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

Unknown fatty acid ethoxylate samples have been transesterified in supercri tical methanol, using a loop made of a stainless-steel tubing as the reacto r vessel. The initiator acids, now present as the corresponding methyl este rs, were determined by gas chromatography-mass spectrometry (GC-MS). Quanti tative transesterification is achieved by heating a solution of the ethoxyl ate sample in methanol at 280 degreesC for 10 min under pressure. The influ ence of reaction time, temperature, and presence of a Lewis acid catalyst h as been investigated. The method of transesterification was optimized in re spect of low cost, short reaction time, and availability to laboratories wi th standard analytical equipment.