New insights to improve the storage stability of pesticide residues in analytical samples

Abstract

The factors affecting the storage stability of dichlorvos, malathion, diazinon and chlorpyrifos in celery were studied, and the mechanism of improvement of storage stability was explained. Residues of dichlorvos and malathion may be more stable in homogenized celery than in coarse form. The important role of storage form may be attributed to the difference of enzymes in the matrix. The results showed that POD activity in homogenized celery was lower than that in coarse one, and pesticide residues were more stable in homogenate. The interaction between POD and pesticide molecules was confirmed by computational chemistry method. Moreover, exogenous metal ions (Fe3+ and Al3+) could significantly inhibit POD activity and improve stability of malathion, dichlorvos, and chlorpyrifos. When the concentration of ions increased to 40 mmol/L, the residue remaining of dichlorvos and malathion increased significantly. Instead, the significant reduction in diazinon was found because it was more susceptible to changes in pH, where acidic conditions were not conducive to its stable presence. Except in a few cases, the addition of metal ions can directly or indirectly improve storage stability of organophosphorus pesticide residues by inhibiting enzyme activity.