Chromatography Using Ternary Water–Acetonitrile–Ethyl Acetate Mixture as a Carrier Solution on a Microchip Incorporating Microchannels

Abstract

Abstract An open-tubular capillary chromatography system has been developed using a ternary mixed solvent solution, i.e., water–hydrophilic/hydrophobic organic solvent mixture as a carrier solution. The system is called “tube radial distribution chromatography (TRDC).” In this study, we tried to carry out the TRDC on a microchip incorporating microchannels. A model analyte solution of isoluminol isothiocyanate (ILITC) and ILITC-labeled bovine serum albumin (BSA) was injected to the double T-junction part (0.5 mm length, ca. 2 nL) on the microchip. The analyte solution was then delivered in the separation microchannel (40 µm in depth, 100 µm in width, and 22 cm in length) with a ternary water–acetonitrile–ethyl acetate mixture carrier solution (3:8:4, volume ratio). The model analytes, the ILITC and the labeled BSA were separated through the microchannel, where the carrier solvents were radially distributed in the separation channel generating inner and outer phases. This phenomenon of the solvents is called “tube radial distribution phenomenon (TRDP).” The outer phase functions as a pseudo-stationary phase under laminar flow conditions in the chromatography, i.e., TRDC. Finally, the ILITC and the labeled BSA were eluted in this order and detected with chemiluminescence reaction.