A Low-Cost Video-Based Reflectometer for Selective Detection of Cu2+ Using Paper-Based Colorimetric Sensors

This paper presents a low-cost reflectometer for selective detection of Cu. The reflectometer is based on an emission light source using five light-emitting diodes at different wavelengths and a detector using a webcam. The samples were prepared using a filter paper-based colorimetric sensor with ascorbic acid-based quinoxaline derivative. Video analysis using gray color intensity was used to perform both copper ion screening (Cu, Pb, Cr, Ni, Fe, Sn, Mg, Cd, Ag and Co) and quantification of Cu in spiked samples. In addition, a multivariate validation was performed. The system proved to be selective to Cu among the screened ions, and its quantification was performed using partial least square regressions. Good linearity (R = 0.979, coefficient of determination), low root-mean-square error of prediction (RMSEP = 5.20 × 10 mol L) and high recovery (93.39-128.64%) were achieved. This method has potential to be employed for rapid and selective determination of Cu in water using low-cost instrumentation.