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PubMed1990

High-performance liquid affinity chromatography and in situ fluorescent labeling on thin-layer chromatography of glycosphingolipids.

A method combining high-performance liquid affinity chromatography and in situ fluorescent labeling on thin-layer chromatography is introduced for determination of glycosphingolipids. Glycolipids in crude extract from rat liver were separated quantitatively from neutral lipids and phospholipids with a phenylboronic acid-derivatized silica gel column. Glycolipids were eluted quantitatively with approximately 98% of crude extract recovered. This column is useful for selective cleanup of glycosphingolipids in crude extract from tissue. Simultaneously, a fluorometric determination of glycosphingolipids with 7-amino-4-methylcoumarin after NaIO4 oxidation on a TLC plate was introduced and its condition was optimized. Glycolipids in amounts ranging from 1 to 100 pmol are easily detectable and give linear responses over the respective ranges. The method is fast and useful for the determination of glycolipids from small amounts of biological samples and requires a minimum amount of about 1 mg of biological specimen for determination of glycolipids.

Animals↗
PubMed1996

Gel permeation chromatography-high performance liquid chromatography combination as an automated clean-up technique for the multiresidue analysis of fats.

The well-known and almost universally utilizable clean-up technique of gel permeation chromatography (GPC) and subsequent conventional silica-gel column chromatography was automated by an on-line solvent evaporation of the GPC fraction, followed by normal-phase HPLC separation. The ternary solvent system n-hexane-toluene-acetone (88:10:2, v/v/v) was used as the mobile phase which resulted in only one HPLC fraction for all relevant analytes. The HPLC column was cleaned automatically after each sample by backflushing with polar solvents. The recoveries and reproducibilities of 35 analytes (mainly organochlorine compounds) were in the range of 77-90% and 3-7%, respectively; the high efficiency of the HPLC separation provide very clean extracts for the GC analysis. This automated clean-up technique is routinely used for the multiresidue analysis of various fat-containing food and biota samples.

Automation↗
PubMed1985

Identification of phenprocoumon metabolites in human urine by high-performance liquid chromatography and gas chromatography-mass spectrometry.

The oral anticoagulant phenprocoumon is eliminated in urine mainly as the glucuronide conjugate to an extent of 20% of the dose. The urine from patients undergoing phenprocoumon therapy was investigated and the following metabolites were isolated and identified: 7-hydroxyphenprocoumon as the main component, and 4'-hydroxyphenprocoumon and 6-hydroxyphenprocoumon as conjugates. They were characterized by high-performance liquid chromatography and, after methylation, by gas chromatography-mass spectrometry.

4-Hydroxycoumarins↗
PubMed1991

Separation of cholesterol esters by silver ion chromatography using high-performance liquid chromatography or solid-phase extraction columns packed with a bonded sulphonic acid phase.

Two methods for the separation of cholesterol esters, based on the number of double bonds in their fatty acid moieties, are presented. Silver ion chromatography, usually performed on thin-layer chromatographic plates, was made suitable for high-performance liquid chromatography (HPLC) and solid-phase extraction. Separation on a bonded sulphonic acid phase loaded with silver ions was achieved with cholesterol esters containing up to six double bonds in their fatty acid moieties. No cross-contamination between fractions with different numbers of double bonds was detected with the HPLC method, was demonstrated by subsequent gas chromatographic analysis of the fatty acid moieties, following transmethylation. For adequate separations with the solid-phase extraction columns it proved important to avoid overloading. The methods may be of use for the off-line analyses of the sterol compositions of the isolated fractions, which each contain sterol esters with an equal number of double bonds in their fatty acid moieties.

Animals↗
PubMed2004

Identification of organic compounds in atmospheric aerosol particles by on-line supercritical fluid extraction-liquid chromatography-gas chromatography-mass spectrometry.

