Determination of β2-Agonist Residues in Fermented Ham Using UHPLC-MS/MS after Enzymatic Digestion and Sulfonic Resin Solid Phase Purification

β2-agonists are a class of synthetic sympathomimetic drugs with acute poisoning effects if consumed as residues in foods. To improve the efficiency of sample preparation and to overcome matrix-dependent signal suppression in the quantitative analysis of four β2-agonists (clenbuterol, ractopamine, salbutamol, and terbutaline) residues in fermented ham, an enzyme digestion coupled cation exchange purification method for sample preparation was established using ultra-high performance liquid chromatography and tandem mass spectrometry (UHPLC-MS/MS). Enzymatic digests were subject to cleanup treatment on three different solid phase extraction (SPE) columns and a polymer-based strong cation resin (SCR) cartridge containing sulfonic resin was found to be optimal compared with silica-based sulfonic acid and polymer sulfonic acid resins based SPEs. The analytes were investigated over the linear range of 0.5 to 10.0 μg/kg with recovery rates of 76.0-102.0%, and a relative standard deviation of 1.8-13.3% (n = 6). The limit of detection (LOD) and the limit of quantification (LOQ) were 0.1 μg/kg and 0.3 μg/kg, respectively. This newly developed method was applied to the detection of β2-agonist residues in 50 commercial ham products and only one sample was found to contain β2-agonist residues (clenbuterol at 15.2 µg/kg).