A novel catalytic adsorptive stripping voltammetric method for the determination of germanium ultratraces in the presence of chloranilic acid and the V(IV)·HEDTA complex

Abstract

A novel, sensitive catalytic adsorptive stripping voltammetric procedure which can be used to determine trace amounts of germanium is described. The method is based on the interfacial accumulation of the complex formed by Ge(IV) and the product of the reduction of chloranilic acid on the hanging mercury drop electrode or the renewable silver amalgam film electrode, and its subsequent reduction from the adsorbed state followed by the catalytic action of the V(IV)·HEDTA complex. The presence of V(IV)·HEDTA greatly enhances the adsorptive stripping response of Ge. The reduction of the Ge(IV) in the presence of chloranilic acid and V(IV)·HEDTA was investigated in detail and the effects of pH, electrolyte composition, and instrumental parameters were studied. Under optimal conditions, the catalytic peak current of germanium exhibited good linearity for Ge(IV) concentrations in the range of 0.75–60 nM (for 60 s of accumulation at −0.1 V, r2 = 0.995) and a low limit of detection (LOD = 0.085 nM). The procedure was successfully applied to determine Ge in water samples.

Catalytic Adsorptive Stripping Voltammetric Determination of Germanium Employing the Oxidizing Properties of V(IV)-HEDTA Complex and Bismuth-Modified Carbon-Based Electrodes

“…The application of the V(IV)-HEDTA complex to induce catalytic reactions involving Ge(IV) is advantageous for a number of reasons. It was shown that the V(IV)-HEDTA complex is very efficient at enhancing the germanium signals both when applying mercury electrodes [ 10 , 11 , 12 ] and bismuth film electrodes plated on a variety of supports. Satisfactory results were obtained in the case of both homogeneous supports (including glassy carbon and gold coated with a bismuth layer via PVD) and heterogeneous materials (carbon fibers encapsulated in a polymer, carbon, and mesoporous carbon screen-printed electrodes).…”

“…Among voltammetric methods, catalytic adsorptive stripping voltammetry (CAdSV) plays a uniquely important role in trace analysis due to its remarkable sensitivity [5][6][7][8][9]. The CAdSV procedures that may be used for germanium determination were reviewed in our previous papers [10][11][12]. In general, the complexes that Ge(IV) forms with organic ligands in the examined solution are adsorbed on the surface of the working electrode and then they induce the catalytic reduction of certain oxidants, such as BrO 3 − [13,14], V(IV) [15], V(IV)-EDTA [16][17][18] or, most recently, V(IV)-HEDTA (HEDTA: N-(2-hydroxyethyl)-ethylene diamine N,N ,N -triacetic acid) [10][11][12].…”

“…The CAdSV procedures that may be used for germanium determination were reviewed in our previous papers [10][11][12]. In general, the complexes that Ge(IV) forms with organic ligands in the examined solution are adsorbed on the surface of the working electrode and then they induce the catalytic reduction of certain oxidants, such as BrO 3 − [13,14], V(IV) [15], V(IV)-EDTA [16][17][18] or, most recently, V(IV)-HEDTA (HEDTA: N-(2-hydroxyethyl)-ethylene diamine N,N ,N -triacetic acid) [10][11][12]. The derivatives of tri-or tetraacetic acids (HEDTA, EDTA, NTA-nitrilotriacetic acid) are not only applied in CAdSV but are also used as reagents capable to functionalize the surface of nanomaterials such as nanoparticles [19] or carbon nanotubes [20,21].…”