离子液体-石墨烯-二氧化锰复合材料修饰玻碳电极差分脉冲伏安法测定土壤中铅和镉

采用涂滴法将石墨烯(GR)-二氧化锰(MnO₂)分散液滴在玻碳电极(GCE),然后利用循环伏安法将离子液体(OMIMPF₆)聚合制备得OMIMPF₆/GR/MnO₂/GCE复合材料修饰玻碳电极,建立了差分脉冲伏安法测定土壤中铅和镉的方法。实验表明,以4μL 2mg/mL的石墨烯-二氧化锰混合物分散液涂滴,电聚合离子液体30圈所制备的修饰电极,在0.1mol/L的醋酸-醋酸钠缓冲溶液(pH4.5)的支持电解液中,Pb²⁺和Cd²⁺的氧化峰电流值相对较高。Pb²⁺和Cd²⁺的浓度均在5.0×10^-8~1.4×10^-5mol/L范围内呈良好线性关系,Pb²⁺和Cd²⁺检出限分别达到5.0×10^-10mol/L和4.0×10^-9mol/L。对含10μmol/L Pb²⁺和10μmol/L Cd²⁺的标准混合溶液平行测定9次和连续扫描30次,Pb²⁺和Cd²⁺峰电流值的相对标准偏差均分别小于1.3%和4.3%,说明该修饰电极具有良好的重现性、稳定性。采用建立的方法用于土壤中铅和镉的检测,测得结果与原子吸收光谱法(GB/T 17141—1997)基本一致,相对标准偏差(RSD,n=6)均小于5.3%,回收率在97%~105%之间。

Determination of lead and cadmium in soil by differential pulsevoltammetry using ionic liquid/graphene/manganese dioxidecomposite modified glassy carbon electrode

The graphene (GR)-manganese dioxide (MnO₂) dispersion liquid were dripped on glassy carbon electrode (GCE) by dispensing method. Then the ionic liquid (OMIMPF₆) was polymerized by cyclic voltammetry to prepare OMIMPF₆/GR/MnO₂/GCE composite modified GCE. The determination method of lead and cadmium in soil by differential pulse voltammetry was established. The modified electrode was prepared by dispensing 4μL of 2mg/mL GR-MnO₂ dispersion liquid followed by electric polymerization of ionic liquid for 30 cycles. The experiments showed that the oxidation peak current of Pb²⁺ and Cd²⁺ was relatively high in 0.1mol/L acetic acid-sodium acetate buffer solution (pH 4.5) supporting electrolyte. The linearity was good for Pb²⁺ and Cd²⁺ with concentration in range of 5.0×10^-8 and 1.4×10^-5 mol/L. The detection limit was 5.0×10^-10 mol/L and 4.0×10^-9 mol/L for Pb²⁺ and Cd²⁺, respectively. The standard mixed solution containing 10μmol/L Pb²⁺ and 10μmol/L Cd²⁺ was determined parallelly for 9 times and scanned continuously for 30 times. The relative standard deviation (RSD) of peak current was 1.3% and 4.3% for Pb²⁺ and Cd²⁺, respectively. It indicated that the modified electrode had good reproducibility and stability. The proposed method was applied for the detection of lead and cadmium in soil, and the found results were basically consistent with those obtained by atomic absorption spectrometry (GB/T 17141—1997). The RSD (n=6) were less than 5.3%, and the recoveries were between 97% and 105%.