[Determination of fatty acid methyl ester ethoxylates by gas chromatography]

A gas chromatographic (GC) method for the determination of fatty acid methyl ester ethoxylates (FMEO) is described. After hydrolyzed in 0.5 mol/L KOH ethanol solution, ester linkage in FMEO was broken into two parts, i.e., hydrophobic groups and hydrophilic groups, which made feasible for the further derivatization of both groups using appropriate derivatizing agents. Hydrophobic groups were esterified by sulfate acid-methanol mixture and hydrophilic groups were etherified by hexamethyldisilyamine and trimethylchlorosilane prior to GC determination. Quantitative results were obtained by the normalization of peak areas of the chromatograms. Compared with previous methods, this one is simple, quick and has a good reproducibility, especially for FMEOs with hydrophobic groups of mixed chain lengths.