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    气相色谱法和气相色谱-质谱法测定大蒜中甲基嘧啶磷和乙基嘧啶磷残留量

    Determination of Methyl-Pyrimithate and Ethyl-Pyrimithate in Garlic by Gas Chromatography and Gas Chromatography-Mass Spectrometry

    • 摘要: 取经捣碎并混匀的大蒜样品10.00 g,加入水3 mL、乙腈20 mL、氯化钠3 g和2个陶瓷均质子,涡旋提取2 min,离心,取上层清液10.0 mL于40℃下蒸发至近干,用含1%(体积分数)甲酸的甲醇(1+5)混合液溶解残渣。所得溶液流经固相萃取柱(SPE)净化,用3 mL含1%(体积分数)甲酸的甲醇(1+5)混合液淋洗萃取柱,弃去淋洗液。用含0.5%(体积分数)氨水的甲醇混合液将吸附在SPE柱上的分析物洗脱,洗脱液在40℃下吹氮至近干,用丙酮-正己烷(1+9)混合液溶解残渣并定容至1.0 mL。分别采用气相色谱-火焰光度检测器(GC-FPD)和气相色谱-质谱法(GC-MS)测定此溶液中甲基嘧啶磷和乙基嘧啶磷的含量。结果表明:甲基嘧啶磷和乙基嘧啶磷的质量浓度在一定范围内与其峰面积之间呈线性关系,甲基嘧啶磷和乙基嘧啶磷采用GC-FPD和GC-MS进行测定的测定下限(10S/N)均为0.01 mg·kg-1。按照标准加入法进行加标回收试验,采用GC-FPD测得回收率在81.6%~91.6%之间,采用GC-MS测得回收率在94.4%~98.1%之间,两方法测定值的相对标准偏差(n=6)分别在4.1%~8.6%和3.1%~9.4%之间。

       

      Abstract: 10.00 g of the pounded and homogenized garlic sample were taken and extracted vortically with 3 mL of water, 20 mL of acetonitrile and 3 g of sodium chloride for 2 min. After centrifuging, 10.0 mL of the upper layer were taken and evaporated to near dryness at 40℃, and the residue was dissolved in 3 mL of CH3OH-H2O (1+5) solution, which contains φ 1% formic acid. The solution obtained was then purified by passing through SPE column. The analytes were adsorbed on the SPE column, and were eluted from the column by CH3OH containing φ 0.5% of aq. ammonia. The eluates were collected and evaporated to near dryness by N2-blowing at 40℃. The residue was dissolved with its volume made up to 1.0 mL by a mixture of acetone and n-hexane (1+9). Contents of methyl-pyrimithate and ethyl-pyrimithate in the solution were determined separately by GC-FPD and by GC-MS. Linear relationships between values of peak areas of the 2 analytes and their mass concentrations were obtained in definite ranges, with values of lower limits of determination (10S/N) of 0.01 mg·kg-1 for GC-FPD and GC-MS. Recovery was tested by standard addition method, giving values of recovery in the ranges from 81.6% to 91.6% and from 94.4% to 98.1% for the 2 methods respectively, and RSDs (n=6) ranged from 4.1% to 8.6% and from 3.1% to 9.4%.

       

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