Alternative sample treatments for the determination of sulfonamides in milk by HPLC with fluorescence detection

This paper presents two sample treatments, dispersive liquid-liquid microextraction (DLLME) and QuEChERS for the determination of 9 sulfonamides, regulated by the EU Council in milk samples. Both methods represent useful alternatives to conventional procedures based mainly in solid-phase extraction, in terms of simplicity, reduction of organic solvents, sample throughput and effectiveness for cleaning-up complex samples. They have been evaluated and compared in terms of efficiency, trueness, sensitivity and precision, using HPLC with fluorescence detection employing a previous derivatisation step with fluorescamine. Clean extracts were obtained with recoveries between 90.8-104.7% and 83.6-104.8% for DLLME and QuEChERS, respectively. Matrix-matched calibration curves were established for both methods using milk samples spiked at four concentration levels. LODs (3xS/N) lower than 1.21 μg L−1 and 2.73 μg L−1 for DLLME and QuEChERS, respectively, were obtained in all cases. The precision, in terms of repeatability and intermediate precision, was lower than 10% in all cases.