exchange stationary phase for Open Tubular Liquid Chromatography (OT-LC) was investigated. The stationary phase was prepared in 5.4 μm I.D. fused silica capillaries byin situ photopolymerization of a mixture of silicon acrylate and acrylic acid. The influence of pH, counter ion concentration and organic modifier concentration of the mobile phase on the retention was studied with catecholamines as test solutes using LIF detection. Other biological amines like amino acids, small peptides and nucleic acid derivatives could be separated on this stationary phase as well. The kinetic performance of the stationary phase was studied with several cations and neutral solutes.
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    Quantitative analysis of mebeverine in dosage forms by HPLC (1997)
    Springer
    Chromatographia 44 (1997), S. 427-430 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Mebeverine in dosage forms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A simple and rapid, high performance liquid chromatographic (HPLC) procedure for determination of mebeverine in dosage forms (tablet and liquid) is described. Reversed-Phase chromatography was carried out using a mobile phase containing 0.05 M ammonium acetate buffer and acetonitrile, [(45%, v/v) pH 5.2] with UV-detection (263 nm). Replicate regression analyses of three standard plots in the concentration range of 0.5–10 mcg mL−1 obtained on three different days gave a correlation coefficient 〉0.9995 and the coefficient of variation of the slopes 〈2.2%. The assay was precise within day and between days as indicated by ANOVA test. The recoveries from 10 replicate tablets of two commercial mebeverine brands and liquid were in order 99.3, 100.5 and 100.1% of the label amount and their coefficient of variations were 1.41, 0.89 and 0.69%, respectively. The limit of quantitation of mebeverine was 5 ng mL−1.
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    Synthesis of new stable aliphatic isothiocyanate-based chiral derivatizing agent and application to indirect separation of chiral amino and thiol compounds (1997)
    Springer
    Chromatographia 44 (1997), S. 465-472 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Indirect separation ; Chiral derivatization ; Stable CDA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new chiral derivatizing agent (CDA) (1S, 2S) N-[(2-isothiocyanato)-cyclohexyl)-pivalinoyl amide ((S,S)-PDITC) is described. The CDA is available from 1,2-diamino cyclohexane (DACH) via a straightforward synthesis in both the (R,R) and (S,S)-configuration and can serve as a highly selective, stable reagent for the indirect resolution of chiral primary and secondary amines, amino acids and thiol compounds. The resulting diastereomeric thioureas and dithiocarbamates can be separated by simple RP-HPLC as demonstrated with a number of pharmaceutically important examples of amines and amino alcohol-type drugs. The latter diastereomers are compared with the well-established GITC derivatized compounds. The separation factors (α) of the diastereomeric thioureas range between 1.03 and 2.08 and were usually higher than those of the GITC derivatives. The chemical stability of the PDITC derivatives is excellent due to the absence of hydrolyzable ester groups— considered an advantage compared to GITC derivatives.
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    Synthesis and characterization of titania based stationary phases using the silanization/hydrosilation method (1997)
    Springer
    Chromatographia 44 (1997), S. 538-544 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Octadecyl titania ; Hydride surface ; Hydrosilation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The silanization/hydrosilation bonding method is tested on both a laboratory synthesized and commercial titania. The laboratory titania made by the sol-gel process shows evidence of residual organic material that is removed by an initial acid hydolysis followed by bonding of the hydride (triethoxysilane) under acidic conditions. DRIFT and solid state CP-MAS NMR studies are used to confirm the formation of the hydride layer on the titania and the success of the hydrosilation process for attaching an organic moiety (1-octadecene) to the surface. Chromatographic testing, primarily on the commercial titania based C-18 phase, indicates good reverse phase properties and few residual OH groups, either Ti−OH or Si−OH, as determined by the symmetrical peak shapes obtained for anilines and alkylphenylamines using mobile phases with no buffers or masking agents in the aqueous component.
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    Application of micropellicular poly-styrene/divinylbenzene stationary phases for high-performance reversed-phase liquid chromatography electrospray-mass spectrometry of proteins and peptides (1997)
    Springer
    Chromatographia 44 (1997), S. 438-448 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Electrospray ionization mass spectrometry ; Micropellicular poly-styrene/divinylbenzene ; Peptides and proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Short columns packed with highly crosslinked 2.3 μm poly-styrene/divinylbenzene (PS/DVB) particles were used for rapid and efficient separation of proteins and peptides by reversed-phase high-performance liquid chromatography at elevated temperatures. Enhancement of the diffusivities of the sample components at elevated temperatures together with the short diffusion pathlength with the micropellicular polymeric stationary phases were responsible for high efficiency, high speed of analysis, and short column regeneration times. Underivatized PS/DVB beads as well as PS/DVB microspheres which have been modified with polyvinylalcohol or octadecyl chains on the surface were synthesized, employed, and compared to HY-TACH-C18, a commercially available micropellicular octadecyl-silica stationary phase, for the separation of proteins, octapeptides and tryptic protein digests. Highest performance was obtained with the silica- and PS/DVB-based octadecyl stationary phases, which exhibited similar column efficiencies but different selectivities for proteins and peptides. The minimum detectability at 214 nm and the maximum loading capacity for ribonuclease A using analytical 30×4.6 mm I.D. columns were 10 ng (0.6 pmol) and 1 μg, respectively. Finally, reversed-phase HPLC with a 60×2 mm I.D. narrow-bore column packed with micropellicular octadecyl PS/DVB was coupled successfully to electrospray mass spectrometry at a flow-rate of 0.15 mL min−1 and on-line full-scan mass spectra for molecular mass determination and identification of proteins in the lower picomol range were obtained.
