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 C18 column packed with 2.6 μm core-shell particles (diameter 4.6 mm, length 75 mm). 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 1.2 mL min−1 with an injection volume of 6 μL. These chromatographic conditions allowed the efficient separation of 13 sulphonamides in about 8 min. 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 100 μg kg−1, and RSDs% resulted lower than Thompson and Horwitz RSD% reference values for all sulphonamides. The LOQ value (2.7-15 μg kg−1) was low enough to satisfy legal limits suggested by European Regulation 37/2010/EC.