Effects of Tube Materials on Capillary Chromatography Based on Tube Radial Distribution of Ternary Mixture Carrier Solvents under Laminar Flow Conditions

Abstract

A capillary chromatography system was developed using an open capillary tube and a ternary solvents carrier solution of water-hydrophilic/hydrophobic organic solvent mixture. The chromatography is called a tube radial distribution chromatography (TRDC) system. The TRDC system works without applying high voltages or using specific columns, such as monolithic and packed columns. In this study, the effects of tube materials on separation performance were examined in the TRDC system, by using poly(tetrafluoroethylene) (PTFE; 100–400 μm inner diameter), polyethylene (PE; 200 μm inner diameter), and copolymer of (tetrafluoroethylene–perfluoroalcoxyethylene) (PTFE–PFAE; 100 μm inner diameter) capillary tubes. An analyte solution of 2,6-naphthalenedisulfonic acid and 1-naphthol as a model was subjected to the system with a water–acetonitrile–ethyl acetate carrier solution; 15:3:2 volume ratio (water-rich carrier) and 3:8:4 volume ratio (organic solvent-rich carrier). The flow rates were adjusted to be 0.5 μL min−1 for PTFE and PTFE–PFAE tubes as well as 2.0 μL min−1 for PE tube under laminar flow conditions. These analytes in the solution were separated in this order with the water-rich carrier solution with baseline separation in the three capillary tubes, while they were eluted in the reverse order or not separated with the organic solvent-rich carrier solution. The effects of tube temperature on separation were also examined with the water-rich carrier solution; the best resolutions were observed at 0 °C of the tube temperature. The obtained results were compared with those of fused-silica capillary tube and discussed.