DETERMINATION OF NONIONIC SURFACTANTS OF THE ALCOHOL POLYETHOXYLATE TYPE BY MEANS OF HIGH-TEMPERATURE GAS-CHROMATOGRAPHY AND ATOMIC-EMISSION DETECTION

High temperature gas chromatography (HT-GC) coupled to atomic emission detection (AED) has been applied for the determination of alkyl chain distribution, mole average degree of ethoxylation and weight percent distribution of the corresponding homologues of alcohol ethoxylates wi thout all the actual homologues being available as pure references. Ba sed upon its constant elemental response, the HT-GC-AED system has bee n evaluated for its applicability to compound independent calibration within the homologous series of the alcohols and alcohol ethoxylates. Discrimination against high molecular weight components by gas chromat ography requires conversion to the acetyl or trimethylsilyl derivative s. The latter includes introduction of the hetero atom silicon and thu s allows monitoring of the silicon trace. Thus selectivity will be enh anced by excluding detection of compounds which do not react with the derivatization reagent. The method has been validated with the analysi s of the technical product Brij 30, consisting of a mixture of alcohol ethoxylates with a vendor-specified mole average degree of ethoxylati on of four. The experimental result yields a mole average degree of 4. 0 +/- 0.1 in the carbon, silicon and oxygen traces.