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    Simultaneous determination of parathion and metabolites in serum by HPLC with column switching (1997)
    Springer
    Chromatographia 44 (1997), S. 473-476 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Column-switching ; Parathion, and metabolites in serum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new high-performance liquid chromatographic method with column-switching has been developed for the simultaneous determination of parathion and its metabolites such asp-nitrophenol and paraoxon in serum. Serum samples were injected onto a precolumn packed with LiChroprep RP-8 after simple dilution with 20% phosphoric acid. Polar plasma components were washed with 0.02 M phosphate buffer (pH 3.0). After valve switching, the concentrated compounds were eluted in back-flush mode and separated on a Ultracarb ODS 30 column with a gradient of acetonitrile −0.01 M phosphate buffer (pH 3.0) as mobile phase. The method showed excellent precision, accuracy and speed with detection limit of 0.1 μg mL−1. Total analysis time per sample was 〈40 min and coefficients of variation for intra-and inter-assay were 〈4.5%.
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    URL: http://dx.doi.org/10.1007/BF02466739
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    Comparison of GC-MS and HPLC for overcoming matrix interferences in the analysis of PAHs in smoked food (1997)
    Springer
    Chromatographia 44 (1997), S. 497-504 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Gas chromatography-mass spectrometry ; Column liquid chromatography ; Polycyclic aromatic hydrocarbons ; Food analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Several separation and detection methods for polycyclic aromatic hydrocarbons (PAHs) in smoked chicken by GC and HPLC were compared. With HPLC and a gradient solvent system, all 16 PAHs could be simultaneously separated and detected by fluorescence with seven settings of programmable wavelength (excitation/emission). The presence of impurities in smoked chicken could interfere with the subsequent identification and quantification of PAHs by HPLC. With GC and a temperature programming method, all 16 PAHs could be separated and the PAHs in the chicken sample could be detected with an ion-trap mass spectrometer even in the presence of fat-or PAH-like impurities. Nine PAHs were identified by the former method while fourteen PAHs were identified by the latter method. The retention times by HPLC were shorter than those by GC, also, the former had better separation for most PAHs than the latter.
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    URL: http://dx.doi.org/10.1007/BF02466743
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    Computerized optimization of RP-HPLC separation with nonaqueous or partially aqueous mobile phases (1997)
    Springer
    Chromatographia 44 (1997), S. 529-537 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Computer optimization of separation ; Multisolvent mobile phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary “Osiris” optimization software was usedfor optimizing separations with nonaqueous or partially aqueous mobile phases, consisting of 2, 3 or 4 solvents. For nonaqueous eluents used in Nonaqueous Reversed Phase Liquid Chromatography (NARP-LC), classical transfer rules cannot be used to determine isoeluent mobile phase compositions that are generally the starting point of most of the optimization procedures. The ability of this software to determine isoeluent compositions under NARP conditions is demonstrated. This determination is performed by modeling the solute retention from different sets of two gradient runs, each set being carried out for each binary mobile phase studied. The application of retention models to nonaqueous mobile phases is discussed in terms of the accuracy of the predicted retention times. In addition, it is shown that these sets of gradient runs allow selection of the best composition space for the optimum composition search without requiring additional runs. It is demonstrated that such a selection procedure greatly reduces the number of preliminary experiments.
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    URL: http://dx.doi.org/10.1007/BF02466747
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    Reversed phase behaviour of high molar mass polystyrenes in acetonitrile with halogenated methane solvent mixtures (1997)
    Springer
    Chromatographia 44 (1997), S. 421-426 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; RP chromatography ; Polystyrenes ; Mixed solvents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The reversed phase behaviour of high molecular mass polystyrenes was investigated on a C18 bonded phase column using acetonitrile as the polar mobile phase component and dichloromethane, chloroform and carbon tetrachloride, as separate nonpolar components. Solvent solubility compositions, elution compositions and resolutions of the various molar mass polystyrenes were measured and compared for each of the three mobile phases. Anomalous behaviour of the polystyrenes was not observed in any of the three mobile phases and only minor differences in resolution were observed. By comparing these results with previously published work, it is suggested that any mobile phase component that is both nonpolar and a good solvent for the polymer can be combined with acetonitrile for effective separations of polystyrenes by mass and that it is the poor solvent component of the mobile phase that is responsible for the anomalous behaviour that is sometimes observed in this type of chromatography.
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    URL: http://dx.doi.org/10.1007/BF02466321
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    Resolution of the enantiomers of verapamil and gallopamil by chiral liquid chromatography-mass spectrometry (1997)
    Springer
    Chromatographia 44 (1997), S. 477-483 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral separations ; Calcium channel antagonists ; On-line liquid chromatography-mass spectrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An HPLC-CSP method has been developed for the separation of enantiomers of verapamil and gallopamil using the improved version of the α1-acid glycoprotein, chiral stationary phase as selector with a volatile mobile phase. The results of the investigation provide the conditions which allow direct coupling to a mass spectrometer. In addition, the simultaneous enantioseparation of both the enantiomeric pairs of verapamil and gallopamil was achieved.
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    URL: http://dx.doi.org/10.1007/BF02466740
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    Determination of sorbic acid in wines with a hydrogen sulfonated divinyl benzene-styrene copolymer HPLC column (1997)
    Springer
    Chromatographia 44 (1997), S. 645-648 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Wine ; Sorbic acid ; Styrene-DVB sorbents ; Detection limit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method is proposed for the determination of sorbic acid in wines using a hydrogen sulfonated divinyl benzene-styrene copolymer (DVB-H) HPLC column and isocratic elution with 0.01N H2SO4:CH3CN (75:25). UV detection at 258 nm permits analysis by direct injection of white and red wines without significant interference between the peaks of sorbic acid and other sample components. The limit of detectability of the method is 0.01 mg L−1 with an average recovery of 99.6% and an average % RSD of 0.87. Analyses of 30 wine samples by the proposed method and the official EEC spectrophotometric method show that there is a good correlation between the results of the two methods, although the HPLC analyses are clearly more precise and accurate.
