A versatile and robust electrochemical flow cell with a boron-doped diamond electrode for simultaneous determination of Zn2+ and Pb2+ ions in water samples

Abstract

A versatile and robust thermostatted electrochemical flow cell (EFC) with a boron-doped diamond electrode (BDD) detector was employed to perform two distinct flow-injection electrochemical approaches. In the first approach, differential pulse anodic stripping voltammetry (DPASV) using a flow-batch analysis (FBA) is proposed. In the second approach, multiple pulse amperometry (MPA) employing multicommutation flow analysis (MCFA) is also presented. Both approaches were employed to simultaneously determine Zn²⁺ and Pb²⁺ in water samples. For this, a screen-printed electrode (SPE) was developed, and a BDD electrode was coupled to it and was inserted into the EFC. By employing the FBA with the DPASV technique, two analytical curves in concentration ranges from 11.5 to 80.6 μg L⁻¹ and 0.64 to 10.9 μg L⁻¹ for simultaneous determination of Zn²⁺ and Pb²⁺, respectively, were obtained. Moreover, limits of detection (LDs) of 0.62 μg L⁻¹ and 0.19 μg L⁻¹ were estimated respectively and a sampling frequency of 12 h⁻¹ was obtained. For MCFA with MPA, analytical curves from 830 to 4980 μg L⁻¹ and 140 to 820 μg L⁻¹ for simultaneous determination of Zn²⁺ and Pb²⁺ with LDs of 220.0 μg L⁻¹ and 41.0 μg L⁻¹ and a sampling frequency of 67 h⁻¹ were obtained. The developed EFC allowed a full on-line automation of the methods, covering the pretreatment of BDD, addition of standard solutions, dilutions, thermostatted control, and detection with and without electrochemical preconcentration. In addition, the low waste generation of only 700 μL may be useful for green chemistry purposes and sustainable research.