适量水浸润的铁皮石斛样品经乙腈高速涡旋和超声提取。离心后，上清液采用分散固相萃取净化，吸附剂为C₁₈和N-丙基乙二胺。采用分散固相萃取-气相色谱-串联质谱法测定净化液中41种农药的残留量。在气相色谱分离中采用Agilent VF-5MS色谱柱，在串联质谱分析中采用多反应监测模式。以外环氧七氯为内标，41种农药的检出限（3S/N）为0.001~0.024 mg·kg^-1。以空白样品为基体进行加标回收试验，所得回收率为75.1%~115%，测定值的相对标准偏差（n=6）为0.40%~11%。

The dendrobium candidum sample soaked with appropriate amount water was extracted ultrasonically with acetonitrile accompanied by high speed vortex. After centrifugation, the supernatant was purified with dispersive solid phase extraction. C₁₈ and PSA were used as adsorbents. GC-MS/MS was applied to the determination of residual amounts of 41 pesticides in purified liquid with dispersive solid phase extraction. Agilent VF-5MS chromatographic column was used for GC separation and the multiple reaction monitoring mode was adopted in MS/MS determination. cis-Heptachlor epoxide was used as internal standard. Detection limits (3S/N) of the 41 pesticides were in the range of 0.001-0.024 mg·kg^-1. On the base of blank sample, test for recovery was made by standard addition method; values of recovery found were in the range of 75.1%-115%, with RSDs (n=6) of determined values in the range of 0.40%-11%.