Effects of Urine Pretreatment on Calcium Oxalate Crystallization Inhibition Potentials

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Abstract
Activated C and calcium oxalate [CaOx] solids were used as adsorbents to remove crystallization inhibiting species from centrifuged and dialyzed normal [human] urines. The urine supernatants, following adsorption treatments, were examined for their calcium oxalate monohydrate crystallization inhibitory potentials by means of a constant composition potentiostatic seeded growth method. The supersaturation of the reactant solution was maintained constant during the crystallization process by the potentiometrically monitored addition of solutions containing crystal lattice ions controlled by a specific Ca2+ selective electrode. The experimental results indicate that normal urine contains a number of inhibiting species of variable MW and adsorbability. Apparently, substances present in normal urine interfere substantially with the adsorption of crystallization inhibiting species by calcium oxalate monohydrate crystal surfaces. Both charcoal and CaOx adsorbents were successfully used to completely remove a synthetic, model urinary crystallization inhibitor, ethylenediamine-tetramethylene-phosphonic acid (ENTMP) from relatively concentrated solutions in 0.15 M NaCl.