Gas chromatographic analytical method for the analysis of oxygenated polar fatty acids

A gas chromatographic method for analysis of oxygenated polar fatty acids (epoxy, hydroxy and oxo) is described. The challenge of polar fatty analysis in the past has been interferences due to co-elution of the various compounds present in the complex mixture. The method uses a three step SPE separation technique to fractionate the fatty acids so that each fraction is free of interfering compounds thus reducing co-elution. The epoxy and oxo fatty acids have been analysed in one portion. Due to the high polarity of the hydroxy fatty acids it is only possible to analyse them after silylation. The elution profile of the hydroxyl fatty acids can be simplified by hydrogenation which reduces the number of compounds allowing better chromatographic interpretation. The method has proven to be sensitive and exhibits low LODs which is promising towards more robust analytical methods. Application of the validated method on fresh oil samples has revealed that it is an effective tool to quantitatively screen polar fatty acids in trace amounts and can be very useful for exposure assessment studies

Prevalence and factors associated with overweight and obesity among patients with type 2 diabetes mellitus in Uganda-a descriptive retrospective study.

OBJECTIVES: To assess the prevalence and risk factors of overweight and obesity among type 2 diabetes mellitus (T2DM) patients in Uganda. DESIGN: Retrospective chart review. SETTING: This study was conducted in the outpatient's T2DM clinic in St. Francis Hospital-Nsambya, Uganda between March and May 2017. PARTICIPANTS: Type 2 diabetes patients registered in the diabetes clinic between July 2003 and September 2016. OUTCOME MEASURES: Overweight and obesity defined as body mass index (kg/m2) of 25.0-29.9 and obesity as 30.0 or higher. RESULTS: Of 1275 T2DM patients, the median age was 54 (IQR: 44-65) years, 770 (60.40%) were females, 887 (69.6%) had hypertension, 385 (28%) had controlled glycaemia, 349 (27%) were obese, while 455 (36%) were overweight. Overweight/obesity were lower among men (OR: 0.45, 95% CI: 0.340 to 0.593, p≤0.001) and among patients aged ≥65 years (OR: 0.52, 95% CI: 0.350 to 0.770, p=0.001); patients who rarely ate fruits and vegetables (OR: 0.66, 95% CI: 0.475 to 0.921, p=0.014) but higher among patients of middle (OR: 1.83, 95% CI: 1.320 to 2.550, p≤0.001) and upper (OR: 2.10, 95% CI: 1.450 to 2.990, p≤0.001) socioeconomic status; on dual therapy (OR: 2.17, 95% CI: 1.024 to 4.604, p=0.043); with peripheral neuropathy (OR: 1.40, 95% CI: 1.039 to 1.834, p=0.026) and hypertension (OR: 1.70, 95% CI: 1.264 to 2.293, p≤0.001). CONCLUSIONS: Overweight and obesity are high among T2DM patients in this population and may contribute significantly to poor outcomes of T2DM. Therefore, strategies to address this problem are urgently needed

Improved gas chromatography-flame ionization detector analytical method for the analysis of epoxy fatty acids

In this study an improved method for analysis of epoxy fatty acids is reported. Data obtained from analysis of polar fatty acids has previously been presented, but due to the high number of compounds that co-elute in the polar fraction, the resultant chromatograms are complex which may lead to compromising the accuracy of the data. A three steps separation of fatty acid methyl esters (FAMEs) by solid-phase extraction (SPE) on a silica gel column to remove hydroxy fatty acid interferences was proposed. This approach is opposed to a two step separation procedure that has been often used to prevent analytical interferences caused by non-altered fatty acids. A gas chromatograph with a flame ionisation detector (GC-FID) equipped with a polar CP-Sil 88™ column was used. Quantification was based on the use of methyl nonadecanoate (C19:0), as an internal standard. Individual mono epoxy fatty acids were well separated without co-eluting compounds. The optimised method was finally applied to screen epoxy fatty acids in 37 fresh oil samples. Results obtained for the total epoxy fatty acids were in the range 0.03 – 2 mg g-1 of oil with repeatability coefficient of variation (CV) ranging from 2.8 to 9.9 % for duplicate analysis showing that the results obtained are repeatabl

