An integrated system for on-chip temperature gradient interaction chromatography
This paper reports the first integrated MEMS high performance liquid chromatography (HPLC) chip that consists of a parylene high-pressure liquid chromatography (LC) column, an electrochemical sensor, a resistive heater and a thermal-isolation structure for on-chip temperature gradient interaction chromatography (TGIC) application. Two sets of devices for different chromatography criteria were fabricated. The separation column was 8-mm long, 100-μm wide, 25-μm high and was packed with 5-μm sized, C18-coated beads using conventional slurry-packing technique. A novel parylene-enhanced air-gap thermal isolation technology was used to reduce heater power consumption by 58% and to reduce temperature rise in the off-column area by 67%. To test the chromatography performance of the fabricated system, a mixture of derivatized amino acids was chosen for separation. A temporal temperature gradient scanning from 25 °C to 65 °C with a ramping rate of 3.6 °C/min was applied to the column during separation. Successful chromatographic separation of derivatized amino acids was obtained on the chip. Compared with conventional temperature gradient HPLC system which incorporates "macro oven" to generate temporal temperature gradient on the column, our chip's thermal performance, i.e., power consumption and thermal response, is greatly improved without sacrificing chromatography quality.