Analysis of wax esters in seven commercial waxes using C30 reverse phase HPLC

Abstract

Commercial waxes are difficult to analyze due to their limited solubility in most organic solvents. Recently, our laboratory published a new reverse phase HPLC-MS method using a C30 column, a gradient of methanol and chloroform, an evaporative light-scattering detector (ELSD), and atmospheric pressure chemical ionization mass spectrometry (APCI-MS) to analyze jojoba wax (jojoba oil), carnauba wax, and sorghum wax. In the current study, the published HPLC method was modified by reducing the solvent gradient program to 60 minutes and this new method was evaluated for its usefulness for the analysis of five other commercial waxes (beeswax, rice bran, sunflower, candelilla and paraffin waxes). The ELSD appeared to detect all types of wax components, whereas the APCI-MS was most useful for the identification of wax esters and was unable to detect hydrocarbons, such as those in candelilla wax and paraffin wax. Previous HPLC methods for waxes and most GC methods for waxes only separate wax esters with size up to 54 carbons (C54) but this method was able to separate those with size up to 60 carbon wax esters. This report presents the first HPLC chromatograms for rice bran, sunflower, candelilla, and paraffin waxes. The main contribution of this work is the evidence that a C30 reverse phase HPLC system provides acceptable chromatographic separation of major components in commercial waxes.