The effect of pillar array in semi-packed micro gas chromatography

Micro pillars within separation columns (SC) offer higher sample capacity but also promote fluidic eddy motion which unlike other applications has a negative effect on gas chromatography (GC). Three different semi-packed column (SPC) configurations have been evaluated with respect to pillar spacing along the flow direction and number of pillars across channel. The efficiencies of SPCs have been compared to 2 MEMS open-rectangular columns (ORCs). Simulation and experimental results demonstrated that SPC can operate at higher efficiency when spacing the pillars such that stagnation regions are created. SPC with 20μm pillar diameter and spacing achieved height-equivalent-to-a-theoretical-plate (HETP) of 0.10mm at 18cm/sec optimal velocity. ORC design with comparable channel width yielded HETP of 0.25mm at 45cm/sec. The SPC presented herein has produced 15,000 plates/m, one of the highest reported to date on coated MEMS SC while requiring only 9kPa back pressure.