A simple scanner-based colorimetric method for fluoride determination using Alfusone reagent

The quantitative determination of fluoride ions is important for water quality monitoring and public health. This study aimed to develop a simple and simultaneous multi-sample digital colorimetric method for fluoride determination using a 96-well plate and a flatbed scanner, without requiring conventional analytical instruments.

Fluoride solutions were color-developed using Alfusone reagent in a 96-well plate and scanned with a flatbed scanner. Color information was extracted from the scanned images and analyzed using red-green-blue (RGB), cyan-magenta-yellow-key (CMYK), hue-saturation-value (HSV), CIE XYZ, and CIELAB parameters. Among the evaluated parameters, the HSV H parameter showed the lowest limit of detection and limit of quantification of 0.086 and 0.29 mg/L, respectively. The CIELAB b* parameter showed the lowest values among the evaluated CIELAB parameters, with a limit of detection and limit of quantification of 0.19 and 0.64 mg/L, respectively. These values were below the World Health Organization guideline value for fluoride and the Japanese drinking water quality standard. Spike-and-recovery tests using bottled and tap water showed that the R and a* parameters provided recoveries closer to 100% than b*. The method offers a simple, attachment-free approach that enables simultaneous analysis of multiple samples and calibration standards using commercially available reagents and office automation equipment.