A technique for direct spectrophotometric determination of total fluorine in products for oral hygiene using a mixed ligand complex La(III) and alizarincomplexone with fluoride ion in the presence of a non-ionic surfactant has been developed. A number of complexes of different stoichiometry formed in the system has been found. The La:alizarin-complexone:F-= 1:2:1 complex was shown to be used as an analytical form. The complex in the presence of Tween 80 is characterized by the molar absorptivity ε 620 = 11000 mol•dm-3 •cm-1. The calibration curve is linear in the concentration range of fluoride ions 0.06-0.5 μg/ml. A simple, rapid, sensitive, and green procedure for the spectrophotometric determination of Fusing lanthanum alizarin-complexonate in the presence of Tween 80 was proposed and this technique was tested on samples of toothpastes and mouth rinses.

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