Thioglycolic Acid as an Amperometric Reagent for Trace Determination of Mn(II), Mn(VII), Cr(III) and Cr(VI)

Amperometric determination of Mn(II), Mn(VII), Cr(III) and Cr(VI) was carried out successfully with the help of thioglycolic acid (TGA) at d.m.e. in 0.1 M NaOH [for Mn(II) and Mn(VII)], 0.1 M KCl [for Cr(III)] and acetate buffer having pH-4.99 [for Cr(VI)] medium. Metal ions solutions were employed as titrant in all the cases (anodic titrations). Titrations of Mn(VII) and Cr(VI) solutions using acid as titrant (cathodic titrations) were also performed successfully. Metal species – TGA molar stoichiometric ratio of 1:2 for Mn(II) and 1:1 for Mn(VII), Cr(III) and 3.32:1 for Cr(VI) have been obtained when respective metal ions were employed as titrant (anodic titrations). 2:1 titrimetric molar ratio for Mn(VII) and 1:3.32 for Cr(VI) have been obtained using TGA as titrant (cathodic titrations). Solutions as dilute as 5.49 ppm Mn(II), 2.74 ppm Mn(VII), 5.20 ppm Cr(III) and 0.52 ppm Cr(VI) were estimated with high degree of accuracy. Tolerance limit for foreign ions has also been worked out.