The aim was to compare potential methods for fluoride analysis in microlitre-volume plasma samples containing nano-gram amounts of fluoride. Methods: A group of 4 laboratories analysed a set of standardised biological samples as well as plasma to determine fluoride concentration using 3 methods. In Phase-1, fluoride analysis was carried out using the established hexamethyldisiloxane (HMDS)-diffusion method (1 mL-aliquot/analysis) to obtain preliminary measurement of agreement between the laboratories. In Phase-2, the laboratories analysed the same samples using a micro-diffusion method and known-addition technique with 200 µL-aliquot/analysis. Coefficients of Variation (CVs) and intra-class correlation coefficients (ICCs) were estimated using analysis of variance to evaluate the amount of variation within- and between-laboratories. Based on the results of the Phase-2 analysis, 20 human plasma samples were analysed and compared using the HMDS-diffusion method and known-addition technique in Phase-3. Results: Comparison of Phase-1 results showed no statistically significant difference among the laboratories for the overall data set. The mean between- and within-laboratory CVs and ICCs were < 0.13 and ≥0.99, respectively, indicating very low variability and excellent reliability. In Phase-2, the overall results for between-laboratory variability showed a poor CV (1.16) and ICC (0.44) for the micro-diffusion method, whereas with the known-addition technique the corresponding values were 0.49 and 0.83. Phase-3 results showed no statistically significant difference in fluoride concentrations of the plasma samples measured with HMDS-diffusion method and known- addition technique, with a mean (SE) difference of 0.002 (0.003) µg/mL. In conclusion, the known-addition technique could be a suitable alternative for the measurement of fluoride in plasma with microlitre-volume samples.

Becker D, Christensen R, Currie L, Diamondstone B, Eberhardt KR, Gills T, Hertz H, Klouda G, Moody J, Parris R, Schaffer R, Steel E, Taylor J, Watters R, Zeisler R: Use of NIST Standard Reference Materials for Decisions on Performance of Analytical Chemical Methods and Laboratories. Gaithersburg, NIST Special Publication 829, 1992.
Buzalaf MA: Fluoride and the Oral Environment. Basel, Karger, 2011.
Ekstrand J: A micromethod for the determination of fluoride in blood plasma and saliva. Calcif Tissue Res 1977; 23: 225–228.
Hallsworth AS, Weatherell JA, Deutsch D: Determination of subnanogram amounts of fluoride with the fluoride electrode. Anal Chem 1976; 48: 1660–1664.
Martinez-Mier E, Buckley C, Chandrappa P, Soto-Rojas AE: Development of a standard fluoride analytical method for dental plaque. J Dent Res 2010; 89: 931.
Martínez-Mier EA, Cury JA, Heilman JR, Katz BP, Levy SM, Li Y, Maguire A, Margineda J, O’Mullane D, Phantumvanit P, Soto-Rojas AE, Stookey GK, Villa A, Wefel JS, Whelton H, Whitford GM, Zero DT, Zhang W, Zohouri V: Development of gold standard ion-selective electrode-based methods for fluoride analysis. Caries Res 2011; 45: 3–12.
Mthethwa MT, du Plessis JB: A comparison of results of fluoride determinations by different laboratories. SADJ 2005; 60: 238–240.
Pacaud D, Lemay JF, Guay P, Buithieu M, Yale JF: Assessment of blood volumes obtained by capillary punctures in older children and adolescents with diabetes. Pediatr Res 1996; 39: 558–558.
PALL Medical: Plasma Optimization Guide: Improving Plasma Yields from Whole Blood Donations. Washington, Pall Corporation, 2010.
Pinheiro J BD, DebRoy S, Sarkar D, R Core Team: nlme: Linear and Nonlinear Mixed Effects Models. R package version 3.1–131., 2017.
Pinheiro JC, Bates DM: Mixed Effects Models in S and S-plus. Springer Verlag, 2000.
Rugg-Gunn AJ, Villa AE, Buzalaf MR: Contemporary biological markers of exposure to fluoride. Monogr Oral Sci 2011; 22: 37–51.
Taves D: Separation of fluoride by rapid diffusion using hexamethyldisiloxane. Talanata 1968; 15: 969–974.
Venkateswarlu P: Evaluation of analytical methods for fluorine in biological and related materials. J Dent Res 1990; 69: 514–521; discussion 556–517.
Vogel GL, Carey CM, Chow LC, Ekstrand J: Fluoride analysis in nanoliter- and microliter-size fluid samples. J Dent Res 1990; 69: 522–528; discussion 556–527.
Wang C, Yuan H, Duan Z, Xiao D: Integrated multi-ISE arrays with improved sensitivity, accuracy and precision. Sci Rep 2017; 7: 44771.
Whitford GM: The Metabolism and Toxicity of Fluoride. Basel, Karger, 1996.
WHO Expert Committee on Oral Health Status and Fluoride Use & World Health Organization: Fluorides and oral health: report of a WHO Expert Committee on Oral Health Status and Fluoride Use. Geneva, World Health Organization, 1994.
Copyright / Drug Dosage / Disclaimer
Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.
You do not currently have access to this content.