Determination of trans fatty acids in hydrogenated vegetable oils by attenuated total reflection infrared spectroscopy: Two limited collaborative studies |
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Authors: | M Adam M Chew S Wasserman A McCollum R E McDonald M M Mossoba |
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Affiliation: | (1) Lipton, 21229 Baltimore, Maryland;(2) Food and Drug Administration, National Center for Food Safety and Technology, 60501 Summit-Argo, Illinois;(3) the Food and Drug Administration (HFS-717), Center for Food Safety and Applied Nutrition, 20204 Washington, DC |
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Abstract: | An attenuated total reflection infrared spectroscopy procedure was collaboratively studied among two sets of five laboratories
for quantitating the total trans fatty acid levels in neat (without solvent) hydrogenated vegetable oils, measured as triacylglycerols in one study, and as
fatty acid methyl ester derivatives in the other. Unlike the fatty acid methyl esters, the triacylglycerols required no derivatization
but had to be melted prior to measurement. To obtain a symmetric absorption band at 966 cm−1 on a horizontal background, the single-beam spectrum of the trans-containing fat was "ratioed" against that of a refined oil or a reference material that contained only cis double bonds. A single-bounce horizontal attenuated total reflection cell that requires 50 μL of undiluted test samples was
used for oils, melted fats, or their methyl esters. For fatty acid methyl esters, the reproducibility relative standard deviations
were in the range of 0.9 to 18.46% for 39.08 to 3.41% trans, determined as methyl elaidate per total fatty acid methyl esters. For five pairs of triacylglycerol blind duplicates, the
reproducibility and repeatability relative standard deviations were in the ranges of 1.62 to 18.97%, and 1.52 to 13.26%, respectively,
for 39.12 to 1.95% trans, determined as trielaidin per total triacylglycerols. Six pairs of spiked triacylglycerol blind duplicates (quality assurance
standards) exhibited high accuracy in the range of 0.53 to 40.69% trans and averaged a low bias of 1.3%. These statistical analysis results were compared to those collaboratively obtained by the
recently adopted AOCS Cd14-95 and AOAC 994.34 Infrared Official Methods. |
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Keywords: | Attenuated total reflection collaborative study infrared trans fatty acids |
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