Rapid method for the quantification of 13 sulphonamides in milk by conventional high-performance liquid chromatography with diode array ultraviolet detection using a column packed with core-shell particles.

In the present study, a column packed with core-shell particles was used for the separation and the quantification of 13 sulphonamides in milk by conventional high-performance liquid chromatography coupled with diode array ultraviolet detection (HPLC/UV-DAD). Preliminary experiments were carried out to investigate selectivity of different stationary phases. Best results were achieved using a C column packed with 2.6μm core-shell particles (diameter 4.6mm, length 75mm). A binary gradient elution based on acetate buffer solution at pH 4.50 and a mixture of methanol acetonitrile 50:50 (v/v) was employed at the flow rate of 1.2mLmin with an injection volume of 6μL. These chromatographic conditions allowed the efficient separation of 13 sulphonamides in about 8min. To evaluate the suitability of the method for official control analysis, the most important validation parameters were investigated according to the European Decision 657/2002/EC as established for analysis of drug residues in food. Sulphonamides were recovered from milk samples by a simple and quick preparation procedure consisting of an extraction step with chloroform/acetone and a purification step with n-hexane. Mean recoveries from raw milk ranged between 55% and 86% at the Maximum Residual Limit of 100μgkg, and RSDs% resulted lower than Thompson and Horwitz RSD% reference values for all sulphonamides. The LOQ value (2.7-15μgkg) was low enough to satisfy legal limits suggested by European Regulation 37/2010/EC.