Solid-phase extraction for multi-residue analysis of pesticides in honey

A fast and simple multi-residue method for the analysis of 15 organophosphorus (OP), 17 organochlorine (OC), 8 pyrethroids (PYR), 12 N-methyl-carbamate (NMC) pesticide residues and bromopropylate in honey is presented. Ready-to-use EXtrelut (R) NT 20 column, eluted with dichloromethane, was used to extract the pesticide residues from the aqueous-acetone honey sample, obtaining a clean extract directly analyzable. Determination was carried out by gas chromatography (GC) coupled with flame photometric detector (FPD) for OP compounds and by GC coupled with mass spectrometry detector (MSD) for OC and PYR pesticides and bromopropylate. The NMC pesticides were analysed by liquid chromatography-double derivatization coupled with spectrofluorimetric detector (LC/DD/Fl). This method allows the determination of the 53 pesticide residues at low concentrations (0.0005-0.074 mg/kg) and can be used to assess the compliance with the Maximum Residues Levels (MRLs) set by the European Union. The performance of the method was evaluated and specificity, linearity, recovery, repeatability, reproducibility, limit of quantification (LOQ) and limit of detection (LOD) were determined. A good linearity (r2 epsilon 0.99) was found in the range 0.0005-0.074 mg/kg for the majority of the compounds studied. Most of the pesticides had recoveries in the range 70-103 % and values of relative standard deviation (RSD) 20 for repeatability and reproducibility, showing good accuracy and precision of the method. Aldicarb partially degraded in aldicarb sulphoxide during the analytical procedure, giving anomalous values. The LOQ for all pesticides investigated was from 0.0005 to 0.025 mg/kg while the LOD ranged from 0.0002 to 0.008 mg/kg.