A New Facile and Sensitive Method for the Spectrophotometric Determination of Chromium

Abstract

A simple, rapid and sensitive spectrophotometric method for the indirect determination of
trace amounts of chromium(VI) is described. The nitrite generated by the oxidation of
hydroxylamine with chromium(VI) is used to diazotize p-aminophenol (PMP). The diazonium salt
formed is coupled with isatin (IS) or isonipecotamide (ISO) or frusemide (FRU) in an alkaline
medium to form azo dye showing absorption maxima at 524 or 533 or 558 nm respectively.
Chromium(III) is determined after it is oxidized to Cr(VI) by bromine water. The range of linearity
for PMP – IS, PMP-ISO and PMP-FRU couples are 0.02- 0.6 μg mL-1
, 0.04-2.0 μg mL-1
and 0.4-
2.0 μg mL-1 of chromium respectively. The molar absorptivity, Sandell sensitivity for each
system were calculated. The developed method is successfully applied to the determination of
chromium in water samples, soil samples and dietary supplement.