Advanced spectrofluorimetric determination of ascorbic acid via serotonin hydrochloride quenching using a twin solar cell device with eight-angled blue radiation sources

A novel spectrofluorimetric flow injection analysis (FIA) method was developed for the selective quantification of ascorbic acid via fluorescence quenching of serotonin hydrochloride. The system employs a custom-designed photometric array comprising 16 irradiation sources arranged in a dual-axis matrix—eight aligned horizontally and eight orthogonally, enabling multi-angle excitation and enhanced spectral resolution. Fluorescence signals were captured using a twin-pair solar cell detector, offering high sensitivity and minimal optical interference. The method exhibited a linear calibration range of 0.1–30 μg/mL with a correlation coefficient (r 2 ) of 0.9966, a limit of detection (LOD) of 0.025 μmol /L, equivalent to 4.403 * 10 −4 μg/mL per sample (0.1 mL (and limit of quantitative (LOQ) of 99.381 * 10 −3 μg / ml . Precision and accuracy were confirmed through intra- and inter-day validation, yielding relative standard deviations (RSD) below 2% and recovery rates exceeding 99%. Statistical comparison with conventional fluorometric techniques using a paired t -test revealed no significant difference at the 95% confidence level ( p > 0.05), affirming the method's reliability. The proposed system supports high-throughput analysis of up to 50 samples per hour, with reduced reagent consumption and minimal environmental impact. Its robustness, cost-efficiency, and analytical performance render it a promising tool for routine pharmaceutical quality control and environmental monitoring. Single-line flow injection system for the determination of ascorbic acid via quenching of serotonin hydrochloride fluorescence: A–serotonin hydrochloride solution at pH 6, B–peristaltic pump, C–injection valve with sample segment (ascorbic acid as a quencher), D a custom-built fluorescence detector and E-recorder. • Novel dual-LED/solar-cell platform for AA determination. • Dynamic electron-transfer quenching of serotonin fluorescence. • Ultra-sensitive detection with LOD of 0.025 μmol/L. • Wide linear range (0.1–30 μmol/L) with high precision ( r = 0.9983).