Trace determination of La(III), Ce(III), Sm(III), Eu(III) and Gd(III) with thioglycolic acid using amperometric technique

Amperometric method for microdetermation of La(III), Ce(III), Sm(III), Eu(III) and Gd(III) based on complex forming tendency of these species with TGA are reported. Titrations were carried out in acetate buffer medium of pH 4.99 (total acetate concentration = 0.2M) at 40°C with the help of thioglycolic acid (TGA). Titration voltage has been selected at -0.10V which falls in anodic limiting region of TGA. Anodic titrations using lanthanide (metal ion) solutions as titrant resulted in an upside down L shaped curve and the null point corresponded to M:L ratio of 1:3 in case of La(III) and Ce(III) where as in case of Sm(III), Eu(III) and Gd(III) the M:L ratio was 1:2. Precision, accuracy and reproducibility was attained with lanthanide ion solutions of concentration 1 × 10-4 M or greater while more dilution up to 10-5 M has been estimated within accuracy limit of ± 2% which compares favourably with that obtained with other sophisticated methods for analysis of very dilute solutions. Newly developed amperometric methods being simple and economic can be exploited for estimation of these lanthanide ions in trace amounts in environmental samples. © Research India Publications.