Capillary Gas-liquid Chromatography Research Articles

Simultaneous quantitation of fatty acids, sterols and bile acids in human stool by capillary gas–liquid chromatography

A simple method for the simultaneous gas–liquid chromatographic quantitation of fatty acids, sterols and bile acids from human fecal samples is described. The various compounds are directly converted into the n-butyl ester-trimethylsilyl ether derivatives, without prior isolation from the stool. Under these conditions, fecal bile acid derivatives are well resolved from each other and from those of fecal fatty acids and sterols without overlaps. The method was found to be reproducible and recoveries were similar to those obtained after exhaustive solvent extraction of fecal sterols, fatty acids and bile acids. Optimum derivatization conditions that allowed maximum recovery of fecal components with minimal destruction and application of the method for simultaneous bile acid, fatty acid and sterol analysis in human stool are described.

Free and Esterified Sterol Composition of Edible Oils and Fats

The free and esterified sterol concentrations in 31 edible oils and fats were determined, including individual values for sitosterol, campesterol, stigmasterol, brassicasterol, Δ5-avenasterol, sitostanol, campestanol, and cholesterol. Free and esterified sterols were separated by solid-phase extraction (SPE), saponified, and quantified as trimethylsilyl ether derivatives using capillary gas–liquid chromatography. Considerable variability in the proportion of free and esterified sterols was observed among different oils and fats, with free sterols ranging from 32 to 94% of total sterols. Refining or hydrogenation tended to decrease total sterols and increase esterified sterols. Differences in total phytosterol content and the proportion of free and esterified sterols also were evident for different samples of some oils. Among four soybean oils, total phytosterols ranged from 205 to 287 mg/100 g, and free sterols constituted 68–81% of total sterols; two different shortenings differed 62% in total sterol content (185–301 mg/100 g). Such variability in phytosterol composition likely reflects differences in processing, growing season, or variety of a particular plant source.

Fatty acid composition of Portuguese spreadable fats with emphasis on trans isomers

The fatty acid composition of 17 brands of spreadable fats available in the Portuguese market was determined by capillary gas liquid chromatography as fatty acid methyl esters on a highly polar cyanopropylpolysiloxane liquid phase column. The total saturated fatty acids ranged from 23.9 to 52.6% with palmitic acid being 11.9–37.7% and stearic acid 4.0–12.3%. A wide range in the polyunsaturated fatty acids levels was noted (10.8–57.4%) with linoleic acid ranging from 10.6 to 54.0% and linolenic acid from 0.1 to 5.2%. Oleic acid levels ranged from 18.2 to 41.4%. Concerning total trans fatty acids, the mean level was 2.6%, ranging from 0.2 to 9.0%. The most frequent occurrence of trans fatty acids content in spreadable fats was in the 0.2–0.5% range (9 of the 17 brands were in this range) and only 1 brand contained trans fatty acids levels higher than 6.0%.

Qualitative Identification of Milk Fat from Chromatographic Data

The data on the amount of fatty acids in milk, animal, vegetable, and mixed fats were obtained by capillary gas–liquid chromatography. Statistical data on the concentrations of myristic, palmitic, stearic, oleic, linoleic, and linolenic acids in milk fat were considered as criteria of its natural origin. Concepts were formulated for the detection of a multicomponent adulterating additive of variable composition in a product containing variable amounts of the same components. A graphical interpretation of the results of the analysis was proposed based on the identification zone.

Binding of lactones by polysaccharides of corn and potato starches

Sorption of gamma- and delta-lactones from aqueous solutions by cryotropic gels of corn and potato starches was studied using capillary gas-liquid chromatography and Fourier transform infrared spectroscopy. The sorption patterns were similar for both types of starch. However, the sorption of lactones by potato starch was 5-10% lower than their sorption by cornstarch. The amount of substances bound by cryotextures of the starches depended linearly on their initial concentrations in gel. Increase in the length of the alkyl substituent improved sorption of lactones. It was shown that six-membered rings play a greater role in total lactone sorption than five-membered rings. The apparent constants and numbers of binding sites were estimated for compounds that reached the stage of saturation. The interaction between lactones and polysaccharides was accompanied by a decrease in their conformational lability and changes in the rheological characteristics of thermotropic and cryotropic starch gels.

