Abstract
Silver amalgam screen-printed electrodes (AgA-SPEs) were designed, prepared and tested for the first time as perspective representatives among SPEs that allow measuring at high negative potentials. For this purpose, the precise electrochemical (coulometric) preparation procedure for mercury deposition at the silver working electrode surface of the commercial silver-SPE was developed and a universal method of preparing amalgam electrodes from different metal-SPEs was described.
An optimal electrolyzer construction for the mercury deposition, electrolyte composition, electrolysis potential, and a way to activate the electrode surface for its uniform coverage by mercury were proposed. The effect of the mercury content in amalgam on the potential of hydrogen evolution (PHE) at AgA-SPEs was investigated.
The maximum PHE value (-1979 +/- 4 mV; RSD = 0.17 %; N = 5) was found on AgA-SPE with 50 % (w/w) of Hg content in 0.1 mol L-1 NaOH, which is more negative than in the case of the original silver-SPE for 387 mV (-1592 +/- 12 mV; RSD = 0.69 %; N = 5). Determination of the iodine content in iodinated table salt was used for the AgA-SPEs practical testing.
Measurement parameters were optimized for three electrochemical cell arrangements: i) the electrodes area of AgA-SPE was covered by 50 mu L of the sample solution and differential pulse voltammetric (DPV) measurements were carried out; ii) 3-electrode batch arrangement with only working electrode from AgA-SPE connected with an analyzer for DPV-measurements; iii) amperometric measurements in a flow system. The results of iodine analysis by all three methods were consistent with the manufacturer declared values.