ABSTRACT
Sample preparation is the step between sampling and analysis. This is the point at which the pollutants are transferred from the environmental matrix to a form suitable for analysis. Extraction is often the first step in sample preparation. The analytes must be separated from the sample because most environmental samples cannot be directly introduced into an instrument. Extraction is done for both organic and inorganic pollutants. Some of the methods of extraction and the types of sample for which they are appropriate are shown in Figure 6.1. For example, traces of pesticides can be extracted from a large volume of water using a relatively small quantity of an organic solvent such as methylene chloride. I f the pollutants are strongly bound to the matrix, the extraction may be difficult. Many metals are strongly bound to soil and require aggressive solvents to recover them quantitatively. Organics may also be strongly attached and the solvents in this case cannot be too aggressive or the organic compounds will be destroyed. Similarly, the more soluble an organic analyte is in water, the more difficult it is to extract it into an organic solvent.