Effect of different types of feeding on fatty acid composition of erythrocyte membrane lipids in full-term infants.

Significantly higher levels of arachidonic acid (AA) and docosahexaenoic acid (DHA) in plasma lipids have previously been reported in 2 to 8-wk-old as well as in 6 to 12-mo-old full-term infants fed exclusively human milk than in infants exclusively receiving formula without AA and DHA. However, in real life many infants receive both human milk and breast milk substitute formula. Healthy, full-term infants aged 2 to 12 mo and fed exclusively human milk (n = 29, age: 29.2 [14.6] wk, mean [SD], no human milk substitute formula), exclusively formula without AA and DHA (n = 30, age: 26.6 [15.2] wk, no human milk after the age of 1 mo) or combined diet (n = 38, age: 30.3 [12.8] wk, human milk for > 1 mo and breast milk substitute formula) were investigated in this cross-sectional study. Fatty acid composition of erythrocyte membrane phosphatidylethanolamine (PE), phosphatidylcholine and sphingomyeline lipids was determined by high-resolution capillary gas-liquid chromatography. The most pronounced diet-related differences were seen in PE lipids. Values of PE alpha-linolenic acid (0.07 [0.05] vs 0.26 [0.18] vs 0.19 [0.19], median [range from the 1st to the 3rd quartile], exclusively breastfed vs. exclusively formula fed vs combined diet), eicosapentaenoic acid (0.19 [0.13] vs 0.35 [0.23] vs 0.27 [0.31]) and dihomo-gamma-linolenic acid (1.34 [0.42] vs 1.86 [0.62] vs 1.58 [0.73]) were significantly lower in exclusively breastfed infants than in those fed formula, exclusively or partially. In contrast, PE AA (26.48 [2.50] vs 24.34 [4.74] vs 24.94 [3.64]) and DHA (4.93 [2.91] vs 3.51 [2.14] vs 3.58 [2.27]) values were significantly higher in exclusively breastfed infants than in the other two groups. In full-term infants aged 2 to 12 mo, erythrocyte membrane AA and DHA values are significantly higher with exclusive breastfeeding than with partial breastfeeding or exclusive feeding of formula without AA and DHA.

TRANS FATTY ACID CONTENT OF SOME FOOD PRODUCTS IN POLAND

ABSTRACTThe fatty acid composition of chips, cakes and ice creams was determined with particular attention to their trans fatty acid content. The trans C18:1 content was determined by a combined capillary gas‐liquid chromatography (GLC) and silver thin‐layer chromatography (Ag‐TLC). Six of ten types of chips examined contained more than 10%trans C18:1 (in the range of 10.3 to 17.3% of the total fatty acids), and the other four had below 0.5%. In the lipids of cakes trans C18:1 isomers occurred at 1.49 to 41.44% and only four types of cakes contained less than 5% of trans C18:1. The cis‐trans and trans‐cis C18:2 isomers were present among the fatty acids of the majority of chips and cakes investigated. Six types of chips contained trans‐trans C18:2 in the 1.2–1.6% range. Trans fatty acids were absent in the lipids of 6 types of ice cream, but two types contained 11.3 and 19.4%trans C18:1.

Results from the monitoring of pesticide residues in fruit and vegetables on the Danish market, 1998?99

The objective of the Danish pesticide monitoring programme for fruit and vegetables was to check for compliance with the maximum residue levels in foods and to monitor the residue levels to assess the pesticide exposure of the Danish population. Sampling plans were designed based on previous findings and on food consumption data. Approximately 60% of the samples were selected on the basis of positive findings in samples from the previous 5 years. The remaining samples reflected the pattern of food consumption in Denmark. In addition, a rolling programme is maintained for commodities with a low consumption and no detected residues. Within each commodity, the sampling was random. Samples (n = 4150) of mainly fresh, conventionally grown fruit and vegetables were taken throughout the chain of suppliers including foodprocessing companies. Of the samples, 3% were frozen products and 2% were organically grown. Of the samples, 3% were of Danish origin, with 65% originating from other countries. Three accredited laboratories performed analyses of the samples using capillary gas chromatography, liquid chromatography and spectrophotometric methods. Results were registered online into a central database. Residues were found in 54% of the samples of fruit but only in 13% of the vegetables. Residues above the MRL were found in 4% of all samples of fruit and in 1% of vegetables.

