Capillary Column Gas Chromatographic Method for Analysis of Encapsulated Fish Oils and Fish Oil Ethyl Esters: Collaborative Study

Abstract

A gas chromatographic (GC) method using a capillary column for analysis of encapsulated fish oils and ethyl esters was studied collaboratively in 21 laboratories. Each collaborator analyzed 6 soft-gelatin encapsulated samples; 5 were trlacylglycerol oils (one was a blind duplicate), and one was an ethyl ester concentrate of omega-3 (n-3) polyunsaturates. Constituent fatty acids of the oils were converted to methyl esters by base-catalyzed transesterlflcatlon of the oils; any free acids in the oils were esterlfied by subsequent reaction with BF3/CH3OH. The ethyl ester concentrate required no further derlvatlzation. Results were reported as area percentages of 24 analytes of nutritional or biochemical interest. In addition, weights (mg/g sample) of EPA (all-c/s-5,8,11,14,17-elcosapentaenolc acid or 20:5n-3) and DHA (all-c/s- 4,7,10,13,16,19-docosahexaenoic acid or 22:6n-3) were determined through the use of the internal standards, respectively, methyl tricosanoate (23:0) and ethyl 23:0, for the methyl and ethyl esters. The only instrumentation specifically required was a flexible fused silica capillary GC column coated with a bonded polyglycol such as Carbowax-20M, an oxygen scrubber Installed In the carrier gas supply line, and a flame Ionization detector (FID). Most of the collaborators experienced little difficulty In applying the method, and, of 2526 values reported, only 4.3% were identified as outlier values. The reproducibility relative standard deviations (RSDR) compared favorably in most instances with, or were substantially better than, those of 2 earlier collaborative studies of fish oils. Because the variances were homogeneous, standard deviations and relative standard deviations determined on the area percent analyses of the blind duplicate oils were pooled to give the following mean values: sr = 0.15, RSDr = 4.88%, sR = 0.41, and RSDR = 12.91%. Analytes that rarely occur at greater than 0.5% In marine oils (22:0,22:4n-6,22:5n-6,24:0, and 24:1) were not Included in these calculations. The method was adopted first action by AOAC International as an American Oil Chemists' Society (AOCS)-AOAC method.

Chemical Characterization of Liver Lipid and Protein from Cold‐Water Fish Species

“…Palmitic acid (16:0) was the most abundant SFA in all species but varied widely from a high of 139.8 mg/g of oil in WP to a low of 81.8 mg/g of oil in RF. Concentration of linoleic acid was low in all samples as expected for marine oils from wild fish stocks (Joseph and Ackman 1992). Levels of arachidonic acid (20:4ω6) varied greatly from 27.7 to 2.9 mg/g oil, with PS and BS livers containing (P < 0.05) higher amounts (23.5 and 27.7 mg/g oil) than liver tissues from all other fish species (2.9 to 9.3 mg/g oil).…”

Comparison of fatty acid contents of wild and cultured rainbow trout Onchorhynchus mykiss in Turkey

“…Methyl esters of fatty acids were prepared according to the method of Joseph and Ackman 12 following transesterification with methanol borontrifluoride. The fatty acid methyl esters were analyzed by gas chromatography-mass spectrometry (HP 6890 Series GC System; Hewlett Packard, Wilmington, DE, USA) fitted with an electronic pressure control and mass selective detection (ionizating energy, 70 eV; source temperature, 300°C) using a DB-WAXETR capillary column (30 m ¥ 0.25 mm i.d.…”

Effect of Annatto Seed and Coriander Leaves as Natural Antioxidants in Fish Meatballs during Frozen Storage

“…Approximately 25 mg of oil, obtained from the lipid extraction according to Folch and others (1957) were saponificated and the FA converted to methyl esters according to Joseph and Ackman (1992). The methyl esters were diluted with hexane to achieve injection and separation in gas chromatograph.…”