TITRATION OF LANTHANOIDS BY PH-METRIC MEASUREMENTS - THE USE OF UNBUFFERED SOLUTIONS

A method is proposed for the potentiometric titration of lanthanoids i n unbuffered aqueous solutions at constant ionic strength. It exploits the complexing reaction of the cations with EDTA and the protons deli vered during the titrations, which can be monitored by a glass-indicat or electrode. The particular experimental conditions employed make it possible for such titrations to be perform at concentration levels as low as 1 muM. Criteria for detecting the end points, influence of pH o n the equilibria involved and precision of the measurements are discus sed on the basis of theoretical titration curves obtained by means of a digital simulation procedure.