Chapter 14 On-line sample preparation: High throughput techniques and strategies for method development

Abstract This chapter introduces some of the most popular and proven on-line sample preparation techniques used for pharmaceutical bioanalysis. While the conventional procedures are performed off-line in discrete steps before the analysis, on-line techniques combine the sample preparation and analysis steps into one integral process. The key component among the numerous formats of on-line sample preparation methods is a specially made extraction column. It is generally the characteristic nature of the extraction column that distinguishes one method from the other. Four types of extraction columns to be discussed in this chapter are: turbulent flow, restricted access media (RAM), monolithic and immunoaffmity. An additional column can be utilized after the extraction column to provide enhanced separation of components. Column switching is used to activate this separation function. Techniques and applications for turbulent flow, restricted access media and immunoaffmity columns will be discussed. On-line solid-phase extraction in a single use, disposable cartridge will also be discussed; an analytical column follows the extraction cartridge for additional separation. Comparisons of these different on-line choices will be made, as well as traditional off-line techniques for sample preparation. Strategies for method development will be introduced with the focus on the use of turbulent flow chromatography and disposable solid-phase extraction cartridges. Method optimization and troubleshooting of on-line methods are also presented.