Differential pulse adsorptive voltammetric determination of chromium in aluminum

Abstract

A method is presented for determining the trace amount of chromium in aluminum. Aluminum is dissolved in sodium hydroxide containing hydrogen peroxide. The method is based on the catalytic activity of nitrate ions on the reduction of Cr( 111 )-triethylenetetraminehexaacetic acid (-'ITHA) complex. The sensitivity of this method is further improved by adsorptive preccncentration o f Cr(II1)-TTHA complex at a hanging mercury drop electrode (HMDE). The adsorbed complex is then reduced at a peak potential o f -1.28 V, and the peak height of Cr(II1) reduction is measured. The Cr(II1) formed at the electrode surface by the reduction of Cr(VI), which is present in the bulk solution, is immediately complexed by TTHA. This method is suitable for the determination of chromium at levels as low as 0.5 pg g-' (with about 25 mg o f sample) and a relative standard deviation of 15%.

Application of an Optimization Procedure for the Determination of Chromium in Various Water Types by Catalytic-Adsorptive Stripping Voltammetry

“…other complexing agents [10][11][12][13]. It has been assumed that the nitrate ion chemically oxidizes the Cr(II)-HEDTA complex formed by the reduction of the Cr(III)-HEDTA complex so that a catalytic reduction current results.…”

“…In particular, adsorptive stripping voltammetry, following adsorptive accumulation complexes of chromium with organic complexing agents, such as diphenylcarbazide (DPCI) [9], triethylenetetraaminehexaacetic acid (TTHA) [10,11], diethylenetriaminepentaacetic acid (DTPA) [12,13], N-nitroso-Nphenylhydroxylamine ammonium salt (cupferron) [14], 2,2-bipyridine [15] and pyrocatechol violet (PCV) [16] on a hanging mercury drop electrode (HMDE) has been seen to be a very sensitive and effective technique for the determination of trace amounts of chromium.…”

Application of an Optimization Procedure of Adsorptive Stripping Voltammetry for the Determination of Chromium in Wine

“…Thus, at an appropriate potential, Cr VI is reduced to Cr III . Then Cr III -TTHA complexes are formed and accumulated at a HMDE by adsorption giving a well-de®ned peak [6] due to the reduction of Cr III -TTHA complex to Cr II -TTHA. The Cr III -DTPA complexes are reduced in a one-electron step yielding a well-de®ned peak at À1.22 V (Fig.…”

Speciation of Chromium by Adsorptive Stripping Voltammetry Using Pyrocatechol Violet

“…In particular, stripping voltammetry, following adsorptive accumulation of complexes of chromium using organic complexing agents, such as diphenylcarbazide [5], TTHA [6,7], DTPA [8,9], Cupferron [10], 2,2-bipyridine [11] and PCV [12] have, in many cases, been seen to be effective.…”