取西洋参粉末约2 g,加入1%(体积分数)冰乙酸溶液10 mL,均质5 min,加入体积比3∶1的乙腈-甲苯混合溶液10 mL和混合内标(由磷酸三苯酯、倍硫磷-d₆和阿特拉津-d₅组成)储备溶液1 mL,振荡1 min。加入质量比4∶1的无水硫酸镁-无水乙酸钠混合粉末7.5 g,振荡3 min,冰水浴冷却10 min,离心5 min。分取上清液9 mL置于装有无水硫酸镁900 mg、N-丙基乙二胺(PSA) 300 mg、C₁₈ 300 mg、硅胶300 mg和石墨化碳黑(GCB) 45 mg的净化管中,涡旋1 min,振荡5 min,离心1 min。上清液用0.22 μm滤膜过滤。取续滤液1 mL,加入分析保护剂(由D-(+)-核糖酸-1,4-内酯和山梨醇组成)溶液0.3 mL,用乙腈定容至2 mL,供气相色谱-三重四极杆质谱仪分析。各目标物在SH-Rxi-5Sil MS色谱柱上用程序升温条件分离,以电子轰击离子(EI)源电离,多反应监测模式检测,基质匹配法联合内标法定量。结果显示,53种农药工作曲线的线性范围均为2.5~200 μg·L^-1,检出限(3S/N)为0.001~0.002 mg·kg^-1;按标准加入法进行回收试验,回收率为69.1%~107%,测定值的相对标准偏差(n=6)均小于10%。方法用于50批进口西洋参样品的分析,检出了p,p'-滴滴伊、o,p'-滴滴涕、p,p'-滴滴滴、p,p'-滴滴涕和五氯硝基苯,西洋参的农药污染风险整体可控。

About 2 g of American ginseng powder was taken, and 10 mL of 1% (volume fraction) glacial acetic acid solution was added. The mixture was homogenized for 5 min, and 10 mL of acetonitrile-toluene mixed solution at volume ratio of 3∶1, and 1 mL of mixed internal standards (consisting of triphenyl phosphate, parathion-d₆ and atrazine-d₅) stock solution were added. The mixture was shaken for 1 min, and 7.5 g of mixed powder composed of anhydrous magnesium sulfate and anhydrous sodium acetate at mass ratio of 4∶1 was added. The mixture was shaken for 3 min, cooled in ice water bath for 10 min, and centrifuged for 5 min. An aliquot (9 mL) of the supernatant was taken and placed into a purification tube containg 900 mg of anhydrous magnesium sulfate, 300 mg of PSA, 300 mg of C₁₈, 300 mg of silica gel and 45 mg of GCB, and the mixture was vortexed for 1 min, shaken for 5 min, and centrifuged for 1 min. The supernatant was passed through a 0.22 μm filter membrane, and 1 mL of the continued filtrate was taken, and mixed with 0.3 mL of analyte protectant solution composed of D-(+)-riboacid-1,4-lactone and sorbitol. The mixed solution was made its volume up to 2 mL by acetonitrile, which was introduced into gas chromatograph-triple quadrupole mass spectrometer for analysis. The targets were separated on SH-Rxi-5Sil MS column under temperature programmed conditions, ionized by electron impact ion source, detected by multiple reaction monitoring mode, and quantified by matrix matching method combined with internal standard method. As shown by the results, the same linear range of working curves of 53 pesticides was 2.5-200 μg·L^-1, with detection limits (3S/N) in the range of 0.001-0.002 mg·kg^-1. Test for recovery was made according to standard addition method, giving results in the range of 69.1%-107%, and RSDs (n=6) of the determined values were less than 10%. The proposed method was applied to the analysis of 50 batches of imported American ginseng samples, and 1,1-bis(4-chlorophenyl)-2,2-dichloroethylene, 2,4'-dichlorodiphenyltrichloroethane,1,1-dichloro-2,2-bis(4-chlorophenyl)-ethane, 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane and pentachloronitrobenzene were detected, and the overall risk of pesticide pollution in American ginseng was controllable.