HPLC of grain sorghum wax classes highlighting separation of aldehydes from wax esters and steryl esters

Abstract

This study was performed to develop HPLC methods for determining the composition of grain sorghum wax using a silica column and an ELSD. The method development emphasized separation of aldehydes from wax esters (WE) and steryl esters (SE). Gradient mobile systems using 0.2% (v/v) acetic acid and 0.02% (v/v) methyl tert-butyl ether (MTBE) in hexane and 0.2% (v/v) acetic acid in MTBE or hexane and 0.2% (v/v) acetic acid in MTBE separated aldehydes, acids, and alcohols, as well as minor components such as mixtures of WE and SE, and triacylglycerols (TG). Grain sorghum wax was composed of 46. 3% (w/w) fatty aldehydes, 7.5% fatty acids, 41.0% fatty alcohols, 0.7% hydrocarbons, 1.4% WE and SE, and 0.9% TG, based on HPLC data. The gradient HPLC systems were also useful for compositional analysis of carnauba wax. Carnauba wax contained of 34.3% (w/w) WE, 5.1% fatty acids, undetermined amount of fatty alcohols, and 3.0% TG.