Determination of carbonate in biologic solids.

THIS PAPER REPORTS A METHOD for determining carbonate in carbonate-containing solids by means of the Van Slyke-Neill manometric apparatus, which is widely used for the determination of carbon dioxide in biologic fluids. The method is rapid, convenient, and quantitative, and it makes possible the determination of carbonate in solids by the average clinical laboratory without the purchase of additional equipment. Standard methods for the determination of carbonate involve the liberation of carbon dioxide by the addition of excess standard acid followed by back titration with standard base or the absorption of carbon dioxide in a base and determination by either gravimetric or volumetric methods. The method for carbonate determination reported here utilizes a basic solution of disodium ethylenediamine tetraacetate (EDTA) to dissolve a metal carbonate salt without the liberation of carbon dioxide. The dissolved carbonate is then measured as carbon dioxide in the Van Slyke-Neill manometric apparatus following minor modifications of the procedure described by Peters and Van Slyke (1) for the determination of carbon dioxide in urine. In practice, the method has been used for the determination of carbonate in powdered calcium carbonate and in renal calculi composed of carbonate apatite. However, it may be used for the analysis of any metal carbonate which is chelated by EDTA (2).