Trans fatty acid determination in fats and margarine by Fourier transform infrared spectroscopy using a disposable infrared card

The use of a disposable polyethylene infrared (IR) card as a sample carrier for the quantitative determination of trans content of fats and oils and m argarine by Fourier transform IR spectroscopy was investigated. Standards p repared by dissolving trielaidin in a zero-trans oil were used to develop p artial least squares (PLS) calibrations for both the IR card,and a 100-mu m transmission flow cell. These calibrations were then used to predict a ser ies of gas chromatographically-preanalyzed unknowns, the trans predictions obtained using the card being comparable to those obtained with the transmi ssion flow cell. Somewhat improved performance could be obtained when the s pectral data from the card were normalized to compensate for inherent varia tions in path length and variability in sample loading. Both IR methods tra cked the gas chromatographic reference trans values very well. A series of margarine samples was also analyzed by the card method, producing results s imilar to those obtained using a flow cell. For the analysis of margarines, the card method, has the advantage that the trans analysis can be performe d directly on microwave melted emulsions because moisture is not retained o n the card. Overall, the disposable IR card was shown to work well and has the benefit of allowing trans analyses to be carried out without requiring investment in a heated flow cell or attenuated total reflectance accessory. Paper no. J9206 in JAOCS 76, 1399-1404 (December 1999).