1 - Solid-Phase Microextraction in Perspective

Abstract

Microextraction techniques are developed to address the need for a reduction in solvent use and in the size of extraction instrumentation. These techniques are also developed to explore the ability of this approach to facilitate rapid and convenient sample preparation, both in the laboratory and for on-site applications. Microextraction systems also minimize the impact on the sampled system. There are many advantages of microextraction, which can be realized to a higher or lesser degree depending on the geometric configuration of the instrument. The use of microextraction-based strategies results in better characterization and more accurate information about the investigated system or process compared to exhaustive techniques. Non-exhaustive microextraction techniques provide signal magnitudes that are proportional to the free concentration of target analyte, defining the fraction of the analyte that is bioavailable. Although equilibrium non-exhaustive techniques are fundamentally analogous to equilibrium-exhaustive techniques, the capacity of the extraction phase is smaller and is usually insufficient to remove most of the analytes from the sample matrix. This is because a small volume of the extracting phase is being used relative to the sample volume, such as is employed in microextraction [solvent microextraction or solid-phase microextraction (SPME)] or a low sample matrix-extraction phase distribution constant, as is typically encountered in gaseous headspace techniques. SPME was developed to address the need for rapid sample preparation, both in the laboratory and at the site of the investigated system. In this technique, a small amount of extracting phase dispersed on a solid support is exposed to the sample for a well-defined period of time.