Gas chromatographic analysis of fatty acid methyl esters: Avoiding discrimination by programmed temperature vaporizing injection

Eder, Klaus; Reichlmayr‐Lais, Anna M.; Kirchgeßner, M.

doi:10.1016/0021-9673(91)85032-b

Cited by 41 publications

(9 citation statements)

References 36 publications

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“…The detector temperature was 300°C. Fatty acid methyl esters were identified by comparing their retention times with those of individual purified standards and quantified with heptadecanoic acid methyl ester as internal standard (15). The amounts of individual hepatic phospholipids [phosphatidylcholine (PC) and phosphatidylethanolamine, diacyl (PE)] were calculated by the amount of their bound fatty acids.…”

Section: Methodsmentioning

confidence: 99%

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Different degrees of moderate iron deficiency modulate lipid metabolism of rats

Stangl

Kirchgeßner

1998

Lipids

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Severe iron deficiency affects lipid metabolism. To investigate whether moderate iron depletion also alters lipid variables-including lipid levels in serum and liver, hepatic lipogenesis, and fatty acid composition indicative of an impaired desaturation-we carried out experiments with rats fed 9, 13, and 18 mg iron/kg diet over a total of 5 wk. The study also included three pair-fed control groups and an ad libitum control group, fed with 50 mg iron/kg diet. The iron-depleted rats were classified as iron-deficient on the basis of reduced serum iron, hemoglobin concentration, and hematocrit. All moderately iron-deficient rats had significantly lower cholesterol concentrations in liver and serum lipoproteins than their pair-fed controls. Rats with the lowest dietary iron supply had higher concentrations of hepatic phosphatidylcholine (PC) and phosphatidylethanolamine (PE), lower activities of glucose-6-phosphate dehydrogenase, malic enzyme and fatty acid synthase, and higher triacylglycerol concentrations in serum lipoproteins than the corresponding pair-fed control rats. Moderate iron deficiency also depressed the serum phospholipid level. Moreover, several consistent significant differences in fatty acid composition of hepatic PC and PE occurred within moderate iron deficiency, which indicate impaired desaturation by delta-9 and delta-6 desaturases of saturated and essential fatty acids. We conclude that lipid variables, including cholesterol in liver and serum lipoproteins as well as fatty acid desaturation, reflect the gradations of iron status best and can be used as an indicator of the degree of moderate iron deficiency.

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Section: Methodsmentioning

confidence: 99%

“…15 Table 2 for column heading explanations. b Means were compared by Fisher's multiple range test; means not sharing a common superscript letter are significantly different at P < 0.05. c Fe− means iron-deficient groups, Fe+ means iron-adequate groups, PF means control group pair-fed to the iron-deficient group.…”

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confidence: 99%

Different degrees of moderate iron deficiency modulate lipid metabolism of rats

Stangl

Kirchgeßner

1998

Lipids

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“…The early pioneer work by Ackman and Sipos [12], and Bannon [13], proposed using a theoretical relative response factor (RRF (Theo) ), based on the ionized carbon atoms, to correct the FID response to FAMEs of different composition. We realized from the previously published results [16][17][18][19][20], and also from our preliminary analysis, that the RRF for different FAMEs can be varied depending upon the GC run conditions, and therefore may cause an error in the determination of fatty acid concentrations in a given sample. The data shown in Fig.…”

Section: Relative Response Factormentioning

confidence: 98%

“…The widely used RRF (Theo) was originally calculated based on ''active atom'' theory without considering the instrument conditions [6,14]. However, it has been realized that the instrument parameters, sample running conditions and the fatty acid composition in samples can influence the RRF and hence may affect the analysis [15][16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

An Improved Method for Determining Medium‐ and Long‐Chain FAMEs Using Gas Chromatography

Xu¹,

Harvey²,

Pavlina³

et al. 2010

Lipids

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The existing protocols for analyzing fatty acid methyl esters (FAMEs) using a one-step acetyl chloride (AC) catalyzed transesterification and extraction procedure cannot accurately determine the medium- and long-chain fatty acids simultaneously in clinical (enteral, parenteral) formulations. For example: (1) addition of AC at room temperature generates an exothermic reaction that often results in loss of sample and possible injury to the analyst; (2) certain polyunsaturated fatty acids (PUFAs) are less stable at elevated temperatures during the transesterification and contribute to the over-estimation of the C16:0 and C18:1 fatty acids; and (3) the flame-ionization detector (FID) response varies depending on the carbon chain length of the fatty acids, that consequently impacts the underestimation of medium-chain fatty acid (C6-C10) recoveries. To overcome these deficiencies and accurately determine FAMEs, we have developed an improved one-step transesterification method that employs the addition of AC in tubes kept on a dry ice bath, the transesterification at room temperature, and the data analysis using relative response factors. Using this modified protocol, we determined the fatty acid composition of lipid emulsions (Omegaven and Lipidem) on a Shimadzu GC2010 gas chromatography (GC) system using a capillary GC column (Zebron ZB-WAX plus, 30 m, 0.25 mm ID, 0.25 microm). Our data suggest that the improved method can be easily used to accurately determine fatty acids (C6-C24) in functional foods and lipid emulsions.

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“…Biological samples typically contain a wide variety of molecular species and it has been observed in some studies that, owing to their relative lack of momentum, smaller molecules are more likely to be diverted to waste than larger molecules (Eder, Reichlmayr-Lais, & Kirchgessner, 1991). This phenomenon is known as sample discrimination and a number of strategies have been successfully used to limit its effect on the quality of chromatographic analysis.…”

Section: Chromatographic Analysismentioning

confidence: 99%

Extraction and Characterization of Lipids From Microalgae Grown on Municipal Wastewater

Hutton¹

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Gas chromatographic analysis of fatty acid methyl esters: Avoiding discrimination by programmed temperature vaporizing injection

Cited by 41 publications

References 36 publications

Different degrees of moderate iron deficiency modulate lipid metabolism of rats

Different degrees of moderate iron deficiency modulate lipid metabolism of rats

An Improved Method for Determining Medium‐ and Long‐Chain FAMEs Using Gas Chromatography

Extraction and Characterization of Lipids From Microalgae Grown on Municipal Wastewater

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