加压溶剂萃取-气相色谱法测定荞麦中残留的有机氯农药

Analysis of organochlorine pesticides in buckwheat using pressurized liquid extraction and gas chromatography

用所研制的24位全自动加压溶剂萃取仪（APLE），以丙酮-正己烷（体积比为1：1）为溶剂，在100℃和10MPa条件下，对荞麦样品中残留的7种有机氯农药进行了萃取，并通过气相色谱对萃取液进行定量分析。萃取的绝对回收率为68％～126％．相对标准偏差为1．2％～14．7％，检测下限为0．051～0．18ng／g。与索氏提取法对比，相对提取回收率为116％～148％，表明萃取收率高于索氏提取法。

Seven organochlorine pesticides （OCPs） in buckwheat were extracted by a homemade 24 cells auto-pressurized liquid extraction instrument （APLE） and then analyzed by gas chromatography with electronic capture detection. The optimal extraction condition was found to be 100 ℃ and 10 MPa for 5 min with acetone/n-hexane （ 1 ： 1, v/v） as the extraction solvent. The extraction was performed twice for each sample to obtain complete extraction. The buckwheat was mixed with florisil and active carbon before filling into extraction cells. Concentrated sulfuric acid was used in clean up step of the extractant. The standard mixture of OCPs including a-benzene hexachloride （BHC）, γ-BHC, δ-BHC, p,p＇-dichloro-diphenyl-dichloroethylene （p, p＇-DDE ）, p, p＇-dichloro-diphenyl-dichloroethane （ p, p＇-DDD ）, o, p-dichlo- ro-diphenyl trichloro-ethane （o ,p-DDT）, p ,p＇-DDT was used for the identification and quantification in gas chromatographic analysis. The absolute recoveries of the 7 organochlorine pesticides were between 68% - 126% with the relative standard deviations lower 14.7%. The detection limits were between 0. 051 -0. 18 ng/g. The relative recoveries were as high as 116% - 148% compared with Soxhlet extraction. It shows that the recoveries of APLE are much better than Soxhlet extraction, and the time of extraction for APLE is only about 15 min which is much less than conventional extraction methods.