Amperometric Trace Determination of Arsenic with 2-Mercapto and 3- Mercaptopropanoic Acids

Abstract

Amperometric determination of trace amounts of As(lII)
and As(V) is reported with the help of 2-men:aptopropanoic
acid (RSH)  and 3-mercaptopropanoic acid (MPSH) at d.m.e.
0.5 M NH₃ + 0.5 M NH₄ Clmedium has been employed for As(lII)
while determination of As(V) with RSH has been carried out in
0.5 M K₂CO₃  and that with MPSH in 0.1 M K₂SO₄ medium.
Titration potentials have been selected in the limiting region of the
anodic wave of organic acids and metal ion solutions used as titrants.
M : L titrimetric molar ratio has been found to be 1 : 1 for both the
metal species. Complexation of metal ions has been proposed as
the basis of the new amperometric methods. Solutions as dilute as
7.5 ppm have been estimated with high degree of accuracy.
Tolerance limits for foreign ions have also been worked out.