Normal Pulse Voltammetric Determination of Subnanomolar Concentrations of Chromium(VI) with Continuous Wavelet Transformation

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.