Utilization of Iodine in the Spectrophotometric Determination of Azide and Thiocyanate Anions in Acetonitrile

Abstract

A simple, rapid, accurate and highly sensitive spectrophotometric
method for the determination of azide thiocyanate
anions in acetonitrile (MeCN) medium is described. The method is
based on the formation of yellow colour complexes, l₂N₃^- and
l₂SCN^- , by the reaction of N₃^- and SCN^- anion with iodine in
MeCN. Beer's law is obeyed within the concentration range
1.5-21.2 and 0.5-24  μg/mL of N₃^- and SCN^- respectively. A spectrophotometric
method has been developed for the titration of azide
and thiocyanate anions with iodine in MeCN. The concentration
ranges as evaluated by the direct titration are 1.68-22 and 0.58-25.2
μg/mL for N₃^- and SCN^-, respectively. The molar absorptivity, Sandell
sensitivity, relative standard deviation and recovery percent are
evaluated. The formation constants (log K_f) of the I₂SCN^- and
I₂N₃^- complexes have been evaluated spectro photometrically at
25 ± 0.1 °C as 6.60 ± 0.02 and 6.02 ± 0.03, respectively. Iodide and
bromide anions interfere in the determination of thiocyanate and
azide anions, transition metals and chloride anion interfere in the
determination of thiocyanate and azide, respectively, when present
in any percentage.