Inverse association between trans isomeric and long-chain polyunsaturated fatty acids in cord blood lipids of full-term infants

Previous studies showed significant inverse correlations between values of trans isomeric and long-chain polyunsaturated fatty acids in plasma lipids of preterm infants and healthy children aged 1-15 y. We sought to evaluate the same correlations in full-term infants at birth. We studied healthy full-term infants (n = 42) born after normal pregnancies and deliveries. All infants had a family history of atopy (both parents or one of the parents and a sibling had atopic symptoms). The fatty acid composition of venous cord blood lipids was determined by high-resolution capillary gas-liquid chromatography. The mean (+/-SEM) sum of trans fatty acids was 0.49 +/- 0.02% by wt in phospholipids, 2.47 +/- 0.20% by wt in cholesterol esters, 1.73 +/- 0.09% by wt in triacylglycerols, and 1.59 +/- 0.07% by wt in nonesterified fatty acids. Linear correlation analysis showed significant inverse correlations between the sum of trans fatty acids and both arachidonic acid and docosahexaenoic acid in phospholipids (r = -0.56, P < 0.001, and r = -0.48, P = 0.01, respectively), cholesterol esters (r = -0.52, P < 0.001, and r = -0.39, P = 0.018, respectively), and nonesterified fatty acids (r = -0.41, P = 0.007, and r = -0.41, P = 0.006, respectively). Because trans fatty acids in the fetal circulation must originate from the maternal diet, our results indicate that maternal exposure to trans fatty acids may represent a previously neglected variable that inversely influences long-chain polyunsaturated fatty acid status in full-term infants at birth.

Erratum

Objective: The aim of this study was to examine the distribution of trans fatty acids (TFA) in plasma lipid classes and the relationship with dietary intake of TFA. Design: After a 2 week baseline (habitual) diet, all subjects consumed a moderate fat (MF) diet for 3 weeks with the fat being derived mainly from margarine and the rest from lean beef and then a very low fat (VLF) diet for 3 weeks with the TFA being derived only from the lean beef. Blood samples were collected 2 days prior to the end and also on the last day of each dietary period. Setting: Deakin Institute of Human Nutrition, Deakin University, Geelong, Australia. Subjects: Ten free-living mildly hypercholesterolaemic subjects aged 22–66 were recruited in Geelong. Outcome measures: TFA intake was calculated from analyses of Australian margarines, butter, lean meat and animal fat. The TFA in plasma lipid fractions were separated by AgNO3 thin-layer chromatography and quantitated by capillary gas–liquid chromatography using internal standards. Results: The phospholipid (PL) fraction contained more than 60% of the trans-18:1 isomers in the plasma lipids in all subjects. On the baseline diet, the predominant positional isomer of trans-18:1 in PL was Δ11, whereas in the other lipid classes it was the Δ9 isomer. The concentration of the Δ9 isomer increased on the MF diet, particularly in the PL fraction, while the concentration of the Δ11 isomer decreased in all fractions. On the VLF diet, the total TFA level decreased by approximately 50%, mainly due to decreases in the TFA isomers in the PL and TG fractions. Changes in plasma total and PL TFA, PL Δ9, Δ10 and Δ11 were strongly correlated with dietary TFA intake (P<0.0001). There were also significant association between dietary TFA intake and PL Δ12 (P=0.003), triacylglycerol Δ9 (P=0.009), Δ11 (P=0.0005), total triacylglycerol (P=0.023) and free fatty acid TFA (P=0.042). Conclusions: The results suggest that the measurement of trans-18:1 in plasma PL and TAG and plasma total TFA could be used to estimate the intake of TFA. Sponsorship: Meat Research Corporation of Australia. European Journal of Clinical Nutrition (2001) 55, 59–64

Ammonia as carrier gas in capillary gas–liquid chromatography

Influence of helium and ammonia as carrier gases on retention of neutral solutes on polyethylene glycol has been studied theoretically and experimentally. It was shown that the influence of ammonia on the retention varied significantly depending on the solute’s nature. For example, the influence is great for C 22 n-alkane and it is small for phenol. Taking into account the results obtained by various researchers it makes sense to express an opinion on the expediency of development of gas chromatography operated under the conditions of acidic–basic chromatography.

