15 Zusammenfassung Within this work an online data acquisition and process control software (DART) had been designed first. This programme enables the user to define, record and evaluate measurements by different apparatus in a uniform way.
To begin with the automation of inverse voltammetry was realized by an analogous system. Up to three polarographic analyzers were used simultaneously for the inverse voltammetric determination of heavy metals.
Even though an increase of precision of the inverse voltammetric measurements could be obtained by progressive automation and improvements of the autosampler control, limits are set to the analogous experimental setup of the simultaneous determination of heavy metals in biological samples. For the further development of the fully automated voltammetry therefore equipments with digital interfaces of different manufacturers were combined for the first time in a data acquisition programme.
By transferring individual device adjustments (dilution and cleansing operations) of the predefined series of measurements to the autosampler and because of an measuring instrument with autoranging, sample solutions with greatly different elementary contents could be measured.
The improvement of the setup and measuring methods as well as a combination of the evaluation with implemented statistical processes led to a successful application of this voltammetric system for large series of measurements. This could be proved by the successful determination of trace and ultratrace amounts of heavy metals in sea water and arctic samples, which were limited by blank amounts and not by limits of detection.
For the determination of Zn, Cd, Pb and Cu in food and biological materials a suitable digestion procedure had to be adapted to the voltammetric requirements first. Therefore an UV digestion apparatus was constructed in order to remove by UV photolysis the interfering organic materials which remained after pressure digestion.
The examination of this combined digestion procedure by voltammetric analysis of various biological standard reference materials shows a good recovery with high precision. Because of the qualitiy of the digestion method it was not possible to determine Cd in biological materials with an amount less than 0,03 µg/g. Due to organic residues the determination of Cu was interfered. With regard to Zn and Pb contaminations further steps were taken in order to reduce the risks of contamination. The materials and working procedures required for the sample pretreatment were adapted to the analysis` scheme and the limit of detection under clean bench conditions.
Due to the application and improvement of a combined pressurized microwave digestion and evapuration procedure, the quality of the digestion procedure could be considerably increased and the time consumption was minimized. The determination of Ni and Co in food was only possible by using this digestion procedure.
With this procedure a 2-fold excess of the regulated values of Cd and Pb can be detected reliably in the used animal and vegetable food.
The determination of heavy metals in liver samples from breams caught in the river Elbe led to comparable results concerning the elementary contents of Cd, Cu and Zn when using voltammetry and different atomic spectrometrical methods. Concerning the voltammetrical determination of Pb it was clear to see that small amounts of organic residues led to a lower recovery.
Within this work it could be shown that the voltammetry can be used in fully automatic operation with high detection sensitivity in the ultra trace analysis. The further developped microwave induced digestion and evapurating method (MWE) can be used for food and biological materials. Thus the samples for the voltammetric measurements can be prepared within one day and measured over night in large series of measurements. For the examined heavy metals the time consumption is comparable with the atomic spectrometrical methods. The high detection sensitivity and the low operating costs are extremely advantageous for the voltammetry.
The developped data acquisition and process control system DART was also used for the analysis of polychlorinated biphenyls through capillary gas chromatography in biological samples (AK Steinhart, Univ. Hamburg) and for the fully automated data acquisition and process control of several ion-chromatographs for the determination of anions in routine analysis (AK Dannecker, Univ. Hamburg).
Moreover the system was further developped for some projects and used e.g. as stand-alone-system in a rain collector (ATMOMAR-Projekt, AK Dannecker, Univ. Hamburg) or for the psycho-physiological examination of the effect of skeleton- muscular activity on the breathing resistance (Psychological Inst. III, Univ. Hamburg).
The described fully automated voltammetric analysis system is used by AGFA-Gevaert (Bayer AG, Werk Leverkusen) in routine analysis.