Use of the PhotoMetrix app in the monitoring of fluoride concentration in alternative water supply systems

Abstract

Frequent ingestion of water containing fluoride concentration above the limit established by Brazilian legislation causes an illness called dental fluorosis. Currently, water fluoride level monitoring for human consumption is performed using potentiometric, chromatographic or colorimetric methods, which are relatively expensive and uses equipment difficult to displace. Therefore, the need for developing alternative methods arises, aiming at speed, practicality and reduction of analyzes cost. The smartphone application PhotoMetrix® is a free tool that captures and analyzes digital images through univariate and multivariate mathematical models. Capturing images can be done through the smartphone's own or through an external USB camera. Thus, this research aimed at evaluating the PhotoMetrix® use to monitoring the fluoride concentration in water supply. Two reference methods were used for comparison: the spectrophotometric method and selective ion electrode. The results indicated agreement between methods, showing a determination coefficient (R²) of 0.995 and prediction errors RMSEP (Root Mean Square Error of Prediction) about of 0.05 mg L^-1. Then, PhotoMetrix® is a satisfactory method for fluoride determination, becoming a viable alternative for monitoring water quality, especially for alternative water supply systems.