Solid-phase microextraction method for gas chromatography with mass spectrometric and pulsed flame photometric detection: studies of organoarsenical speciation

The development, optimization, and application of a novel method for arsenic speciation based on capillary gas–liquid chromatography with simultaneous quadrupole ion-trap mass spectrometric (MS) detection and pulsed flame photometric detection (PFPD) is described. The method couples the sensitive arsenic-selectivity of PFPD with the structure elucidation capability of molecular MS detection for the determination of trace levels of unknown organoarsenicals in complex matrices. The conditions that affect the PFPD response in the presence of interfering species were optimized using the sequential Simplex algorithm for three key factors: gate delay (18.3 ms), gate width (9.1 ms), and combustion gas composition (16.6 ml/min H 2). Complete discrimination in the PFPD of the arsenic signal from interfering S-, C-, and OH-emitting species that are problematic in existing methods was achieved. Additionally, a revised interpretation of our previously reported mechanism [J. Chromatogr. A 807 (1998) 253] for the dithiol derivatization and subsequent GC–MS determination of dimethylarsinic acid is presented.

Leptin and phospholipid-esterified docosahexaenoic acid concentrations in plasma of women: observations during pregnancy and lactation.

The n-3 fatty acid status changes during pregnancy and lactation. Plasma leptin concentrations and gene expression have been related to n-3 fatty acids. To investigate the relation between plasma leptin concentration and the docosahexaenoic acid (22:6n-3) content of plasma phospholipids during early pregnancy and the postpartum period. Leptin (radioimmunoassay) and the phospholipid fatty acid profile (capillary gas-liquid chromatography) were measured in plasma of women during two independent longitudinal observational studies. Dietary intake of n-3 fatty acids was also determined. Within the first 10 weeks after the last menstrual period, an almost parallel increase in leptin concentration and the 22:6n-3 content (mg/l and % wt/wt) of plasma phospholipids was seen (study 1, n = 21). During the postpartum period (study 2, n = 57), leptin levels decreased quickly, preceding the changes in 22:6n-3 concentrations. During both studies, leptin concentrations did not consistently relate to dietary intake of n-3 fatty acids or to 22:6n-3 concentrations in plasma phospholipids. Before and during early pregnancy (study 1), significant positive associations between leptin levels and the total amount of phospholipid-associated fatty acids were found. No such association was seen during late pregnancy or the postpartum period (study 2). The postpartum decrease in leptin levels did not differ between lactating and non-lactating women. Not the 22:6n-3 content, but the total amount of phospholipid-associated fatty acids was related to plasma leptin concentration, before and during early pregnancy but not during late pregnancy and the postpartum period.

Capillary Gas–Liquid Chromatography on Short and Ultrashort Columns

Capillary Gas–Liquid Chromatography on Short and Ultrashort Columns

The occurrence of trans-18:1 isomers in plasma lipids classes in humans.

The aim of this study was to examine the distribution of trans fatty acids (TFA) in plasma lipid classes and the relationship with dietary intake of TFA. After a 2 week baseline (habitual) diet, all subjects consumed a moderate fat (MF) diet for 3 weeks with the fat being derived mainly from margarine and the rest from lean beef, and then a very low fat (VLF) diet for 3 weeks with the TFA being derived only from the lean beef. Blood samples were collected 2 days prior to the end and also on the last day of each dietary period. Deakin Institute of Human Nutrition, Deakin University, Geelong, Australia. Ten free-living mildly hypercholesterolaemic subjects aged 22-66 were recruited in Geelong. TFA intake was calculated from analyses of Australian margarines, butter, lean meat and animal fat. The TFA in plasma lipid fractions were separated by AgNO3 thin-layer chromatography and quantitated by capillary gas-liquid chromatography using internal standards. The phospholipid (PL) fraction contained more than 60% of the trans-18:1 isomers in the plasma lipids in all subjects. On the baseline diet, the predominant positional isomer of trans-18:1 in PL was delta11, whereas in the other lipid classes it was the delta9 isomer. The concentration of the delta9 isomer increased on the MF diet, particularly in the PL fraction, while the concentration of the delta11 isomer decreased in all fractions. On the VLF diet, the total TFA level decreased by approximately 50%, mainly due to decreases in the TFA isomers in the PL and TG fractions. Changes in plasma total and PL TFA, PL delta9, delta10 and delta11 were strongly correlated with dietary TFA intake (P < 0.0001). There were also significant association between dietary TFA intake and PL delta12 (P = 0.003), triacylglycerol delta9 (P=0.009), delta11 (P=0.0005), total triacylglycerol (P=0.023) and free fatty acid TFA (P = 0.042). The results suggest that the measurement of trans-18:1 in plasma PL and TAG, and plasma total TFA could be used to estimate the intake of TFA.

