DETERMINATION OF SOLUBLE FLUORIDE AND MONOFLUOROPHOSPHATE IN DENTAL CREAM USING GRADIENT ELUTION ION CHROMATOGRAPHY

Abstract

A single column, stability indicating, Ion Chromatographic method has been developed for the determination of Soluble Fluoride and Monofluorophosphate (MFP) in dental cream. The limits of detection (3x signal-to-noise) for Fluoride and MFP in dental cream are 5.0 ppm and 87 ppm (wt./wt.), respectively, using the sample preparation procedure described. These LODs correspond to operating concentrations of F and MFP of 0.05 ppm and 0.87 ppm (wt./vol), respectively. The method is linear for F⁻ (r = 0.9998) over an operating range of 1.0 to 4.5 ppm (wt./vol) (40%–180% of 2.5 ppm target) and for MFP (r = 0.9999) over an operating range of 35.7 to 66.3 ppm (wt/vol) (70%–130% of 51.0 ppm target). Both anions (MFP and F) were found to have no interference with a placebo dentifrice and each passed resolution and tailing factor requirements of R ≥ 2.0 and T<1.5. Quantitative recoveries were obtained for both species from placebos spiked with 70, 100, and 130% of target. Twenty replicate preparations and analyses of a homogenized commercial sample, conducted by two operators over the course of 4 days, showed agreement to within 5.5%RSD for F and 2.23%RSD for MFP.

ACKNOWLEDGMENTS

We gratefully thank the Colgate-Palmolive Company, specifically, Christopher Borgia and Henrik Rassmussen for their generous help.