Smartphone-based microfluidic chip modified using pyrrolidine-1-dithiocarboxylic acid for simultaneous colorimetric determination of Cr and Al ions.

A portable µ-chip-based colorimetric device was developed for the determination of Cr and Al ions. The silver nanoparticles were modified with pyrrolidine-1-dithiocarboxylic acid ammonium salt as a novel ligand for the first time. The color of modified AgNPs in the test zone immediately changes after the addition of Cr and Al ions. The resulting color changes were detected by the naked eye or were taken by a smartphone camera. The obtained images were analyzed by RGB software to assay the Cr and Al ions concentration. Under optimized experimental conditions, the linear ranges are 0.1-220 and 0.01-250 µM for Cr and Al ions, respectively. The probe has a limit of detections of 10.66 and 3.55 nM for Cr and Al in an aqueous solution. In the case of µ-chip, the concentration ranges are 0.1-200 μM and 0.01-220 μM for Cr and Al ions, with detection limits of 9.18 and 2.30 nM, respectively. The µ-chip showed great potential as a fast detection tool for the monitoring of Cr and Al ions in real samples such as river water samples.