UPLC-MS/MS同时测定蔬菜中阿维菌素等5种常用农药残留量

建立了同时测定蔬菜样品中阿维菌素、甲氨基阿维菌素苯甲酸盐(甲维盐)、吡虫啉、茚虫威及代森锌残留量的超高压液相色谱-串联质谱法(UPLC-MS/MS)。样品经0.1%氢氧化钠溶液(含10 mmol/L L-半胱氨酸和10 mmol/L EDTA-Na2)预处理后,以乙腈作为提取溶剂,经0.2 g C18+0.05 g石墨化碳(GCB)基质分散固相萃取净化。各待测物经Thermo Hypersil BDS C18(100 mm×4.6 mm,2.6μm)色谱柱进行分离,以10 mmol/L氨水-乙腈作流动相梯度洗脱,串联质谱法对5种农药残留量进行测定。结果表明,代森锌在50~2 000μg/L范围内,另4种农药在5~200μg/L范围内线性关系良好,相关系数(r2)为0.995 1~0.999 9。在0.5~500μg/kg加标浓度下,豆角、辣椒、青菜、黄瓜、芦笋、蕃茄中5种农药的加标回收率为70.8%~103.6%,相对标准偏差(RSD)为4.5%~13.9%;代森锌的检出限为8.2~30μg/kg,定量下限为27~100μg/kg,其余4种农药的检出限为0.02~0.7μg/kg,定量下限为0.07~2.3μg/kg。方法快速准确、经济实用,可满足日常检测的需要。     

Quantification of ziram and zineb residues in fog-water samples

The present paper describes the extractive quantification of zinc-dithiocarbamate fungicides, i.e. ziram (zinc bis-dimethyldithiocarbamate) and zineb (zinc ethylene-1,2-bis-dithiocarbamate) in fog-water samples. The method is based on the releasing of equivalent amount of zinc from the fungicides and its subsequent determination by visible spectrophotometry or by flame-atomic absorption spectrometry (flame-AAS). For spectrophotometry, the sample contained up to 48 μg of ziram and 42 μg of zineb was first equilibrated with chloroform. The recovery results show that only ziram content was extracted into chloroform. Then, the sample was treated with NH₄SCN and surfactants (i.e. CPC and TX-100) solutions, and extracted with toluene to remove interference of inorganic zinc and other metal ions, if present in the sample. The residue was further used for zineb determination. The chloroform extract and residue were then digested separately with nitric acid to release Zn(II), which were then analyzed spectrophotometerically with 4-(2-pyridylazo)-resorcinol in the micellar medium (TX-100) for the determination of ziram and zineb, respectively. The complex shows λ_max at 495 nm. The molar absorptivity in terms of ziram/zineb was determined to be (8.05) × 10⁴ L mole⁻¹ cm⁻¹. The detection limits for ziram and zineb were calculated to be 20 and 21 μg L⁻¹ (with R.S.D. < 1.5%), respectively. Whereas, the optimum concentration ranges were 0.08-1.6 and 0.07-1.4 mg L⁻¹, respectively. Alternatively, the Zn contents present in chloroform extract and in residue were directly analyzed using flame-AAS without undergoing the digestion procedure, and ziram and zineb were determined, respectively. The optimum concentration ranges were 0.9-4.8 and 0.8-4.3 mg L⁻¹, while the detection limits were calculated to be 145 and 144 μg L⁻¹, respectively with R.S.D. < 2.5%. The methods are free from interference of almost all ions [including Zn(II)] and other dithiocarbamate pesticides, which can commonly associate with ziram/zineb in fog-water.     

微分脉冲溶出伏安法结合化学计量学测定3种农药

代森锌、代森锰和除草通在汞电极上采用微分脉冲溶出伏安扫描时均具有良好的还原峰,但各个组分的伏安峰之间呈现严重的重叠,在不分离的情况下很难进行测定。讨论3种农药在汞电极上的还原反应机理,并采用化学计量学方法对重叠伏安波进行解析和定量分析,结果表明,偏最小二乘法能得到最好的结果。选择萃取率较大的三氯甲烷作为萃取剂,对几种蔬菜水果样品中的农药进行萃取分离,并用提出的方法进行分析,回收率在99%~104%之间。