Development and evaluation of two low-cost strategies for chemiluminescence detection in paper-based devices

This study reports the development of two automated systems for chemiluminescence measurements in paper-based analytical devices (PADs) using smartphone-based digital image detection. The first system enables controlled contact between a PAD containing eight circular detection zones and suspended reagent droplets, allowing real-time monitoring of luminescence through a custom mobile application. The second system is based on the controlled immersion of a PAD with eight rectangular detection zones into reagent reservoirs, enabling automated signal acquisition. In both platforms, calibration and sample analysis are performed simultaneously within a single run. The first system was applied to the determination of vitamin B₁₂ (cyanocobalamin) in injectable formulations, based on the catalytic activity of Co²⁺ in the luminol-hydrogen peroxide reaction. The second system was used for the indirect determination of captopril in tablets, based on the decrease in luminol-hypochlorite chemiluminescence after analyte oxidation. Both approaches showed suitable analytical performance, with linear responses (R² > 0.99), satisfactory precision (RSD <8%), and no significant differences compared to reference methods, demonstrating the potential of the proposed systems for rapid and reliable analysis.