A Blue-Light Attenuation Optical Analyzer Based on Dual Solar Cells for Copper(II) Quantification in Metallic Alloys

This study presents a novel spectrophotometric continuous flow injection analysis (CFIA) system for the quantification of copper(II) ions (Cu²⁺) via the Cu ²⁺ –thiocyanate (Cu(SCN) ₂ ) precipitate. A homemade photometric instrument was designed and constructed to serve as the detection unit. The analytical cell was engineered in a brass incubator that contained a central flow tube positioned longitudinally through the incubator. Two orthogonal arrays of eight apertures were machined: the 0–180° and 0–90° axes aligned to the flow tube to contain the accommodated high-intensity blue LEDs arranged to surround the flow cell at each side with a twin solar cell photonic detector. This configuration guaranteed accurate optical alignment between radiation sources and the detector. The Cu(SCN) ₂ precipitate was analyzed for its scattering and absorbance properties. A strict optimization of chemical and physical parameters was conducted to maximize signal intensity and reproducibility. Calibration graph demonstrated excellent linearity in the range 0.05–15 mmol/L, with a correlation coefficient (r) of 0.9987 and a limit of detection (LOD) of 12.5 µmol/L, superior to conventional turbidity (LOD ≈ 250 µmol/L). Application to certified alloys confirmed accuracy, with paired t-tests and individual t-tests showing no significant difference (t-tab > t-cal) between the proposed and reference methods