Comparison of the Gold Reduction and Stripping Processes at Platinum, Rhodium, Iridium, Gold and Glassy Carbon Micro- and Macrodisk Electrodes

Abstract

The gold AuIII + 3e(-)-->Au0 reduction and Au0-->AuIII + 3e- oxidation stripping processes in dilute aqua regia electrolyte (0.1 M HCl + 0.32 M HNO3) were examined at platinum, rhodium, iridium, gold and glassy carbon disk electrodes. After ascertaining that the preferred material was platinum, the effect of electrode size was evaluated by using nine different platinum disk electrodes having diameters ranging from 2 to 2000 microns. The optimum analytical response was obtained with a 50 microns diameter platinum disk electrode. With this electrode diameter, a sharp symmetrical gold stripping peak was obtained and the deposition process occurred predominantly under conditions of radial diffusion so that stirring of the solution was not required. In contrast, larger sized platinum electrodes produced a broader, asymmetric stripping response for the gold oxidation peak, whereas electrodes of smaller diameter provided poorer signal-to-noise ratios. The limit of detection and limit of quantification were calculated to be 4.4 x 10(-7) M (86 ppb) and 13.1 x 10(-7) M (258 ppb), respectively, at the 50 microns diameter platinum disk electrode under conditions of linear sweep stripping voltammetry at a scan rate of 200 mV s-1 and a 140 s deposition time. The optimum electrode gave a very well defined gold oxidation signal with negligible background current when applied to the determination of gold in a gold ore sample.

Voltammetric and EQCM Studies on Selenium(IV) at Mercury, Gold and Glassy Carbon Electrodes in the Presence of Cu(II), Au(III), Pb(II) and Cd(II)

“…These elements could be determined only after the glassy carbon electrode had been gold-plated [20]. Gold alone has been determined at the platinum electrode [21]. However, the copious deposition of Se-Au examined by the EQCM technique on the gold electrode inclined us to use quantitative voltammetry with a mixture of these elements at the glassy carbon electrode.…”

Reduction of Tetrachloroaurate(III) at Boron-Doped Diamond Electrodes: Gold Deposition Versus Gold Colloid Formation

“…Gold analysis is required in mining processes [22] and for gold recovery from electronic components. A wide range of electrode materials [23,24] and sizes [25] has been studied for gold detection.…”

Screen-printed carbon electrode modified with poly-L-histidine applied to gold(III) determination

“…This peak current can be attributed to the reduction of gold(III) species to gold(I). 17,19,33 The response on the screen-printed carbon electrode coated with poly-L-histidine (SPCE/PH) film is essentially the same. However, there is an increase in the peak intensity for both experiments (curve b), while a bigger increase is observed in the chloride medium.…”

“…Because the levels of gold in the body fluids of patients receiving treatments are usually < 5 µg mL -1 , analytical methods for determinations of total gold and of intact drugs and their metabolites have required detectors which are sensitive to very low concentrations of gold. Literature [14][15][16][17][18][19] has shown that both gold(III) and gold(I) can be determined by electrochemical analysis, in general using chemically modified electrodes under stripping analysis conditions. The main problem with electrochemical stripping analysis of gold(III) is finding a working electrode onto which gold can be deposited for subsequent stripping.…”

“…In order to improve the efficiency of gold deposition onto a carbon electrode, co-deposition with other metals and activation of the electrode with small amounts of gold have been reported. 15,16 Bond et al 17 have studied the electrochemistry of gold in dilute aqua regia at Pt, Rh, Ir and Au and C microdisk electrodes. The best results were obtained with a 50 mm diameter Pt disk, which offered a detection limit of 4.4 × 10 -7 mol L -1 (140 s deposition) by anodic stripping voltammetry.…”