Determination of sulfonamides in milk samples by HPLC with amperometric detection using a glassy carbon electrode modified with multiwalled carbon nanotubes

A sensitive and accurate method for determining five sulfonamides based on HPLC with amperometric detection and using a glassy carbon electrode modified with multiwalled carbon nanotubes is proposed. Optimal conditions for the quantitative separation of selected sulfonamides were studied, and glassy carbon electrodes with and without modification with carbon nanotubes were systematically investigated as electrodic materials. Statistical analysis of the obtained results demonstrated that these modified electrodes achieved considerably better stability and sensitivity than the conventional unmodified ones. Detection limits were in the 1.2–6.0 ng/mL range. The usefulness of the method was demonstrated by the analysis of milk samples, taking into account the European legislation on residues in food products, following both a screening method to classify the samples and a confirmation method to provide more detailed information in the case of positive samples.