Determination of phospholipid fatty acids in biological samples by solid-phase extraction and fast gas chromatography

Normal-Fat vs. High-Fat Diets and Olive Oil vs. CLA-Rich Dairy Fat: A Comparative Study of Their Effects on Atherosclerosis in Male Golden Syrian Hamsters

The relationship between milk fat intake (because of its high saturated fatty acid content) and the risk of suffering from cardiovascular diseases remains controversial. Thus, Golden Syrian hamsters were fed two types of fat-sheep milk fat that was rich in rumenic (cis9,trans11-18:2) and vaccenic (trans11-18:1) acids and olive oil-and two doses (a high- or normal-fat diet) for 14 weeks, and markers of lipid metabolism and atherosclerosis evolution were analyzed. The results revealed that the type and percentage of fat affected most plasma biochemical parameters related to lipid metabolism, while only the expression of five (CD36, SR-B1, ACAT, LDLR, and HMG-CoAR) of the studied lipid-metabolism-related genes was affected by these factors. According to aortic histology, when ingested in excess, both fats caused a similar increase in the thickness of fatty streaks, but the high-milk-fat-based diet caused a more atherogenic plasma profile. The compositions of the fats that were used, the results that were obtained, and the scientific literature indicated that the rumenic acid present in milk fat would regulate the expression of genes involved in ROS generation and, thus, protect against LDL oxidation, causing an effect similar to that of olive oil.

Polymerized phosphonium ionic liquid functionalized silica microspheres as mixed-mode stationary phase for liquid chromatographic separation of phospholipids

There is a large and growing demand for the vigorous development of new high performance liquid chromatography stationary phases in order to solve complex phospholipids separation. Herein, phosphonium-based ionic liquid trioctyl(allyl)phosphonium bromide ([P_888Allyl]Br) was first synthesized with trioctylphosphine and allyl bromide. With [P_888Allyl]Br as the polymerizable monomer, polymerized phosphonium ionic liquid functionalized silica microsphere (PIL@SiO₂) was further synthetized via click chemistry reaction. Significantly, based on the inherent amphiphilic nature of the introduced [P_888Allyl]Br, the packed PIL@SiO₂ column displayed hydrophilic/hydrophobic mixed-mode retention mechanisms. The PIL@SiO₂ column can achieve separation of nucleic acid bases and nucleosides, sulfonamides, amides and anilines with excellent selectivity in a shorter separation time. The column efficiency reached 109,700 N/m for 2-iodoacetamide. One of the important characteristics of the PIL@SiO₂ column is that both phospholipid classes and species can be efficiently separated via the same column, outperforming that of the commercial amino column. Furthermore, the application potential of the PIL@SiO₂ column was further verified via separation of phospholipids extracted from soy lecithin. The proposed PIL@SiO₂ column provides a promising candidate for separation of complex phospholipid samples.

The Sum of Plasma Fatty Acids iso16:0, iso17:0, trans11-18:1, cis9, trans11-CLA, and cis6-18:1 as Biomarker of Dairy Intake Established in an Intervention Study and Validated in the EPIC Cohort of Gipuzkoa

The questioned reliability of 15:0, 17:0, and trans9-16:1 acids as biomarkers of dairy fat intake also questions the relationship between the intake of these products and their health effects. Two studies were conducted in the same geographical region. In an intervention study, volunteers followed a diet rich in dairy products followed by a diet without dairy products. Plasma and erythrocyte fatty acids (FA) were analyzed, and their correlations with dairy product intakes were tested. The FA biomarkers selected were validated in the Gipuzkoa cohort of the European Prospective Investigation into Cancer and Nutrition (EPIC) observational study. The correlation coefficients between plasma concentrations of iso16:0, iso17:0, trans11-18:1, cis9, trans11-18:2, and cis6-18:1 and the dairy fat ingested are similar in both studies, indicating that their concentration increases by 0.8 µmol/L per gram of dairy fat ingested. The biomarkers are positively related to plasma triglycerides (r = 0.324 and 0.204 in the intervention and observational studies, respectively) and total cholesterol (r = 0.459 and 0.382), but no correlation was found between the biomarkers and atherogenicity indexes. In conclusion, the sum of the plasma concentration of the selected FAs can be used as biomarkers of dairy product consumption. A linear relationship exists between their plasma concentrations and ruminant product intake. These biomarkers allow for obtaining consistent relationships between dairy intake and plasma biochemical parameters.

