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Determination of total trans fatty acids in foods: Comparison of capillary‐column gas chromatography and single‐bounce horizontal attenuated total reflection infrared spectroscopy
Author(s) -
Ali Laila H.,
Angyal Gerald,
Weaver Carol M.,
Rader Jeanne I.,
Mossoba Magdi M.
Publication year - 1996
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/bf02517975
Subject(s) - chemistry , gas chromatography , attenuated total reflection , chromatography , fatty acid , infrared spectroscopy , analytical chemistry (journal) , hydrolysis , organic chemistry
The total trans fatty acid content of 18 food products was determined, after acid hydrolysis, extraction and methylation of fatty acids, by gas chromatography with a polar 100% cyanopropylsiloxane capillary column and by single‐bounce horizontal attenuated total reflection spectroscopy (SB‐HATR). The trans fatty acid methyl esters (FAME) of 9‐hexadecenoate (9 t ‐16:1), 9‐octadecenoate (9 t ‐18:1), and 9,12‐octadecadienoate (9 t ,12 t ‐18:2) were identified by comparison of their retention times with those of known standards and quantitated. The isomers c,t ‐ and t,c ‐18:2 were identified from their published retention times and included in the quantitation of trans FAME. Neat 50‐μL portions of the FAME that were used for gas‐chromatographic analysis also were analyzed by SB‐HATR. This technique requires neither weighing nor quantitative dilution of test portions prior to spectroscopic quantitation of isolated double bonds of trans configuration. A symmetric 966‐cm −1 absorption band on a horizontal background was obtained from unhydrogenated soybean oil FAME as the reference material. For 9 of 11 products with trans fat content>5% of total fat, results obtained by SB‐HATR were higher than those obtained by gas chromatography. Results obtained by the gaschromatographic procedure were slightly to significantly higher than those obtained by SB‐HATR for the six foods in which trans fat content was <5% of total fat.