Methyl esters from a partially hydrogenated vegetable oil is a better infrared external standard than methyl elaidate for the measurement of total trans content

An infrared spectrophotometric procedure, based on the fatty acid methyl ester mixture derived from a partially hydrogenated vegetable oil as the calibration standard, has been developed for accurate analysis of the total trans content of hydrogenated fats. This procedure produces more accurate results than the current official methods of Association of Official Analytical Chemists and American Oil Chemists' Society, both of which use methyl elaidate as the external standard. The results obtained with this procedure were in close agreement to those determined by the combined procedure of silver-nitrate thin-layer chromatography and capillary gas-liquid chromatography. The improved results, obtained with the partially hydrogenated vegetable oil methyl esters as the calibration standard, may be attributable to its assortment of trans isomers, which may have different absorptivities relative to methyl elaidate.