Determination of trace fluoride in water samples by silylation and gas chromatography/mass spectrometry analysis.

Rationale: Due to the ubiquity of fluorides and the small gap between a safe dose and a harmful one, it is necessary to develop a robust analytical method for determination of fluoride ions in various water samples with complex matrices.

Methods: Silylation of the fluoride ion was carried out by treatment with hydrochloric acid and phenyldimethylchlorosilane at room temperature. The formed phenyldimethylfluorosilane was detected by gas chromatography/mass spectrometry (GC/MS).

Results: Under the optimized conditions, linearity in the analytical method ranged from 0.050 to 5.0 μg/mL for the fluoride ion with R  >0.9999. Reasonable reproducibility was obtained with the intraday relative standard deviation (RSD) (N = 5) of 2.04% and interday RSD (N = 5) of 3.75% at the concentration of 0.10 μg/mL. The developed method has been successfully applied to determine the fluoride ion in real water samples, including waste water samples, with the recovery between 81.12% and 113.04%.

Conclusions: A robust method for the determination of the fluoride ion has been developed by silylation with phenyldimethylchlorosilane and GC/MS analysis. The established method showed good anti-interference and precision, and it has been applied for determination of the fluoride ion in various water samples.