Ahmad N, Guo L, Mandarakas P, Appleby S, Bugueno G
New South Wales Department of Agriculture, Biological and Chemical Research Institute, Rydalmere, Australia.
J AOAC Int. 1995 Nov-Dec;78(6):1450-4.
A novel procedure is described for simple removal of coextractives prior to analysis of fruits and vegetables for azinphos-methyl and azinphos-ethyl residues. The solvent extract is concentrated, placed in a polymeric membrane tube, and then dialyzed in cyclohexane. Both azinphos-methyl and azinphos-ethyl diffuse into the surrounding solvent while coextractants remain inside the membrane. The dialyzing solvent is exchanged during concentration with n-hexane and analyzed without further cleanup by gas-liquid chromatography with a specific thermionic detector. The detection limit for a 25 g grape sample with final volume of extract made to 15 mL was 0.01 mg/kg. Recoveries of both residues from grapes averaged 107% (spike levels of 0.3 to 2.0 mg/kg). From a 20 g spinach sample, recoveries averaged 82% for azinphos-methyl and 72% for azinphos-ethyl when final volume of extract was made to 5 mL (spike levels of 0.1 to 1.0 mg/kg). Recoveries from 20 types of fruits and vegetables (20 g sample spiked at 1 mg/kg for both azinphos-methyl and azinphos-ethyl) were consistently greater than 70%, except for strawberries (61-67%) and avocado (28-34%). The high lipid content of avocado may impede diffusion of azinphos-methyl and azinphos-ethyl through the polymeric membrane. A field evaluation of the procedure showed a strong correlation (r = 0.957) between azinphos-methyl residues on grapes and treatments with 2 spray formulations. The membrane cleanup procedure is a simple and cost-effective alternative to other column or liquid-liquid partitioning procedures for azinphos-methyl and azinphos-ethyl residue analysis.
本文描述了一种新颖的方法，用于在分析水果和蔬菜中甲基谷硫磷和乙基谷硫磷残留之前，简单地去除共萃取物。将溶剂提取物浓缩，置于聚合物膜管中，然后在环己烷中进行透析。甲基谷硫磷和乙基谷硫磷都扩散到周围的溶剂中，而共萃取剂则留在膜内。在浓缩过程中，用正己烷交换透析溶剂，无需进一步净化，即可用特定的热离子检测器通过气液色谱法进行分析。对于最终提取物体积为15 mL的25 g葡萄样品，检测限为0.01 mg/kg。葡萄中两种残留的回收率平均为107%（加标水平为0.3至2.0 mg/kg）。对于20 g菠菜样品，当提取物最终体积为5 mL（加标水平为0.1至1.0 mg/kg）时，甲基谷硫磷的回收率平均为82%，乙基谷硫磷的回收率平均为72%。从20种水果和蔬菜（20 g样品，甲基谷硫磷和乙基谷硫磷的加标量均为1 mg/kg）中回收的残留量一直大于70%，草莓（61 - 67%）和鳄梨（28 - 34%）除外。鳄梨的高脂肪含量可能会阻碍甲基谷硫磷和乙基谷硫磷通过聚合物膜的扩散。该方法的现场评估表明，葡萄上的甲基谷硫磷残留量与两种喷雾制剂处理之间存在很强的相关性（r = 0.957）。对于甲基谷硫磷和乙基谷硫磷残留分析，膜净化方法是一种简单且经济高效的替代其他柱色谱或液 - 液分配方法的方法。