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    URL: http://dx.doi.org/10.1007/BF02466668
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    Chromatographic classification of commercially available reverse-phase HPLC columns (1997)
    Springer
    Chromatographia 44 (1997), S. 151-161 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reverse-phase LC columns ; Chromatographic classification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The ever-increasing number of commercially available reversed phases with which the analyst is confronted can cause problems in column selection. These and the non-standard test procedures used by the column manufacturers and packing companies cause further confusion. In order to independently compare and contrast a range of well established C18 stationary phases, we have performed a modified column characterization approach, based on Tanaka's methodology, on thirty commonly used phases in our laboratory. These results have been evaluated and presented in various formats as Principal Component Analysis, Cluster Analysis, Tabular Format and Radar Plots in order to assist in observing similarities and differences between phases. The results indicate that, while no two phases are exactly the same (with the exception of “me-to” clones), it is possible to characterize phases into different classes based on their chromatographic performance against selected test probes. The paper illustrates the similarities and differences between these phases. The column characterization described in the paper can form the basis of a rational column selection protocol by either careful matching of the appropriate column characteristics to the analyte's physico-chemical properties or by a systematic evaluation of columns from our various categories.
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    URL: http://dx.doi.org/10.1007/BF02466449
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    Influence of temperature and mobile phase composition on retention properties of oligomeric bonded phases in reversed-phase liquid chromatography (RPLC) (1997)
    Springer
    Chromatographia 44 (1997), S. 135-144 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Oligomeric stationary phases ; Enthalpy-entropy compensation ; Methylene and phenyl selectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The effect of temperature and mobile phase composition (methanol-water) on the retention behaviour of an oligomeric series of n-octylsilyl bonded phases in reversed-phase liquid chromatography has been investigated. Plots of lnk against 1/T (van't Hoff plot) and the enthalpy of transfer (ΔHo) yields linear relationships under the conditions studied. The ΔHo values of the aromatic hydrocarbons and n-alkyl benzoates are higher than those of the polar compounds due to their higher level of interaction with the stationary phase. A linear plot of ΔHo vs. ΔSo suggest that the retention process, which is essentially controlled by non-specific (dispersive) interactions between the solutes and the bonded ligands, is identical for all cases evaluated. The existence of similar retention mechanisms is confirmed by the constant value of the enthalpy-entropy compensation temperature of the columns for a given class of componds. As expected, decreasing the methanol content (% v/v) of the mobile phase results in increased eluite retention times. The methylene and phenyl selectivities are found to be independent of the carbon content of the stationary phases and varied only with the eluent composition. In addition to their high stability under aggressive mobile phase conditions as previously reported, the results of this study generally showed that the solute retention process on oligomeric phases are similar to those exhibited by the conventional reversed phases.
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    Determination of drug-protein interactions by combined microdialysis and high-performance liquid chromatography (1997)
    Springer
    Chromatographia 44 (1997), S. 205-208 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Microdialysis ; Carbamazepine ; Human serum albumin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A simple and rapid method for determination of the parameters of the interaction between drugs and protein, including the association constant and the number of binding sites, has been developed by use of a microdialysis sampling technique combined with high-performance liquid chromatography. The drug and protein (carbamazepine (5H-dibenz[b,f]flazepine-5-carboxamide, CBZ) and human serum albumin (HSA) were used as examples) were mixed in different molar ratios in 0.067 M potassium phosphate buffer, pH 7.4, and incubated at 37°C in a water-bath. The microdialysis probe was the used to sample the mixed CBZ-HSA solution at a perfusion rate of 1 μL min−1. The concentration of CBZ in the microdialysate was determined by reversed-phase high-performance liquid chromatography. Relative recovery (R), determined in vitro under similar conditions, was approximately 42.7%; theRSD ofR was approximately 1.85%. The estimated association constant (K) and the number of the binding sites,n, on one molecule of HSA were 1.06×104 M−1 and 0.880, respectively, which is in good agreement with the literature values determined by high-performance frontal analysis. The potential use of microdialysis is also discussed.
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    Interactions between cisplatin derivatives and mobile phase during chromatographic separation (1997)
    Springer
    Chromatographia 44 (1997), S. 19-24 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Cisplatin stability ; Cisplatin metabolites ; Platinum phosphato-derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Althoughcis-dichlorodiammineplatinum(II) (cisplatin or CDDP) is widely used for the treatment of several kinds of tumour, its stability and metabolism in biological fluids have not been completely elucidated. Conditions in which mobile phases of formic or phosphoric acids interact with platinum derivatives during chromatographic separation performed by high performance liquid chromatography on-line with inductively coupled plasma-mass spectrometry (ICPMS) are investigated. During chromatographic separation of CDDP the formic acid mobile phase does not interact with CDDP itself nor with its hydrolysis products. In contrast, the phosphoric acid mobile phase interacts, not with the CDDP itself, but with its hydrolysis products which are present only in an aged aqueous solution, to generate two platinum phosphato-derivatives. This study suggests that the phosphoric acid has greater affinity for the CDDP hydrated complexes than formic acid and the latter is more appropriate for the study of cisplatin behavior in aqueous and biological media.
