Analysis of wax esters in edible oils by automated on-line coupling liquid chromatography–gas chromatography using the through oven transfer adsorption desorption (TOTAD) interface

An automated method for the direct analysis of wax esters in edible oils is presented. The proposed method uses the TOTAD (through oven transfer adsorption desorption) interface for the on-line coupling of normal phase liquid chromatography and gas chromatography. In this fully automated system, the oil with C32 wax ester as internal standard and diluted with heptane is injected directly with no sample pre-treatment step other than filtration. The proposed method allows analysis of different wax esters, and is simpler and faster than the European Union Official Method, which is tedious and time-consuming. The obtained results closely match the certified values obtained from the median of the analytical results of the inter-labs certification study. Relative standard deviations of the concentrations are less than 5%. The method is appropriate for routine analysis as it is totally automated.