Determination of Fluoride in Mouthwash Using Flow-injection Analysis with Spectrophotometric Detection

In this work, the development of flow system that is simple, precise and accurate for determining fluoride in mouthwash is described. The determination of fluoride was based on the on-line formation of a Fe(III)–salicylate complex, which is consumed in the presence of fluoride, generating the colourless hexafluoroferrate(III) complex ion, [FeF6]³-. The proposed procedure exhibits a linear concentration range of 8.0 × 10^-5–1.2 × 10^-3 mol L^-1, a detection limit of 3.5 x 10^-5 mol L^-1, a higher sampling frequency of 44 h^-1 and relative standard deviations below 0.2%. The interference of the red colour of the samples was removed using waste-seed specimens of Mabea fistulifera Mart. as a biosorbent material.