A GC – magnetic sector MS method for identification and quantification of fatty acids in ewe milk by different acquisition modes

Abstract

A general method for qualitative and quantitative determination of fatty acids (FAs) using GC-MS was developed and tested on ewe milk. A total number of 38 poly unsaturated FAs, monounsaturated FAs and saturated FAs, from C6:0 to C24:1, were used in a comparative study of scan, reconstructed ion chromatogram and SIM. Fatty acid methyl esters in standard solutions as well as in milk from ewe were analyzed by these techniques, using a sector instrument. Instrument precision, linearity, LOD and LOQ, as well as calibration behavior and response factors were investigated for each approach. The quantitative results obtained by each technique were compared. All techniques had values for LOD and LOQ in the ng/mL region. IntroductionLipids are a large group of compounds that are important constituents in all plant and animal tissue. Together with carbohydrates and proteins, they constitute the principal structural components of all living cells. Triglycerides are storage lipids and they are commonly called fats and oils [1,2]. The most commonly occurring fatty acids (FAs) in plant and animal tissues are monocarboxylic acids with even numbers of carbon atoms in straight chains. The term ''essential FAs'' is used on FAs, which have vital importance for biological functions, and cannot be synthesized in human tissues. Essential FAs must be included in the diet. Linoleic acid (C18:2n-6c) and linolenic acid (C18:3n-3c) are such components. They are precursors for other FAs formed by chain-elongation and desaturation, for example arachidonic acid (C20:4n-6c), eicosapentaenoic acid (C20:5n-3c), and docosahexaenoic acid (C22:6n-3c), also known as ARA, EPA and DHA, respectively. Long-chained n-3 FAs are said to have protective effects against hypertension, hypertriacylglycerolaemia, vascular dysfunction, atherosclerosis, cardiac arrhythmias, myocardial infarction, inflammatory conditions, immune dysfunction, insulin resistance, bone loss, neurodegenerative diseases of aging and some cancers [3]. A high proportion of short-chain FAs is characteristic for the milk fat of ruminants. This is caused by anaerobic fermentation of carbohydrates by the microorganisms in the rumen. The small amounts of branched-chain FAs that are found in ruminant milk are caused by the same microorganisms [4]. The FA composition in milk from mammals is linked to several factors such as animal breed, genotype, lactation and pregnancy stages and environmental factors [5].To develop sensitive methods for the determination of the FA composition in different foods is a task of great importance, mainly because of the nutritional relevance of FAs in human health. There are several ways to accomplish this. One way is to extract the lipids with proper solvents, convert the lipids into fatty acid methyl esters (FAMEs) and separate them using a GC coupled to a detector. The by far most common detector in the analysis of FAMEs has been the flame ionization detector [6,7]. The complexity of biological samples limits the usefulness of this detector, since the only inf...

Oxidation progress in an emulsion made from metmyoglobin and different triacylglycerols

“…Detection was performed using an Autospec Ultima GC-MS (Micromass, Manchester, England) in electron ionization mode. Conditions used were according to Devle et al (2009). NIST08 (Gaithersburg, MD) was used as reference library.…”

“…The fatty acid composition of the marine oils was determined (as methyl esters) by gas chromatography, according to Devle, Rukke, Naess-Andresen, and Ekeberg (2009). In short; 200 lg of oil were dissolved by adding 2.0 ml of hexane and esterified by adding 1.5 ml of sodium methanolate solution (3 mg/ml).…”

Fatty Acid Profiles of Stipe and Blade from the Norwegian Brown MacroalgaeLaminaria hyperboreawith Special Reference to Acyl Glycerides, Polar Lipids, and Free Fatty Acids

“…The analysis of the FAMEs was based on a previously published method [29]. Shortly, the analyses were carried out on an Agilent 6890 Series gas chromatograph (GC; Agilent Technology, Wilmington, DE, USA) in combination with an Autospec Ultima mass spectrometer (MS; Micromass Ltd., Manchester, England) using an EI ion source.…”

“…MassLynx version 4.0 (Waters, Milford, MA, USA) and NIST 2014 Mass Spectral Library (Gaithersburg, MD, USA) were used. Relative response factors previously determined by Devle et al [29] were employed for quantitative determination. The resulting amounts are given in µ g/g dry weight (DW).…”

Rapid method for analysis of sphingomyelin by microwave derivatisation for gas chromatography–mass spectrometry

“…The chemical structures of the FAMEs were confirmed by comparison to authentic analytical standards using GC retention time and by comparing the mass spectra with spectra available from the NIST database. The method for quantitation of FAMEs from SM was based on a previously established method [9]. The SM from bovine brain mainly consisted of the following FAs: C16:0, C18:0, C20:0, C22:0, C23:0, C24:0 and C24:1 n-9.…”