Kinetic-Spectrophotometric Determination of Tungsten(VI) Based on Azure I-Ti(III) Reaction in the Presence of Thiocyanate as an Activator

Abstract

The catalytic effect of tungsten(VI) and activating effect
of thiocyanate on the reduction reaction of Azure I by Ti(III)
was used to develop a sensitive and rapid kinetic spectrophotometric
method for the determination of tungsten(VI). The
reaction was monitored spectrophotometrically by measuring
the change in absorbance (ΔA) at 646 nm using a fixed
time method (2.5 min). The effect of different variables on
the reaction was investigated and optimized in order to achieve
the highest sensitivity. The calibration graph was linear
in the range 5-90 ng mL^-1 and the detection limit was 2.9
ng mL^-1. The relative standard deviation for ten replicate
measurements of 10 and 50 ng mL^-1 of tungsten was 4.7 and
3.5, respectively. The method was successfully applied to the
determination of tungsten in spring water samples.