Gas Chromatographic Analysis Of Fatty Acids Research Articles

Influence of the derivatization procedure on the results of the gaschromatographic fatty acid analysis of human milk and infant formulae.

Many different analytical procedures for fatty acid analysis of infant formulae and human milk are described. The objective was to study possible pitfalls in the use of different acid-catalyzed procedures compared to a base-catalyzed procedure based on sodium-methoxide in methanol. The influence of the different methods on the relative fatty acid composition (wt% of total fatty acids) and the total fatty acid recovery rate (expressed as % of total lipids) was studied in two experimental LCP-containing formulae and a human milk sample. MeOH/HCl-procedures were found to result in an incomplete transesterification of triglycerides, if an additional nonpolar solvent like toluene or hexane is not added and a water-free preparation is not guaranteed. In infant formulae the low transesterification of triglycerides (up to only 37%) could result in an 100%-overestimation of the relative amount of LCP, if these fatty acids primarily derive from phospholipids. This is the case in infant formulae containing egg lipids as raw materials. In formula containing fish oils and in human milk the efficacy of esterification results in incorrect absolute amounts of fatty acids, but has no remarkable effect on the relative fatty acid distribution. This is due to the fact that in these samples LCP are primarily bound to triglycerides. Furthermore, in formulae based on butterfat the derivatization procedure should be designed in such a way that losses of short-chain fatty acids due to evaporation steps can be avoided. The procedure based on sodium methoxide was found to result in a satisfactory (about 90%) conversion of formula lipids and a reliable content of all individual fatty acids. Due to a possibly high amount of free fatty acids in human milk, which are not methylated by sodium-methoxide, caution is expressed about the use of this reagent for fatty acid analysis of mothers milk. It is concluded that accurate fatty acid analysis of infant formulae and human milk requires a careful and quantitative derivatization of both polar and nonpolar lipid classes. Sodium methoxide seems to be a reliable and time-saving method for routine fatty acid analysis of infant formulae, which should be validated by interlaboratory comparison. Anhydrous procedures based on methanolic hydrogen chloride including an additional nonpolar solvent are also suitable for infant formulae but seem to be preferable for human milk samples.

Isolation and Identification of Autotrophic and Heterotrophic Bacteria from an Autohydrogenotrophic Pilot-plant for Denitrification of Drinking Water

Summary The bacterial population of an autohydrogenotrophic pilot-reactor for denitrification of drinking water was characterized. Two samples were taken from the reactor under mesotrophic and psychrotrophic conditions, respectively. We purified 82 mesotrophs and 54 psychrotrophs. After screening by sodium dodecyl sulphate-polyacrylamide gelelectrophoresis of whole-cell proteins we obtained 30 and 36 different strains, respectively. These strains were identified by gaschromatographic fatty acid analysis, phenotypic tests (API), DNA-rRNA hybridizations and % G+C determination. Furthermore, their autohydrogenotrophic and heterotrophic denitrification capacities under mesotrophic or psychrotrophic conditions were tested. Some of the mesotrophs were assigned to: Aeromonas hydrophila (5 strains), Acinetobacter johnsonii (3 strains), Comamonas acidovorans (2 strains) and Shewanella putrefaciens (1 strain). The following identifications were obtained at the genus level: Serratia sp. (2 strains), Pseudomonas sp. (possibly P. stutzen, 4 strains, P. mendocina, 1 strain; P. syringae, 2 strains). Some of the psychrotrophs were assigned to: Shewanella putrefaciens (5 strains), Aeromonas hydrophila (1 strain), Aeromonas sobria (1 strain) and Micrococcus lylae (1 strain). The following identifications were obtained at the genus level: Acinetobacter sp. (16 strains) and Pseudomonas sp. (P. aureofaciens, 4 strains; P. syringae, 2 strains). The identification of the other strains was unreliable. Computer-assisted comparison of the individual strain data showed that Aeromonas hydrophila, Shewanella putrefaciens, Acinetobacter sp. and Pseudomonas sp. are present both in the mesotrophic and the psychrotrophic sample. None of the isolates was capable of autohydrogenotrophic denitrification. Under heterotrophic conditions, 7 Pseudomonas members and one unidentified isolate showed complete denitrification. This could indicate that the denitrification process in the reactor is not strictly autohydrogenotrophic or that the causal organisms were not yet isolated. Due to the presence of opportunistic human pathogens such as Aeromonas hydrophila, Shewanella putrefaciens, Acinetobacter sp. and Serratia sp. this denitrification reactor can only be used as a pretreatment step, which should be followed by a desinfection of the water.

Induction of lipid peroxidation and change of fatty acid composition in rats fed methylmercury.

