Gas chromatographic separation of R/ S-α-hydroxy fatty acid esters

Gas chromatographic (GC) separations of R/ S-α-hydroxy fatty acids (AHFAs) are carried out on several columns, including α-cyclodextrin derivative (CYDEX-B) chiral column. R/ S-AHFAs are well separated on achiral columns (BP-1, non-polar phase and Rtx-2330, very polar phase) as diasteriomeric esters of the optically active alcohols, whereas the shorter chain length of the alcohol tends to give lower separation factor ( α) on the same column. The longest chain length of alcohol used in this study is 2-octanol and its ester shows the highest α on the Rtx-2330 capillary column. Thus, the four thermodynamically related column constants ( a, b, c and d) of Eq. (1) for R- and S-AHFAs standard are determined. ln k′=a+bn+ c T + dn T where k′ is the retention factor, n the equivalent carbon number and T the absolute temperature. This equation is used to estimate the equivalent n, and also subsequently used to identify and determine the configuration of AHFAs in wool wax without using a standard AHFA as a reference.