Microwave-assisted flow digestion systems open up newpossibilities in fully automated sample preparation for element analysis. For an extensive and fast oxidation of organic materials with nitric acid, temperatures of more than 200 °C are necessary. To achieve the desired temperatures of ∼250 °C, it is essential that the pressure in the system can be increased up to 35 bar. The teflon tubes used, however, do not withstand the vapor pressure of the digestion mixture at these temperature levels. A high-pressure flow digestion device is described that enables the application of such high temperatures by means of a novel pressure equilibration system. PTFE or PFA tubes can be used up to 250 °C if no mechanical stress is applied to the tube wall. The pressure equilibration system keeps the pressure inside and outside the digestion tube equal even for extremely fast oxidation reactions. The digestion of easy, medium, and difficult oxidizable substances (glucose, glycine, and phenylalanine, respectively) shows the importance of digestion temperatures around 250 °C. The extremely violent digestion of glucose with concentrated nitric acid can be carried out as easy as the difficult oxidation of phenylalanine by means of this system. The SRM TORT 2 (defatted lobster hepatopancreas tissue) was digested under different conditions to indicate the high oxidation capabilities in comparison with a commercial mediumpressure flow digestion device. The analysis of the SRMs milk powder (BCR 063, BCR 151), bovine liver (BCR185), and pig kidney (BCR 186) after digestion at 245 °C and 5 min showed good agreement with the certified values.

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Automated preconcentration techniques for off/on-line determination with ICP-OES have been developed for various metal ions of environmental interest. Preconcentration studies were performed on two different types of chemically bonded chelating ion-exchangers, namely EDTrA-cellulose (iminoacetate groups) and HSO 3 9 oxine-cellulose. Enrichment studies were carried out at various preconcentration factors and also at different loadings.Inductively coupled plasma emission spectroscopy has been widely used in determination of trace elements in environmental samples. Although the method is very sensitive, it sometimes poses problems on direct determination at detection limits and also in presence of large amounts of interfering matrix constituents. Preconcentration techniques combined with ICP-OES either off-[1, 2] or on-line [-3, 4], are found to be useful in solving these complex analytical problems. These methods provide high enrichment factors and lower detection limits by selective extraction of metals of interest from the complex matrix. As the sample throughput with ICP-OES is fairly high for multi-element analysis, it therefore demands faster sample preparation procedures. Hence the need of an automated preconcentration apparatus is justified. It not only helps in reducing the time, but also the closed system for sample handling makes it contamination-free. Additionally, on coupling it directly to a simultaneous ICP-AE [3,4] or flame AA [-5, 6] spectrometer and integrating the transient elution peak, detection limits can be lowered by an order of magnitude. Also these on-line methods require lesser volumes for enrichment as compared to manual off-line ones.

New TaC coated platforms have been tested as atomisation surfaces for ETA-AAS. The aim of this study was t o investigate the behaviour of these platforms towards common interferents, compared with those of standard total pyrolytic graphite platforms. A fractional factorial design was applied t o determine the interferences and potential interactions between interferents. The analytes studied were Sn, Se and Rh, the interfering cations were Cr, Fe, Na, Mg, Zn and At. Although no increase in analytical performance was found for Sn or Rh, sensitivity to interferences could be considerably decreased for Se.

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