Four groups of rats, with 5 animals in each, were fed a diet to which 1, 2, 4 or 8 ppm of methylmercury (MeHg) were added while another group of 5 rats was fed a diet containing no MeHg as a control. Moreover, each rat was daily supplied the same volume of these diets. During the experimental period of 40 days, body weights of the rats were daily checked individually. On day 40, expired air of the rats was collected to analyse for ethane and pentane production, and then the rats were sacrificed to obtain the liver, kidneys, brain and plasma. Thio-barbituric acid (TBA)-reactants in the selective organs and plasma were measured to investigate the effects of MeHg on lipid peroxidation. Further, gas-chromatographic analyses of fatty acids were carried out on the samples of the selective organs and plasma to examine the effects of MeHg on lipid metabolism. Results obtained were as follows: 1. The fifth day after the experiment started, the growth rates of the groups fed a diet containing MeHg (the MeHg groups) were higher than those of the control group. Moreover, the growth rates tended to increase with increases of MeHg concentrations in food from days 25 to 32 of the experimental period. Furthermore, the weights of the kidneys increased with increases in MeHg concentrations in food. 2. The amounts of expired ethane and pentane did not increase proportionally with increases in MeHg concentrations in food but those of expired ethane and pentane were higher in the MeHg groups than in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Highly sensitive determination and characterization of intact cellular ester-linked phospholipids using liquid chromatography-plasma spray mass spectrometry

Liquid chromatographic class separations of common cellular phospholipids combined with plasma spray ionization of the effluents were investigated. Comparison with true thermospray ionization involving ammonium acetate buffering revealed a gain in total ionization in the plasma spray of a factor of approximately 10 using a cation-exchange column and a solvent mixture consisting of acetonitrile-methanol-water (400:100:15, v/v). Plasma spray ionization studies of bovine brain polyphosphoinositides interrelated by the phosphate content in the inositol moeity showed almost identical monoglyceride and diglyceride ion clusters, indicating possibilities of studying the biochemical turnover of such phospholipids. Plasma spray ionization liquid chromatography-mass spectrometry of bacterial membrane phospholipids ( Pseudomonas fluorescens) revealed possibilities of obtaining indications of individual fatty acid compositions from the spectra of the phosphatidylinositol and phosphatidylethanolamine fractions present. Conventional gas chromatographic fatty acid analysis agreed with the direct mass spectrometric structure elucidations. Interestingly, the two phospholipid classes had different relative fatty acid compositions with a significantly higher degree of cyclic fatty acids in the phosphatidyl ethanolamines. Plasma spray ionization yielded linear dose-response curves for both the monoglyceride and diglyceride fragment signals in the selected-ion monitoring mode. The detection limit for the monoglyceride and diglyceride species of phosphatidylcholine under the chromatographic and mass spectrometric conditions used was found to be in the picogram range.

An outbreak of Bacillus cereus food-poisoning in Finland associated with boiled rice.

A food-poisoning outbreak caused by Bacillus cereus occurred in a Finnish industrial plant in January 1975. Eighteen of the 36 persons who ate a lunch including boiled rice, meat and vegetables became ill. The disease pattern was similar to previously reported short incubation time B. cereus food-poisonings associated with cooked rice. The median incubation time was two hours, the main symptoms being nausea, abdominal pain and vomiting. Rice and certain seasonings were the contaminated raw materials. Gas chromatographic fatty acid analysis of a bacterial cell was used as a diagnostic method as well as to identify a certain strain of B. cereus.

Gaschromatographic analysis of fatty acids of serum cholesterol esters, phospholipids and triglycerides in subjects affected by hyperlipaemia before and after treatment with non-salified d-thyroxine

Gaschromatographic analysis of fatty acids of serum cholesterol esters, phospholipids and triglycerides in subjects affected by hyperlipaemia before and after treatment with non-salified d-thyroxine

A Comparison of Some Stationary Phases Having Many Ester Groups by Gas-Chromatographic Fatty Acid Analysis

A Comparison of Some Stationary Phases Having Many Ester Groups by Gas-Chromatographic Fatty Acid Analysis

Stannic phosphate as a new support for the gas-chromatographic analysis of fatty acids

新しいガスクロマトグラフ用担体として,リン酸スズ担体の性能を遊離脂肪酸のガスクロマトグラフィーを行なうことにより検討した.リン酸スズ担体合成時のPO4/Sn比は担体と固定相液体との反応性から2に決定した.熱てんびんによる加熱減量の測定からリン酸スズ担体の使用可能温度範囲の上限は400℃であり,このことは赤外線吸収スペクトルからも支持された.リン酸スズ担体の表面状態は電子顕微鏡写真の測定によって金属切断面の表面状態に似ており,このことからその表面積はガラスビーズ担体の表面積に近いと思われる.リン酸スズ担体を使用したガスクロマトグラフィーの結果,炭素数2～18の遊離脂肪酸について良好なガスクロマトグラムを得た。これはリン酸スズ担体が脂肪酸を吸着する性質が少なく,かつ脂肪酸の会合を切り,その揮発性を改善する性質を有するからであろう.

Gaschromatographic analysis of higher fatty acids; up to and including cerotic acid.

THE rapid gas-chromatographic analysis of fatty acid methyl esters was applied by Cropper and Heywood1 and by Dijkstra, Keppler and Schols2 to the saturated fatty acids up to and including behenic acid. James and Martin3 and James and Wheatley4 analysed unsaturated and saturated fatty acid methyl esters up to and including a C19-acid.