Improved gas chromatography-flame ionisation detector analytical method for the analysis of epoxy fatty acids

In this study an improved method for analysis of epoxy fatty acids is reported. Data obtained from analysis of polar fatty acids has previously been presented, but due to the high number of compounds that co-elute in the polar fraction, the resultant chromatograms are complex which may lead to compromising the accuracy of the data. A three steps separation of fatty acid methyl esters (FAMEs) by solid-phase extraction (SPE) on a silica gel column to remove hydroxy fatty acid interferences was proposed. This approach is opposed to a two step separation procedure that has been often used to prevent analytical interferences caused by non-altered fatty acids. A gas chromatograph with a flame ionisation detector (GC-FID) equipped with a polar CP-Sil 88™ column was used. Quantification was based on the use of methyl nonadecanoate (C19:0), as an internal standard. Individual mono epoxy fatty acids were well separated without co-eluting compounds. The optimised method was finally applied to screen epoxy fatty acids in 37 fresh oil samples. Results obtained for the total epoxy fatty acids were in the range 0.03 – 2 mg g-1 of oil with repeatability coefficient of variation (CV) ranging from 2.8 to 9.9 % for duplicate analysis showing that the results obtained are repeatabl

Development and validation of a gas chromatography-flame ionization detection method for the determination of epoxy fatty acids in food matrices

A reliable and suitable method for the determination of epoxy fatty acids in various food matrices based on the Bligh and Dyer lipid extraction procedure was developed and validated. The method involves use of a methylated epoxy fatty acid as internal standards (IS), extraction of the analytes from the matrices followed by room temperature methylation, a three step SPE separation of the FAMEs and detection with gas chromatography flame ionisation detection (GC-FID). The method was validated in four different food matrices chosen as model systems namely, vegetable oils, unprocessed meat, fried potato crisps and infant formula. The extraction technique allows the method to be applied for routine analysis of a large amount of samples. Intra-day repeatability ranged from 1 to 19 % and inter-day reproducibility ranged from 2 to 9 %. The limit of quantification (LOQ) ranged from 3.32 to 20.47 µg g-1of sample with recoveries ranging from 94 to 115 %. The results verify the accuracy and reproducibility of the analytical technique and its ability to provide reliable quantification of epoxy fatty acids. Finally, levels of epoxy fatty acids in several food products on Belgian market were screened and presented

Malondialdehyde measurement in oxidized foods: evaluation of the spectrophotometric thiobarbituric acid reactive substances (TBARS) test in various foods

The ability of the spectrophotometric thiobarbituric acid reactive substances (TBARS) test to determine malondialdehyde (MDA) in various food matrices was evaluated. MDA was extracted from the foods; the extract reacted with thiobarbituric acid (TBA); and the formed TBA-MDA adduct was measured spectrophotometricaly at 532 nm. In parallel, the TBA-MDA adduct was analyzed with high-performance liquid chromatography (HPLC) coupled with fluorescence detection. Oils and unprocessed and uncooked meat and fish products did not exhibit any significant difference in the amount of MDA measured by the two methods, indicating that the major substance reacting with TBA and forming an adduct that absorbs at 532 nm was MDA. However, in products such as dry nuts, pork sausages, cooked fish, and gouda cheese, an overestimation of MDA was observed, indicating that TBARS test was unsuitable for accurate determination of MDA. Furthermore, the results in the present work suggest that the overestimation of MDA by the TBARS test as it was applied is related to the interference of other than secondary lipid oxidation products

Development of a sensitive and accurate stable isotope dilution assay for the simultaneous determination of free 4-hydroxy-2-(E)-nonenal and 4-hydroxy-2-(E)-hexenal in various food matrices by gas chromatography–mass spectrometry

