Study On The Neonicotinoid Insecticides Residues In Tea And The Standard Analysis

Neonicotinoid insecticides with high efficiency against on broad-spectrum pests,widely used in our country.However,there is a great gap in tea pesticide standards between European Union countries and China.For instance,the imidacloprid and acetamiprid MRLs of EU are 0.05 mg/kg,in contrast to that of China 0.5 mg/kg and 10mg/kg respectively.For standardizing the use of neonicotinoid pesticides in tea to improve the safety and quality of tea,and to avoid trade barriers,here we focused on pesticide residual analysis of imidacloprid and acetamiprid in fresh tea leaves,primary tea with diverse processing technologies or from different areas,different types of tea and different seasons of tea,by LC-MS-MS.The main results are as below:?1?In fresh tea,the degradation of imidacloprid and acetamiprid were in conformity with the first-order dynamic equation.The digestion rate of 0-3^rd day after pesticide application were faster and then slower distinctly after 14^th day.At the recommended dosage,the half-life of imidacloprid was 2.63 days,and the half-life of acetamiprid with 3.09 days.?2?After pesticide application,the 3^rd day fresh tea made into different type of primary tea with different processing.The imidacloprid residuals of red tea,green tea and oolong tea,approximately 1.64-2.64 times than that of fresh tea were 0.87 mg/kg,1.40 mg/kg and 1.04mg/kg respectively.Similarly,the 3^rd day acetamiprid residuals of red tea,green tea and oolong tea,approximately 2.21-2.71 times than that of fresh tea were 2.32 mg/kg,were2.85 mg/kg and 2.73 mg/kg respectively.The trend of the residual data after 14 days was similar with that of imidacloprid and acetamiprid above.?3?According to the residual data of imidacloprid and acetamiprid,the differences of pesticide residuals in different areas were probably related to pesticide application habit,local weather and types of tea.?4?The largest amount of neonicotinoid insecticides was detected in green tea and oolong tea.Interestingly,more than 80% of jasmine tea made from jasmine and green tea,shown low level of residuals.?5?The imidacloprid and acetamiprid distribution in summer tea of not detected?0.01mg/kg?and between 0.01 mg/kg and 0.5 mg/kg are 100%.According to GB 2763-2016MRLs of imidacloprid and acetamiprid,qualification rates of diverse season tea were as follows:summer tea=winter tea>spring tea>autumn tea.?6?Because of different MRLs and pesticide using plans in tea plantation,88%of tea samples showed lower level residuals of imidacloprid than that of acetamiprid.12%of tea samples got an opposite result.