Determination of neonicotinoid insecticides residues in bovine milk samples by solid-phase extraction clean-up and liquid chromatography with diode-array detection

In this paper we have developed an analytical method for the simultaneous determination of four nicotinoid insecticides [acetamiprid (ACT), imidacloprid (ICL), thiacloprid (TCL) and thiamethoxam (TMX)] in bovine whole milk. These analytes were extracted, in a single step with dichloromethane, from fortified milk samples, using Chem Elut cartridges, containing diatomaceous earth material. Insecticide's determination and quantification were performed by HPLC with diode-array detection (DAD). Average recoveries of the four insecticides from bovine milk samples were between 85.1 and 99.7% at spiking levels 0.01, 0.05 and 0.1mgkg(-1). Relative standard deviations (RSDs) were no larger than 10% for all of the recovery tests. The calculated limits of quantitation (LOQ) ranged from 0.01 to 0.04mgkg(-1) for the four insecticides, being equal to or lower than the maximum residue limits (MRLs) established by European legislation (0.01-0.05mgkg(-1)). The developed method is linear at concentrations within the tested interval, with coefficients of determination higher than 0.9990. According to Commission Decision 2002/657/EC, decision limit (CCalpha) and detection capability (CCbeta) have been calculated. The proposed method is rapid, simple and could be utilized for the routine analysis of pesticides residues