An optical micromethod for the determination of relative crystallisation rates of calcium oxalate in gels: method and preliminary results.

This paper describes a new, highly efficient micromethod for the determination of relative crystallisation rates of calcium oxalate (CaOx). Crystallisation is performed in the upper layer of a gel (bactoagar, agarose) which contains one component (oxalate) of the sparingly soluble salt. Precipitation is started by pipetting Ca++ containing solutions (in the presence and absence of crystallisation inhibitors) onto the gel. The process is followed quantitatively as a function of time by means of vertical light path photometry carrying out quasi-simultaneous multideterminations within a 50-fold multicuvette. The test volume is 0.1 ml. The method is suitable for large scale determinations. About 50 single crystallisation kinetics can be measured within 5-15 min. Testing three known inhibitors of CaOx crystal formation, relative inhibitory activities were obtained with standard errors of 1%-4%.