L-天冬氨酸-L-半胱氨酸-石墨烯修饰玻碳电极测定铅的研究

Study on determination of lead by L-aspartic acid-Lcysteine-graphene modified glassy carbon electrode

利用L-半胱氨酸-石墨烯-L-天冬氨酸纳米复合膜构建Pb2+的新型电化学传感器实现了环境水样中铅的灵敏测定。首先将石墨烯和L-半胱氨酸通过电聚合制备了L-半胱氨酸-石墨烯修饰玻碳电极,然后利用戊二醛通过共价键合连接上L-天冬氨酸,制备了L-天冬氨酸-L-半胱氨酸-石墨烯修饰玻碳电极。由于L-天冬氨酸的良好选择性以及石墨烯的好导电性能,提高了传感器对Pb2+的信号响应和选择性。试验结果表明,测定1×10-7 mol/L的Pb2+,10倍量的Cu2+、Ca2+、Co2+、Cd2+、Mn2+、Zn2+、Ni 2+、Hg2+几乎不干扰测定(峰电流改变小于5%)。在pH4.5的醋酸盐缓冲溶液中,铅离子的浓度与峰电流呈良好的线性关系,线性范围为2.0×10-9～6.0×10-6 mol/L,检出限为6.0×10-10 mol/L(S/N=3)。该修饰电极用于环境水样中铅的测定,测定值与ICP-AES的测定值基本一致。

The L-cysteine--grapheme--L-aspartic acid nanocomposite film was used to prepare novel electrochemical sensor for Pb2＋ , realizing the sensitive determination of lead in environmental water sample. Firstly, the L-cysteine--graphene modified glassy carbon electrode was prepared by graphene and L-cysteine via electro-polymerization. Then, L-aspartic acid--L-cysteine--graphene modified glassy carbon electrode was prepared by grafting L-aspartic into the L-cysteine--graphene modified glassy carbon electrode via covalent bonding using glutaraldehyde. Since the good selectivity of L-as- partic acid and good conductivity property of graphene, the signal response and selectivity of sensor to Pb2＋ were improved. The testing results showed that, 10-fold of Cu2＋ , Ca2＋ , Co2＋ , Cd2＋ , Mn2＋ , Zn2＋ , Ni2＋ and Hg2＋ had no interference with the determination of 1 × 10 7 mol/L Pb2＋ （the change of peak current was less than 5 %）. In acetate buffer solution at pH4.5, the concentration of Pb2＋ showed good linearity to the peak current. The linear range was 2.0 × 10.9 --6.0 ×10-6mol/L, and the detection limit was 6.0 × 10 10 mol/L （S/N=3）. The modified electrode was applied to the deter- mination of lead in environmental water sample. The determination results were consistent with those obtained by ICP-AES.