Extraction techniques for solid samples

Extraction is normally a laboratory procedure prior to analysis. The choice of extraction technique is often made based on what is available and what has been used before. The skill and experience of the analyst is often the key to the operation of extraction and analysis procedures. Extraction of organic pollutants from solid environmental samples has frequently been done using organic solvents with or without the addition of heat. This process is typified by the technique of Soxhlet extraction. A flow diagram detailing a procedure for the extraction of analytes from soils using Soxhlet extraction is shown. Soxhlet extraction normally requires large volumes of chlorinated solvent to be refluxed through the solid sample for an extended period. Although it is not uncommon for the analyst to assemble several experimental set-ups at the same time, it can be labor-intensive at the start and end of the process. As the process is time-consuming, alternative extraction strategies have been developed based on instrumentation that allows the process to be controlled more effectively. This chapter mainly focuses on these newer instrumental approaches to compare and contrast both their application base and robustness for extraction.