An advantageous analytical method for the determination of fluoride in saliva exploiting smartphone-based digital-image colorimetry

In this study, it was aimed to perform the colorimetric determination of fluoride in human saliva using smartphone camera. The SPADNS method (The mixed acid-zirconyl-SPADNS reagent (4,5-Dihydroxy-3-(p-sulfophenylazo)-2,7-naphthalene disulfonic acid)) was adapted to digital image-based colorimetric detection system. Relationship between F- concentrations and RGB (Red, Green, Blue) values was used to obtain analytical linearity. The method was validated by ultraviolet visible (UV-vis) spectroscopy for fluoride in human saliva. In the optimal experimental conditions, detection limit, relative standard deviation and R-2 values were determined as 0.06 mg/L, 0.31% and 0.995, respectively. Recovery results (99-118%) were calculated for saliva samples in different humans at two different concentrations. In addition, the amount of residual fluorine passing from toothpaste to human saliva in 5 min was calculated as 0.14 mg/L. The same results were obtained with the UV-vis device, proving that the developed method can be used easily in dentistry and medicine. [GRAPHICS] .