Meyer E., Borrey D., Lambert W., Van Peteghem C., De Leenheer A., Piette M.^*

Laboratorium voor Toxicologie, Universiteit Gent, Harelbekestraat 72
^* Laboratorium voor Gerechtelijke Geneeskunde, Universiteit Gent, J.Kluyskensstraat 29, B-9000 Gent, Belgium

Fenthion (O,O-dimethyl-O-[3-methyl-4-(methylthio)-phenyl]-thiophosphate) is an organophosphate insecticide used worldwide in different types of cultivation and in the control of pest bird species. A suicidal case involving non-suspected fenthion poisoning is presented. The cholinesterase activity in blood was 202 U/L. Fenthion levels were determined quantitatively in all available postmortem matrices. Fenitrothion (O,O-dimethyl-O-[3-methyl-4-nitrophenyl]-thiophosphate) was selected as the internal standard. For sample clean-up a simple but very selective solid phase extraction described for water analysis (1) was chosen. Homogenized and appropriately diluted aqueous samples are applied and the analytes are desorbed with 5 mL of dichloromethane. Aliquots of the extract are used for HPLC-DAD and GC/MS analysis. The LC and GC conditions were as follows: gradient elution with a mixture of methanol and water (10:90 to 90:10, v/v) containing 0.0125 N NaOH on an Aluspher RP-Select B column at 250 nm, and temperaure programming from 60 to 300° C at 10° C/min on a dimethylpolysiloxane column in the SCAN mode, respectively. A calibration graph was prepared for each of the matrices. The method was validated demonstrating satisfactory recoveries, linearity and LOQ-values (e.g. 71%, up to 10 µg/mL and 0.25 µg/mL for blood, respectively). The obtained concentrations (e.g. 3.8 µg/mL in blood) disclosed fenthion ingestion as the cause of this fatality (2).

References

1. M.Psathaki et al., J.Chromatogr., 1994, 66, 241-8.
2. A.M.Tsatsakis et al., Vet. Human Toxicol., 1996, 38, 101-7