Advances in the Hyphenation of Flow Analysis Techniques with Liquid Separations for Pharmaceutical Analysis

This commentary critically discusses the main advances in the field of flow analysis techniques hyphenated with liquid separations for pharmaceutical analysis over the last 15 years. Flow analysis techniques provide a convenient way to perform chemical assays with significant benefits in terms of rapidity, simplicity and cost of instrumentation, economy, precision, versatility in sample handling and potential for automation. The first-generation flow injection analysis (FIA), developed in the 1970’s, has been supplemented by a host of second-generation and third-generation flow methods developed in the 1990’s and 2000’s such as sequential injection analysis (SIA) and multi-syringe flow injection analysis (MSFIA) [1]. However, the main drawback of these techniques is their limited ability to simultaneously determine several analytes. Therefore, the hyphenation of flow techniques with separation techniques is a very attractive because it enables multi-component analysis. It was the introduction of monolithic columns [2] that has made possible the direct coupling of flow techniques with liquid separations platforms and has led to the development of hyphenated approaches such as FIC, SIC and MSC [3-5]. In all these techniques, a separation column is inserted in the flow path between the point of sample introduction and the detector; the main principles of operation can be found in the relevant literature [3-7]. FIC, SIC and MSC offer distinct advantages in terms of rapidity, simplicity, versatility and capital costs compared with high performance liquid chromatography (HPLC) and have been applied to the determination of a large number of pharmaceuticals [3-5]. When simple mixtures are considered, these hyphenated methods produce results that are comparable to HPLC [8,9]. The main advances in the hyphenation of flow analysis techniques with liquid separations for the purposes of pharmaceutical analysis are identified below.