| Deltamethrin(DM)in paddy measured by QuEChERS pretreatment combining with UPLC-Triple-TOF-MS method was explored in the paper,and determined data were compared with data from GC-MS analysis method.The degradation of Deltamethrin at different storage temperatures,different Deltamethrin levels and different part in paddy were also disscused.The main research contents include the following:(1)The UPLC-Triple-TOF-MS method to analyze Deltamethrin pesticides in paddy was established.Optimum operational parameters were obtained as fellow:QuEChERS rapid pretreatment technology was used,The mobile phase of UPLC-Triple-TOF-MS was methanol(B)and 10 mmol/L ammonium acetate with 0.1%formic acid water(A),the mobile phase flow rate was 0.5mL/min,the mobile phase elution program was 0-5.0 min,80%B;5.0?10.0 min,80%?100%B;10.0?15.0 min,100%B;15.0-20.0 min,100%-80%B;20.0 min,stop.The column temperature was 40?,and positive ion detection mode was chosen.The linear range of Deltamethrin detected by UPLC-Triple-TOF-MS method was 0.01-5.0 mg/L,the detection limit and the quantitative limit were 0.0012 mg/kg and 0.0078 mg/kg,respectively.The Deltamethrin recoveries were between 90.14%and 99.86%,RSD was less than 5%,the method could meet the requirements for analysis and detection of paddy pesticide residues.(2)Measured data on Deltamethrin residues in paddy by UPLC-Triple-TOF-MS were compared with GC-MS method when QuEChERS was used as pretreatment technique.The results showed that detection limit of UPLC-Triple-TOF-MS was 0.0012 mg/kg,the recovery rate was between 90.14%and 99.86%,RSD was 2.15%-4.72%,while the detection limit of GC-MS was 0.0091 mg/kg,the sample recovery rate between 88.23%?98.64%,RSD was 3.25%?5.84%.Therefore,UPLC-Triple-TOF-MS has a lower detection limit and a higher recovery rate than the GC-MS.Both UPLC-Triple-TOF-MS method and GC-MS method could be used to measure Deltamethrin in the paddy husk,and similar degradation kinetic equations and half-life of the Deltamethrin were obtained.However,Deltamethrin content in brown rice couldn't be accurately quantified by GC-MS.Not only Deltamethrin in paddy husk but also in brown rice could be accurately quantified.It is further illustrated that the UPLC-Triple-TOF-MS method had higher sensitivity.(3)Deltamethrin in paddy,paddy husk,brown rice and soybean stored at different temperature were discussed.It was found that the degradation equation of Deltamethrin at different matrices and different storage temperatures was an exponential function model.The half-lives of Deltamethrin in paddy were 15.8 d(20?),12.4 d(25?)and 10.8 d(30?).The half-lives of Deltamethrin in paddy husk were 15.1 d(20?),12.0 d(25?)and 10.5 d(30?).The half-lives of Deltamethrin in brown rice were 16.9 d(20?),14.1 d(25?)and 11.6 d(30?).The half-lives of Deltamethrin in soybean were 15.1 d(20?),12.8 d(25?)and 11.2 d(30?).The results showed that the degradation rate of Deltamethrin is accelerated with the increase of storage temperature,and the half-life is shortened with the increase of storage temperature.Under the same storage temperature,the half-life of Deltamethrin was slightly different in paddy,paddy husk,brown rice and soybean.The half-life of Deltamethrin in paddy,paddy husk and soybean was similar,while in brown rice half-life is longer.(4)The degradation rates of Deltamethrin in paddy,paddy husk and brown rice were related to the initial pollution level.When Deltamethrin concentration in paddy were 1.7102 mg/kg,6.4314 mg/kg and 15.6610 mg/kg,the degradation half-lives were 12.4 d,13.9 d and 14.8 d,respectively.When paddy husk was polluted Deltamethrin at 9.7263 mg/kg,39.3319 mg/kg and 73.6931 mg/kg.the degradation half-lives were 12.0 d,13.6 d,15.4 d,respectively.When initial Deltamethrin concentration in brown rice were 0.0511 mg/kg,0.2434 mg/kg and 0.5255 mg/kg,the degradation half-lives were 14.1 d,15.4 d,16.5 d,respectively.It can be seen that the higher Deltamethrin level was polluted,the longer the degradation half-life was. |
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