Atmospheric particles were collected with a high-volume sampling system at an urban site in Helsinki (Finland). The samples were analysed by on-line coupled supercritical fluid extraction-liquid chromatography-gas chromatography-mass spectrometry (SFE-LC-GC-MS). The aerosol sample was first extracted by SFE. The extract was then transferred to a liquid chromatograph where it was fractionated into four fractions according to polarity. Each fraction from the liquid chromatograph was transferred to a gas chromatograph by large-volume injection, where final separation was carried out. The first LC fraction (280 microl) contained nonpolar compounds, such as n-alkanes, hopanes and steranes. The second fraction (840 microl) included polycyclic aromatic hydrocarbons (PAHs) and alkyl-PAHs, while the third and fourth fractions (840 microl each) contained more polar compounds, such as n-alkan-2-ones, n-alkanals, oxy-PAHs and quinones.

Aerosols↗
PubMed2004

State-of-the art of selective detection and identification of I-, Br-, Cl-, and F-containing compounds in gas chromatography and liquid chromatography.

This review article presents an overview of halogen-specific detection in gas chromatography (GC) and liquid chromatography (LC). Attention is primarily focused on the use of plasma emission spectroscopy and plasma mass spectrometry as detectors, but other halogen-selective detection principles are also mentioned. Different instrumental configurations are discussed both with respect to technical set-up and performance, the principal reasons for halogen-selective detection are highlighted, and recent applications are reviewed from areas such as environmental chemistry, petroleum characterization, and drug analysis.

Animals↗
PubMed1988

On-line high-performance liquid chromatography-post-column reaction-capillary gas chromatography analysis of lipids in biological samples.

The versatility of on-line liquid chromatography and gas chromatography is further expanded by the addition of on-line derivatization. The on-line fractionation, derivatization and separation system is applied to the characterization of lipids in biological samples. Separation of the triglycerides from the phospholipids was accomplished on a narrowbore (2.0 mm I.D.) 5 microns silica column. The entire triglyceride fraction was transferred to a heated fixed bed reactor for esterification of the fatty acid constituents. Transfer of the derivatized zones to the gas chromatograph was accomplished by the use of a retention gap. Application of the system to the separation and characterization of Staphylococcus aureus is presented.

Chromatography, Gas↗
PubMed1977

Analysis of polychlorinated biphenyls by high-performance liquid chromatography and capillary gas-liquid chromatography.

Seventy fractions were obtained by vacuum distillation of a PCB mixture containing 42% of chlorine. Four of these fractions were chosen, the composition of which covered the whole of the observed region, and analysed by means of high-performance liquid chromatography (HPLC) on silica gel using n-pentane as the mobile phase and capillary gas-liquid chromatography (GLC) using OV-101 and Carbowax 20M as stationary phases at 200 degrees C. The chosen distillation fractions were further prepared by HPLC, each yielding 10-14 samples. Individual PCB standards and all samples were analysed by HPLC and capillary GLC. These procedures permitted the identification of those compounds which are eluted simultaneously under the conditions used in either HPLC or capillary GLC alone.

Chromatography, Gas↗
PubMed1998

Analysis of pesticides in red wines by on-line coupled reversed-phase liquid chromatography-gas chromatography with vaporiser/precolumn solvent split/gas discharge interface.

Pesticides in red wines were analysed by on-line coupled reversed-phase liquid chromatography-gas chromatography where a vaporiser/precolumn solvent split/gas discharge interface enabled direct transfer of aqueous eluent to the GC system. The LC part of the system provided sample clean-up and re-concentration, and the GC the final analytical step. The method developed allowed automated and quantitative analysis of the wine samples, where the only manual step was filtration. The limits of quantification were clearly below the maximum residue limits established for grapes, being lower than 10 micrograms l-1 for all pesticides studied.

Chromatography, Gas↗
PubMed1980

Determination of hydralazine metabolites: 4-hydrazino-phthalazin-1-one and n-acetylhydrazinophthalazin-1-one by gas chromatography and s-triazolo[3,4-alpha]phthalazine and phthalazinone by high-performance liquid chromatography.

Methods are described for the determination of 2-N-acetylhydrazinophthalazin-1-one, 4-hydrazinophthalazin-1-one, phthalazinone and s-triazolo[3,4-alpha]phthalazine in human urine. 4-Hydrazinophthalazin-1-one and 4-N-acetylhydrazinophthalazin-1-one (following acid hydrolysis) are reacted with acetylacetone to give a distinctive pyrazole derivative which can be determined by gas chromatography using a nitrogen-specific detector. Phthalazinone and s-triazolo[3,4-alpha]phthalazine are measured underivatised by high-performance liquid chromatography.

