MEMS-based semi-packed gas chromatography columns

Separation of complex gaseous mixtures using gas chromatography (GC) is an important process in analytical systems for environmental monitoring, medical diagnosis, and forensic sciences. Miniaturizing GC columns using microfabrication techniques is an important step in achieving micro-total analytical systems (μTAS) as complete lab-on-a-chip devices. This paper reports the fabrication and performance of a new generation of silicon-on-glass MEMS-based GC columns named “semi-packed.” These columns, fabricated on a 1.8 cm square die in a double square spiral layout, are 1-m long, 150-μm wide, and 180-μm deep and contain embedded square posts which are 20 μm on a side. The posts increase the overall surface area of the columns and reduce the effective width of the column to 126 μm. The semi-packed columns achieved a higher separation efficiency and sample capacity as compared to their open rectangular counterparts without significant eddy diffusion effects or drops in pressure which are common issues with conventional packed columns. The semi-packed column achieved a separation efficiency of about 10,000 plates/m which is the highest reported, to date, by a MEMS-based column with comparable outer dimensions.