Sensitive determination of fluoride in biological samples by gas chromatography-mass spectrometry after derivatization with 2-(bromomethyl)naphthalene.

A gas chromatography-mass spectrometric method was developed in this study in order to determine fluoride in plasma and urine after derivatization with 2-(bromomethyl)naphthalene. 2-Fluoronaphthalene was chosen as the internal standard. The derivatization of fluoride was performed in the biological sample and the best reaction conditions (10.0 mg mL(-1) of 2-(bromomethyl)naphthalene, 1.0 mg mL(-1) of 15-crown-5-ether as a phase transfer catalyst, pH of 7.0, reaction temperature of 70°C, and heating time of 70 min) were established. The organic derivative was extracted with dichloromethane and then measured by a gas chromatography-mass spectrometry. Under the established condition, the detection limits were 11 μg L(-1) and 7 μg L(-1) by using 0.2 mL of plasma or urine, respectively. The accuracy was in a range of 100.8-107.6%, and the precision of the assay was less than 4.3% in plasma or urine. Fluoride was detected in a concentration range of 0.12-0.53 mg L(-1) in six urine samples after intake of natural mineral water containing 0.7 mg L(-1) of fluoride.