A simple and rapid procedure for the calibrationless determination of trace concentrations of As(III) and total As in contaminated water samples is presented. Arsenic is preconcentrated as As(III) in a flow-through cell with a gold plated porous electrode and is then stripped anodically by a constant current. The stripping chronopotentiogram is registered and evaluated. The As concentration is calculated directly from the combined Faraday's laws. The total As content was determined after converting all As species to As(III) by microwave-assisted reduction with hydrazine hydrochloride in a closed vessel. The detection limit was found to be 0.15 microg/L and the linear response range was 0.5 to 10,000 microg/L. Tap water, surface water, and waste water samples were analyzed.

Zn, Cd, Pb and Cu are deposited in a porous¯ow-through electrode plated with mercury and then are stripped by constant current while the stripping time is measured. Since complete electrochemical deposition can be achieved, the analyte concentrations can be directly obtained from Faraday's laws i.e., the method is denoted as calibrationless. The in¯uence of the deposition potential, stripping current, carrier electrolyte composition, Cu content and sample matrix was investigated. The optimum conditions are: deposition potential: À1600 mV, stripping current: 200 mA, carrier electrolyte: 0.1 molaL sodium sulfate at pH 4±5. The dynamic range of the method is from about 0.1 ngamL to few mgamL. The repeatability of the method is 1±2 % in the optimum concentration range. The procedure was applied to the analyses of water samples, geological, and biological materials.

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Determination of humic acids spectral characteristics performed fast and convenient method for their quality evaluation. Humic acids (HA) were isolated from five different soil types (Luvi-haplic Chernozem, Haplic Luvisol, Haplic Cambisol, Leptic Cambisol and Eutric Cambisol) and from compost. Basic soil characteristics were determined by commonly used methods. Fractional compositon of humus showed that humic acids content was decreasing in order: compost > Luvi-haplic Chernozem > Haplic Luvisol > Eutric Cambisol > Haplic Cambisol > Leptic Cambisol. Isolated humic acids preparations were characterized comparatively by chemical and spectroscopic methods. Elemental analysis showed the highest carbon content in Luvi-haplic Chernozem HA. The lowest carbon amount was in Eutric Cambisol. Energy–dispersive X-ray spectroscopy detected elementsin situin HA molecule. All samples contained Fe, Cu, Zn, Ti, Ca, K, S, P, Si and Br. Practically no differences in elements content between soil humic substances and compost were detected. The amount of aromatic carbon was higher in Luvi-haplic Chernozem to compare with other samples. Humic acids isolated from Cambisols, on the basis13C NMR spectroscopic data, showed that all samples contained less aromatic carbon and significantly more aliphatic carbon.