Development of a new Cucumber Reference Material for Pesticide Residue Analysis: Feasibility Study for Material Processing, Homogeneity and Stability Assessment

Abstract

The feasibility of the production of a reference material for pesticide residue analysis in a cucumber matrix was investigated. Cucumber was spiked at 0.075 mg/kg with 15 pesticides, namely acetamiprid, azoxystrobin, carbendazim, chlorpyrifos, cypermethrin, diazinon, (α+β)-endosulfan, fenitrothion, imazalil, imidacloprid, iprodione, malathion, methomyl, tebuconazole and thiabendazole. Three different strategies were considered for material processing, based on the physicochemical properties of the vegetable and the target pesticides. As a result, a frozen spiked slurry of fresh cucumber, a spiked freeze-dried cucumber powder, and a freeze-dried cucumber powder spiked by spraying of the powder were studied. The effects of processing and aspects related to material reconstitution were evaluated by monitoring the pesticide levels in the three materials. Two analytical methods based on LC-MS/MS and GC-MS/MS respectively were developed and validated in-house. The spiked freeze-dried cucumber powder was selected as the most feasible material and more exhaustive studies of homogeneity and stability of pesticide residues in the matrix were carried out. Homogeneity between units was satisfactory at a sample intake of dried material as low as 0.1 g. A 9-week stability study was undertaken following an isochronous design at -20 ºC, 4 ºC and 18 ºC, with -70 ºC as reference temperature. The pesticides tested showed adequate stability at -20 ºC during the 9 weeks period as well as at -70 ºC for a period of 18 months. These results constitute a good basis for the development of a new candidate reference material for selected pesticides in a cucumber matrix.JRC.D.5-Standards for Food Bioscienc