Amino Acid-Fabricated Glassy Carbon Electrode for Efficient Simultaneous Sensing of Zinc(II), Cadmium(II), Copper(II), and Mercury(II) Ions

Tayyaba Kokab; Afzal Shah; Faiza Jan Iftikhar; Jan Nisar; Mohammad Salim Akhter; Sher Bahadur Khan

doi:10.1021/acsomega.9b03189

Amino Acid-Fabricated Glassy Carbon Electrode for Efficient Simultaneous Sensing of Zinc(II), Cadmium(II), Copper(II), and Mercury(II) Ions

ACS Omega. 2019 Dec 9;4(26):22057-22068. doi: 10.1021/acsomega.9b03189. eCollection 2019 Dec 24.

Authors

Tayyaba Kokab¹, Afzal Shah^{1

2}, Faiza Jan Iftikhar^{1

3}, Jan Nisar⁴, Mohammad Salim Akhter², Sher Bahadur Khan⁵

Affiliations

¹ Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan.
² Department of Chemistry, College of Science, University of Bahrain, Sakhir 32038, Bahrain.
³ NUTECH School of Applied Sciences and Humanities, National University of Technology, Islamabad 44000, Pakistan.
⁴ National Centre of Excellence in Physical Chemistry, University of Peshawar, Peshawar 25120, Pakistan.
⁵ Department of Chemistry, King Abdul Aziz University, Jeddah 21589, Kingdom of Saudi Arabia.

Abstract

Herein, we present a greener approach to achieve an ultrasensitive, selective, and viable sensor engineered by amino acids as a recognition layer for simultaneous electrochemical sensing of toxic heavy metals (HMs). Electrochemical techniques like electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and square-wave anodic stripping voltammetry (SWASV) were applied to demonstrate sensing capabilities of the designed analytical tool. The comparative results of different amino acids demonstrate alanine's superior performance with a well-resolved and enhanced current signal for target metal ions due to strong complexation of its functional moieties. The working conditions for alanine-modified GCE were optimized by investigating the effect of alanine concentration, different supporting electrolytes, pH values, accumulation potentials, and time. The limits of detection for Zn²⁺, Cd²⁺, Cu²⁺, and Hg²⁺ were found to be 8.92, 5.77, 3.01, and 5.89 pM, respectively. The alanine-modified electrode revealed absolute discrimination ability, stability, and ultrasensitivity toward metal ions even in the presence of multifold interfering species. Likewise, greener modifier-designed electrodes possessed remarkable electrocatalytic activity, cost affordability, reproducibility, and applicability for picomolar level detection of HM ions in real water sample matrixes. Theoretical calculations for the HM-amino acid interaction also support a significantly improved mediator role of the alanine modifier that is consistent with the experimental findings.