Implementation of Tube Radial Distribution Chromatography by Using a Commercially Available HPLC System

Tube radial distribution chromatography based on tube radial distribution flow, or annular flow, in an open-tubular capillary has been reported. The chromatographic system requires specific instruments and treatments for microfluidic flow in the capillary tube. In this study, we have developed a new model of tube radial distribution chromatography, which is comprised of a commercially available HPLC system without any packed separation columns. Separation is performed in an open-tubular pipe (100-μm inner diameter and 350-cm length; temperature, 5°C) connected between the pump and the detector in the HPLC system. An analyte solution is introduced with a sample injector (2-μL volume) and a ternary water/acetonitrile/ethyl acetate mixed solution (volume ratio of 3:8:2) is delivered as an eluent solution into the pipe at a flow rate of 10-μL min−1. Fused silica and stainless pipes can separate 1-naphthol and 2,6-naphthalenedisulfonic acid, but a polyetheretherketone pipe cannot. The obtained data provides an important clue to practical developments in separation science.