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.