title: Multiresidue screening methods for the determination of pesticides in tomatoes.
abstract: The possibility of applying thin layer chromatography (TLC) detection for the analysis of pesticide residues in tomatoes was investigated. Samples of tomatoes that have never been treated with pesticide were fortified with atrazine, carbaryl, carbofuran, chloroxuron, diuron, dimethoate, imazalil, oxamyl and methamidophos. The samples were extracted, cleaned-up by gel permeation chromatography and then applied on silica gel plates. The pesticides were eluted with ethyl acetate and dichloromethane. Two eluting solvent systems were tested, one using the reagents o-toluidine + potassium iodite (o-TKI) and the other p- nitrobenzene fluoroborate (NBFB). After the development of the plates, the diameter of the spots was measured. The lowest minimum detection quantity (MDQ) for o-TKI system for atrazine was 12 ng. The highest was 125 ng for carbofuran. Using NBFB system, the lowest MDQ was 60 ng for carbaryl and the highest was 70 ng obtained for carbofuran. Considering the concentration of these pesticides in the spiked tomato samples, the minimum concentration was 1.1 ng/microL and 32.3 ng/microL for atrazine and carbofuran, respectively, by using o-TKI system. For NBFB system the minimum concentration reached was 3.5 ng/microL and 4.3 ng/microL for carbaryl and carbofuran, respectively. This study showed that TLC can be used for semi-quantitative analysis.
authors.affiliation: Institute of Chemistry of São Carlos, University of São Paulo, São Carlos, SP, Brazil.
authors.forename: Solange Leite
authors.initials: SL
authors.lastname: Moraes
authors.forename: Maria Olímpia Oliveira
authors.initials: MO
authors.lastname: Rezende
authors.forename: Lia Emi
authors.initials: LE
authors.lastname: Nakagawa
authors.forename: Luiz Carlos
authors.initials: LC
authors.lastname: Luchini
mesh_terms: D002138:Calibration; D002850:Chromatography, Gel / Q000379:methods; D002855:Chromatography, Thin Layer / Q000379:methods*; D005506:Food Contamination / Q000032:analysis*; D018551:Solanum lycopersicum / Q000737:chemistry*; D010573:Pesticide Residues / Q000032:analysis*; D012680:Sensitivity and Specificity; D012997:Solvents
chemical_list: D010573:Pesticide Residues; D012997:Solvents