Utilization of Nanometre-order Diameter Columns inside Porous Anodic Alumina for Chromatography Chip System

Abstract

Porous anodic alumina (PAA) membranes were used as a nanometre-order diameter column for chromatography chip with acetonitrile-water mobile phase using gradient elution. In a chromatogram, 9-anthracenemethanol (AM), 9-anthracenecarboxylic acid (AC), and dansyl-glycine (DG) showed different retention times, indicating that PAA membranes are applicable to stationary phase for chromatography chip.Porous anodic alumina (PAA) membranes, 1-5 which consist of a self-assembled honeycomb array of uniformly sized parallel channels, have attracted considerable interest in various areas such as electronics, chemistry, and biomedical science because of their ordered structure, superior resistance to organic solvents, and potentially low cost. The diameter of PAA channels can range from about ten to several hundred nanometers, and membrane thickness is 10 to 100 mm. When solutes permeate through the PAA membrane, the interior of the columnar channels interacts with the solutes molecules. The elution of solutes from the channels depends on the strength of the interaction with the interior.6 Alumina is widely used for chromatographic matrix in liquid chromatography, and its chromatographic properties have been studied in detail. [7][8][9] However, few studies have been carried out on the utilization of PAA in liquid chromatography.A PAA membrane is very thin, which is favorable for reducing the sizes of analysis systems. In this study, we used PAA membranes (Anodisk, 100-nm-diameter pores, 60-mm thick, Whatman) as stationary phase in the chromatography chip and tested whether PAA membranes can function as chromatographic columns in chip system. The chromatography chip, which has been intensively studied, 10-21 is a small tool that can function as chromatographic system. Figure 1 shows a schematic illustration of the experimental setup for chromatographic measurements and a picture of a chip. Five PAA membranes were set in the chip as stationary phase.24 Glycol-modified polyethylene terephthalate (PETG, Mitsubishi Rayon Co., Ltd.) was used for the chip substrate. As solute molecules, 9-anthracenemethanol (AM), 9-anthracenecarboxylic acid (AC), and dansyl-glycine (DG) were selected. The chromatograms of each solute were presented in Figure 2. The retention times of each solute were different, indicating that PAA membranes can function as chromatographic columns with acetonitrile-water mobile phase.The retention time reflects the strength of the interaction between solutes and interior of the nanochannels. The strength of the interaction was measured by putting a solution of the solutes to be tested in two bottles, one with one without a PAA mem-

Liquid chromatography on chip

“…Porous anodic alumina was investigated as a stationary phase [60]. Demonstration of chromatographic behavior was achieved on porous alumina membrane incorporated in a chip.…”

Separation of adenine, adenosine-5′-monophosphate and adenosine-5′-triphosphate by fluidic chip with nanometre-order diameter columns inside porous anodic alumina using an aqueous mobile phase

“…The chips were made as previously described. 11 Five PAA membranes were set in the chip as the stationary phase. Glycol-modified polyethylene terephthalate was used for the chip substrate.…”