Analysis of thorium levels by titrimetry using HEDTA titrant and SPADNS indicator

Thorium content was analyzed by titrimetric method using HEDTA as titrant and SPADNS indicator to know precision value and accuracy of thorium analysis result in low concentration (mg/L). Analytical solution used is thorium standard solution 1000 mg/L. The analysis was performed by adjusting the pH of the analytical solution between 2.0 - 3.0 by adding 1 M NaOH solution and the Dihydroxy-2-(4-sulfophenylazo)-naphthalene-3,6-disulfonic acid trisodium salt (SPADNS) indicator. The titration was then carried out using 0.01 M ethylenediamine-N, N', N'-triacetic acid (HEDTA) solution until the end point marked by the color change of the solution from violet to scarlet. From the analysis of standard thorium solution 1000 mg/L with the analytical solution volume of 25 mL (25 mg Th) measured thorium concentration of 955.177 mg/L with standard deviation (SD) of 20.124 mg/L, RSD of 2.107 % and accuracy of 4.482 %. While the result of analysis with 10 mL analytical solution volume (10 mg Th) thorium concentration measured equal to 976,720 mg/L, SD equal to 7,458 mg/L, RSD equal to 0,764 % and accuracy equal to 2,286 %. Thorium analysis results with titrimetric with analytical solution containing 10 mg Th more precision and has a higher accuracy than analytical containing 25 mg Th. (author)