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A sensitive, simple and fast adsorptive stripping voltammetric procedure for trace determination of cadmium in natural samples containing high concentrations of surface active substances and humic substances has been developed. The method is based on adsorptive accumulation of the Cd(II)-cupferron complex onto a hanging mercury drop electrode, followed by the reduction of the adsorbed species by a voltammetric scan using differential pulse modulation. The detection limit was 3 10 À10 mol L À1 (33.6 ng L À1) with an accumulation time 30 s. The procedure was applied to the determination of Cd(II) in natural water samples without any pre-treatment with satisfactory results.Keywords: Cadmium, Determination, Adsorptive stripping voltammetry, Natural water, Organic matrix DOI: 10.1002/elan.201100357One of heavy metals of considerable environmental and occupational concern is cadmium [1]. Cadmium compounds are classified as human carcinogens by several regulatory agencies [2][3][4][5].Since the concentration of cadmium is extremely low in various natural samples, a sufficiently sensitive procedure for its reliable determination would be of great interest. Electroanalytical techniques such as stripping voltammetry are considered as powerful tools for trace metal determination [6,7]. The most widely used stripping voltammetric mode for determination of Cd(II) is an anodic stripping voltammetry (ASV) [8][9][10][11][12][13][14][15][16][17][18]. An alternative method for the determination of cadmium is based on adsorptive rather than electrolytic accumulation. Primary predominance of adsorptive stripping voltammetry (AdSV) over ASV is a potentiality to obtain lower limit detection. Only several procedures within the last 15 years have been reported for the determination of cadmium by AdSV using different complexing agents [19][20][21][22][23][24][25][26].This paper describes a novel adsorptive stripping voltammetric procedure for the determination of traces of cadmium in natural water in the presence of cupferron as a complexing ligand. Cupferron is a commonly used organic compound which can form stable complexes with many metal elements [27-31]. As it was proved in the paper [32], cupferron also forms a stable electrochemical active complex with Cd(II), but has never been used for voltammetric determination of cadmium so far.The AdSV is a very sensitive technique notably influenced by variables such as time and potential deposition, the concentration of the complexing agent (cupferron) and the pH value. Therefore, optimization of these parameters was performed.An acetate buffer was used as a supporting electrolyte and the influence of pH of supporting electrolyte on the stripping peak current of cadmium was studied in the range from 4 to 7. The experiments were performed using Procedure B (see Experimental). In acidic solution at a pH equal to 4 the peak was not observed. Next the peak current of cadmium increased as the pH of the buffer increased to 5.2 and then was almost stable up to pH 6.5.The effect of the cupf...

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A modification of the voltammetric procedure for the determination of uranium in the presence of cupferron using hanging mercury drop electrode is presented. The pulsed potential accumulation was proposed for the minimization of interferences of surface active substances. The calibration plot for U(VI) in the presence of 2 ppm Tritonu X-100 was linear from 1.7 10 À10 to 2.0 10 À8 mol L À1 for an accumulation time of 60 s, with correlation coefficient of 0.996. The application of this method was tested in the determination of uranium in certified reference material NASS-5 and river water samples.

The level of MT immunoreactivity found in the fibroblasts and macrophages within the tumor microenvironment seems to be indicative of the intensity of the remodeled cervical tumor microenvironment, and this in turn may be related to the local advancement of the disease. Moreover, it appears that the intensity of the metallothionein immunoreactivity in the immunoreactivity profile of the cervical tumor may be linked to both the depth of the local invasion and the extent of the distant advancement of the disease.

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The application of cupferron as a complexing agent for a simultaneous voltammetric determination of U(VI) and Cd(II) in a single scan in environmental water samples has been developed. Optimal conditions were found to be: 0.05 mol L−1 acetate buffer (pH 5.3) as a supporting electrolyte, 1×10−3 mol L−1 cupferron, the accumulation potential −0.25 V, the accumulation time 30 s. The linear range of uranium(VI) and cadmium(II) were observed over the concentration range from 1×10−8 mol L−1 to 5×10−7 mol L−1 and from 2.5×10−9 mol L−1 to 2×10−7 mol L−1, respectively. The procedure was applied to the determination in natural water samples.