Fatty Acid Composition of Human Colostrum in Slovenian Women Living in Urban and Rural Areas

Colostrum samples were collected on the third day postpartum from 41 Slovenian women living in urban (n = 27) or rural (n = 14) areas. The fatty acid composition of total lipids, analysed by capillary gas-liquid chromatography, was very similar in women from both areas. The only difference was a higher content of oleic acid (18:1n–9) in rural vs. urban areas (36.85 vs. 34.94 wt%, p < 0.05). The fatty acid composition of colostrum lipids in Slovenia was as follows (mean wt%): saturated 37.68, monounsaturated 40.49, polyunsaturated 21.82, linoleic acid (18:2n–6) 15.25, α-linolenic acid (18:3n–3) 0.91, docosahexaenoic acid (22:6n–3) 0.43 and arachidonic acid (20:4n–6) 1.03. The ratio of polyunsaturated to saturated fatty acids was 0.58 and the ratio of n–6 to n–3 fatty acids was 8.0. Compared to published data on the colostrum fatty acid composition in other European, American and Asian countries, colostrum from Slovenian women is most similar to Spanish and French colostrum, probably due to a similar fatty acid composition of dietary lipids.

Monitoring of the Sources of Environmental Pollution with Crude Oil

The possibility of preliminary identification of sources of environmental pollution with crude oil was studied by IR Fourier spectroscopy, gamma-ray spectrometry, chromatography-mass spectrometry, and capillary gas-liquid chromatography with oil samples from six fields of the Khanty-Mansi Autonomous District and samples of soil and ground water contaminated with these oils.

Competitive incorporation of arachidonic acid analogs by cultured rat keratinocytes.

Arachidonic acid (20:4 n-6) and its metabolic products, such as prostaglandins and leukotrienes, have been known to be associated with skin inflammatory reactions. However, the mechanism of the competitive incorporation of 20:4 n-6 into keratinocytes among polyunsaturated fatty acids (PUFAs) remains uncertain. To investigate the relationship between the molecular structure of PUFAs and the rate of incorporation of PUFAs into cells, a fetal rat skin keratinocyte (FRSK) cell line was used. The cells were incubated for 24 h with any two of the following arachidonic acid analogs: mead acid (20:3 n-9), dihomo-gamma-linolenic acid (20:3 n-6), 11,14,17-cis-eicosatrienoic acid (20:3 n-3), arachidonic acid (20:4 n-6), eicosapentaenoic acid (20:5 n-3) and 5,8,11,14-cis-nonadecatetraenoic acid (19:4 n-5), at the ratio of 1:0, 0.5:0.5, or 0:1; and their incorporation into lipid was measured by capillary gas-liquid chromatography. The experiments indicated that 20:3 n-6 was preferentially incorporated into phospholipids of FRSK rather than 20:3 n-9 or 20:3 n-3, and 19:4 n-5 as well as 20:4 n-6 was preferentially incorporated into total cellular lipid and phospholipids rather than 20:3 n-9 or 20:5 n-3. When two PUFAs were added simultaneously to the medium, 19:4 n-5 most effectively reduced the competitive incorporation of 20:4 n-6 into phospholipids. These results suggest that keratinocytes discriminate 20:4 n-6 from other arachidonic acid analogs by its double bond positions from the carboxyl group.