Winter camelina seeds as a raw material for the production of erucic acid-free oil

Camelina oil is increasingly popular as consumption as oil. Erucic acid is an unwanted fatty acid in oil. First studies on several genotypes have shown that this oil contains varying amounts of eriuc acid. The aim of the study was to analyses content of eriuc acid in all genotypes camelina. Hypothesis was that the content of erucic acid in winter forms is lower than in spring ones. A field experiment with 65 spring genotypes and 9 winter genotypes of camelina was conducted in Poland from 2016 to 2018. The analyses based on two chromatographic methods, i.e. UPLC-DAD and GC-MS, showed no differences in the results for the camelina samples. The average percentage content of the erucic acid in the spring genotypes was 3.432%, and in the winter genotypes was 0.1%. Our three-year research shows that some winter varieties can be used as low erucic acid forms.

Phospholipid fatty acid (PLFA) analysis for profiling microbial communities in offshore produced water

A method based on phospholipid fatty acid (PLFA) analysis for profiling microbial communities in offshore produced water was optimized. The operation parameters affecting final PLFA profiling performance from the solid phase extraction (SPE) purification and fatty acid methyl esters (FAMEs) yielding process were investigated. Under the selected conditions, 92.9%, 96.3% and 92.8% of the spiked phospholipid standards C16:1 (cis-9) PC, C18:1 (cis-9) PC, and C19:0 PC were recovered, respectively, using 10mL methanol as elution solvent on a non-commercial SPE column. Over 90% of spiked C19:0 PC was recovered before sample transesterification. Four parameters including alkaline reagent, volume of acid for neutralization, time and temperature for FAMEs derivatization were examined. Gas Chromatography-Mass Spectrometry (GC-MS) was used to analyze FAMEs and the method linearities, recoveries of 29 FAMEs during transesterification, detection limits, relative standard deviations were presented. The results provided valuable information for biological reservoir souring control.

Screening for Ricinoleic Acid as a Chemical Marker for Secale cornutum in Rye by High-Performance Thin-Layer Chromatography with Fluorescence Detection

Ricinoleic acid as the characteristic fatty acid of Secale cornutum oil is a good marker for Secale cornutum impurities in cereal. The presented screening for ricinoleic acid in rye by high-performance thin-layer chromatography with fluorescence detection (HPTLC-FLD) offers a selective and sensitive method for the determination of Secale cornutum and is very different from existing gas chromatographic analyses. Lipid extraction was followed by transesterification and solid-phase extraction cleanup; thereafter, extracts were selectively derivatized with 2-naphthoyl chloride and analyzed by HPTLC-FLD with silica gel plates and cyclohexane/diisopropyl ether/formic acid (86:14:1, v/v/v) as mobile phase. For quantitation, the enhanced fluorescence was scanned at 280/>340 nm. Limits of detection and quantitation of 0.1 and 0.4 mg ricinoleic acid/kg of rye were obtained, which enables the determination of Secale cornutum far below the maximum admitted level. With near-100% recoveries and low standard deviations at relevant spiking levels, reliable results were guaranteed.

Maternal PPARG Pro12Ala polymorphism is associated with infant's neurodevelopmental outcomes at 18 months of age

BACKGROUND

Peroxisome proliferator activated receptors (PPARs) are ligand activated transcription factors with crucial functions in lipid homeostasis, glucose metabolism, anti-inflammatory processes, placental development, and are involved in cognitive functions and neurodegenerative diseases. Polymorphisms in PPAR genes are shown to influence the activity of these receptors.

AIMS

1) To examine the association of PPARG Pro12Ala polymorphism in pregnant women and their offspring on infant's neurodevelopmental outcomes during the first 18 months of life; 2) to determine the influence of Pro12Ala polymorphism on fatty acid concentrations in plasma phospholipids and placental tissue.

STUDY DESIGN

138 mother-infant pairs from the PREOBE observational study were genotyped for PPARG Pro12Ala. Plasma phospholipids and placental fatty acid concentrations were measured at delivery. Infants' neuropsychological assessment at 6 and 18 months of age was performed using Bayley III.

RESULTS

The effect of Pro12Ala on infant's neurodevelopmental outcomes was detected at 18 months, but not at 6 months of age. 18 months old infants born to mothers with wild-type Pro12 genotype had better cognitive (OR=5.11, 95% CI: 1.379-18.96, p=0.015), language (OR=3.41, 95% CI: 1.35-11.24, p=0.044), and motor development scores (OR=4.77, 95% CI: 1.243-18.33, p=0.023) than the Ala allele carriers. Pro12Ala variants did not seem to affect fatty acids concentrations in blood nor in placenta at delivery.

