Fallacies in the determination of total fluorine and nonionic fluorine in the diffusates of unashed sera and ultrafiltrates

Abstract

The fluorine values obtained by the spectrophotometric determination of fluoride in the diffusates of acidified unashed body fluids are often higher than the ionic fluoride values. The former higher values, so far believed to represent total fluorine content (ionic fluoride plus nonionic fluorine) of the body fluids, are in fact a consequence of lack of specificity of the colorimetric reagents for fluoride determination under the experimental conditions used. The values so obtained reflect ionic fluoride plus interfering substances, the latter masquerading as nonionic fluorine. Fluorine in representative fluoro-organic compounds now tested and in the nonionic fluorine concentrates prepared from human sera is not readily available for diffusion. The continued use of the diffusion colorimetric procedures for the determination of total F and nonionic F in unashed body fluids would yield more misleading information; and this practice should be discontinued.