Comparison between GC-MS-SIM and GC-ECD for the determination of residues of organochlorine and organophosphorus pesticides in Brazilian citrus essential oils

brazilian citrus essential oils (mandarin, orange, lemon, bergamot and tangerine) were analyzed for the determination of pesticides residues of organochlorine (aldrin, chlordane, dieldrin and dicofol) and organophosphorus (methyl chlorpyrifos, dimethoate, methidathion and methyl parathion) . a comparative study between gas chromatography-mass spectrometry in selective ion monitoring mode (gc-ms-sim) and gas chromatography-electron capture detector (gc-ecd) was performed using solid phase extraction (spe) with florisil？ cartridge for the pre-concentration of pesticides. the average recovery of pesticides was from 71 to 83% as determined by gc-ms-sim analysis and 99 to 104% by gc-ecd. the limit of quantification was from 0.93 to 3.93 mg l-1 in gc-ms-sim and 0.09 to 0.12 mg l-1 in gc-ecd. fifteen samples of commercial brazilian citrus essential oils were analyzed and six samples showed contamination with values above the maximum residue limit (mrl) allowed by the codex alimentarius.