Separations of
cis, trans fatty acid isomers of C
16C
22 chain-lengths were successfully carried out by packed column gas chromatography (GC) using a cyanosiloxane liquid phase, OV-275.
Peak separations of C
18 : 1 and C
22 : 1 isomers were examined at various column temperatures. The best separations of these isomers were obtained at 220°C and 240°C, respectively.
No linear relationship between carbon numbers and logarithmic values of retention times of saturated esters was found. Therefore, the equivalent chain lengths (ECL) of unsaturated esters were calculated from the logarithmic retention times of neighboring saturated homologous pairs.
The ECL values were significantly affected by column temperature, and selection of adequate column temperature permitted separations of critical pairs. For example, no separation of linoleate-arachidate pair was obtained at 210°C but baseline separation was obtained at 240°C. Δ
t ECL, an increase of ECL for one degree raising of column temperature, was calculated for some unsaturated esters. The Δ
t ECL increased with increasing of degree of unsaturation of methyl esters. The values of linoleate and linolenate on the OV-275 were approximately twice of that on SILAR 10C and three times of that on DEGS. The Δ
t ECL of
cis isomers was smaller than that of the corresponding trans isomers.
The packed column GC was first applied to determinations of
trans fatty acids of beef tallows, partially hydrogenated pollach oil and commercial margarines containing partially hydrogenated fish oils. The analytical results fatty acid compositions were in good agreement with them obtained by DEGS column.
抄録全体を表示