Trace Determination of Arsenite with an Ionophore-Coated Selective Micro Sensor

This paper reports a highly sensitive micro sensor utilizing an ion selective membrane to determine trace arsenite with anodic stripping voltammetry in the presence of interferences. The sensor was fabricated by depositing an arsenite (As (III)) ion selective membrane on a gold electrode surface. Compared with the traditional sensor without an ionophore membrane, the proposed sensor achieved better voltammetric performance due to its superior selectivity to As (III). After applying the ionophore film, the sensor's background current decreased from 1.375μA to 0.320μA, and its standard deviation decreased from 0.150μA to 0.007μA, leading to lower background noise and higher conformity. Meanwhile, the sensor demonstrated high selectivity with the existence of interference ions, such as Cd²⁺, Pb²⁺, and Hg²⁺. The detection and statistical analysis of As (III) were performed in the linear concentration range of 10-100 ppb (R2 = 0.993) and a low limit of detection (LOD) of 1.10 ppb was obtained for 300s deposition. The sensor was successfully employed for the determination of As (III) in waste water and the results were in good agreement with those from a standard procedure. This highly sensitive and selective portable sensor holds great potential for on-line environmental monitoring.