Simple, accurate, and precise detection of total nitrogen in surface waters using a smartphone-based analytical method.

In this study, a simple, accurate, and precise analytical strategy was developed for the determination of total nitrogen (total dissolved nitrogen + particulate nitrogen) in surface waters using smartphone technology. The spectrophotometric method based on digestion with persulfate, commonly used in water analyses, was integrated with a digital image-based colorimetric detection system (DIC). To evaluate the accuracy of the total nitrogen-digital image-based colorimetric detection system (TN-DIC), results obtained from the Hach method and UV-VIS spectrophotometer were compared with the RGB values obtained from the smartphone imaging system. T-Test results indicated no statistically significant difference between the results obtained from the TN-DIC method and the standard methods. The linear range of the TN-DIC method was determined to be 0.25-5 mg/L. The analytical quality indicators of the system were established as follows: limit of detection (LOD) 0.095 ppm, limit of quantification (LOQ) 0.29 ppm, %RSD 0.32, and R² value 0.9982. Recovery percentages (99-112%) used to measure the analytical performance of the method were calculated through spike applications at concentrations of 1 and 2 ppm in real water samples. Unlike traditional spectrophotometric methods, this smartphone-based approach is fast, simple, and cost-effective, requiring no complex equipment during analysis.