Transesterification of fatty acid ethoxylates in supercritical methanol, then gas chromatography–mass spectrometric determination of the derived methyl esters, for identification of the initiators

Abstract.

Unknown fatty acid ethoxylate samples have been transesterified in supercritical methanol, using a loop made of a stainless-steel tubing as the reactor vessel. The initiator acids, now present as the corresponding methyl esters, were determined by gas chromatography–mass spectrometry (GC–MS). Quantitative transesterification is achieved by heating a solution of the ethoxylate sample in methanol at 280 °C for 10 min under pressure. The influence of reaction time, temperature, and presence of a Lewis acid catalyst has been investigated. The method of transesterification was optimized in respect of low cost, short reaction time, and availability to laboratories with standard analytical equipment.