Determination of fluoride in urinary calculi using a quantitative microdiffusion method.

A microdiffusion method for the separation of fluoride from other ions in urinary calculi has been developed, tested and assessed. The procedure involves digestion at 75 degrees C of samples with silicone-impregnated mixtures of nitric and perchloric acids in a specially designed diffusion cell and determination of the diffused fluoride with an ion-sensitive electrode. Several test samples were used to assess the recovery, accuracy and reproducibility of the procedure. Results for 20 stones of Indian origin are presented and discussed.