CONCLUSIONS

Infants born to mothers with Pro12 genotype have better neurodevelopmental outcomes at 18 months of age than Ala allele carriers, indicating a long-term transplacental action of PPARγ variants on foetal brain development.

Marine fish oils are not equivalent with respect to B-cell membrane organization and activation

We previously reported that docosahexaenoic-acid (DHA)-enriched fish oil (DFO) feeding altered B-cell membrane organization and enhanced B-cell function. The purpose of this study was to evaluate whether menhaden oil (MO) and eicosapentaenoic-acid (EPA)-enriched fish oil (EFO) alters B-cell function/phenotype similarly. Mice were fed control (CON), MO, EFO or DFO diets for 5weeks. We evaluated the fatty acid composition of B-cell phospholipids, membrane microdomain organization, ex vivo B-cell functionality and in vivo B-cell subsets. Red blood cells and B cells were found to be strongly (r>0.85) and significantly (P<.001) correlated for major n-3 and n-6 long-chain polyunsaturated fatty acids (LCPUFAs). Compared to CON, MO and DFO resulted in decreased clustering of membrane microdomains, whereas EFO increased clustering. All fish oil treatments had 1.12-1.60 times higher CD40 expression following stimulation; however, we observed 0.86 times lower major histocompatibility complex class II expression and 0.7 times lower interleukin (IL)-6 production from EFO, but 3.25 times higher interferon-γ from MO and 1.5 times higher IL-6 from DFO. By 90min of incubation, MO had 1.11 times higher antigen uptake compared to CON, whereas EFO was 0.86 times lower. All fish oil treatments resulted in decreasingly mature splenic and bone marrow B-cell subsets. We conclude that diets high in n-3 LCPUFAs may elicit similar B-cell phenotypes but different organizational and functional outcomes. More specifically, these data suggest that the EPA and DHA content of a diet influences immunological outcomes, highlighting the importance of understanding how specific n-3 LCPUFAs modulate B-cell development and function.

Is the omega-3 index a valid marker of intestinal membrane phospholipid EPA+DHA content?

Despite numerous studies investigating n-3 long chain polyunsaturated fatty acid (LCPUFA) supplementation and inflammatory bowel diseases (IBD), the extent to which dietary n-3 LCPUFAs incorporate in gastrointestinal (GI) tissues and correlate with red blood cell (RBC) n-3 LCPUFA content is unknown. In this study, mice were fed three diets with increasing percent of energy (%en) derived from eicosapentaenoic acid (EPA)+docosahexaenoic acid (DHA). Dietary levels reflected recommended intakes of fish/fish oil by the American Heart Association. We analyzed the FA composition of phospholipids extracted from RBCs, plasma, and GI tissues. We observed that the 0.1%en EPA+DHA diet was sufficient to significantly increase the omega-3 index (RBC EPA+DHA) after 5 week feeding. The baseline EPA levels were 0.2-0.6% across all tissues increasing to 1.6-4.3% in the highest EPA+DHA diet; these changes resulted in absolute increases of 1.4-3.9% EPA across tissues. The baseline DHA levels were 2.2-5.9% across all tissues increasing to 5.8-10.5% in the highest EPA+DHA diet; these changes resulted in absolute increases of 3.2-5.7% DHA across tissues. These increases in EPA and DHA across all tissues resulted in strong (r>0.91) and significant (P<0.001) linear correlations between the omega-3 index and plasma/GI tissue EPA+DHA content, suggesting that the omega-3 index reflects the relative amounts of EPA+DHA in GI tissues. These data demonstrate that the GI tissues are highly responsive to dietary LCPUFA supplementation and that the omega-3 index can serve as a valid biomarker for assessing dietary EPA+DHA incorporation into GI tissues.

Rapid and simple extraction of lipids from blood plasma and urine for liquid chromatography-tandem mass spectrometry

