Establishment Of QuEChERS Purification Liquid Chromatography-Mass Spectrometry For Rapid Screening Of Pollutants In Wheat

Through the research and experiment on the commonly used method of detecting the contaminants of wheat,an efficient and low-cost method based on QuEChERS extraction and purification for liquid chromatography-tandem mass spectrometry has been developed.This method of optimization is as follows:Crushed samples?5g?added with acetonitrile/water/formic acid?85/14/1?,a small amount of NaCl and 4g of NaSO₄ in 50mL centrifuge tube to vortex for 15 min add 15mL oscillation extraction 10 mins,then centrifuged for 5 min at 4500 rpm.5 ml of supernatant into a 10 ml centrifuge tube filled with 0.1 g C18 sorbent to vortex for 2 min,then centrifuge at 8,000 rpm for 10 min at-18?C,and 3 mL of supernatant at 40?C evaporated under reduced pressure,500?L of a mixture of methanol/water?V/V,3/2?was added to dissolve the solution.The solution was filtered through a 0.2?m filter and then placed on a machine.HPLC conditions:Column:BEH C18?2.1 mm×50 mm,1.7?m?;column temperature40°C;flow rate:0.4 mL/min;mobile phase A:water Water?0.1%formic acid?;Gradient:0 min,90%A;3 min,90%A;10 min,30%A;10.1 min,10%A;12 min,10%A;12.1 min90%A;Injection volume:1?L;sample room temperature:10?C.Mass spectrometry conditions:Ion mode:ESI positive mode;Capillary voltage:1.0KV;Desolvation gas:nitrogen,800 L/Hr at 450°C;Cone gas:nitrogen,50 L/Hr;ion source temperature:150°C;Argon,3.6×10-3mBar;Acquisition Mode:Multiple Reaction Monitoring Mode?MRM?.The method could be used to qualitatively and quantitatively determine 14 kinds of wheat contaminants at the same time,and the correlation coefficients of the linear equations were both more than 0.9900.the lower detection limits were all within the existing limited range.Compared with other detection methods,the method had the advantages of large flux,well-defined qualitative and simple pre-treatment,and was particularly suitable for rapid screening in a wide range of grain harvests.Compared with screening means that can only be qualitative and semi-quantitative,the method can achieve accurate quantification at the same time.This method avoided the past inspection agencies using qualitative means of screening completed,the positive samples need to be re-measured on the machine.And This method also avoided false-positive results,resulting in the cost and manpower waste.Although only 14 compounds were listed in this method,there was still room for extension of pesticide residues based on this method.In the future,we will try to include the mainstream pesticide residues in the method as much as possible in order to achieve faster,larger throughput and more accurate results.