Interchannel Mixing Minimization in Semi-Packed Micro Gas Chromatography Columns

Semi-packed columns containing an array of micropillars embedded within an open rectangular column structure are a new class of micro gas chromatography $(\mu{\rm GC})$ columns introduced to provide higher separation efficiency and higher sample capacity. Three different semi-packed column configurations are evaluated with respect to pillar spacing along the flow direction and number of pillars across channel. The efficiencies of semi-packed columns, in terms of height-equivalent-to-a-theoretical-plate (HETP), are compared with two microfabricated open-rectangular columns. According to simulation results, arranging the pillars in a symmetrical configuration with spacing equal to the post dimension can suppress multi-path flows. Experimental results confirm the simulation prediction as the design with 2 $\mu{\rm m}$ post spacing (SP1) demonstrates the highest performance among other designs. SP1 is found to have HETP of 0.010 cm (15 000 plates/m) at an optimal velocity of 18 cm/s. An open channel design with comparable channel width yields an HETP of 0.025 cm (6000 plates/m) at an optimal velocity of 45 cm/s. The pressure drop in semi-packed columns is experimentally measured to be ${\sim}{\rm 9}~{\rm kPa}$ which falls within the practical range of microfabricated pumps.