Analysis of benzoylphenylurea insecticides in fruits and vegetables - Methodology and residue data

The analysis of benzoylphenylurea insecticides (BPUs) has been traditionall y causing problems. Despite their wide spread use in agriculture, little da ta is available regarding the residue situation in crops. Aim of our study was to develop a methodology, which would allow the analysis of BPU insecti cides on a routine basis. This method should be applied for the analysis of fruit and vegetable samples in order to elucidate the residue situation of these compounds in the market. Two multiresidue methods were used to prepare the extracts: a traditional o ne, involving extraction with acetone and liquid-liquid partitioning with c yclohexane/ethyl acetate (1:1) and a fast method involving automated extrac tion with supercritical carbondioxide (CO2-SFE), Further analysis was perfo rmed by LC/MS using an HP series 1100 instrument. An RP-18 column was used for separation and detection was performed in the ESI (neg.) or APCI (neg.) mode. Due to the high sensitivity and selectivity of the measurement no ad ditional clean-up of the extracts was necessary. Several matrices were test ed for the occurrence of matrix effects during LC/MS, however, no significa nt effects were observed. The recoveries, limits of determination and repea tability achieved by both methods satisfy the needs of pesticide residue an alysis. In order to test the possibility of using GC/MSD as a screening method, exp eriments were performed to elucidate the GC-behavior and the formation of t he thermal degradation products of the BPUs. However, due to major interfer ence with matrix components, the specificity achieved is very pure making t his approach inappropriate for this purpose, especially when MRLs are low. The analysis of more than 650 commercial samples has confirmed the widespre ad use of BPUs in agriculture. The highest percentage of positive samples w as found in pome fruit (32 %) followed by sweet pepper and grapes. In 25 sa mples (3.7 %) BPU residues exceeded the German tolerances. Most violations occurred in sweet pepper (8 samples) followed by pome fruit (7) and grapes (6). Lufenuron was violative in 12 cases followed by flufenoxuron (10), hex aflumuron (2) and teflubenzuron (1).