A Portable Microfluidic Device-Based Colorimetric Naked-Eye Sensors for Determination of Mercury and Arsenic Ions in River Water Samples

The contamination of drinking water by heavy metals, such as arsenic and mercury, is a global concern. Herein, we have developed a sensitive, cost-effective, and novel 3D-printed microfluidic device featuring two V-channels (Hg-sensor and As-sensor) for naked-eye colorimetric detection of mercury and arsenic in water samples from Tigris River. In Hg-sensor, a rapid and eco-friendly colorimetric sensor of silver nanoparticles (AgNPs) has been prepared using Boswellia sacra extract as a stabilizing and reducing agent to selectively detect mercury ions. Several techniques have been used to characterize the morphology of the prepared nanosensor of AgNPs, as well as the optical properties. AgNPs decorated with Boswellia sacra molecules (AgNPs@BS) showed high sensitivity and selectivity detection of Hg (II) in river water samples, based on AgNPs’ aggregation and the converting brown color of AgNPs to colorless. In As-sensor, a colorimetric sensor was used to detect arsenic ions using leucomalachite (LMG) green dye, where arsenic (III) reacts with potassium iodate in an acidic medium to release iodine, which rapidly oxidizes LMG to malachite green (MG). The application of the microfluidic device for analysis at the point of collection was assessed utilizing colorimetric determination of mercury and arsenic, permitting free imaging of both sensors using a smartphone camera. The limit of detection (LOD) and limit of quantification (LOQ) of this method were reported to be 0.089 and 0.297 mg/L for Hg (II), and 0.042 and 0.143 mg/L for As (III), respectively. The calibration curve that ranged from 2 to 20 mg/L for Hg (II) and 1–15 mg/L for As (III) was obtained for the point of collection device, which reveals a good agreement (97