A multidimensional micro gas chromatograph employing a parallel separation multi-column chip and stop-flow μgC × μgCs configuration

A dual-chip, multidimensional micro gas chromatographic module was designed, built and evaluated. Column chips were fabricated on a silicon wafer with an etched rectangular channel 100 μm (width) × 250 μm (depth) using a deep reactive ion etching (DRIE) process. The column chip for the first GC dimension was 3 m long and was coated with polydimethylsiloxane (DB-1) as the stationary phase. The columns on the second dimensional chip were etched with the same width and depth as the first chip, but the flow channel was split into three parallel columns, 1 m long, on the same sized silicon chip (i.e., 3 cm × 3 cm). These three parallel columns on the second chip were coated with polyethylene oxide (DB-Wax), trifluoropropylpolymethylsilicone (OV-210) and cyanopropylmethylphenylmethylpolysilicone (OV-225), accordingly, in order to provide diversified chromatographic retention. These two chips were connected via a stop-flow configuration to simultaneously generate multiple two-dimensional gas chromatograms for every analysis. This stop-flow μGC × μGCs design allowed the first column to function as a pre-separator and as a sequencing injector for the second parallel-separation chip. Fifteen volatile organic compounds with boiling points that ranged from 80-131 °C with various functional groups were tested using this μGC × μGCs module. Three discrete 2-D chromatograms were generated simultaneously, which demonstrated the advantages of simultaneously combining GC × GC with parallel separation GCs in microchip chromatography. The total traveling length in the column was only 4 m for each eluted peak and fully resolved separation was achieved through the cross reference among triplet 2-D chromatograms.