Oxidation Pretreatment For Organophosphorus Pesticide

Current agricultural production develop pesticides to organophosphorus pesticides are widely used in our country,led by food,vegetables,fruits.And irrational use of most pesticides has caused serious environmental and food safety issues,excessive pesticide residues commonly occurred.Therefore,choosing efficient,fast,simple and economical method for rapid detection of pesticide residues has great practical value and potential economic value,but also to solve our food pesticide detection priority.It is the focus of researchers worldwide pesticide residues.In this study,12 kinds of organophosphorus pesticides in accordance with the classification group,compared the two types of organophosphorus pesticides on cholinesterase inhibition,the assumption appears to inhibit reason for the difference,combined with pre-oxidation treatment of differences to explore,and finally by GC-MS organophosphate pesticides qualitatively determine the structural transformation of the relationship between the two types of organophosphorus pesticides.The results of this research are as follows:The optimum of cholinesterase color reaction system as follows: 50 u L enzyme solution+50u L iodide thiocholine+25u L chromogenic agen.7 kinds of organophosphorus pesticides containing P = S group,the inhibition rate of ACh E show a linear relationship within 15 min suppression time for BCh E inhibition rate and suppress the influence of time is negligible;five kinds containing P = O group inhibition of ACh E organophosphate pesticides and suppression no significant relationship between greater impact within 3-15 min suppression time for BCh E inhibition rate,the maximum inhibition rate of 20% increase in value.Considering the fast detection,and the realization of organophosphorus pesticide maximum inhibition of ACh E and BCh E in the shortest possible time,to determine the 12 organophosphorus pesticides on inhibition of both enzymes best time of 15 min.Analysis the sensitivity of two kinds of cholinesterase comparatively,and ultimately determine the electric eel acetylcholinesterase as the best optional.The five levels of three kinds of oxidants separately to oxidation pretreatment of 12 organophosphorus pesticides,filtered through the final inhibition rate,to determine the concentration of 0.05% calcium hypochlorite,bromine 3%,1% hydrogen peroxide.Comparing of three oxidant oxidation under optimal concentration of 12 organophosphorus,select 0.05% calcium hypochlorite as this study the most suitable oxidant,and through the exploration of oxidation time,selected 15 min as calcium hypochlorite optimal oxidation time of pesticide.After oxidation with calcium hypochlorite 0.05% for seven kinds of Ops 15 min,respectively inhibition rates have been significantly improved;And to the five Ops with P=O,oxidizing treatment had no significant difference in the rate of inhibition.Calcium hypochlorite is added to seven kinds of P = S group Ops,which caused half inhibitory concentration greatly reduce,the five P = O Ops IC50 did not significantly affect the base,the inhibition rate of mixture standard(8 kinds of Ops according to certain ratio,mixture of columns)increased by 30% or more,half inhibitory concentration(IC50)value reduced by 3orders of magnitude.Three kinds of organophosphorus pesticides with P = O groups were been oxidated by 0.05%calcium hypochlorite in 15 min and detected in GC-MS.The results show peaks are significant changes.Through a variety of qualitative discriminant analysis,we can draw their corresponding oxidizing substances generated.Organophosphorus pesticides containing the P= S group inhibition rate enhancement after the oxidant because the oxidizing substance generate the generation of greater enzyme inhibition.Dimethoate standard liquid retention time is 11.487 min,two peaks occur after adding an oxidizing agent.With the fragment ions at the peak location and CAS numbers drawn,we identified two peaks representing two substances dimethoate and omethoate.Chlorpyrifos standard liquid retention time is16.958 min,the retention time is 14.561 min after oxidation,with new substances fragment ion analysis of chlorpyrifos identification CAS number obtained oxidation product-a clopidogrel parathion oxygen.Malathion standard liquid retention time is 14.560 min,after oxidation two peaks appear,time is 14.073 min and 8.050 min respectively.Analysis the two peaks with fragment ions,identification CAS number,we concluded the retention time at 8.050 min represent malathion oxidation product-malaoxon,14.073 min substance at a retention time was malathion.