Chromatography, Gas↗
PubMed1999

Validation of urine drug-of-abuse testing methods for ketobemidone using thin-layer chromatography and liquid chromatography-electrospray mass spectrometry.

High-performance thin-layer chromatography (TLC) with visual detection (post-chromatographic derivatization) was used in screening for the drug ketobemidone in human urine samples. High-performance liquid chromatography with electrospray mass spectrometry (LC-ESI-MS) was used for final confirmation of the result. The clean-up was performed by mixed-mode solid-phase extraction, and nalorphine was used as internal standard. A screening cut-off for TLC was established at 0.2 microg/ml. The mean recovery for LC-MS was 91% (n=60) with coefficients of variation (C.V.) in the range of 7 to 16%. Qualifying fragment ions of ketobemidone (m/z 190, 201 and 230) were generated by up front collision-induced dissociation (CID) on a single quadrupole instrument. Relative ion intensities were within +/- 15% deviation compared with standards in the same batch. The limit of detection for LC-MS was 0.025 microg/ml. Positive clinical samples from drug abusers (n=10) had concentrations in the range 0.07 to 3.2 microg/ml, which could be determined by LC-MS without matrix interference. During screening of unknown clinical samples (n=27) the results from TLC was in agreement with LC-MS data. After acid hydrolysis of conjugates in clinical samples the analyte response of ketobemidone and norketobemidone was increased by a factor of approximately two and twelve, respectively. A qualitative GC-MS technique was demonstrated for the detection of the spasmolyticum A29 (N,N-dimethyl-4,4-diphenyl-3-buten-2-amine), which can be found in a preparation combined with ketobemidone (Ketogan).

Analgesics, Opioid↗
PubMed2001

Isolation and identification of the metolachlor stereoisomers using high-performance liquid chromatography, polarimetric measurements, and enantioselective gas chromatography.

Because of the presence of two chiral elements (an asymmetrically substituted carbon and a chiral axis), the herbicide metolachlor consists of four stereoisomers stable at ambient temperature with aSS-, aRS-, aSR-, and aRR-configurations (aSS, the isomer with aS,1'S-configuration, etc.). Metolachlor, initially introduced into the market as the racemic product containing all four stereoisomers, is currently being replaced worldwide by S-metolachlor, the product enantiomerically enriched with the herbicidally active 1'S-isomers (aSS, aRS). The isomer-specific analysis of metolachlor requires not only enantioselective ("chiral") analytical techniques but also suitable reference compounds. In this study, two of the four metolachlor isomers were isolated from rac-metolachlor in enantio- (ee > 98%) and diastereomerically pure forms by a combination of achiral and chiral high-performance liquid chromatography (HPLC). The two isomers were identified as the aSS- and the aRR-isomers by polarimetric measurements, in reference to previous data. The two isomers were then thermally equilibrated to 1:1 mixtures of the aSS/aRS and aRR/aSR diastereomers, respectively, so that analytical data of all four metolachlor isomers became available; they were then used to identify these isomers in technical products by chiral high-resolution gas chromatography (HRGC). The kinetics of the thermally induced interconversion of the atropisomers was studied and the consequences, such as for GC analysis, are discussed. A comparison of on-column and split/splitless injection indicated that the latter technique results in significant isomerization prior to separation and, therefore, cannot be used for accurate isomer analysis.

Acetamides↗
PubMed2002

Analysis of antioxidants from orange juice obtained by countercurrent supercritical fluid extraction, using micellar electrokinetic chromatography and reverse-phase liquid chromatography.

Antioxidants from orange juice were determined by the combined use of countercurrent supercritical fluid extraction (CC-SFE) prior to reverse-phase liquic chromatography (RP-LC) or micellar electrokinetic chromatography (MEKC). The separation of antioxidants found in the SFE fractions was achieved by using a new MEKC method and a published LC procedure, both using diode array detection. The characterization of the different antioxidants was further done by LC-mass spectrometry. Advantages and drawbacks of LC and MEKC for analyzing the antioxidants found in the different orange extracts are discussed. Although LC yields higher peak area and slightly better reproducibility than MEKC, the latter technique provides information about the CC-SFE extracts in analysis times 7 times faster than by LC. This analysis advantage can be used for the quick adjustment of CC-SFE conditions, thus providing a fast way to obtain orange fractions of specific composition.

