毛细管电泳-间接电化学发光法对茶叶中百草枯农药残留的检测

Determination of Paraquat Residue in Tea by Capillary Electrophoresis with Indirect Electrochemiluminescence Detection

基于农药百草枯对钌联吡啶-三丙胺（TPA）体系的电化学发光具有显著的抑制作用，建立了毛细管电泳-间接电化学发光检测茶叶中残留农药百草枯的新方法。讨论了初始电位、钌联吡啶和TPA浓度、进样电压、进样时间、运行缓冲溶液的浓度与pH值等条件对百草枯检测灵敏度的影响。确定最佳实验条件为1．20V初始电压、0．7mmol／L钌联吡啶、0．6mmol／LTPA、9kV进样电压、9s进样时间、35mmol／L磷酸盐（pH8．5）为运行缓冲溶液。在优化实验条件下，百草枯浓度在5×10^-7-5×10^-5mol／L范围内呈良好线性（相关系数为0．9945），检出限为9．4×10^-8mol／L。对5×10^-5mol／L百草枯标准溶液连续测定5次，相对峰高与迁移时间的相对标准偏差分别为3．7％和2．1％。该方法对2．0×10^-6、1．0×10^-5mol／L百草枯标样的萃取回收率分别为74％和83％，相对标准偏差分别为15％、4．2％（n=5）。

Based on a remarkable inhibited effect of paraquat on tris （2, 2＇-bipyridyl）-ruthenium（II） - tripropylamine （TPA） system, a new method for the determination of herbicide residue paraquat in tea was developed by capillary electrophoresis with indirect electrochemiluminescence detection. The tea samples was extracted by C18 ion-pair soild-phase extraction（SPE） column using acidic methanol as eluate. Influence of several factors such as initial potential, concentration of Ru （bpy） ^2＋3 and TPA, injection voltage and time, concentration and pH value of running buffer on detection sensitivity was investigated. The optimized conditions were as follows： initial potential： 1.2 V, concentration of Ru（bpy）^2＋3 ： 0. 7 mmol/L, concentration of TPA： 0. 6 mmol/L, injection voltage： 9 kV, injection time： 9 s, running buffer： 35 mmol/L PBS buffer（pH 8.5）. Under the optimized conditions, the calibration curve was linear in the range of 5 ×10^-7 -5 × 10^-5 mol/L for paraquat with a correlation coefficient of 0. 994 5. The detection limit was 9.4 ×10^-8 mol/L, and the relative standard deviations of ECL intensity and migration time for 5 × 10^-5 mol/L paraquat （ n = 5 ） were 3.7% and 2. 1% , respectively. The proposed method was applied to the determination of paraquat residue in tea. The extraction recoveries were 74% and 83% for paraquat of 2. 0 × 10^-6and 1.0 × 10^-5 mol/L, respectively, and the RSD values were 15% and 4.2% （n = 5） , respeetively.