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    Porous graphitic carbon (PGC) high-performance liquid chromatography of diphosphine-bridged complexes with heteronuclear Au-M (M=Mn, Re) bonds (1997)
    Springer
    Chromatographia 44 (1997), S. 381-385 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous graphitic carbon ; Diphosphine complexes ; Gold, rhenium, manganese organometallics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The isocratic high-performance liquid chromatography of 1,1′-bis(diphenylphosphino)ferrocene (dppf), 1,1′-bis(diphenylphosphino)ruthenocene (dppr), bis(diphenylphosphino)methane (dppm) and triphenylphosphine (PPh3)-substituted heterometallic Au-Mn or Au-Re carbonyl complexes is reported. A column packed with PGC (porous graphitic carbon) was used after preliminary experiments had shown that silica- and bonded-phase (silica-based) stationary phases were unsatisfactory for separation. The PGC column exhibited unique selectivity for the complexes studied. The mobile phases used were water-acetonitrile, dichloromethanehexane and tetrahydrofuran-hexane. The retention behaviour of the compounds was governed by the polar character and size of molecules, and influenced by metal-metal bond polarity. Separation of isomorphous structures with different metallocenyl moieties was achieved.
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    URL: http://dx.doi.org/10.1007/BF02466314
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    HPLC analysis of boldine in pharmaceuticals (1997)
    Springer
    Chromatographia 44 (1997), S. 619-622 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Boldine in pharmaceuticals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method is proposed for extraction, separation, identification and quantitative measurement of boldine (I) in pharmaceuticals. The extraction of (I) from the matrix (syrups, tablets, extracts) was realized with aqueous ammonium chloride (0.02 M, pH=3.0 with perchloric acid) and the clean-up of the extract was performed by solid-phase extraction by means of cartridges containing a strong cation-exchange sorbent, from which (I) was eluted with aqueous ammonium chloride (1 M, pH=10.0 with ammonia). The final eluate was examined by HPLC. Chromatography was performed on a C-8 column with a gradient elution from 15:85 to 30:70 of acetonitrile-water containing 0.1 M sodium perchlorate (pH=3.0), in 20 min. A diode array detector was used at 302 nm for detection. The method gives recovery values greater than 98% and the reproducibility is within 6.0%.
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    An exprimental design approach to selecting the optimum liquid chromatographic conditions for the determination of vitamins B1, B2-phosphate, B3, B6 and C in effervescent tablets containing saccharin and sunset yellow FCF (1997)
    Springer
    Chromatographia 44 (1997), S. 634-644 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Vitamin B and C in tablets ; Experimental design ; Optimization of separation ; Multiple regression modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The ion-pair liquid-chromatographic separation of the water-soluble vitamins thiamine mononitrate, riboflavin phosphate, nicotinamide, pyridoxine hydrochloride, ascorbic acid, saccharin, and the dye Sunset Yellow FCF (E110) has been examined for the analysis of the compounds in effervescent tablets. A Draper-Lin small composite design was used to study the impact on the compounds' retention times and peak-widths (the response variables) of four different mobile phase variables: percentage of methanol as organic modifier, the concentrations of hexanesulfonate as ion pairing reagent and of triethanolamine as competitive base, and pH. The interactions of these variables were also studied. The proposed design enabled derivation of multiple linear regression equations to model each compound's retention time and peak-width at half-height. The statistical reliability of the regression models was established by comparing predicted and experimental values. By introducing the regression models into a spreadsheet program (Excel 5.0), retention times and peak-widths for each compound were calculated at fixed mobile phase pH. The values of all the other combinations of the three mobile phase variables were changed in increments of two units within their examined boundaries, resulting in 225 different rows. For each combination the compounds' calculated retention times and their corresponding peak-widths were sorted in increasing order and the resolution between successive peaks was calculated. The minimum effective resolution (R s min) between each pair of peaks and the maximum retention time (t R max) in each row were then selected and used to construct contour plots indicating the location of zones of mobile phase parameter combinations whereR s min〉1.5 and the analysis was rugged, and wheret R max values were minimum. Their common regions resulted in optimum chromatographic separations. Examples are shown of chromatographic separations obtained using mobile phase combinations which were the best compromise of the three criteria selected.
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    Determination of clenbuterol in urine by azo-dye precolumn derivatization and micellar liquid chromatography (1997)
    Springer
    Chromatographia 44 (1997), S. 145-150 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Thermal lens spectrometric detection ; Diazotization and coupling derivatization ; Clenbuterol in urine ; N-(Naphthyl)ethylenediamine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Clenbuterol has been determined in urine by solidphase extraction on a C18 cartridge, diazotization of the eluate with nitrite, coupling of the diazonium ion with 1-(naphthyl)ethylenediamine, and separation of the azo dye formed by HPLC with a C18 column and a micellar mobile phase containing 0.1 M sodium dodecyl sulphate, 12%n-butanol and 0.05 M citrate buffer, pH 3. Recoveries higher than 90% were obtained by mixing the samples with a 20% 0.2 M NaOH before extraction. Limits of detection of 51 and 6.7 ng L−1 were obtained with spectrophotometric and thermal lens spectrometric detection, respectively; respective repeatabilities were 3.1% (5 μg mL−1) and 5.6% (0.16 μg mL−1).
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    Simple and rugged SPE method for the determination of tetracycline antibiotics in serum by HPLC using a volatile mobile phase (1997)
    Springer
    Chromatographia 44 (1997), S. 187-190 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Solid phase extraction ; Tetracycline in serum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A simple and rugged SPE method for the determination of tetracycline (TC), minocycline (MC) and demeclocycline (DCC) in porcine serum by high performance liquid chromatography (HPLC) was developed. The spiked serum sample was pretreated with 2% phosphoric acid followed by a simple and rugged solid-phase extraction procedure using the OasisTM HLB extraction cartridges. High and reproducible recoveries were obtained even though the cartridges were run dry. The extracted sample analytes were injected onto a Waters SymmetryShieldTM RP8 column. The mobile phase was a simple volatile solution containing 0.1% TFA, 2% methanol and 7% acetonitrile in Water. The antibiotics were detected at 350 nm. The calibration curves were linear from 2.0 to 25.0 μg mL−1 of TC and MC with DCC as the internal standard at a concentration of 25.0 μg mL−1. For six replicate analyses, the average recoveries of TC and MC from porcine serum sample fortified at the level of 2.5 μg mL−1 were 96.1% with 1.3% RSD and 101% with 0.54% RSD; at level of 0.5 μg mL−1 the average recoveries were 88% with 1.6% RSD and 97.8% with 1.4% RSD.
