分散固相萃取-液相色谱-串联质谱法测定蜂蜜中新型烟碱类杀虫剂及其代谢物的残留量

Simultaneous Determination of Neonicotinoid Insecticides and Their Metabolites in Honey by High Performance Liquid Chromatography-Tandem Mass Spectrometry with Dispersive Solid-Phase Extraction

称取蜂蜜样品2.00g至具塞离心管中,加入100μL同位素内标溶液(200μg·L^(-1))和10mL水,涡旋混匀,加入甲醇至20mL,涡旋混匀,以8 500转·min^(-1)离心5min,移取上清液0.50mL,用甲醇定容至10.0mL,涡旋混匀后,以8 500转·min^(-1)离心5min,取1.0mL上清液转移至具塞离心管中(内含混合均匀的吸附剂:30mg N-丙基乙二胺、15mg C_(18)粉末和50mg无水MgSO_4),涡旋混匀进行吸附净化,以8 500转·min^(-1)离心5min,转移全部上清液,于40℃下用氮气吹至近干,用甲醇-0.15%(体积分数,下同)甲酸溶液(1+9)混合液溶解残渣并定容至1.0mL,过0.22μm滤膜后供液相色谱-串联质谱分析。采用Agilent Eclipse XDB-C_(18)色谱柱进行分离,以不同比例的含5mmol·L^(-1)乙酸铵的0.15%甲酸溶液和甲醇为流动相进行梯度洗脱。质谱中采用电喷雾离子源正离子扫描方式和多反应监测模式,采用同位素内标法和外标法进行定量。吡蚜酮、呋虫胺、烯啶虫胺、噻虫嗪、氟啶虫酰胺、吡虫啉、噻虫胺、氯噻啉、啶虫脒、噻虫啉、4-(三氟甲基)烟酰胺和N-去甲基啶虫脒的质量浓度在一定范围内呈线性,测定下限(10S/N)在2.5～12.5μg·kg^(-1)之间。对空白蜂蜜样品进行加标回收试验,回收率在79.9%～108%之间,测定值的相对标准偏差(n=6)在1.7%～15%之间。

The honey sample (2.00 g) was added into in a centrifuge tube with a cover, and 100 μL of isotope internal standard solution (200 μg·L^-1) and 10 mL water were added. After mixing well by vortex, the mixture was made up to 20 mL with methanol, and mixed well, centrifuged at 8 500 r·min-1 for 5 min. 0.50 mL of the supernatant was taken and diluted to 10.0 mL with methanol, and the mixture was mixed well by vortex, then centrifuged at 8 500 r·min-1 for 5 min. 1.0 mL of the supernatant was transferred into a centrifuge tube containing a homogeneously mixed adsorbent (30 mg of N-propyl ethylenediamine, 15 mg of C18 powder and 50 mg of anhydrous MgSO4). After vortexing and mixing for adsorption purification, the tube was centrifuged at 8 500 r·min-1 for 5 min. All the supernatant was blowed to near dryness using nitrogen at 40 ℃, and the residue was disolved and made up to 1.0 mL with a mixture of methanol and 0.15%(volume fraction) formic acid solution (1+9). The solution was passed through a 0.22 μm filter, and the filtrate was analyzed by liquid chromatography-tandem mass spectrometry. Chromatographic separation was carried out using an Agilent Eclipse XDB-C18 column, with a mixture in varying proportions of 0.15% formic acid solution containing 5 mmol·L-1 ammonium acetate and methanol as mobile phase for gradient elution. Electrospray ion source, positive ion scanning mode and multireaction monitoring mode were used in the mass spectrometry, and the isotope dilution internal standard method and external standard method were used for quantification. The mass concentration of pyridoxine, dinotefuran, nitenpyram, thiame-thoxam, flonicamid, imidacloprid, clothianidin, chlorothiazide, acetamiprid, thiacloprid, 4-(trifluoromethyl)nicotinamide and N-desmethylpyrazole, was linear within definite ranges, and the lower limits of determination (10S/N) were between 2.5-12.5 μg·kg-1. Tests for recovery was made by standard addition method to blank honey samples, giving results in the range of 79.9%-108%, and RSDs (n=6) were between 1.7% and 15%.