ABSTRACT
SPE is the more modern of these techniques, and it is amply described in several recent books [5,6]. By means of a solid sorbent, available in many chemical and physical forms, analytes are extracted from the sample phase (normally aqueous) and subsequently eluted with an organic solvent. There are a number of ways to automate SPE in high-performance liquid chromatography (HPLC), either by using dedicated instruments, so-called SPE workstations, or by precolumn techniques [6]. The related technique of solid-phase microextraction (SPME) [7,8] is easily automated, especially in connection with gas chromatography. Some drawbacks with the SPE techniques are insufficient retention of very polar compounds, limited selectivity, and high costs associated with disposable sorbent materials. In addition, even if the amount of solvent needed for SPE is decreased compared to LLE, it might still be significant.