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    Uptake of hydrophobic amino acids and sodium chloride by a strong cation exchanger: Application to desalting and separation by preparative liquid chromatography (1997)
    Springer
    Chromatographia 44 (1997), S. 240-246 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Preparative scale separations ; Strong cation-exchange resin ; Amino acids ; Desalting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The uptake of sodium chloride, leucine and phenylalanine by a strong cation-exchange resin in the sodium form have been compared. Sodium chloride was excluded from the resin, as indicated by its parabolic upwards curved isotherm, and the corresponding desorption edge was sharpened (constant pattern). Isotherms for both amino acids constructed from a single elution experiment displayed slightly downwards curvature; the corresponding desorption edges spread in contrast to the breakthrough ones. The affinities of both amino acids for the resin were higher (from 15 to 40 %) in the presence of 1 M sodium chloride, indicating that hydrophobic interactions played a significant role in the mechanism of sorption. As expected from the isotherms, a mixture of 1 M sodium chloride, leucine and phenylalanine was separated with satisfactory recovery of both amino acids for a column loading of 10 % of the bed volume. Real mother liquors have also been separated under the same conditions.
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    The role of mobile-phase pH in the determination of catecholamine-related compounds by reversed-phase liquid chromatography with amperometric detection (1997)
    Springer
    Chromatographia 44 (1997), S. 348-354 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Catecholamine-related compounds ; pH optimization of mobile phase ; Amperometric detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A study was conducted for the optimization of the reversed-phase high performance liquid chromatographic separation of different types (acidic, basic, amphoteric and neutral) of catechol-related compounds by varying the pH. For pH to be used as the optimizing parameter, its effects on retention, peak width and peak shape had to be investigated. Therefore, the pH dependence of the amperometric detector response, as measured by the oxidation peak height or peak area, was taken into account.
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    Chemical modification of the polymeric sorbent containing hydroxyl functional groups (1997)
    Springer
    Chromatographia 44 (1997), S. 25-30 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous copolymer with hydroxyl groups ; Chemical modification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Dimethyldichlorosilane and stearic acid chloride were used for deactivation of hydroxyl functional groups present in the skeleton of the methacrylic ester ofp,p′-dihydroxydiphenylpropane diglycidyl ether-divinylbenzene, porous copolymer used as HPLC packing. The influence of chemical modification on the chromatographic behaviour of the copolymer was studied. To characterize selectivity of the packings, retention indices of five homologous series and test compounds were determined. The data obtained suggest that modification with stearic acid chloride affects both the chemical and porous structure of the copolymer while modification with dimethydichlorosilane changes only the chemical character of the packing.
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    Influence of mobile phase conditions on the clean-up effect of restricted-access media precolumns for plasma samples injected in a column-switching system (1997)
    Springer
    Chromatographia 44 (1997), S. 589-594 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Column-switching systems ; Restricted-access media precolumns ; Mobile phase composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Various mobile phases including phosphate buffer, pure water and five kinds of biological buffers (pH around 7) were systematically studied in terms of their ability to clean-up plasma matrix on precolumns of restrictedaccess media in a column-switching system. The necessary washing time, buffer pH, type and content of organic modifier were evaluated with respect to plasma elution profiles on restricted-access media precolumns. The influence of different mobile phases on the recovery of plasma matrix from alkyl-diol silica precolumns was studied by means of a scanning spectrophotometer. Our results show that phosphate buffer near physiological pH with small amounts of 2-propanol or acetonitrile was prefereble for direct injection of large plasma volumes (500 μL). More than 93% of the proteins in a plasma matrix can be recovered within 3 min from the alkyl-diol silica C18 column (25 mx 4 mm I.D.) as measured at 280 nm for all selected mobile phases except for tris (hydroxymethyl) aminomethane buffer, from which only about 88% was obtained.
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    Analysis of azines and diazines by HPLC on bonded alkyl stationary phases. Pyridine and quinoline in environmental samples (1997)
    Springer
    Chromatographia 44 (1997), S. 253-256 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Environmental samples ; Azines and diazines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Several heterocyclic compounds have been investigated by HPLC on RP-8 and RP-18 with methanol-water mixtures as mobile phase. The chromatographic systems developed showed good selectivity for determination of azines and diazines. Pyridine and quinoline have been determined in environmental samples and in food. Samples for analysis were preconcentrated by solid phase extraction on-column with octadecyl silane packing.
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    Polysiloxane-encapsulated stationary phase for reversed-phase high-performance liquid chromatography (1997)
    Springer
    Chromatographia 44 (1997), S. 263-266 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Encapsulated stationary phase ; Poly(methylvinylsiloxane)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Silica beads of 6-μm average diameter were silanized with methylvinyldiethoxysilane and then subjected to encapsulation with poly(methylvinylsiloxane). The resulting product is a new stationary phase for reversed-phase high performance liquid chromatography (RP-HPLC) which has superior ability for the separation of polar, non-polar and basic compounds. The chromatographic peaks are symmetric. Its stability has been studied; after continuous use for three months the carbon content and chromatographic behaviour of the phase were unchanged. on to the silica surface to given an uniform organic film. Material prepared in this way has both good chromatographic behaviour and superior selectivity. Because contact of the silica matrix with the mobile phase is avoided, the alkali-resisting ability of the stationary phase is increased. The non-specific adsorption of alkaline solutes on to the silica surface is also avoided because of the complete coverage of surface silanol groups. Reports of stationary phases encapsulated with polystyrene [6], polybutadiene [I] and octadecylsiloxane polymers have recently appeared in the literature [3]. In this paper we report the encapsulation of poly-(methylvinylsiloxane) (analogous to the phase SE-31 often used in GC) on to a silica matrix previously modified with methylvinyldiethoxysilane. The resulting phase has superior performance in reversed-phase HPLC.
