Using Silica-titania Xerogels for Solid Phase Spectrophotometric Determination of Fluoride in Oral Hygiene Products

New materials - silica-titania xerogels modified with polyphenols (caffeic acid, catechol, and quercetin) or hydrogen peroxide - have been used for solid phase spectrophotometric determination of fluoride ions. The fast and simple method is based on the xerogel incorporated titanium(IV) complexes discoloration in the presence of fluoride ions. Parameters, such as modifying reagent nature pH, and time of contact, affecting the interaction of fluoride with modified silica-titania xerogels have been investigated. A linear response for the fluoride determination has been observed in the concentration ranges: 50-200, 100-500 and 100-700 mg·L-1 for caffeic acid, catechol, and quercetin modified xerogels, accordingly. The developed method allows determining fluoride ions in ethanol-containing mouthwashes. The proposed method has been applied to the analysis of mouthwash solutions and toothpastes. Time of analysis is 5 min.