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.