An analytical method suitable for the determination of 4-hydroxy-2-(E)-nonenal (HNE) and 4-hydroxy-2-(E)-hexenal (HHE) in various food matrices was developed and validated. The method involves the use of deuterated HNE and HHE as internal standards, extraction of the analytes from the matrices followed by derivatization and detection with gas chromatography–mass spectrometry. Four different food matrices were chosen as model systems including vegetable oils, unprocessed meat, fried potato crisps, and infant formula and three different extraction techniques suitable for the different matrices were applied including the Quick Easy Cheap Effective Rugged Safe method. The simplicity of the extraction techniques allows the method to be applied for routine analysis of a large amount of samples. The results verify the accuracy and reproducibility of the analytical technique and its ability to provide reliable quantification of both analytes at concentrations as low as 12.8 ng g−1 in meat samples. Furthermore, a short overview of the levels of HNE and HHE in several products available in the Belgian market is presented

Exposure assessment of epoxy fatty acids through consumption of specific foods available in Belgium

Epoxy fatty acids (EFAs) are secondary oxidation products formed from unsaturated fatty acid hydroperoxides. Seventeen food categories were analysed for C18 monoEFAs of food products available on the Belgian market. A quantitative exposure assessment was performed based on deterministic and probabilistic approaches combining these concentration data with consumption data obtained from the Belgian National Food Consumption Survey of 2004. A preliminary evaluation of any potential risk related to the intake of the studied EFAs through the studied foods was performed by applying the threshold of toxicological concern (TTC) concept. Three food categories out of 17 foods, mayonnaise, butter-margarine and ready-to-eat meals were found to contribute most to the intake of EFAs. According to probabilistic determination, these foods had P50 intakes of 0.4085, 0.3328 and 0.2997mg kg(-1) bw day(-1) respectively. They had P99.5 intakes of 3.7183, 2.7921 and 38.6068mg kg(-1) bw day(-1) respectively. The intake below the TTC was from the consumption of cooked meat, smoked salmon and raw cured ham, with P50 intakes of 0.0006, 0.0007 and 0.0011 mg kg(-1) bw day(-1) respectively, and the other foods were above the TTC. Based on the TTC concept, a risk to human health could be identified related to the consumption of cheese, snacks foods, plant oils, French fries, dry nuts, chips, cured minced raw meat, cookies, fresh and frozen salmon and bacon

Accuracy and Incremental Yield of the Chest X-Ray in Screening for Tuberculosis in Uganda: A Cross-Sectional Study

The WHO END TB strategy requires ≥90% case detection to combat tuberculosis (TB). Increased TB case detection requires a more sensitive and specific screening tool. Currently, the symptoms recommended for screening TB have been found to be suboptimal since up to 44% of individuals with TB are asymptomatic. The chest X-ray (CXR) as a screening tool for pulmonary TB was evaluated in this study, as well as its incremental yield in TB diagnosis using a cross-sectional study involving secondary analysis of data of 4512 consented/assented participants ≥15 years who participated in the Uganda National TB prevalence survey between 2014 and 2015. Participants with a cough ≥2 weeks, fever, weight loss, and night sweats screened positive for TB using the symptoms screening method, while participants with a TB defining abnormality on CXR screened positive for TB by the CXR screening method. The Löwenstein-Jensen (LJ) culture was used as a gold standard for TB diagnosis. The CXR had 93% sensitivity and 65% specificity compared to LJ culture results, while symptoms had 76% sensitivity and 31% specificity. The screening algorithm involving the CXR in addition to symptoms led to a 38% increment in the yield of diagnosed tuberculosis. The number needed to screen using the CXR and symptoms screening algorithm was 32 compared to 45 when the symptoms are used alone. Therefore, the CXR in combination with symptoms is a good TB screening tool and increases the yield of diagnosed TB