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The utility of the cylindrical silver-based mercury film electrode of prolonged analytical application in stripping chronopotentiometry (SCP) was examined. This electrode allowed us to obtain good reproducibility of results owing to the special electrode design, which enables regeneration of the thin layer before each measurement cycle. The accessible potential window in KNO 3 (pH 2), acetate and ammonia buffers was defined, and the optimal conditions (i.e., stripping current, deposition potential and deposition time) for the determination of Cd and Pb traces were selected. The detection limits, obtained for an accumulation time of 60 s, were 0.023 mg/L for Cd and 0.075 mg/L for Pb. The response increases linearly with Cd, Pb and Zn concentration, up to at least 100 mg/L. It was also shown that the proposed procedure ensures excellent separation of the In and Tl, Pb and Tl or the In and Cd signals. The method was tested with dolomite and lake sediment samples, and good agreement with reference values was achieved. The obtained results showed good reproducibility (RSD ¼ 5 -6%) and reliability.

The paper features a description of a sensitive adsorptive stripping voltammetric protocol for the palladium(II) determination in the presence of dimethylglyoxime (DMG) at an amalgam film electrode (Hg(Ag)FE) of prolonged analytical applicability. The procedure is based on the adsorptive preconcentration of the Pd(II)-dimethylglyoxime complex onto the (Hg(Ag)FE) at À 0.45 V, followed by a negatively going square-wave voltammetric scan. Factors affecting the stripping performance, such as the composition of the supporting electrolyte, including different ligands, DMG concentration, pH, potential and time of preconcentration, and SW frequency have been investigated and optimized. The optimized procedure yields favorable and highly stable stripping responses with good precision (RSD ¼ 3% for a Pd concentration of 2 mg/L), low detection limit (0.15 mg/L Pd(II)), and good linearity (from 1.0 mg/L up to 50 mg/L, R 2 ¼ 0.998) with a deposition time of 60 s. Possible interferences from coexisting ions and surface active substances were studied.

In the present paper, catalytic adsorptive stripping voltammetry (CAdSV) has been applied for the first time in a chromium speciation study conducted in pore sediments and overlying waters containing Cr(VI) in the presence of a great excess of Cr(III) and organic matter. The method is based on the adsorptive accumulation of the active Cr(III)-DTPA (diethylenetriammine-N,N,N 0 ,N 00 ,N 00 -pentaacetic acid) complex, which is formed instantaneously on the electrode surface as a result of Cr(VI) reduction to Cr(III), its complexation with DTPA, reduction to Cr(II)-DTPA, and its catalytic oxidation to Cr(III)-DTPA with nitrate. The main efforts were focused on the elimination of the influence of dissolved organic matter including organic surface-active substances (SAS) that adsorb at the electrode surface, and disturb the Cr(VI) determination or, in extreme cases, make it impossible. Of the three procedures applied for the elimination of this negative effect caused, namely, the matrix-exchange method, the removal of SAS by means of fumed silica, and their adsorption on the XAD-7 Amberlite resin present directly in voltammetric vessel, the last one proved to be the most useful. The matrix-exchange procedure also provides accurate and precise results but requires more reagents and time. The CAdSV method combined with the adsorption of surface-active substances on the XAD-7 Amberlite resin was successfully applied for the determination of the Cr(VI) in vertical profile in sediments from Dunajec River, which are severely polluted with chromium from tannery wastes.

The paper reports on the application of stripping chronopotentiometry for the determination of chromium(VI) at a silver-based amalgam film electrode. It is the first attempt to apply such a detection system for the speciation of chromium. The procedure utilized catalytic reduction of nitrate ions induced by the instantaneous chromium(III)-DTPA complex, accumulated at the electrode surface. The chronopotentiometric step is realized in the constant current mode. Several key parameters, such as the deposition potential, deposition time, nitrate concentration and stripping current were optimized. The detection limit obtained for 15 s of accumulation time was estimated at 0.025 mg/L. The repeatability of the signal was 6.1 %.Keywords: Silver-based amalgam film electrode, Catalytic adsorptive stripping chronopotentiometry, Chromium(VI), River water DOI: 10.1002/elan.201100237 Stripping chronopotentiometric analysis (SCP) is a valuable alternative to stripping voltammetry; it is, however, far less popular and utilized in analytical practice. The SCP technique, as in the case of stripping voltammetry, involves two steps, i.e. potentiostatic pre-concentration followed by stripping accompanied by oxidation, reduction or desorption of the pre-concentrated analyte [1]. During the latter step, two different stripping mechanisms can be exploited: chemical oxidation/reduction caused by the oxidant/reductant present in the solution, or oxidation/reduction by means of constant current (CC-SCP). The application of the constant-current approach ensures more standardized conditions and better control of the stripping process. During the course of the second step, the potential of the working electrode varies with time, and the potential-time curve is usually recorded and then transformed into the dt/dE vs. E form. Since it has been proved empirically that SCP is less sensitive to the presence of relatively high concentrations of organic matter, this technique found its application as an alternative to non-electrochemical techniques (e.g. GFAAS, ICP-OES) in the determination of total metal concentration in food or beverage samples [2,3]. Depending on the working electrode applied, the mechanism of analyte accumulation may vary. The utilization of electrodes based on mercury enables the accumulation of some heavy metals via their amalgam formation [4] in the anodic version of SCP.The second approach utilizes the deposition of analyte in the form of complexes adsorbed on the electrode surface. Usually, these complexes are subsequently reduced with the negative stripping current.In SCP various types of electrodes have been used, such as: glassy carbon electrodes [5], gold electrode [6,7], carbon fiber [8], carbon paste electrode [9, 10], bismuth or antimony plated film electrodes [11][12][13] and screenprinted carbon-ink electrodes [14]. The electrodes used most frequently are the mercury-based electrodes [15][16][17][18]. Their excellent analytical performance and their advantages are obvious. However, liquid mercury electro...