Rapid Detection Of 28 Pesticides Residue In Tea By GC-MS

China has the longest history of planting tea and drinking tea in the world,and it is also well known for its most abundant resources of tea.However,with the prosperity of tea industry,the problem of pesticides residue in tea has also become increasingly serious,which is one of the most prominent problems in Chinese tea industry.In recent years,excessive pesticides residue has become one of main technical barriers in the export of Chinese tea to developed areas such as Europe,America and Japan.Targeting the 28 pesticides involved in standard GB 2763-2014,this thesis sets up new methods for the rapid and synchronous analysis of the pesticides residue,including gas chromatography(GC)for acephate detcetion and gas chromatography-mass spectrometry(GC-MS)for the other pesticides residue detection.The outcomes are as follows.1.A new method based on gas chromatography is established for the detection of acephate in tea.Samples were firstly extracted by ethyl acetate,then purified by a column of graphitized carbon black(GCB)with the solid phase extraction(SPE)method,and finally examined by flame photometric detector(FPD).Results show that the calibration curve for acephate has a good linearity with a fine correlation coefficient of 0.9997 in the range from 0.01-1.0 μg/m L.When adding acephate at the levels of 0.05 μg/m L and 0.30 μg/m L,the average recovery rates are 80.0% and 83.2%,and the relative standard deviations(RSD)are 3.35% and 3.85%,respectively.The limit of detection(LOD)of this method is as low as 0.009 mg/kg.This method is simple,rapid,environmental friendly and safe for the quantitatively detection of acephate residue in tea.2.The detecting conditions of gas chromatography-mass spectrometry were optimized for the better detection of multi-pesticides residue in tea.The results show that setting the temperature of sample inlet at 250°C,applying pulse splitless injection method to injecting samples,choosing and characteristic fragment ion of high mass-to-charge ratio could effectively enhance the signal responses to pesticides and improve the sensibility of instrumental analysis.3.A new method based on gas chromatography-mass spectrometry is established for the detection of the other 27 pesticides residue in tea synchronously.Samples were extracted by a solvent of acetonitrile and acetone(7:3,V/V)by ultrasound extraction.The extracted solution was purified by solid phase extraction column fulfilled with GCB and Florisil.The analysis of 27 pesticides was firstly separated by the HP-5MS column,then electrolytic ionization was detected by selected ion monitoring(SIM)method,external standard method for quantitation.Results show that the retention time of 27 pesticides is less than 22.50 min,the calibration curves of 27 pesticides all have good linearity with a fine correlation coefficient surpass 0.9947,and the limit of detections of 27 pesticides is from 0.005 to 0.050 mg/kg.When the addition levels of pesticides are set at 0.50 μg/m L and 0.10 μg/ m L,the average recovery rates are 66.7%-98.7% and 75.9%-113.1%,relative standard deviations are 3.29%-9.84% and 3.85%-10.38%.Research shows that this method could meet the need of pesticides residue detection in various kinds of tea.