Determination of Ultra-Trace Levels of Phenazopyridine in Environmental and Biological Samples Using a Smartphone-Based Colorimetric Method with Alumina Nanoparticles for Preconcentration

This research introduces a highly sensitive and portable colorimetric sensor designed to detect phenazopyridine (PZP) at ultra-trace levels. The method utilizes alumina nanoparticles for the preconcentration of PZP, followed by the analysis of changes in red pixel intensity via smartphone imaging. Key experimental parameters, such as solution pH, adsorbent dosage, and contact time, were optimized to achieve ideal conditions (pH 6.5, 30 mg adsorbent, 15 min contact time). Under these conditions, a calibration curve was developed for PZP concentrations between 0.1 and 1.0 mg/L, with a detection limit of 0.04 mg/L. The alumina nanoparticle adsorbent demonstrated reliable reusability across six cycles without loss of efficiency. Selectivity tests against 20 potential interfering substances confirmed no significant interference. Practical applicability was assessed by measuring PZP in six industrial and biological samples, with results validated against high-performance liquid chromatography using statistical analysis. The method proved accurate, repeatable, and cost-effective, offering significant advantages over traditional techniques like HPLC. Its portability, sensitivity, and selectivity make it a promising solution for detecting phenazopyridine in diverse applications.