Amperometric determination of La(III) with thiomalic acid

Amperometric determination of La(III), Ce(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Tb(III), Dy(III), Ho(III), Er(III) and Yb(III) with the help of thiomalic acid (TSH) is reported. Ce(III) can be determined in presence of Ce(IV) as well. Total Ln(III) (lanthanide) of mixture solutions of lighter and heavier lanthanides separately has also been determined. Titration voltages have been selected in the anodic limiting region of TSH and metal ions used as titrants. Amperometric curves of upside down L-shape are obtained for Ln(III) except Sm(III) and Eu(III). The null point corresponds to M:L molar ratio of M:2 in case of La(III), Ce(III), Pr(III), Nd(III) and 1:3 in case of the rest. Metal solutions as dilute as 1x10-4 have been titrated with reasonable amount of accuracy at 50degC. Interference by diverse ions has been studied and reported. (author). 12 refs., 2 tabs., 1 f ig