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  • 1
    Electronic Resource
    Electronic Resource
    A high-speed computerized polarographic system for cathodic stripping voltammetry in seawater (1994)
    Weinheim : Wiley-Blackwell
    Electroanalysis 6 (1994), S. 1141-1146 
    Details
    ISSN: 1040-0397
    Keywords: Stripping voltammetry ; Computer control ; Seawater ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A low-cost computer-controlled high-speed polarographic system has been devised to determine heavy metals in seawater using adsorptive stripping voltammetry. The system consists of a potentiostat that has been developed in our Department, a 303A PAR polarographic cell, a personal computer with an I/O digital board PIO-96, and a hp7440 plotter. The potentiostat operates between -2.5 and +2.5 V, with a multirange selection current between ±100 nA and ±1000 μA. There are various outlet channels with different time constants and noise levels. The quickest channel can detect processes in a 10 μs range with a noise level of ±4 nA (seawater matrix), while for a range of 30 ms, the noise is ±100 pA. The software controls different signal patterns, techniques, and a complete set of operations and has been developed in the C language to accelerate the data acquisition. The system has been successfully applied to high-speed cathodic stripping voltammetry (HSCSV) on seawater samples, showing promising results in that there is an increase in the sensitivity over standard methods in the presence of oxygen and in stirred solutions. The analysis time can be reduced significantly at a high speed, and also, determinations aboard a ship are improved.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140061138
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  • 2
    Electronic Resource
    Electronic Resource
    High-Performance adsorptive cathodic stripping voltammetry of nickel and cobalt in seawater (1994)
    Weinheim : Wiley-Blackwell
    Electroanalysis 6 (1994), S. 1069-1076 
    Details
    ISSN: 1040-0397
    Keywords: Nickel ; Cobalt ; Stripping voltammetry ; Seawater ; Staircase modulation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The voltammetric determination of trace metals in seawater suffers from the interference of dissolved oxygen and engine vibrations onboard ship. It is here attempted to overcome these interferences using a high-frequency (1 to 20 kHz) staircase modulation during the voltammetric scan (high-performance adsorptive cathodic stripping voltammetry, HPACSV). Comparative experiments using the square-wave modulation showed that this modulation was not effective at such a high frequency. A comparison between various complexing agents (DMG and nioxime) and pH buffers (HEPES/NH4OH, borate/NaOH, and TEA/NH4OH) showed that the determination of nickel and cobalt was similarly improved by the high-speed potential scan in all conditions. Fast potential scans cause a large increase of the peak area and peak heights using staircase modulation. The peaks are wider, and the peak potentials are shifted toward negative values due to the ohmic drop, but the analytical determination is not disturbed. Optimal sensitivity for the determination of cobalt and nickel in seawater was obtained using TEA buffer and DMG as the adsorptive ligand. The nioxime wave was found to interfere in the cobalt peak at high scan rates so that this ligand is not recommended for HPACSV. Comparative tests showed that the sensitivity for nickel and cobalt determinations was highly improved by the fast scan rates. Furthermore, the reduction current of dissolved oxygen was partially masked so that measurements could be taken without a previous purge of the sample. Finally, the scans were insensitive to the solution turbulence so measurements could be readily carried out onboard of an oceanographic vessel or without switching off the stirrer. Low levels of nickel (2 nM) could be determined in seawater by using a deposition time of 20 seconds and of 120 seconds for 0.05 nM cobalt from turbulent and unpurged solutions. A fast determination method for labile nickel and cobalt is proposed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140061126
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