Determination of propoxur residues in eggs by liquid chromatography–diode array detection after treatment of stocked housing facilities for the poultry red mite (Dermanyssus gallinae)

A sensitive and selective liquid chromatography–diode array detection method for the determination of propoxur in eggs is described. Eggs were homogenized, extracted with acetonitrile and partitioned with n-hexane. Further clean-up of the acetonitrile extract was undertaken using silica gel column chromatography. Quantitative detection was performed by liquid chromatography with UV detection at 220 nm and confirmation of the residue was achieved via diode array detection (200–350 nm). Recovery rates (performed at the 5–100 μg kg−1 level) were in the range 84.9–92.5% with relative standard deviations of 1.9–8.6%. The limit of detection of the assay based on a signal to noise ratio of 3 was approximately 2 μg kg−1. The applicability of the method was demonstrated in eggs from laying hens kept in three different systems (i.e. battery cages, enriched cages and an aviary system). The henhouses were sprayed three times with CBM 8® (containing propoxur in a final concentration of 1%). In this study, propoxur residues could be detected from day 1 after the first treatment until day 39. The mean residue concentration found in the eggs obtained from the battery cages was significantly higher (P