A tube radial distribution chromatography (TRDC) system has been developed using an open capillary tube and an aqueous–organic solvent mixture as a carrier solution under laminar flow conditions. In this study, we examine the elution behavior of carboxylated polymer particles (1.0 μm diameter) together with fluorescein isothiocyanate in the TRDC system in order to extend our knowledge regarding the separation performance of the system. The model analyte solution of fluorescein isothiocyanate and carboxylated polymer particles was injected into the open polyethylene capillary tube by the gravity method, and subsequently delivered through the capillary tube with the carrier solution of the water–acetonitrile–ethyl acetate mixture (15:3:2 volume ratio) using a microsyringe pump. On-capillary detection was performed for the analytes using an absorption detector, which indicated individual elution times and peak shapes on the chromatograms. We discuss the observed phenomena considering the separation mechanism of the TRDC system.