Antioxidants↗
PubMed2005

Multiresidue analysis of pesticides in soil by supercritical fluid extraction/gas chromatography with electron-capture detection and confirmation by gas chromatography-mass spectrometry.

The applicability of supercritical fluid extraction (SFE) in pesticide multiresidue analysis (organohalogen, organonitrogen, organophosphorus, and pyrethroid) in soil samples was investigated. Fortification experiments were conducted to test the conventional extraction (solid-liquid) and to optimize the extraction procedure in SFE by varying the CO2 modifier, temperature, extraction time, and pressure. The best efficiency was achieved at 400 bar using methanol as modifier at 60 degrees C. For the SFE method, C-18 cartridges were used for the cleanup. The analytical screening was performed by gas chromatography equipped with electron-capture detection (ECD). Recoveries for the majority of pesticides from spiked samples of soil at different residence times were 1, 20, and 40 days at the fortification level of 0.04-0.10 mg/kg ranging from 70 to 97% for both methods. The detection limits found were <0.01 mg/kg for ECD, and the confirmation of pesticide identity was performed by gas chromatography-mass spectrometry in a selected-ion monitoring mode. Multiresidue methods were applied in real soil samples, and the results of the methods developed were compared.

Chromatography, Gas↗
PubMed1989

Purification of Plasmodium falciparum exoantigens by spun-column chromatography and by inverse affinity chromatography.

Exoantigens released into the medium during the in vitro culture of Plasmodium falciparum were purified to obtain a better characterization. This purification was done in two steps. First the crude culture medium was passed through a cationic exchange gel on a spun-column. This preliminary step is efficient and rapid. The serum contaminants were removed from the effluent by an inverse affinity chromatography with, as adsorbant, anti-human serum from the horse. The quality of the antigens obtained was analysed by metabolic radioactive labelling with tritiated leucine and by exclusion high pressure liquid chromatography, and the antigenicity measured by ELISA.

Animals↗
PubMed1989

Isolation of the nonprotein nitrogen fraction from human milk by gel-filtration chromatography and its separation by fast protein liquid chromatography.

Human milk (HM) is unique compared with the milk of other species in that nonprotein nitrogen (NPN) constitutes 20-25% of the total N. The NPN fraction consists of a diverse group of compounds with molecular masses less than 10,000 Da (in the picogram to microgram per milliliter range), which have only been partially characterized. We developed a methodology to separate and concentrate the NPN fraction for further analysis. NPN was initially separated from other milk components by Sephadex G-25 gel filtration. Further isolation and separation was carried out by fast protein liquid chromatography gel filtration and ion-exchange chromatography. Molecular masses of unknown peaks were determined by using known molecular mass markers and standards. The methodologies developed lead to the discrete separation of NPN from other milk compounds and can be particularly valuable for isolating peptides in HM.

Chromatography, Gel↗
PubMed1977

Trace analysis of diethylstilbestrol [DES] in animal chow by parallel high-speed liquid chromatography, electron-capture gas chromatography, and radioassays.

An analytical method is described for determining residues of the synthetic estrogen diethylstilbestrol (DES) in animal chow at levels as low as 1 ppb. A methanol extract of the chow is subjected to a 3-step cleanup procedure including a Sephadex LH-20 column, liquid-liquid partitioning at pH 14 and 10.2, and a silica gel column. Residues of DES in the cleaned-up extract are analyzed directly by high-speed liquid chromatography or derivatized to pentafluoropropionyl-DES and assayed by electron-capture gas chromatography. Tests with 14C-DES were used to develop and validate the procedure. Ancillary data concerning extraction efficiencies of various solvents, comparisons of various derivatizing reagents, rates of trans-cis isomerization in two solvents, P-values of DES in various solvent-systems and thin-layer chromatographic behavior i

Animal Feed↗