Study of tau-fluvalinate persistence in honey.

The persistence of the acaricide tau-fluvalinate with time and the factors that can affect its degradation in honey were investigated. Two honey types of extreme pH values (3.85 and 5.40) were spiked with tau-fluvalinate at two levels (50 and 200 micrograms kg-1) and incubated at 35 degrees C. Samples were analyzed in duplicate at various time intervals for up to 248 days. A simple, rapid and accurate method for the determination of tau-fluvalinate residues in honey is proposed. Tau-fluvalinate extraction and sample cleanup was carried out using C8 SPE cartridges with dichloromethane as the elution solvent. Analysis of samples was accomplished using gas chromatography with electron-capture detection (GC-ECD). The overall recovery of the method was 90.25 (+/- 0.85)% and the limit of determination 1 microgram kg-1. The results showed that tau-fluvalinate stays stable in honey for more than 8 months, even at 35 degrees C. The effect of higher temperatures, similar to those used for honey packing, on tau-fluvalinate persistence in honey was also studied. Honey samples fortified with 20 and 200 micrograms kg-1 tau-fluvalinate were subjected to heat treatment similar to that in the honey blending and packing process. No degradation of tau-fluvalinate due to the heat treatment was recorded. This long persistence increases the risk of honey contamination due to repeated and/or extended tau-fluvalinate applications.