A method was established for the simultaneous detection of 12 prohibited veterinary drugs, including β2-receptor agonists, nitrofuran metabolites, nitroimidazoles, chlorpromazine, and chloramphenicol, in pig urine. The sample was pretreated by enzymolysis, acid hydrolysis/derivatization, and liquid-liquid extraction combined with solid-phase extraction. Detection was performed using ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Ammonium acetate solution (0.2 mol/L, 4.5 mL) and β-glucuronidase/aryl sulfatase (40 μL) were added to the sample, which was subsequently enzymolized at 37 ℃ for 2 h. Then, 1.5 mL of 1.0 mol/L hydrochloric acid solution and 100 μL of 0.1 mol/L o-nitrobenzaldehyde solution were added to the sample. The mixture was incubated at 37 ℃ for 16 h, and the analytes were extracted with 8 mL of ethyl acetate by liquid-liquid extraction. The lower aqueous phase obtained after extraction was extracted and purified using a mixed cation-exchange solid-phase extraction column. The extracts were combined, the extraction solution was blow-dried with nitrogen, and the residue was redissolved for determination. The samples were analyzed under multiple-reaction monitoring mode with both positive and negative electrospray ionization, and quantified using an isotope internal standard method. The correlation coefficients (r) of the 12 compounds were >0.99. The limits of detection (LODs) and quantification (LOQs) of chloramphenicol were 0.05 and 0.1 μg/L, respectively, and the LODs and LOQs of the other compounds were 0.25 and 0.5 μg/L, respectively. The mean recoveries and RSDs at 1, 2, and 10 times the LOQ were 83.6%-115.3% and 2.20%-12.34%, respectively. The proposed method has the advantages of high sensitivity, good stability, and accurate quantification; thus, it is suitable for the simultaneous determination of the 12 prohibited veterinary drug residues in pig urine.
研究建立了超高效液相色谱-串联质谱测定猪尿中β2-受体激动剂类、硝基呋喃代谢物类、硝基咪唑类、氯丙嗪、氯霉素等5类12种禁用兽药残留量同时检测的方法。试样中加入4.5 mL 0.2 mol/L乙酸铵溶液和40 μL β-葡萄糖醛酸酶/芳基硫酸酯酶,37 ℃酶解2 h后,再加入1.5 mL 1.0 mol/L盐酸溶液和100 μL 0.1 mol/L邻硝基苯甲醛溶液,经37 ℃衍生16 h,用8 mL乙酸乙酯萃取,下层水相用混合型阳离子交换固相萃取柱萃取,合并2次萃取液,氮气吹干复溶,正负离子多反应监测模式下检测,同位素内标法定量。12种化合物在各自范围内线性关系良好,相关系数(r)>0.99;氯霉素的检出限为0.05 μg/L,定量限为0.1 μg/L,其他化合物的检出限为0.25 μg/L,定量限为0.5 μg/L;在定量限1倍、2倍、10倍添加水平下的平均回收率为83.6%~115.3%, RSD为2.20%~12.34%。方法灵敏度高,稳定性好,定量准确,适用于猪尿中12种禁用兽药残留量的同时测定。
Keywords: acidolysis; derivatization; enzymatic hydrolysis; pig urine; prohibited veterinary drugs; ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS).