A portable m-chip-based colorimetric device was developed for the determination of Cr3+ and Al3+ 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 Cr3+ and Al3+ 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 Cr3+ and Al3+ ions concentration. Under optimized experimental conditions, the linear ranges are 0.1–220 and 0.01–250 mM for Cr3+ and Al3+ ions, respectively. The probe has a limit of detections of 10.66 and 3.55 nM for Cr3+ and Al3+ in an aqueous solution. In the case of m-chip, the concentration ranges are 0.1–200 lM and 0.01–220 lM for Cr3+ and Al3+ ions, with detection limits of 9.18 and 2.30 nM, respectively. The m-chip showed great potential as a fast detection tool for the monitoring of Cr3+ and Al3+ ions in real samples such as river water samples
