Fluoride occurs naturally in many foods and water. Fluoride helps prevent tooth decay by making the tooth more resistant to acid attacks from plaque bacteria. Thus, it is one of the common ingredients in tooth gels and mouth rinses. The US Food and Drug Administration has approved the use of three fluoridated compounds in tooth gels: stannous fluoride, sodium fluoride, and sodium monofluorophosphate (MFP). Most over-the-counter (OTC) tooth gels contain 0.24% w/w sodium fluoride, dentist prescribed tooth gel contain up to 1.1 % w/w sodium fluoride. It is important to carefully monitor the levels of sodium fluoride in tooth gels.<br/>As part of the United States Pharmacopeia’s (USP) monograph modernization initiative a revision to the Sodium Fluoride Gel monograph was proposed Pharmacopeia Forum 44(4). That proposal contains an ion chromatography (IC) method for fluoride assay in sodium fluoride gel to replace the current ion-selective electrode procedure. Here we demonstrate that a Thermo Scientific™ Dionex™ IonPac™ AS15-5µm column can be used to analyze tooth gel samples for the presence of fluoride. Using this column, fluoride is separated from other anions using KOH eluent generated electrolytically with a Thermo Scientific™ Dionex™ EGC III KOH cartridge and detected by suppressed conductivity. Method performance is evaluated according to the monograph’s system suitability requirements and the acceptance criterion for sodium fluoride content in a tooth gel sample. Method ruggedness was evaluated by measuring the response of sodium fluoride standards and samples under the same conditions but on two separate columns. The fluoride retention time on two columns differed by ~0.7%; i.e. 7.39 min on Column 1 and 7.34 min on Column 2. The USP monograph system suitability and assay acceptance criterion (90-110%) were met by both columns.

Determination of fluoride in sodium fluoride tooth gel by ion chromatography

2019 Spring National Meeting

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