Selection of Optimal Ligand and Vanadium(IV) Complexonate for Sensitive Catalytic Adsorptive Stripping Voltammetric Quantification of Germanium

Abstract

The study describes the properties of catalytic adsorptive stripping voltammetric (CAdSV) systems based on complexes of Ge(IV) with gallic acid, catechol or pyrogallol as well as vanadium complexes with complexones such as NTA, DHPTA, EDTA, and HED-TA, used as catalytic agents. The most pronounced CAdSV response was observed when the Ge(IV)-pyrogal-lol complex was coupled with V(IV)-HEDTA. In 0.05 M of acetate buffer containing 1 mM of pyrogallol, 2 mM of V(IV) and 4 mM of HEDTA, the peak current of germanium exhibited good linearity for Ge(IV) concentrations over the range from 0.25 nM to 25 nM and a low limit of detection (LOD = 0.02 nM). The method was verified by measuring Ge(IV) in real 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].…”