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    URL: http://dx.doi.org/10.1007/BF02466392
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    Reversed-phase high-performance liquid chromatographic separation of mono- and divinyl chlorophyll forms using pyridine-containing mobile phases and a polymeric octadecylsilica column (1997)
    Springer
    Chromatographia 44 (1997), S. 43-49 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Mono-and divinyl chlorophylls ; Polymeric ODS phases ; Pyridine containing mobile phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The separation of chlorophyll forms was studied employing a wide bore polymeric octadecylsilica column and pyridine containing mobile phases, giving consideration to considering the influence of mobile phase composition and column temperature on the resolution of monovinyl forms from their divinyl analogues. A method involving gradient elution and operating at 15°C is proposed for the separation of several polar and non-polar mono- and divinyl chlorophylls from etiolated tissues of higher plants and from marine phytoplankton. The advantages of pyridine as a mobile phase additive in the reversed-phase liquid chromatography of chlorophylls are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466514
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  • 185
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    Optimisation of chromatographic separations by use of a chromatographic response function, empirical modelling and multivariate analysis (1997)
    Springer
    Chromatographia 44 (1997), S. 74-80 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral separation ; Optimisation ; Multiple linear regression ; Neural networks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The chiral separation of the drug substance R,S-oxybutynin chloride on a reversed phase HPLC system has been optimised by use of empirical modelling and multivariate analysis. The separation was characterised by a new chromatographic response function developed to modulate both quality of separation and retention time. The study includes a comparison between three different multivariate techniques (multi-layer feed-for-ward neural networks, multiple linear regression and partial least squares regression) of their capabilities to model the new chromatographic response function and predict its value for new experiments. It was indicated that the most accurate models were achieved with neural networks, although partial least squares regression could also be used to solve the problem since it gives the major directions for the optimal settings of the variables.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466519
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    Ultrasonic extraction and LC determination of linear alkylbenzene sulfonate in plant tissues (1997)
    Springer
    Chromatographia 44 (1997), S. 417-420 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Plant tissues ; Linear alkylbenzene sulfonate (LAS) ; Rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new method has been developed for the extraction and determination of linear alkylbenzene sulfonate (LAS) in plant tissues (rice stems and leaves). It consists of methanol-ultrasonic extraction followed by clean-up with aluminum oxide, enrichment with C18 solid-phase extraction column and determination by HPLC. Both efficiency and accurracy of the overall method were high, i.e. mean recovery of: 89% (84 to 93% for LAS concentrations ranging from 1 to 100 mg kg−1) and repeatability of: 3% relative standard deviation for 6 replicate analyses. With a 2 g sample for analysis, LAS levels of 0.5 mg kg−1 in plants could be detected with the proposed method. Further advantages were: it was less time consuming (1 h for extraction), less solvent consumption, and smaller samples (2 to 3 g) required when compared with Soxhlet extraction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466320
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  • 187
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    Analysis of semipermanent hair dyes by HPLC with on-line post-column photochemical derivatisation (1997)
    Springer
    Chromatographia 44 (1997), S. 431-437 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Photochemical derivatisation ; Semipermanent hair dyes ; Cosmetic formulations ; Stability study
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The development of a selective and sensitive HPLC method for the determination of semipermanent hair colorants in cosmetic formulations is proposed. The separation and identification of N-hydroxyalkyl nitrophenylenediamines and nitroaminophenols were performed by HPLC with on-line, post-column, photochemical derivatisation, using a reversed phase, ion-pair system with 1,8-diaminooctane and heptansulfonate in the mobile phase. Two UV spectra (photoreactor on and off) were obtained for each analyte, adding information for confirming peak identity. Analyte-modified spectral properties were used to increase the method sensitivity. The proposed method was successfully applied to quality control and stability studies of cosmetic formulations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466323
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  • 188
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    Chromatographic properties in normal-mode HPLC of chiral stationary phases based on substituted β-cyclodextrins (1997)
    Springer
    Chromatographia 44 (1997), S. 411-416 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral stationary phases ; Bonded substituted cyclodextrins ; Normal mode separations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Substituted β-cyclodextrin chiral stationary phases having different types of phenyl carbamate substituents have been prepared and evaluated (retention, selectivity, resolution) for the liquid chromatographic separation of several series of enantiomers. The influence on separations of the degree of substitution and the structure of the substituent are discussed. Different mechanisms are suggested to explain separations in normal mode conditions.
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    URL: http://dx.doi.org/10.1007/BF02466319
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    High performance liquid chromatography —Electrospray tandem mass spectrometry (HPLC-ESI-MS-MS) for the analysis of heterocyclic aromatic amines (HAA) (1996)
    Springer
    Chromatographia 42 (1996), S. 7-11 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Heterocyclic aromatic amines (HAA) ; Electrospray MS-MS detection ; Selected reaction monitoring (SRM)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Sensitive and selective detection of the sixteen most abundant heterocyclic aromatic amines (HAA) has been achieved by application of high performance liquid chromatography-electrospray tandem mass spectrometry (HPLC-ESI-MS-MS) in combination with selected reaction monitoring (SRM). Detection limits between 0.1 and 50 ng mL−1 were established by use of HAA model solutions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02271047
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  • 190
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    The optimization of step-gradient elution conditions in liquid chromatography: Application to pesticide residue analysis using coupled-column reversed-phase LC (1996)
    Springer
    Chromatographia 42 (1996), S. 17-24 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Column switching ; Step-gradient elution ; Optimization ; Trace analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A computer spreadsheet application has been developed for the optimization of step-gradient elution conditions as applied in coupled-column RPLC for online clean-up and separation in the analysis of pesticide residues. The procedure is based on the experimentally determined retention behaviour of the analytes as a function of mobile phase composition. Retention and peak volumes of the analytes eluting under isocratic and one- and/or two-step gradient conditions can be calculated. For a given set of analytes, the spreadsheet systematically calculates the resolution of the least efficiently separated pair of peaks in the space defined by the eluotropic strengths of the mobile phases and the time at which the step-gradient takes place. The performance of the proposed procedure was tested and evaluated for the analysis of nine polar pesticides for which in a previous study adequate conditions had been found by computer-aided chromatogram simulation. the optimum conditions predicted by the procedure were in good agreement with those established experimentally and by simulation. The simultaneous production of data on retention, peak volume and resolution for a group of analytes under selected one- and/or two step-gradient elution conditions makes the calculation procedure highly productive and flexible in searching for and/or adjusting appropriate separation conditions.
