A microchip pressure-driven liquid chromatographic system with a packed column has been designed and fabricated by using poly(dimethylsiloxane) (PDMS). The liquid chromatographic column was packed with mesoporous silica beads of Ia3d space group. Separation of dyes and biopolymers was carried out to verify the performance of the chip. A mixture of dyes (fluorescein and rhodamine B) and a biopolymer mixture (10？kDa Dextran and 66？kDa BSA) were separated and the fluorescence technique was employed to detect the movement of the molecules. Fluorescein molecule was a nonretained species and rhodamine B was attached onto silica surface when dye mixture in deionized water was injected into the microchannel. The retention times for dextran molecule and BSA molecule in biopolymer separation experiment were 45？s and 120？s, respectively. Retention factor was estimated to be 3.3 for dextran and 10.4 for BSA. The selectivity was 3.2 and resolution was 10.7. Good separation of dyes and biopolymers was achieved and the chip design was verified. 1. Introduction High-performance liquid chromatography (HPLC) is a widely used separation technique with numerous implementations in both preparative and analytical systems [1–4]. A wide variety of chromatography media available provides different requirements for various molecular separation modes. The miniaturized HPLC system would offer the advantage of smaller sample size, reduction of dead volume, lower solvent consumption, faster, higher-throughput analysis, and portability of the analytical system, enabling on-site and remote analysis [5, 6]. Despite these advantages, miniaturization of chromatographic systems needs to address some technical issues such as fabrication of chip-based chromatographic systems without compromising separation efficiency [6]. One such challenge is the introduction of stationary phase materials into a microfabricated microchannel [7]. Numerous examples of chip-based chromatographic systems in pharmaceutical and biomedical applications have been reviewed extensively [6, 8–10]. Open-tubular liquid chromatography microchips integrated with a sample injector and electrode demonstrated low chromatographic efficiency [11]. The low efficiency could be attributed to small surface area and relatively large injection volume of the system. A microfabricated device with C18 coated channels was used to demonstrate on-chip phase extraction [12]. However, using a separation column packed with beads may yield better separation efficiency because of higher available surface area per unit volume and reduced
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