Multi-walled carbon nanotubes–dispersive solid-phase extraction combined with liquid chromatography–tandem mass spectrometry for the analysis of 18 sulfonamides in pork

A simple and cost-effective pre-treatment procedure was developed for 18 sulfonamides in pork using dispersive solid phase extraction (dSPE) with multi-walled carbon nanotubes (MWCNTs). The sample was analysed after purification by ultra high-performance liquid chromatography–positive electrospray ionisation tandem mass spectrometry (UHPLC–ESI-MS/MS). After extraction with phosphate buffer (pH 6.0), a dSPE procedure was conducted with MWCNTs. The pH value of the extract, extraction time with MWCNTs, type and amount of MWCNTs and type of eluent were optimised to increase the sample throughput and sensitivity. The samples were quantified using sulfamethazine-13C6 as an internal standard. The recoveries of the target compounds from the pork samples were most efficient when 150 mg of MWCNTs with an outer diameter of less than 8 nm and a length of 0.5–2 μm was used. A mixture of acetonitrile/50 mM ammonium acetate (95:5, v/v) was shown to be the most suitable solvent for desorbing the compounds from the MWCNTs. The proposed method was validated according to the European Commission Decision 2002/657/EC, which determines linearity, specificity, decision limit (CCα), detection capability (CCβ), recovery, precision and stability.