A simple and fast lipid extraction method from human blood plasma and urine is introduced in this study. The effective lipid extraction from biological systems with a minimization of the matrix effect is important for the successful qualitative and quantitative analysis of lipids in liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS). The method described here is based on the modification of the quick, easy, cheap, effective, rugged and safe (QuEChERS) extraction method, which was originally developed for pesticide residue analysis in food, for the purpose of isolating lipids from biological fluids. Applicability of QuEChERS method for lipids was evaluated by varying organic solvents for the extraction/partitioning of lipids in MgSO4/CH3COONa for the removal of water and by varying sorbents (primary secondary amines, graphitized carbon black, silica, strong anion exchange resins and C18 particles) for the dispersive solid-phase extraction (dSPE) step. This study shows that 2:1 (v/v) CHCl3/CH3OH is effective in the extraction/partitioning step and that 50mg of C18 particles (for 0.1mL plasma and 1mL of urine) are more suitable for sample cleanup for the dSPE step of the QuEChERS method. Matrix effects were calculated by comparing the recovery values of lipid standards spiked to both plasma and urine samples after extraction with those of the same standards in a neat solution using nanoflow LC-ESI-MS/MS, resulting in improved MS signals due to the decrease of the ion suppression compared to the conventional Folch method. The modified QuEChERS method was applied to lipid extracts from both human urine and plasma samples, demonstrating that it can be powerfully utilized for high-speed (<15min) preparation of lipids compared to the Folch method, with equivalent or slightly improved results in lipid identification using nLC-ESI-MS/MS.

Determination of the fatty acid profile of neutral lipids, free fatty acids and phospholipids in human plasma

BACKGROUND

Knowledge of the fatty acid composition of lipid classes in human plasma is an important factor in the investigation of human metabolism. Therefore, a method for the analysis of neutral lipid (NL), phospholipid (PL) and free fatty acids (FFA) in human plasma has been developed and validated.

METHODS

Separation of lipid classes was carried out by solid phase extraction of the lipid extract. The fractions were transesterified and the resulting fatty acid methyl esters were determined by GC/FID. For the method to be validated, precision, detection and quantification limits, as well as recovery, were determined for combined lipid extraction, solid phase extraction and GC analysis.

RESULTS

The lipid extraction was miniaturized and simplified by application of an ultrasound ‘Sonotrode’. The resolution of lipid classes was optimized with appropriate standards added to a representative plasma sample. In addition, a rapid derivatization procedure using trimethylsulfoniumhydroxide was established. Low determination limits (1.5, 0.2 and 1.3 μg/g plasma for NL, PL and FFA, respectively) indicate that the method’s sensitivity is sufficient to quantify even minor components. Furthermore, recovery for NL and PL fatty acids was found to range from 80% to 110%. The results were similar for FFA apart from more polar free fatty acids due to their higher solubility in water. Repetitive measurements showed very good precision apart from the long chain PUFA for which the coefficients of variation were significantly higher.

CONCLUSIONS

The present method is applicable to the quantitation of fatty acids in lipid classes of human plasma including several minor components.

SATgenε dietary model to implement diets of differing fat composition in prospectively genotyped groups (apoE) using commercially available foods

Response to dietary fat manipulation is highly heterogeneous, yet generic population-based recommendations aimed at reducing the burden of CVD are given. The APOE epsilon genotype has been proposed to be an important determinant of this response. The present study reports on the dietary strategy employed in the SATgenε (SATurated fat and gene APOE) study, to assess the impact of altered fat content and composition on the blood lipid profile according to the APOE genotype. A flexible dietary exchange model was developed to implement three isoenergetic diets: a low-fat (LF) diet (target composition: 24 % of energy (%E) as fat, 8 %E SFA and 59 %E carbohydrate), a high-saturated fat (HSF) diet (38 %E fat, 18 %E SFA and 45 %E carbohydrate) and a HSF-DHA diet (HSF diet with 3 g DHA/d). Free-living participants (n 88; n 44 E3/E3 and n 44 E3/E4) followed the diets in a sequential design for 8 weeks, each using commercially available spreads, oils and snacks with specific fatty acid profiles. Dietary compositional targets were broadly met with significantly higher total fat (42·8 %E and 41·0 %E v. 25·1 %E, P ≤ 0·0011) and SFA (19·3 %E and 18·6 %E v. 8·33 %E, P ≤ 0·0011) intakes during the HSF and HSF-DHA diets compared with the LF diet, in addition to significantly higher DHA intake during the HSF-DHA diet (P ≤ 0·0011). Plasma phospholipid fatty acid analysis revealed a 2-fold increase in the proportion of DHA after consumption of the HSF-DHA diet for 8 weeks, which was independent of the APOE genotype. In summary, the dietary strategy was successfully implemented in a free-living population resulting in well-tolerated diets which broadly met the dietary targets set.

Visual acuity in fish consumers of the Brazilian Amazon: risks and benefits from local diet

OBJECTIVE

To examine the associations between near and distant visual acuity and biomarkers of Hg, Pb, n-3 fatty acids and Se from the local diet of fish-eating communities of the Tapajós River in the Brazilian Amazon.