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    URL: http://dx.doi.org/10.1007/BF02271049
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    Determination of the specific interaction of disubstituted aromatic compounds on hydrous zirconium oxide-loaded porous polymer resin (1996)
    Springer
    Chromatographia 42 (1996), S. 396-400 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Hydrous zirconium oxide ; Porous polymer resin ; Disubstituted phenols ; ortho-Benzoic acid derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A porous polymer resin loaded with hydrous zirconium oxide (Zr-gel) was evaluated as a stationary phase for the liquid chromatographic separation of disubstituted aromatic compounds. The prepared Zr-gel was used to separate disubstituted phenols andortho-substituted benzoic acid derivatives in reversed-phase mode. The retention time of catechol was greater than those of other disubstituted phenols; this implies that the Zr-gel has specificity for the phenolic hydroxyl group. The retention behavior ofortho-substituted benzoic acid derivatives on the Zr-gel was also evaluated in reversedphase mode using buffer. Phthalic acid was specifically retained in the vicinity of pH 6.0, which has been regarded as the equal adsorbic point. Similar behavior was also observed for salicylic acid, although the retention time of salicylic acid was less than that of phthalic acid. It seems that the specific retention behavior of hydrous zirconium oxide is a result of complexation with ligands such as hydroxyl and carboxyl groups. The results of this study have revealed that the retention mechanism of hydrous zirconium oxide is a combination of ion exchange and interaction based on complexation with ligands.
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    URL: http://dx.doi.org/10.1007/BF02272129
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    HPLC determination of tryptophan enantiomers with photometric, fluorimetric and diode-laser polarimetric detection (1996)
    Springer
    Chromatographia 42 (1996), S. 494-498 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Tryptophan ; Chiral separations ; Diode-laser polarimetric detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The combined utilization of photometric, fluorimetric and polarimetric detection liquid chromatography detectors in series for the identification and quantification of D-tryptophan and L-tryptophan was evaluated. Detection limits of about 1 μg were established with the range of linearity extending to about 100 μg. The relative standard deviation of the D-form and L-form tryptophan were 7.32 and 4.22%, respectively. The amount unknown of tryptophan enantiomers in the different mixtures was determined with an accuracy of 1.58% at the 40 μg injection level.
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    URL: http://dx.doi.org/10.1007/BF02290282
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    Chroamtographic behaviour of un-sulphated and sulphated oligoethyleneglycol nonylphenyl ether surfactants in normal-phase liquid chromatographic systems containing water (1996)
    Springer
    Chromatographia 42 (1996), S. 539-546 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Un-sulphated and sulphated surfactants ; Oligoethyleneglycol nonylphenyl ethers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention behaviour of un-sulphated and sulphated, oligoethyleneglycol nonylphenyl ether, anionic surfactants was investigated in normal-phase LC systems with chemically bonded amino stationary phase in organic mobile phases containing water and cetyl trimethylammonium bromide (CTAB). Addition of water to the mobile phase improves efficiency of separation and linearity of the dependences of logk′ versus number of oxyethylene units in the sulphated oligomers, so that it is possible to describe simultaneous effects of this number and of the concentration of CTAB on retention by a simple equation. In this system, it is possible to separate lower sulphated and un-sulphated oligomers in a single run in 10–15 min under isocratic conditions.
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    URL: http://dx.doi.org/10.1007/BF02290288
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    Identification of vitamin B12 analogues by liquid chromatography with electrothermal atomic absorption detection (1996)
    Springer
    Chromatographia 42 (1996), S. 566-570 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Electrothermal atomic absorption spectrometry ; Vitamin B12 analogues ; Cobalamins and cobalt ; Meat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The coupling of liquid chromatography and electrothermal atomic absorption spectrometry (LC-ETAAS) lowers the detection limit for identification of vitamin B12 analogues. Cobalamins and aqueous cobalt (II) were separated by reversed-phase liquid chromatography using a linear gradient: 26∶74 (v/v) methanol:0.05 M phosphate buffer (pH 4.2) to 50∶50 mixture over 8 min. The vitamins were quantitatively determined in the column effluent by measuring total cobalt by ETAAS. The analysis of meat and liver extracts by LC-ETAAS showed that the matrix did not interfere with the determination of cobalt. Hence, recoveries of cobalt in spiked meat and liver samples were satisfactory.
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    URL: http://dx.doi.org/10.1007/BF02290293
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    High-performance liquid chromatographic determination of meropenem in rat plasma using column-switching (1996)
    Springer
    Chromatographia 42 (1996), S. 405-408 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Meropenem in rat plasma ; Column-switching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The purpose of this study was to develop a columnswitching HPLC method for the determination of meropenem in plasma. This method showed excellent precision and accuracy with good sensitivity and speed. The total analysis time per sample was less than 20 min and the mean coefficients of variation for intra- and inter-assay were less than 4.0%. The method has been successfully applied to plasma samples from rats receiving an intraperitoneal injection of meropenem.
