Sample preparation of complex biological samples in the analysis of trace-level contaminants

Determination of trace-level contaminants in complex biological samples has been of increasing demand. Conventional means of this determination for matrices such as urine, blood, and milk may involve multistep sample preparations with a high probability of loss of analytes, and are mostly time-consuming. As a result, simple minimized microextraction procedures such as solid-phase microextraction, stir bar sorptive extraction, liquid-phase microextraction, and electromembrane extraction, which are mostly carried out in one or two steps, are preferred. Recently a number of tailored solid-phase extraction and molecularly imprinted polymer extraction procedures for nonviscous biological liquid samples have been reported. However, for animal tissues and other solid, semisolid, and highly viscous samples, extraction methods may encounter greater difficulties than those for conventional liquid samples. Consequently the preferred sample preparations are simple, step-minimized methods such as pressurized liquid extraction, supercritical fluid extraction and the like. The main advantages of these modern techniques are that they can be customized for simultaneous extraction and cleanup. To date, these techniques have been successfully applied as sample preparation and preconcentration steps in the determination of various analytes of toxicological importance in different biological matrices.