Method Development and Validation of a Rapid Silica Plate-Based Smartphone-Assisted Device in the Detection of Iron in Water

Iron (Fe) is a micronutrient that can be toxic at elevated concentrations, prompting its significance in frequent environmental monitoring. Typically analyzed using methods such as FAAS, ICP-OES and ICP-MS, the challenge of expensive instrumentation operated only in the laboratory presents a barrier for rapid and frequent testing. This study aimed to develop a silica-based smartphone-assisted on-site method for rapid detection of Fe in water using ImageJ software. Suitable conditions, including reagents and a color intensity measurement tool, were optimized for this method. Figures of merit such as detection limit, accuracy and precision were determined. The results showed that adding polyacrylic acid to detection points for silica worsened the results, in contrast to results for paper devices. It was also found that, on ImageJ, it is best to use an integrated density tool to measure color intensity, contrary to the previously reported mean gray tool. Results showed a limit of detection of 0.2 ng, a limit of quantification of 0.6 ng, a linear range of 0.6 ng to 4.5 ng and RSD of <20%. This method is therefore an alternative in field pre-testing and screening. Future studies include application of this method in the field with real samples and in the analysis of other metals.