Study On The Rapid Determination Methods For Organophosphorus And Pyrethroids Pesticide Residues Of Tea

Food Safety and Sanitation is closely linked with human's health,but pesticides were unreasonably used in agricultural products,which has brought a series of food potential security risk.Pesticide residues in tea threatened human health and cause environmental pollution.At present the problem has become more and more obvious.Presently,chromatography is the most commonly used method to detect pesticide residues in tea with high accuracy,but the instruments are too expensive and awkward to handle,the examination cost is high,so is not suitable for the detection of dispersible household and small factories.A quick and efficient method for rapid detection of pesticide residues in tea at low cost,should be investigated,combined with the precise analysis methods,to detect polluted tea.Currently,the rapid detection methods of pesticide residues are often used in fruits and vegetables,but rarely in tea.This paper based on the enzyme inhibition methods and thin layer chromatography(TLC)to determinate organophosphate(OPs)and pyrethroid pesticides which are often used in tea gardens.The main findings are as follows1.Acethlcholinesterase(AChE)is an important enzyme sources in enzyme-based methods for pesticide rapid determination.In this study,Procainamide affinity chromatography method was adopted to purify AChE from the head of housefly Musca domestica.The results showed that AChE purification times was 108.42,while the yield was 57.3%.2.AChE-ATChI method and AChE-Indophenol method were investigated to detect OPs.The results showed the highest activity of purified AChE through AChE-ATChI reaction system was observed when the experiment conditions were pH8.0,35 ?,100?L AchE,1.5 mmol.L-1 ATChl and 0.5 mmol.L-1 DTNB.The highest activity of purified AChE through AChE-Indophenol acetate reaction system was observed when the experiment conditions were pH7.5,40?,100?L AchE,2 mmol.L-1 Indophenol acetate.There is good liner correlation between the inhibitory rate of DDVP,trichlorfon,methamidophos,omethoate on AChE and the logarithmic value of pesticide concentration within certain range of concentrations.3.OPs in tea samples were extracted by ethyl acetate,and a simple pre-treatment was used.The detection limit of DDVP,trichlorfon,methamidophos and omethoate in fresh tea were 0.07 mg/kg,0.32 mg/kg,3.65mg/kg,2.67 mg/kg.The detection limit of DDVP and trichlorfon in made tea were 0.28 mg/kg,1.26mg/kg.The detection limit of DDVP,trichlorfon,methamidophos and omethoate in fresh tea were 0.19 mg/kg,0.37 mg/kg,3.10mg/kg,3.63 mg/kg while the detection limit of DDVP and trichlorfon in made tea were 0.76 mg/kg,1.48mg/kg.Good recoveries and RSD were obtained when detect OPs in fresh tea.However,the detection limit ofmethamido-phos and omethoate in made tea were too high.4.TLC was used to detect delthamethrin and cypermethrin in fresh tea and made tea.The optimal conditions of TLC were as follows:silica gel G254 as stationary phase,Petroleum ether-acetone(9:1,v/v)as mobile phase.The detection limit of deltha-methrin and cypermethrin were 200ng.Detection results of delthamethrin and cypermethrin in tea by TLC were basically the same as that by GC when pesticide concentrations were above the detection limit of TLC.