This work describes a novel working electrode - the renewable glassy carbon annular band electrode (R-GC-ABE). The strategy to create the R-GC-ABE is based on the mechanical removal of solid and gas contaminants and electrochemical activation in the electrolyte which fills the electrode body. The main constituents of the R-GC-ABE: a specially constructed glassy carbon annular band electrode, a silver wire used as silver counter/quasi-reference electrode and a silicon O-ring are fastened together in a polypropylene body.The R-GC-ABE was constructed and evaluated as a sensor for determination of paracetamol (PAR) by differential pulse (DP) and normal pulse (NP) voltammetry. Also a signal processing algorithm which utilizes continuous wavelet transform was described and applied for transformation of the sigmoidal-shaped NPV signals - to the peak-shaped curves.In the effect, the new strategy of PAR determination is 32 times more sensitive than DPV technique. The repeatability is below 2-3% (n=3) for the 0-50 mg L-1 concentration range of PAR. The detection limit is 4 mu g L-1 with sensitivity of 2.75 +/- 0.04 mu A/mg L-1. The correlation coefficient is equal to 0.9990.The proposed method was successfully applied for determination of PAR in commercial tablets and in spiked human urine (CRM). The obtained results show substantial improvement of the performance of R-GC-ABE electrode and NPV technique. (C) 2013 Elsevier Ltd. All rights reserved.

The renewable mercury film-modified silver solid amalgam annular band electrode (MF-AgSAE) applied for quantitative determination of sub-nanomolar concentrations of Cr(VI) using differential pulse (DP) and normal pulse (NP) catalytic adsorptive striping voltammetry (CAdSV) is presented. In this context a signal processing algorithm is described and applied for the transformation of sigmoidal shaped NP curves to peak shaped curves. The method utilizes continuous wavelet transform (CWT) and a specially constructed mother wavelet defined using the ideal wave-shaped curve. It simplifies the interpretation of sigmoidal curves. In the effect the new strategy of Cr(VI) determination is 10 times more sensitive than differential pulse and square-wave techniques. The reproducibility is below 35?% (n=3) for the 0.22.2 nM concentration range of Cr(VI). The detection limit for 30 s preconcentration is equal to 0.05 nM with sensitivity of 0.809 +/- 0.012 mu A nM(-1) and is limited by the purity of the used reagents. The correlation coefficient is equal to 0.9993. For 2 nM of Cr(VI), in the tested range, 0 <= t(acc) <= 60 s, the relation wave height?accumulation time (I(w)t(acc)) is linear. The operation and effectiveness of the proposed procedures was confirmed by the quantitative determination of Cr(VI) in supporting electrolyte and CRM (surface water samples and urine) with known amounts of the analyte. The obtained results show substantial improvement of the performance of NP CAdSV technique.

The renewable mercury film electrode, applied for the determination of tungsten(VI) ultra traces using differential pulse catalytic adsorptive cathodic stripping voltammetry (DP CAdSV) with presence of catechol as a ligand and chlorate(V) is presented. The calibration graph obtained for W(VI) is linear from 0.025 nM (4.5 ng L−1) to 130 nM (23.9 μg L−1) for a preconcentration time of 30 s, with correlation coefficient of 0.9989. For the renewable mercury electrode (Hg(Ag)FE) with a surface area of 4.4 mm2 the detection limit for a preconcentration time of 60 s is as low as 0.2 ng L−1. The repeatability of the method at a concentration level of the analyte as low as 0.09 μg L−1, expressed as RSD is 3.1% (n = 5). The proposed method was successfully applied and validated by studying the certified reference material CTA-VTL-2 and simultaneously recovery of W(VI) from spiked water samples.