Fundamentals, methods and future trends of environmental microwave sample preparation

Microwave (MW) sample preparation has nowadays become a standard analytical tool. A large section of MW systems, such as open vessel and low to high pressure closed vessel device, are used. Theoretical and practical considerations in the development as well as implementation of MW sample preparation are presented, including methods for total implementation of MW sample preparation are presented, including methods for total decomposition and leaching of trace elements in common environmental samples, such as soil, sludge, sediments, oils, biological materials, water and waste water. In particular, the US Environmental Protection Agency Office of Solid Waste methods 3050B, 3051, 3052 are discussed. Supporting reference data and documentation are presented to demonstrate specific alternative capabilities. As a natural extension of this technique, MW-based devices were more recently used to heat solvents and sample matrices as a preparation tool for extraction of organic compounds. Since 1986 analysts have been using MW heating to extract various compounds from a variety of sample matrices. Information is provided about the development of an integrated MW solvent extraction technique and its capabilities, as well as perspective for extraction applications. The ASTM method D5765-95 on solvent extraction of TPH from soils and sediment as well as the draft of a new US EPA for Volatile Organic Compounds (VOCs) and Semi-Volatile Organic Compounds (SVOCs) from environmental samples are presented. The potential benefits are analogous to those achieved by sample decomposition, i.e. reduced reaction/extraction time, improved efficiency, reduced solvent consumption and better working environment. (C) 2000 Elsevier Science B.V. All rights reserved.