Rapid multi-residue method for the determination of azinphos methyl, bromopropylate, chlorpyrifos, dimethoate, parathion methyl and phosalone in apricots and peaches by using negative chemical ionization ion trap technology

A rapid, selective and sensitive multi-residue method for the determination of six common pesticides in stone fruit samples is described. The proposed method involves the extraction of the pesticides with the use of acetone solvent followed by liquid–liquid partition with a mixture of dichloromethane and light petroleum (40–60 °C) and subsequent determination by a gas chromatographic–mass spectrometry system using ion trap technology in negative ion chemical ionization mode. The average percent recoveries of bromopropylate and phosalone in the concentration range 0.2–2.0 mg/kg were 97.3±6.7 to 120±1.0%, while the recoveries of chlorpyrifos and parathion methyl examined in the concentration range 0.02–0.2 mg/kg were 95.5±7.5 to 145±3.6%, the recoveries of azinphos methyl in the range 0.05–0.5 mg/kg were 74.8±29.6 to 96.5±13% and those of dimethoate in the range 0.1–1.0 mg/kg were 73.1±5.7 to 92.8±2.8% for n=3 for all the above pesticides. The high mean recovery (145%) for chlorpyrifos is attributed to a matrix enhancement effect. The limits of quantitation in apricots were 0.01 mg/kg for chlorpyrifos, 0.02 mg/kg for dimethoate and parathion methyl, 0.05 mg/kg for azinphos methyl and phosalone and 0.1 mg/kg for bromopropylate. The usefulness of tandem mass spectrometry for confirmation purposes was also examined. The method was applied successfully to the determination of the target pesticides in 32 samples of stone fruits (apricots and peaches).