Analysis of organophosphorus pesticides in whole blood by GC-MS-μECD with forensic purposes

• Fully validated multiresidue methods for 10 organophosphorus pesticides in whole blood.
• Comparison of extraction procedures with different cartridges (Sep-Pak C18 & Oasis HLB).
• GC–MS used for screening and quantitation, whilst GC-ECD for confirmation.
• Methods applied to the laboratory routine panel.

In the present work, two multi-residue methods for the determination of ten organophosphorus pesticides (OPs), namely chlorfenvinphos, chlorpyrifos, diazinon, dimethoate, fenthion, malathion, parathion, phosalone, pirimiphos-methyl and quinalphos, in post-mortem whole blood samples are presented.The adopted procedure uses GC–MS for screening and quantitation, and GC-μECD (electron capture detector) for compound confirmation. Three different Solid Phase Extraction (SPE) procedures for OPs with Oasis® hydrophilic lipophilic balanced (HLB) and Sep-Pak® C18 cartridges were tested, and followed by GC-μECD and GC–MS analysis. The Sep-Pak® C18 cartridges extraction procedure was selected since it generated analytical signals 5 times higher than those obtained with the two different Oasis® HLB cartridges extraction procedures. The method has shown to be selective for the isolation of selected OPs as well as to the chosen internal standard (ethion) in postmortem blood samples. Calibration curves between 50 and 5000 ng/mL were prepared using weighted linear regression models (1/x2). It was not possible to establish a working range for fenthion by GC-μECD due to the lower sensitivity of the detector to this compound, whereas for pirimiphos-methyl it was set between 500 and 5000 ng/mL. The limit of quantitation was established at 50 ng/mL for all analytes, except for pirimiphos-methyl by GC-μECD analysis (500 ng/mL). The average extraction efficiency ranged from 72 to 102%.The developed methods were considered robust and fit for the purpose, and had already been adopted in the laboratory routine analysis.