Fatty acid composition of the milk lipids of Fulani women and the serum phospholipids of their exclusively breast-fed infants

We previously reported that, relative to milk of women elsewhere in the world, the lipid fraction of milk of Fulani women in northern Nigeria contained relatively low proportions of alpha-linolenic acid and docosahexaenoic acid (DHA). This led us to question the essential fatty acid status of Fulani infants and the relation between the proportion of critical n-3 and n-6 fatty acids in the serum phospholipids of the mothers, their milk, and the serum phospholipids of their exclusively breast-fed infants. We were also interested in the effect de novo intermediate chain length-fatty acids (C10-C14) had on the proportions of critical and non-essential fatty acids in milk. Capillary gas-liquid chromatography was used to analyze the fatty acid content of the total milk lipids of 34 Fulani women, as well as the fatty acid content of serum phospholipids of the women and their breast-fed infants during the first 6 months of life. The proportions of critical n-3 and n-6 fatty acids in the milk of the Fulani women were adequate, but the proportions of these same fatty acids were low in their exclusively breast-fed infants. The serum phospholipids of the infants contained 18.8% linoleic acid, 0.13% alpha-linolenic acid, 12.8% arachidonic acid, and 3.40% DHA, whereas, the mean percentages of linoleic, alpha-linolenic, arachidonic and DHA in the serum phospholipids of the Fulani mothers' were 21.4, 0.20, 9.79, and 1.97, respectively. There was a strong positive correlation between fatty acid content of serum phospholipids of Fulani women and the fatty acid content of their milk lipids. As the proportion of C10-C14 fatty acids in the milk lipids increased, the proportions of critical n-3 and n-6 fatty acids in milk remained relatively constant; however, proportions of three non-essential fatty acids decreased dramatically. C10-C14 fatty acids do not appear to displace critical n-3 and n-6 fatty acids in milk.

Hyperabsorption and retention of campestanol in a sitosterolemic homozygote: comparison with her mother and three control subjects

We measured the percent absorption, turnover, and distribution of campestanol (24-methyl-5α-cholestan-3β-ol) in a sitosterolemic homozygote, her obligate heterozygous mother, and three healthy human control subjects. For reasons relating to sterol hyperabsorption, the homozygote consumed a diet low in plant sterols that contained campestanol at about 2 mg/day. The heterozygote and three control subjects were fed a diet supplemented with a spread that contained campestanol at 540 mg/day and sitostanol (24-ethyl-5α-cholestan-3β-ol) at 1.9 g/day as fatty acid esters. Plasma campestanol concentrations determined by capillary gasliquid chromatography were 0.72 ± 0.03 mg/dl in the homozygote, 0.09 ± 0.04 mg/dl in the heterozygote, and 0.05 ± 0.03 mg/dl for the control mean. After simultaneous pulse labeling with [3α-3H]campestanol intravenously and [23-14C]campestanol orally, the maximum percent absorption measured by the plasma dual-isotope ratio method as a single time point was 80% in the homozygote, 14.3% in the heterozygote, and 5.5 ± 4.3% as the mean for three control subjects. Turnover (pool size) values estimated by mathematical analysis of the specific activity versus time [3α-3H]campestanol decay curves were as follows: 261 mg in the homozygote, 27.3 mg in the heterozygote, and 12.8 ± 7.6 mg in the three control subjects (homogygote vs. controls, P < 0.001). The calculated production rate (mg/24 h) equivalent to actual absorption in the presence of dietary sterols and stanols was 0.67 mg/day or 31% of intake in the homozygote, 2.1 mg/day or 0.3% of intake in the heterozygote, and 0.7 ± 0.3 mg/day or 0.1% of intake in the three control subjects. However, the excretion constant from pool A (KA) was prolonged markedly in the homozygote, but was 100 times more rapid in the heterozygote and three control subjects. Thus, campestanol, like other noncholesterol sterols, is hyperabsorbed and retained in sitosterolemic homozygotes. However, campestanol absorption was only slightly increased in the sitosterolemic heterozygote and removal was as rapid as in control subjects.—Salen, G., G. Xu, G. S. Tint, A. K. Batta, and S. Shefer. Hyperabsorption and retention of campestanol in a sitosterolemic homozygote: comparison with her mother and three control subjects. J. Lipid Res. 2000. 41: 1883–1889.