DESIGN

Visuo-ocular health and biomarkers of Hg (hair, whole blood, plasma), Pb (whole blood), Se (whole blood and plasma) and n-3 fatty acids (plasma total phospholipids) were assessed in a cross-sectional study.

SETTING

Lower Tapajós River Basin (State of Pará, Brazil), May to July 2006.

SUBJECTS

Two hundred and forty-three adults (≥15 years) without diagnosed age-related cataracts or ocular pathologies.

RESULTS

Near visual acuity was negatively associated with hair Hg and positively associated with %DHA, with a highly significant Log Hg × age interaction term. Stratifying for age showed that while young people presented good acuity, for those aged ≥40 years, clinical presbyopia was associated with hair Hg ≥ 15 μg/g (OR = 3·93, 95% CI 1·25, 14·18) and %DHA (OR = 0·37, 95% CI 0·11, 1·11). A similar age-related pattern was observed for distant visual acuity in relation to blood Pb, but the evidence was weaker.

CONCLUSIONS

These findings suggest that Hg and Pb may affect visual acuity in older persons, while DHA appears to be protective for near visual acuity loss. In this population, with little access to eye care, diet may have an important influence on visuo-ocular ageing.

Ricinoleic acid as a marker for ergot impurities in rye and rye products

Ergot alkaloid and ricinoleic acid contents of 63 ergot sclerotia samples from rye throughout Germany of the harvest years 2006-2009 were determined. Alkaloid contents were analyzed by means of high-performance liquid chromatography with fluorescence detection (HPLC-FLD) and ricinoleic acid contents by means of gas chromatography with flame ionization detection (GC-FID). Ergot alkaloid amounts ranged from 0.01 to 0.2 g/100 g of sclerotia with an average amount of 0.08 g/100 g. Ergotamine and ergocristine were identified as lead alkaloids representing 57% (w/w) of the total alkaloid content. The average ricinoleic acid amount in the ergot sclerotia was 10.3 g/100 g. Because of the low variation of ricinoleic acid content in the ergot sclerotia, a new method for the determination of ricinoleic acid in rye products as a marker for ergot contaminations was developed. This method allows the determination of ergot impurities as low as 0.01% (w/w). Furthermore, 29 rye products (flours, bread mix, bread) were investigated for their ricinoleic acid and ergot alkaloid contents.

High-throughput analysis of fatty acid composition of plasma glycerophospholipids

Plasma FA composition, a marker of FA status and dietary intake, is associated with health outcomes on a short- and long-term basis. Detailed investigation of the relationships between plasma FA composition and health requires the analysis of large numbers of samples, but manual sample preparation is very cumbersome and time consuming. We developed a high-throughput method for the analysis of FAs in plasma glycerophospholipids (GPs) with increased sensitivity. Sample preparation requires two simple steps: protein precipitation and subsequent base catalyzed methyl ester synthesis. Analysis of GP FAs is performed by gas chromatography. Coefficients of variation for FAs contributing more than 1% to total FAs are below 4%. Compared with the established reference method, results of the new method show good agreement and very good correlations (r > 0.9). The new method reduces the manual workload to about 10% of the reference method. Only 100 microl plasma volume is needed, which allows for the analysis of samples from infants. The method is well suitable for application in large clinical trials and epidemiological studies.

Marked elevations in pro-inflammatory polyunsaturated fatty acid metabolites in females with irritable bowel syndrome

Irritable bowel syndrome (IBS) is the most common functional gastrointestinal disorder referred to gastroenterologists. Although the pathophysiology remains unclear, accumulating evidence points to the presence of low-level immune activation both in the gut and systemically. Circulating polyunsaturated fatty acids (PUFA) have recently attracted attention as being altered in a variety of disease states. Arachidonic acid (AA), in particular, has been implicated in the development of a pro-inflammatory profile in a number of immune-related disorders. AA is the precursor of a number of important immunomodulatory eicosanoids, including prostaglandin E(2) (PGE(2)) and leukotriene B(4) (LTB(4)). We investigated the hypothesis that elevated plasma AA concentrations in plasma contribute to the proposed pro-inflammatory profile in IBS. Plasma AA and related PUFA were quantified by gas chromatography analysis in IBS patients and controls. Both PGE(2) and LTB(4) were measured in serum using commercially available ELISA assays. AA concentrations were elevated in our patient cohort compared with healthy controls. Moreover, we demonstrated that this disturbance in plasma AA concentrations leads to downstream elevations in eicosanoids. Together, our data identifies a novel proinflammatory mechanism in irritable bowel syndrome and also suggests that elevated arachidonic acid levels in plasma may serve as putative biological markers in this condition.

