A procedure for the determination of total fluorine in whole blood, serum/plasma. and other biological samples is described. The method is based on oxygen bomb combustion reaction with triethylsilanol, and gas chromatography. By eliminating the combustion step, only ionic or acid-labile fluoride is measured. The difference between the two results gives the organic or "bound" fluoride level ofthe sample.
Increasing emphasis has been placed on identifying and quantitating th$ element fluorine in biological samples. The observation by Taves (1,2) that two forms of fluoride exist in human serum has generated a need for a more refined fluorine analysis scheme.
Prior to Taves' work, it had been assumed that there was only one form of fluoride in serum, namely the inorganic F ion. Taves, however, presented good evidence that in addition to inorganic fluoride there is fluoride bound to albumin and suggested that this latter fluoride was organofluorine in nature.
A number of techniques and procedures for fluorine analysis have appeared in the literature. Singer and Armstrong (3) used the ashing technique for decomposition and calorimetric analysis. Taves (4) separated fluoride using acid diffusion (with the aid of hexamethyldisiloxane), followed by determination with either morin-thorium fluorescence or the fluoride electrode. Cox and Backer Dirks (5) used anion exchange to remove fluoride from blood, followed by the alizarin complexan fluoride determination.
Venkateswarlu et al. ( 6) measured ionic and ionizable fluoride in serum using calcium phosphate (to absorb the fluoride ion) and the fluoride electrode.
Bock and Semmler (7) presented a new approach for the separation and determination of fluoride when they combined reactive organosilicon compounds with gas chromatography.
They added a chlorosilane which is converted by water to the silanol, which reacts with fluoride to form the corresponding fluorosilane. The fluorosilane can be extracted with organic solvent and quantitatively determined by using gas chromatography.