DETERMINATION OF DIAZINON RESIDUE IN MELON AND CUCUMBER BY SOLID-PHASE EXTRACTION AND GAS CHROMATOGRAPHY-MASS SPECTROMETRY.

Introduction: Diazinon is a moderately toxic broad-spectrum organophosphate, with a LD50 of 350 to 400 mg/kg for humans. It is largely used for pest control in Iran. As an acetyl cholinesterase inhibitor (ChE) it inhibits acetylcholine (Ach) hydrolysis at the never endings. Accumulation of Ach stimulates muscarinic and nicotinic receptors causing morbidity and mortality. Diazinon is absorbed through the skin and gastrointestinal tract and is rapidly metabolized within a few hours. Objective: Diazinon residue in melons and cucumbers has recently been a health concern in Iran. It was thus aimed to investigate Diazinon residues in melon and cucumbers. Method: Twenty melons and cucumbers were randomly purchased from the market in Mashhad. The extraction procedure was in HR-P columns preconditioned with methanol and water. The subsequent elution of diazinon was performed with a mixture of hexane-ethyl acetate (1:1, v/v) prior to the determination by GC-NPD and GC-MS/MS. Standards were prepared spiking blank juice samples to contract the observed matrix effect. Accuracy (<9.6%), precision (<7.1%), specificity (quantitative, no peaking intraction), sensitivity (LOD 0.1ng/ml and LOQ 5ng/ml) and reproducibility (<95.4%) were acceptable. Detection limit was 1ng/ml. Linear relation with good correlation coefficients (R2 > 0.99) was obtained. Results: Mean recovery for diazinon was 95.4% with relative standard deviation lower than 9% in the concentration range of 5-200ng/ml. Mean and SD of diazinon in melons was 107.64±38.5 ng/kg. Diazinon was not detected in cucumber samples. It was later confirmed that diazinon was not used for the crops of these cucumbers. Conclusions: GC-NPD and MS/MS was developed to determine residue of diazinon in melons and cucumbers. The GC-MS/MS analytical method showed a high efficacy for determination of diazinon residues in the fruits. [ABSTRACT FROM AUTHOR]