Analysis of seven sulphonamides in milk by cloud point extraction and high performance liquid chromatography

An efficient and environmentally friendly analytical methodology is proposed for extracting and preconcentrating seven sulphonamides from milk prior to high performance liquid chromatography with ultraviolet detection (HPLC–UV). It is based on the induction of micellar organised media by using Triton X-100 as an extracting solvent. Optimisation of the factors affecting de-emulsification and phase separation was performed. The limits of detection (LOD) of the sulphonamides ranged from 2.23 to 9.79 μg/L, the linear range of quantitation for all analytes was approximately 0.05–2.0 mg/L and the correlation coefficients of the calibration curves were ⩾0.9999. The average recoveries and relative standard deviations were in the range of 67.0–105.7% and 0.93–8.31%, respectively, for fortified samples at 0.05, 0.10 and 0.20 mg/L of each sulphonamide.