Method and Instrumentation for High-Temperature, Microwave-Assisted, Photochemical Reaction - Application to UV Degradation of Organic Materials

In recent years technological progress has greatly contributed to further development and optimization of analytical instrumentation, followed by considerable improvements of sensitivity, accuracy, and precision in trace element analysis. Rewarding to the modern instrumentation present-day analytical techniques are capable of detecting extremely small quantities of trace elements in biosphere. Analysis techniques commonly used as routine tools offer outstanding sensitivity on the other hand they are rather sensible to many interfering matrix constituents present in a real type sample. Therefore, especially in trace analysis appropriate sample preparation is of immense importance. To guarantee an accurate analysis in most cases separation or decomposition of interfering compounds is inevitable, e.g.; the determination of heavy metals from a wide range of Environmental sample matrices by electrochemical- or spectroanalytical techniques is strongly interfered by dissolved and dispersed organic matter, respectively. Direct determination of metal concentrations from many natural, liquid samples (e.g.; industrial/municipal waste, ground, and surface waters; body fluids; infusions; beverages) is only possible in exceptional cases. Usually, an acid digestion is performed prior to analysis to decompose interfering matrix compounds. However, a minimum reaction temperature of 300C is required for complete mineralization of heavily polluted liquid samples or solid samples predominately consisting of organic matter. The photochemical process of UV oxidation represents a promising alternative for the decomposition of organic matter in liquid samples. This technique uses the synergistic action of UV light in combination with a chemical oxidizer to mineralize the interfering organic compounds converting it almost completely to CO 2 H2 O, and inorganic salts. Advantageous is mainly the low acid demand, followed by the elimination of a potential source of contamination and an improvement of the detection limit. Until now, UV instrumentation especially developed for the purpose of sample preparation is only capable to decompose sample matrices of low organic content due to the limited maximum reaction temperatures of 65-90C. This project attempts to establish for the first time a high-temperature UV digestion device. The system will be based on a common, high-pressure, microwave-assisted digestion device. Main concern will be paid to the development of appropriate electrodeless discharge lamps operated by the oscillating microwave field distributed within the oven cavity. In contrary to already available systems separate UV sources will be applied as immersion lamps inside each of the closed digestion vessels. Consequently, maximum reaction temperature may be raised up to 250C, resulting in considerably increased degradation rates.