Detection of eight sulphonamides and dapsone in milk by a liquid chromatographic method

Abstract

A liquid chromatographic method for the detection of eight sulphonamide drugs (sulphadiazine, -thiazole, -merazine, -methizole, -dimidine, -methoxypyridazine, -doxine and -methoxazole) and the sulphone dapsone in milk was developed. The method is based on a solid-phase extraction on cation-exchange columns using phosphoric acid, acetonitrile and methanol for elution. Analysis was performed after evaporation (concentration 5:1) with a Superspher RP-18 column. The mobile phase was an isocratic mixture of methanol, acetonitrile and sodium acetate and detection was performed at 275 nm. The recovery at the 25 μg kg −1 level was 62–85%, the repeatability at the 25 μg kg −1 was 1.69–10.35% and the sensitivity was 5 μg kg −1, with the exception of sulphadiazine, -dimidine and -methoxazole (10 μg kg −1). This method fulfils the requirements of EEC regulation 675/92 and the US FDA “safe level”. Out of 74 sulpha-suspicious raw milk samples (microbial receptor assay), dapsone was detected in four samples and sulphadimidine in nine samples. In no case was the EEC limit of 100 μg kg −1 exceeded. One sample contained more than 25 μg kg −1 of dapsone.