Sample preparation, also termed pretreatment or clean up, is a pivotal step in analytical method development for pharmaceuticals, illicit drugs, food/flavor constituents, nutritional materials, environmental pollutants and agricultural products such as pesticides, herbicides, and insecticides. The scope of sample preparation is not restricted to these areas of chemical analysis, and can extend to a wide range of other fields of applicability such as synthetic chemistry, diagnostics and purification of biotechnological products. In the arena of pharmaceutical analysis, chromatography in general, and reversed phase high performance liquid chromatography (RP-HPLC) in particular, are extensively used for analyzing samples. Electrophoretic techniques have also gained recognition as viable analytical tools. In this context, sample preparation ideally provides a reproducible and homogeneous solution for injection into an analytical instrument such as a chromatography column. Ideally, sample preparation also serves to furnish a sample aliquot relatively free from interferences, prevents column damage, and is compatible with the intended analysis method. The precision and accuracy of the analysis method are frequently determined by the sample preparation procedure.