A miniature closed-loop gas chromatography system.

This paper reports the characterization of a miniaturized circulatory column system that is capable of magnifying the effective column length by forming a circulatory loop with chip-scale columns, thus ultimately achieving high-efficiency target separation. The circulatory column system is composed of a tandem of 25 cm microcolumns and six valves for fluidic flow control in order to enable chromatographic separation in circulatory motions while requiring only 5.5 kPa of pressure, which current micropumps are currently capable of supplying. The developed column system (1) successfully demonstrated 16 times elongation of a virtual column length up to 800 cm by only utilizing two 25 cm microcolumns, which is the longest column length reported by any MEMS-scale functioning GC column, (2) achieved a high theoretical plate number of 68,696 with pentane circulating after 15.5 circulatory cycles, which corresponds to the plate number per length-pressure of 1611 plate m(-1) kPa(-1), the highest record reported yet, and (3) demonstrated successful separation of target molecules during circulation by utilizing a pentane/hexane mixture, resulting in magnification of the two corresponding peaks via circulation.