A sensitive multiresidue method for the determination of pesticides in marijuana by liquid chromatography-tandem mass spectrometry.

A multiresidue method based on QuEChERS extraction followed liquid chromatography coupled with tandem mass spectrometry was developed and validated for the determination of 42 pesticides in marijuana. Less than 6 min is required for detection of all species. By using original QuEChERS, the sample preparation is also fast and simple. In the range from 1.0 to 50 μg kg-1, the coefficients of determination (r2) were greater than 0.980, and relative standard deviations for replicate injections were lower than 4.6%. The limit of detection (LOD) and limit of quantification (LOQ) were lower than 0.32 μg kg-1 and 1.07 μg kg-1, respectively. Precision and accuracy were verified through recovery of spiked samples at three distinct levels of concentration (1.0, 5.0, and 50.0 μg kg-1) in five replicates. Recovery values ranged from 82 to 119% with RSD lower than 6%. The method was applied to the detection of pesticide residues in six marijuana samples seized by the Police of Rio de Janeiro, Brazil, where imidacloprid, metazachlor, buprofezin, and metalaxyl were found in four of them.