Two fatal intoxication cases with imidacloprid: LC/MS analysis

Imidacloprid [1-(6-chloro-3pyridylmethyl)-N-nitroimidazolidin-2-ylideneamine] is a new and potent nitromethylene insecticide with high insecticidal activity at very low application rates. It is the first highly effective insecticide that, like nicotine, acts on the nervous system, causing blockage of postsynaptic nicotinergic acetylcholine receptors. Two fatal cases with this insecticide in two male individuals, of 33 and 66 years old, are presented.

An LC/MS with electrospray method for measuring imidacloprid and its metabolites in post-mortem samples is described. In the chromatographic separation, a reverse-phase column XTerra™ MS C18 (2.1mm i.d.×150mm, 5μm) was used and the mobile phase composed with acetonitrile and 0.1% formic acid (15:85), at a 0.25mL/min flow rate. Samples were prepared with a liquid–liquid extraction procedure with dichloromethane.

Calibration curves for imidacloprid in blood and urine samples were linear from 0.2 to 15μg/mL. The mean recovery was 86% with a coefficient of variation of ±5.9%. The detection limit was 0.002μg/mL. Quantitative results were obtained for all post-mortem matrices available of the two fatal cases: blood, urine, stomach contents, lung, liver and kidney. The imidacloprid blood concentrations found in two-cases were 12.5 and 2.05μg/mL.

The authors validated a method to detect and quantify imidacloprid in post-mortem samples, and to our knowledge for the first time a post-mortem tissue distribution was performed on various samples for this insecticide.