Determination of fenthion and its oxidative metabolites in olives and olive oil: errors caused by matrix effects.
A method for determination of fenthion residues and its oxidative metabolites (fenoxon, fenthion sulphoxide, fenthion sulphone, fenoxon sulphoxide, fenoxon sulphone) in olive pulp, oil and water obtained from olive pressing is described and evaluated. Recoveries for the improved gas chromatographic conditions were: 92-104% for fenthion, fenoxon, fenthion sulphone and fenoxon sulphone in the olive pulp matrix, whereas the mean recovery values for fenthion sulphoxide and fenoxon sulphoxide were respectively 140% and 118%. In the vegetation water matrix, the recoveries for fenthion, fenthion sulphoxide, fenoxon sulphoxide and fenoxon sulphone averaged between 91% and 103%. Higher values were obtained for fenoxon (139%) and for fenthion sulphone (115%). Recoveries for all metabolites in the oil matrix averaged between 100% and 104%. Detection limits ranged between 0.005 ng for fenthion to 0.02 ng for fenoxon sulphoxide and fenoxon sulphone. Three different gas chromatographic conditions are presented in order to underline how their choice could strongly affect the result because of the matrix effect on the gas chromatographic response. In some cases such an effect can increase the instrumental response up to three times the real value.
Molinari
G P
GP
Istituto di Chimica Agraria ed Ambientale, Facoltà di Agraria, Piacenza, Italy.
Cavanna
S
S
Fornara
L
L
D002849:Chromatography, Gas / Q000379:methods; D005284:Fenthion / Q000032:analysis* / Q000737:chemistry; D005506:Food Contamination / Q000032:analysis*; D005638:Fruit; D006801:Humans; D007306:Insecticides / Q000032:analysis*; D000069463:Olive Oil; D010938:Plant Oils / Q000737:chemistry*
D007306:Insecticides; D000069463:Olive Oil; D010938:Plant Oils; D005284:Fenthion