提出了气相色谱-质谱法测定粮谷中11种酰胺类除草剂的残留量的方法.大米、玉米及小麦样品用丙酮-正己烷(1+2)混合溶剂提取,而大豆样品须用乙腈提取,所得提取液须经净化除去由粮谷基质引入的脂肪酸以消除其对除草剂测定带来的基质干扰.研究结果表明:对大米、大豆和小麦样品的提取液可用弗罗里硅土和固相萃取柱作净化处理;但对玉米样品的提取液须用凝胶渗透色谱法进行净化.方法中采用Bio Beads S-X3凝胶渗透色谱净化柱和环己烷-乙酸乙酯(1+1)混合溶剂作流动相,根据保留时间和特征离子丰度比值作定性检测,根据特征离子强度作定量测定.11种酰胺类除草剂的检出限(3S/N)在0.01~0.02 mg·L-1之间.在3个浓度水平下对方法的回收率和精密度进行试验,测定回收率为72.8%~110.2%,相对标准偏差(n=5)均小于10%.

A method for determination of residual amounts of 11 acetanilide herbicides in cereals by GC-MS was proposed.It was reported that samples of rice,corn and wheat were extracted with mixed solvent of acetone and n-hexane (1+2),but sample of soybean should be extracted with acetonitrile.The extracts obtained should be purified to remove the fatty acids carried over from the matrixes of cereals in order to eliminate matrix interferences on the determination of the herbicides.As shown by the results of study,the Florisil SPE columns was quite efficient for purification of the extracts of rice,soybean and wheat samples,and the gel permeation chromatography (GPC) should be used for corn.The Bio-Beads S-X3 GPC column was used for the purification of corn extract and the mixed solvent of cyclohexane and ethyl acetate (1+1) was used as mobile phase in the proposed method.Qualitative detections were made on the base of ratios of retention time and abundance of characteristic ions,while quantitative analysis was performed on the base of values of intensity of the characteristic ions.Detection limits (3S/N) found for the 11 herbicides were in the range of 0.01-0.02 mg·L-1.Recovery and precision of the method were tested at 3 concentration levels,giving results of recovery in the range of 72.8% to 110.2%,and RSD′s (n=5) less than 10%.