Direct residue analysis of systemic insecticides and some of their relevant metabolites in wines by liquid chromatography - mass spectrometry.

A direct large volume injection (DI-LVI) high performance liquid chromatography - tandem mass spectrometry (HPLC-MS/MS) method was developed and validated for the quantitative determination of 16 systemic insecticides and their main plant metabolites. The assays were conducted on commercial red and white wines made from grapes grown in major wine-producing regions nationally and internationally. Using a 1:20 dilution and an injection volume of 800μL, a limit of quantitation (LOQ) of 1μgL-1 for all analytes was achieved. Matrix-matched standards (MM) were used for accurate quantitation. Imidacloprid (IMI) and methoxyfenozide (MET) were the most frequently detected parent insecticides in the wines reaching concentrations of 1-132μgL-1. Two important plant metabolites imidacloprid-olefin (IMI-OLE) and spirotetramat-enol (SPT-EN) were found at higher concentrations. In five samples SPT-EN was detected in the mgL-1 range with a maximum concentration of 16.3mgL-1 measured in a conventional white wine sample. Most "organic" wines contained no detectable or low insecticide residues, except for one sample, which showed the highest IMI (14.7μgL-1) and IMI-OLE (331μgL-1) concentrations. Considering the maximum residue limit (MRL) definition for the different insecticides, three "conventional" wine samples were non-compliant for SPT. This study highlights the importance to determine both parent and metabolite forms of systemic insecticides in the finished product.