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    URL: http://dx.doi.org/10.1007/BF02272131
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    1,1′-[Ethenylidenebis(sulfonyl)]bis-benzene: A useful pre-chromatographic derivatization reagent for HPLC analysis of thiol drugs (1996)
    Springer
    Chromatographia 42 (1996), S. 515-520 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Thiol drugs ; Pre-chromatographic derivatization ; 1,1′-[ethenylidenebis(sulfonyl)]bis-benzene reagent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The use of 1,1′-[ethenylidenebis(sulfonyl)]bis-benzene as a pre-chromatographic reagent for LC analysis of thiol drugs is proposed. The reagent reacts rapidly (2 min) under mild conditions (pH 7.5, ambient) with thiol drugs and the resulting adducts can be chromatographed under reversed-phase conditions (C-18 column). Excess reagent can be removed from the reaction mixture by simple liquid-liquid extraction with chloroform. The HPLC method using UV detection was successfully applied to the analysis of reduced glutathione (GSH), N-acetylcysteine, N-2-mercaptopropionylglycine and captopril in their commercial formulations.
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    URL: http://dx.doi.org/10.1007/BF02290285
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    Direct enantiomeric HPLC separation of several 2-arylpropionic acids, barbituric acids and benzodiazepines on chiralcel OJ-R chiral stationary phase (1996)
    Springer
    Chromatographia 43 (1996), S. 599-606 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; 2-Arylpropionic acids ; Barbituric acids ; Benzodiazepines ; Cellulose tris(4-methylbenzoate) chiral stationary phase ; Reversed-phase mode ; Chiral recognition mechanisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A newly developed reversed-phase chiral stationary phase, cellulose tris(4-methylbenzoate), known as Chiralcel OJ-R, has been successfully applied to the direct resolution of the enantiomers of several nonsteroidal anti-inflammatory drugs belonging to the profen group. Among the five barbituric acids tested, the chiral resolution of mephobarbital is especially high. The Chiralcel OJ-R column also proved quite efficient for the enantiomeric resolution of a few representatives of the benzodiazepine group. Variations of mobile phase conditions based on acetonitrile and/or methanol were tested. The results obtained are briefly compared with separations performed using a Chiralcel OJ column under normalphase conditions.
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    URL: http://dx.doi.org/10.1007/BF02292974
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    Extraction and identification procedures of polyphenolic compounds and carbohydrates in phillyrea (Phillyrea angustifolia L.) leaves (1996)
    Springer
    Chromatographia 42 (1996), S. 571-577 
    Details
    ISSN: 1612-1112
    Keywords: Liquid-liquid and liquid-solid extractions ; Column liquid chromatography ; Mass spectrometry detection ; Flavonoids inPhillyrea angustifolia leaves
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Liquid-liquid (LLE) and liquid-solid extraction (LSE) procedures were developed to identify polyphenols in phillyrea (Phillyrea angustifolia L.) leaves. The liquidsolid extraction, carried out by using two serial Bond-Elut® CH and Bond-Elut® SAX cartridges allowed the collection of both polyphenols and soluble carbohydrates during a single extraction of leaf. This method seems to be suitable for both phytochemical and physiological study of the species, allowing the identification of two classes of organic compounds which have a central role in the metabolism of phillyrea plants. A method of isolation and concentration of polyphenols for further molecular characterization, using centrifuge chromatography, was also developed. Molecular characterization, carried out by UV-Vis spectrophotometry and mass spectrometry, demonstrated the presence of compounds with interesting biological activity, i.e. flavonoids and oleuropein derivatives. The soluble carbohydrate composition of phillyrea leaves did not substantially differ from that ofOlea europaea L. leaves, except for a higher mannitol/glucose ratio. This carbohydrate distribution may be linked to the evolution pattern of this species which usually grows in severely stressed environments.
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    URL: http://dx.doi.org/10.1007/BF02290294
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    Simultaneous separation and identification of hashish constituents by coupled liquid chromatography-mass spectrometry (HPLC-MS) (1996)
    Springer
    Chromatographia 43 (1996), S. 129-134 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; On-line liquid chromatography-mass spectrometry ; Neutral and acidic cannabinoids ; Hashish samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This paper reports the use of liquid chromatography for the separation and determination of the major cannabinoids extracted from hashish samples. The direct coupling to the mass spectrometer enables the selective identification both of neutral and acidic cannabinoids. The developed method does not require any preliminary derivatization and should, therefore, be of interest in forensic analysis for simple and unequivocal determination of hashish constituents.
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    URL: http://dx.doi.org/10.1007/BF02292940
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    Effect of solute association on the apparent adsorption isotherm. A model of the separation of non-racemic mixtures of enantiomers in achiral chromatographic systems (1996)
    Springer
    Chromatographia 43 (1996), S. 17-24 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Non-linear adsorption isotherm ; Simulation of chromatographic peak profiles ; Separation of optical isomers ; Non-racemic mixtures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This article discusses the effect of solute association on the apparent adsorption isotherm and on the chromatographic peak profile. The modelling performed has shown that dimerization of a solute in a chromatographic system gives rise to an apparent adsorption isotherm of the non-linear type. This results first of all in peak broadening. Tailing or a fronting can be observed depending on the relative retention of the monomer and the dimer. Secondly, the retention of the solute depends on the amount of sample because of the non-linear character of the adsorption isotherm. As a result, an excess of one of two analytes with absolutely identical adsorption properties i.e. optical isomers, can be separated in such chromatographic systems by considering that the sample contains non-equal amounts of two analytes. The phenomenon is illustrated by simulated chromatograms of the separation of non-racemic mixtures of enantiomers.
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    URL: http://dx.doi.org/10.1007/BF02272816
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