IADR Abstract Archives
Determination of Fluoride in Human Saliva by Gas Chromatography
Objective: To develop and validate a new assay method capable of detecting fluoride in human saliva at a limit of quantification (LOQ) of 0.03ppm.
Methods: The most common technique reported in the literature for the analysis of fluoride in saliva is based on use of ion selective electrodes (ISE). At sub ppm concentrations, ISE can suffer from instrument drift, poor measurement repeatability and hydroxide interference. To overcome these problems, a gas chromatography with flame ionisation detection (GC-FID) was developed and validated. The GC-FID method was chosen because it was highly selective and capable of achieving precise and accurate results. This method employed the silanisation of fluoride using trimethylchlorosilane (TMCS) to trimethylfluorosilane (TMFS) and the analysis of the headspace for TMFS which is directly proportional to the fluoride concentration. Method validation comprised of linearity, accuracy, precision, specificity and solution stability over the working range of 0.03ppm to 10ppm.
Results: Linearity, accuracy, precision, specificity and solution stability
Validation Test | Findings |
Linearity (0.03ppm to 10ppm) | Coefficent of determination 0.999 1/x weighted |
Accuracy (0.03ppm, 0.05ppm, 0.1ppm, 1ppm, 5ppm and 10ppm) | Mean recovery between 92% to 113% |
Precision (0.03ppm, 0.05ppm, 0.1ppm, 1ppm, 5ppm and 10ppm) | Relative standard deviation (RSD) less than 15%. |
Specificity | Less than 20% interferance with respect to 0.03ppm fluoride. |
Solution stability (0.03ppm and 10ppm) | 5 days freeze thaw cycling. |
Conclusion: The assessment of the analytical techniques has shown that GC-FID would be the most suitable method for the determination of fluoride. The method demonstrated linearity, accuracy, precision, specificity and solution stability, and is suitable for the determination of fluoride in saliva for clinical studies.