基于多壁碳纳米管(MWCNTs)和聚十六烷基三甲基溴化铵(p-CTAB)的高导电性、高增敏性,制备了MWCNTs、p-CTAB修饰的玻碳电极(GCE),将其作为工作电极(MWCNTs/p-CTAB/GCE),用于快速测定水和土壤中双酚A (BPA)的含量。以GCE为工作电极,采用循环伏安法(CV)对0.5 g·L^-1 CTAB溶液扫描20圈,得到p-CTAB修饰的GCE (p-CTAB/GCE);吸取1.96 g·L^-1 MWCNTs标准溶液5 μL,滴涂在p-CTAB/GCE表面,干燥后得到MWCNTs/p-CTAB/GCE。水样经过滤,分取2 mL与0.3 mol·L^-1磷酸盐缓冲溶液(pH 7.0)8 mL混匀后待测;土壤样品25 g经风干、研磨、过筛后,用乙醇50 mL提取两次,浓缩至约1 mL,用无水乙醇定容至10 mL,分取2 mL与0.3 mol·L^-1磷酸盐缓冲溶液(pH 7.0)8 mL混匀后待测。以MWCNTs/p-CTAB/GCE为工作电极,钛棒为对电极,饱和甘汞电极为参比电极,设置搅拌速率为800 r·min^-1,于0.2 V富集待测样品溶液中的BPA 150 s,采用差分脉冲伏安法(DPV)测定BPA的含量。扫描电子显微镜表征结果显示,MWCNTs/p-CTAB/GCE表面呈多孔空隙和多孔网状结构。以DPV、CV和电化学阻抗谱法考察了BPA在MWCNTs/p-CTAB/GCE上的电化学行为,结果表明BPA在该电极上的电化学氧化反应是一个受吸附控制的不可逆反应,BPA的浓度在0.08~20 μmol·L^-1内与其对应的氧化峰电流呈线性关系,检出限为0.02 μmol·L^-1。用同一支MWCNTs/p-CTAB/GCE重复测定BPA标准溶液10次,测定值的相对标准偏差为5.0%。对实际样品进行加标回收试验,BPA的回收率为82.0%~106%,测定值的相对标准偏差(n=5)为1.6%~8.1%。

Based on high conductivity and high sensitivity of multi-walled carbon nanotubes (MWCNTs) and poly cetyl trimethyl ammonium bromide (p-CTAB), the glassy carbon electrode (GCE) modified with MWCNTs and p-CTAB was prepared and used as working electrode (MWCNTs/p-CTAB/GCE) for the rapid determination of bisphenol A (BPA) in water and soil. GCE modified with p-CTAB (p-CTAB/GCE) was obtained by scanning 0.5 g·L^-1 CTAB solution for 20 cycles by cyclic voltammetry (CV) with GCE as working electrode. 5 μL of 1.96 g·L^-1 MWCNTs standard solution was dropped on the surface of p-CTAB/GCE, and MWCNTs/p-CTAB/GCE was obtained after drying. Water sample was filtered, and 2 mL of an aliquot was mixed with 8 mL of 0.3 mol·L^-1 phosphate buffer (pH 7.0) for test. After drying, grinding and screening, 25 g of soil sample was extracted with 50 mL of ethanol for twice, concentrated to about 1 mL, and made its volume up to 10 mL with ethanol. 2 mL of an aliquot was mixed with 8 mL of 0.3 mol·L^-1 phosphate buffer (pH 7.0) for test. Using MWCNTs/p-CTAB/GCE as the working electrode, titanium rod as the counter electrode and saturated calomel electrode as the reference electrode, BPA in the test solution was enriched at 0.2 V for 150 s with stirring rate of 800 r·min^-1, and determined by differential pulse voltammetry (DPV). The surface of MWCNTs/p-CTAB/GCE showed porous voids and porous network structures by scanning electron microscope characterization. The electrochemical behavior of BPA on MWCNTs/p-CTAB/GCE was investigated by DPV, CV and electrochemical impedance spectroscopy. The results showed that the electrochemical oxidation of BPA on MWCNTs/p-CTAB/GCE was irreversible and controlled by adsorption, and linear relationship between concentration of BPA and its oxidation peak current was kept in the range of 0.08-20 μmol·L^-1, with detection limit of 0.02 μmol·L^-1. The BPA standard solution was determined by the same MWCNTs/p-CTAB GCE for 10 times, with RSDs of the determined values of 5.0%. Test for recovery was made on the actual samples by standard addition method, giving results in the range of 82.0%-106%, and RSDs (n=5) of the determined values were in the range of 1.6%-8.1%.