Department of Chemistry, Tongji University , Siping Road 1239, Shanghai 200092, People's Republic of China.
Anal Chem. 2014 Nov 4;86(21):10668-73. doi: 10.1021/ac502521f. Epub 2014 Oct 16.
A selective, accurate, and sensitive method for monitoring of cadmium ions (Cd(2+)) based on a ratiometric electrochemical sensor was developed, by simultaneously modifying with protoporphyrin IX and 6-(ferroceney) hexanethiol (FcHT) on Au particle-deposited glassy carbon electrode. On the basis of high affinity of biomolecular recognition between protoporphyrin IX and Cd(2+), the functionalized electrode showed high selectivity toward Cd(2+) over other metal ions such as Cu(2+), Fe(3+), Ca(2+), and so on. Electroactive FcHT played the role as the inner reference element to provide a built-in correction, thus improving the accuracy for determination of Cd(2+) in the complicated environments. The sensitivity of the electrochemical sensor for Cd(2+) was enhanced by ∼3-fold through the signal amplification of electrodeposited gold nanoparticles. Accordingly, the present ratiometric method demonstrated high sensitivity, broad linear range from 100 nM to 10 μM, and low detection limit down to 10 nM (2.2 ppb), lower than EPA and WHO guidelines. Finally, the ratiometric electrochemical sensor was successfully applied in the determination of Cd(2+) in water samples, and the obtained results agreed well with those obtained by the conventional ICP-MS method.
基于比率型电化学传感器，通过在金纳米粒子修饰的玻碳电极上同时修饰原卟啉 IX 和 6-(二茂铁)己硫醇（FcHT），开发了一种用于监测镉离子（Cd(2+)）的选择性、准确性和灵敏的方法。基于原卟啉 IX 和 Cd(2+)之间的生物分子识别的高亲和力，该功能化电极对 Cd(2+)具有高选择性，而对其他金属离子如 Cu(2+)、Fe(3+)、Ca(2+)等则具有高选择性。电化学活性 FcHT 作为内参比元素发挥作用，提供内置校正，从而提高了在复杂环境中测定 Cd(2+)的准确性。通过电沉积金纳米粒子的信号放大，电化学传感器对 Cd(2+)的灵敏度提高了约 3 倍。因此，本比率法表现出高灵敏度、从 100 nM 到 10 μM 的宽线性范围和低检测限低至 10 nM（2.2 ppb），低于 EPA 和 WHO 指南。最后，比率型电化学传感器成功地应用于水样中 Cd(2+)的测定，所得结果与传统 ICP-MS 法所得结果吻合良好。
