Geometrically deformed tubes as efficient vessels for post-column derivatization in high-performance liquid chromatography

The technology of optimal geometrically deformed tubes (“knitted tubes”) for post-column derivatization in high-performance liquid chromatography is described. The three-dimensional wave shape induces a controlled Dean's flow that results in a volumetric dispersion that is very small and practically independent of the flow rate for the practical range of solvents and analytes. The three-dimensional wave consists of upward and downward turns that are offset from each other by 90° to 120°. Such a shape is commonly created by “knitting” or “weaving” Teflon® tubing. The strongly reduced dispersion compared to straight tubes or simple coils has made this type of device most popular in post-column derivatization. The hydrodynamics of these devices have only been studied from the standpoint of the result. It is hoped that this publication will encourage further studies that achieve a deeper understanding of the underlying fluid flow.