Determination of dodecylbenzenesulphonates and ethoxylated alkylphenols in liquid pesticide formulations by high-performance liquid chromatography.

A method is presented for determining mixtures of calcium dodecylbenzene-sulphonate (CaDBS) and ethoxylated alkylphenols in pesticidal emulsifiable concentrates. The pesticide formulations are adsorbed on a pre-concentration column. The active ingredients, the solvents and the emulsifiers are eluted successively by using solvents with increasing polarities. The various homologues of CaDBS and the ethoxylated alkylphenols are separated by reversed-phase high performance liquid chromatography using methanol-water containing tetramethylammonium bromide. The oligomers of the ethoxylated phenols are separated on an aminopropyl-modified column using a solvent gradient (propan-2-ol-water and hexane-tetrahydrofuran). Quantitative results are given for synthetic samples. The degree of ethoxylation of the ethoxylated alkylphenols has been determined and the CaDBS components characterized.