Screen-printed back-to-back electroanalytical sensors: Heavy metal ion sensing

Abstract

Screen-printed back-to-back microband electroanalytical sensors are applied to the quantification of lead(II) ions for the first time. In this configuration the electrodes are positioned back-to-back with a common electrical connection to the two working electrodes with the counter and reference electrodes for each connected in the same manner as a normal "traditional" screen-printed sensor. Proof-of-concept is demonstrated for the electroanalytical sensing of lead(II) ions utilising square-wave anodic stripping voltammetry where an increase in the electroanalytical sensitivity is observed by a factor of 5 with the back-to-back microband configuration at a fixed lead(II) ion concentration of 5 μg L-1 utilising a deposition potential and time of -1.2 V and 30 seconds respectively, compared to a conventional (single) microband electrode. The back-to-back microband configuration allows for the sensing of lead(II) ions with a linear range from 5 to 110 μg L-1 with a limit of detection (based on 3σ) corresponding to 3.7 μg L-1. The back-to-back microband configuration is demonstrated to quantify the levels of lead(II) ions within drinking water corresponding to a level of 2.8 (±0.3) μg L-1. Independent validation was performed using ICP-OES with the levels of lead(II) ions found to correspond to 2.5 (±0.1) μg L-1; the excellent agreement between the two methods validates the electroanalytical procedure for the quantification of lead(II) ions in drinking water. This back-to-back configuration exhibits an excellent validated analytical performance for the determination of lead(II) ions within drinking water at World Health Organisation levels (limited to 10 μg L-1 within drinking water).