Chain reactions: early-life stress alters the metabolic profile of plasma polyunsaturated fatty acids in adulthood

The rat maternal separation paradigm can be used to examine the biological consequences of early-life stress. Immunomodulatory polyunsaturated fatty acids (PUFAs) have recently attracted attention in the study of stress-related disorders. We established the plasma PUFA profile of maternally separated rodents compared to controls. Our results identify a proinflammatory PUFA profile as a persistent consequence of early-life stress and suggest new avenues of investigation in stress-related disorders.

Recent trends in the advanced analysis of bioactive fatty acids

The consumption of dietary fats have been long associated to chronic diseases such as obesity, diabetes, cancer, arthritis, asthma, and cardiovascular disease; although some controversy still exists in the role of dietary fats in human health, certain fats have demonstrated their positive effect in the modulation of abnormal fatty acid and eicosanoid metabolism, both of them associated to chronic diseases. Among the different fats, some fatty acids can be used as functional ingredients such as alpha-linolenic acid (ALA), arachidonic acid (AA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), gamma-linolenic acid (GLA), stearidonic acid (STA) and conjugated linoleic acid (CLA), among others. The present review is focused on recent developments in FAs analysis, covering sample preparation methods such as extraction, fractionation and derivatization as well as new advances in chromatographic methods such as GC and HPLC. Special attention is paid to trans fatty acids due its increasing interest for the food industry.

Creating a fatty acid methyl ester database for lipid profiling in a single drop of human blood using high resolution capillary gas chromatography and mass spectrometry

Capillary gas chromatography (CGC) in combination with mass spectrometry (MS) was optimized for the separation and detection of the fatty acids occurring in the lipid fraction of blood. A fingertip blood sample (ca. 50 microL) was transesterified into the methyl esters and analyzed on a 100 m x 0.25 mm ID column coated with a biscyanopropyl polysiloxane (HP-88) stationary phase. The method was retention time locked. Programmed temperature vaporization injection (PTV) in the solvent venting mode was applied to minimize the sample size, while maintaining high sensitivity. The total analysis time was ca. 60 min. Retention times and both electron impact (EI) and positive chemical ionization (PCI) mass spectrometry were combined to elucidate the fatty acids according to alkyl chain, degree of unsaturation and position of the double bonds. Using extracted ion chromatograms about 100 fatty acids and related compounds were detected in blood samples and most of them were identified. This work resulted in a very large fatty acid methyl esters database, containing retention time and mass spectral information that will be applied to metabolomic studies.

Fast analysis by gas–liquid chromatography

Separation of fatty acids as methyl ester (FAME) derivatives has been carried out using short and highly polar capillary column developed for fast gas-liquid chromatography (GLC) applications. The GLC parameters have been optimized in order to achieve separation of FAME ranging from 4:0 (butyric acid) to 24:1 in less than 5 min. Milk fat that has by far the most complex fatty acid composition among edible fats and oils has been used to optimize the method. The volume of the oven has been reduced in order to allow for a heating rate of 120 degrees C/min and to rapidly cool-down to the initial temperature (50 degrees C) of the GLC program. The GLC conditions developed are not suitable to achieve separation of positional and geometrical isomers of octadecenoic acid but are useful to perform separation of major fatty acids in milk fat. The conditions developed could be used to analyze edible fats and oils or biological samples such as plasma or red blood cell lipids. The results confirmed that short and highly polar fast columns operating under optimal conditions could be used to separate the fatty acids in various matrices.

Determination of conjugated linoleic acid in human plasma by fast gas chromatography

A new method for the determination of the main isomers of conjugated linoleic acid (CLA) in human and animal plasma was developed by gas chromatography coupled to flame ionization detection (GC-FID). The new method introduces three main advantages in comparison to the current available methodologies: firstly it does not require previous lipid extraction, secondly the chromatographic separation of CLA isomers was performed on an Rtx-2330 column significantly shorter and thinner than the typical long highly polar capillary columns in use that allows a faster analysis than in current methodologies, and thirdly the amount of sample needed to perform the analyses was substantially lower than the amount used in current routine methodologies. Its application to human plasma and rat plasma showed to be robust and reliable for quick and correct identification of the main CLA isomers in particular, and the total fatty acid profile in general, in routine analysis.