Sample preparation for biomedical analysis.

A review of sample preparation techniques for biomedical analysis is presented. Firstly, sample preparation techniques can be divided into unit operations which can be classified into four groups: release of the analyte from the matrix, removal of endogenous material, liquid handling procedures and the enhancement of selectivity and sensitivity. The concept of unit operations gives an analyst a tool with which to evaluate critically any method for preparing a sample for analysis. Secondly, the major techniques of sample preparation (protein precipitation, liquid-liquid extraction, liquid-solid extraction and high-performance liquid chromatography, HPLC) are discussed and their advantages and disadvantages presented. Thirdly, the rationale for the automation of sample preparation is reviewed; in general liquid-solid extraction and HPLC are the best techniques for automation. The means by which this can be effected (either flexible or dedicated automation) is discussed. Finally, techniques such as supercritical fluid extraction, micellar liquid chromatography, microwave energy and immunoextraction which may be applied to biomedical sample preparation are evaluated briefly.