Molecular Formula Determination of Trimethylsilyl Derivatives of Lipids by Gas Chromatography-Microwave-Induced Plasma-Atomic Emission Spectrometry

Abstract

Gas chromatography-microwave-induced plasma atomic emission spectrometry (GC-MIP-AES) was shown an effective means for determining the empirical formulae of fatty acid (FA), monoacylglycerol (MG) and diacylglycerol (DG) trimethylsilyl (TMS) ester (or ether) derivatives. Negative interference by silicon was demonstrated on an oxygen emission chromatogram. Negative interference and positive oxygen emission intensity decreased with increase in the rate of helium make-up gas flow. At optimal helium make-up gas flow (160mL/min), the oxygen number of the empirical formulae of FA, MG and DG-TMS derivatives were determined within ±0.3 atoms of theoretical formulae, and relative standard deviation (%) was less than 3.1% for FA-TMS, 4.1% for MG-TMS and 4.5% for DG-TMS.