Aim of the study – experimental substantiation of the possibility of quantitative determination of fluoride ions in a model heterogeneous cosmetic system in the form of toothpaste using direct potentiometry with a fluoride-selective electrode.

Materials and methods. The study was carried out using direct potentiometry with a fluoride-selective electrode. A TISAB buffer solution was applied to stabilize the ionic strength of the medium and to minimize the influence of matrix components. Sample preparation included dissolving a weighed portion of toothpaste in distilled water followed by the addition of an equal volume of buffer solution. Calibration of the electrode system was performed using standard sodium fluoride solutions. The object of the study was a heterogeneous cosmetic system in the form of toothpaste containing abrasive components, moisturizers, surfactants, a polymer thickener and sodium fluoride as a source of fluoride ions.

Results. The obtained results demonstrated that the model toothpaste sample is characterized by a stable heterogeneous structure and a uniform distribution of fluoride ions. According to the potentiometric measurements, the average fluoride content in the studied sample was 985.0 ± 5.2 ppm, which complies with regulatory requirements for fluoride-containing toothpastes intended for daily use. The low variability of the obtained values indicates good reproducibility of the method and a minimal influence of the multicomponent toothpaste matrix on the analytical results.

Conclusions. The results confirm the applicability of the direct potentiometric method using a fluoride-selective electrode in combination with a TISAB buffer solution for quantitative determination of fluoride in multicomponent heterogeneous cosmetic systems without prior destruction of the product matrix. The proposed approach can be used for analytical quality control of fluoride-containing toothpastes during product development, manufacturing and standardization of oral hygiene cosmetic products.