Inconsistencies in a highly polar capillary gas chromatography column and necessity of column performance checks for trans fatty acid measurement.

GC with a capillary column (60-100 m length) is widely used to measure trans fatty acids in dietary fats and biological tissues. Recently, we have occasionally observed that isothermal operation of an SP-2560 column at 180 degrees C results in incomplete separation of gondoic acid (11c-20:1) and one of the geometric isomers of alpha-linolenic acid (9t,12c,15c-18:3), although it has been known to produce their baseline separation in American Oil Chemists' Society Official Method Ce 1h-05, as well as in previous studies. Thus, trans isomer (9t,12c,15c-18:3) is one of the main components of trans fatty acids in refined edible oils, and the baseline separation of this peak from that of 11c-20:1 is indispensable. We demonstrate in this study that an isothermal operating temperature of 175 degrees C for an SP-2560 column results in satisfactory resolution of these two fatty acids. Because of the inconsistency in the separation provided by SP-2560 columns, careful monitoring of the relative elution order of different fatty acid methyl esters using standards is necessary for the exact evaluation of trans fatty acid contents in oils and fats.