A microliter method for the gas chromatographic determination of long-chain non-esterified fatty acids in human serum or plasma

Simple thin-layer chromatographic purification procedure for the determination of cholesterol ester fatty acid compositions

A mild procedure for the purification of methyl esters of the fatty acid components of cholesterol esters, from interfering free cholesterol and other contaminating residues, is described. Methyl esters and free cholesterol are formed during the methylation of cholesterol esters. When co-extracted, cholesterol and other contaminating residues interfere with the methyl esters because minute proportions of these residues tend to elute at the same retention times as palmitoleic and stearic acids, to yield unreliable but significantly higher values for palmitoleic (p less than 0.001) and stearic acids (p less than 0.0001), and correspondingly lower values for oleic acid (p less than 0.0001). Purification of methyl esters by thin-layer chromatography eliminates this problem and yields reliable analysis of cholesterol ester fatty acids, without measurable oxidation of unsaturated fatty acids.

Benzyl esters of C2-C20 fatty acids and metabolically relevant carboxylic acids. Preparation and gas chromatography-mass spectrometry

Short-, medium- and long-chain fatty acids, and other types of metabolically relevant carboxylic acids like hydroxy-, keto-, aromatic and dicarboxylic acids, were analyzed by capillary gas chromatography. For separation, benzyl ester derivatives were used, prepared by reaction of the potassium carboxylates with benzyl bromide in acetonitrile catalyzed by a crown ether. The reaction conditions for quantitative benzylation were studied. Keto groups of ketocarboxylic acids were stabilized prior to benzylation by formation of O-methyl oximes using methoxyamine hydrochloride in aqueous-ethanolic solution. The separation of more than 45 carboxylic acids was achieved on a CP-Sil 5 CB fused-silica capillary column in less than 70 min. The electron impact mass spectra of ketocarboxylic acid O-methyl oxime benzyl esters

Short-term biological reproducibility of serum fatty acid composition in children

To assess the biological day-to-day reproducibility of the fatty acid composition in serum lipid fractions in children on their habitual diets, fasting serum specimens were collected from healthy 8- to 9-year-old boys at 2-day (n = 21) or 7-day (n = 19) intervals. Percentage compositions of fatty acids in serum cholesteryl esters (CE), triglycerides (TG), free fatty acids (FFA) and phospholipids (PL) were analyzed by gas chromatography. The reproducibility was estimated by calculating linear correlation coefficients between the values obtained at the two time-points. Generally the correlations were higher in CE and PL than in TG and FFA. In CE the 7-day correlations of major fatty acids were only slightly lower than the 2-day ones. In PL the impairment of correlations was somewhat greater than in CE, but in TG and FFA there was a marked drop in reproducibility from 2- to 7-day intervals. The 2-day correlation coefficients of the percentages of linoleate, dihomo-gamma-linolenate, arachidonate and eicosapentaenoate in CE were 0.95, 0.84, 0.91 and 0.92, respectively. In PL, the respective values were 0.86, 0.82, 0.95 and 0.90. The present results indicate high short-term biological reproducibility of fatty acid composition in serum CE and PL and clearly lower in those of TG and FFA.

Effect of beta-adrenergic stimulation on free fatty acid content in subepicardial and subendocardial layers of the dog heart in situ. Separation and assay by capillary gas chromatography

The effects of beta-adrenergic stimulation produced by an infusion of isoproterenol (1 microgram X kg-1 min-1, 30 min) were studied in situ in the anaesthetized dog placed under a total cardiopulmonary bypass. Samples of the subepicardial and the subendocardial layers were homogenized separately prior to the extraction and methylation of free fatty acids (FFA). Gas chromatography on Carbowax 20 M capillary columns was used for the quantitation of myristic (C 14:0), palmitic (C 16:0), palmitoleic (C 16:1), stearic (C 18:0), oleic (C 18:1), linoleic (C 18:2), and arachidonic (C 20:4) acids. Within 5 min, isoproterenol decreased the tissue content of FFA significantly. The decrease was more pronounced in the endocardial layer where the FFA concentration reached its minimum at the 5th or the 15th min. In the epicardial layer, all the FFA reached their minimal concentration at the 30th min of the isoproterenol infusion. In both layers, lactate content remained unchanged at 5 and 15 min and rose at the 30th min only and content in phosphorylated compounds (ATP, creatine-phosphate-CP) did not show any significant variation during the beta-stimulation period. A significant correlation was found between the chronotropic effect of isoproterenol and the reduction of FFA concentration.

Derivatization reactions in the gas—liquid chromatographic analysis of drugs in biological fluids

Alkylation, acylation, silylation and other derivatization reactions applied to the gas chromatographic analysis of drugs in biological matrices are reviewed. Reaction conditions are discussed in relation to reaction mechanisms. Detector-oriented labelling of drugs, and derivatization with chiral reagents for the separation of enantiomers are surveyed. Data on the sample clean-up, derivatization and GLC analysis of more than 300 drugs and related compounds are listed.

High-performance liquid chromatographic determination of free fatty acids with 1-naphthylamine

A 1% benzene solution of oxalyl chloride was added to saturated and unsaturated fatty acids and the mixture was allowed to react at 70 degrees C for 30 min; by this procedure, each fatty acid was converted into its acid chloride in a considerably quantitative manner. By reacting this acid chloride with 1-naphthylamine at 30 degrees C for 15 min, naphtylamine derivatives were produced, which showed strong ultraviolet absorption around 280-290 nm. Experiments were made on the recovery of the fatty acids added to 0.5 ml of human serum, and the recovery was found to fall in the range of 94-106% (coefficient of variation = 0.5-4.1%) when the following amounts of six fatty acids were added: C14:0, 2 micrograms; C16:0, 20 micrograms; C16:1, 5 micrograms; C18:0, 4 micrograms; C18:1, 20 micrograms; C18:2, 10 micrograms.