A semi-packed gas chromatographic column has the advantages of high specific surface area and low column pressure. We report that the stagnation regions formed in the adjacent posts along the channel of the semi-packed columns can decrease the area and height of chromatographic peaks, which makes it difficult to detect low-concentration mixed gases. A semi-packed column with staggered elliptic cylindrical post arrays (SC-S) made using a micro-electro-mechanical system technique is presented, and the separation performance of SC-S is compared with that of a semi-packed column with aligned elliptic cylindrical post arrays (SC-A). The simulation results show that the width of stagnation regions in SC-S is 86.89% smaller than that in SC-A. The experimental results indicate that the area and height of chromatographic peaks increased as stagnation regions reduced. In the separation of the alkane mixture from C8 through C10 with 10 ppm concentration, the chromatographic peak of decane was hardly identified in SC-A while the chromatographic peak in SC-S was still clearly visible. The chromatographic peak heights of octane and nonane were increased by 65.06% and 130.00%, respectively, in SC-S. The peak areas of octane and nonane were increased by 120.45% and 168.18%, respectively.
Boxin Chen,Fei Feng,Yangyang Zhao,Qiyong Liu,Bin Zhao,Lei Li,Haimei Zhou,Xinxin Li
Semi-packed columns are microfabricated gas chromatography columns which have a large surface area and high aspect ratio. In this paper, a new semi-packed column with high-density elliptic cylindrical posts (SC HECP) made by a micro-electro-mechanical system (MEMS) technique was reported. Compared to a semi-packed column with cylindrical posts (SC CP) under the same effective width, the surface area and aspect ratio of SC HECP were improved by 71.19% and 76.47%, respectively. To compare the performance of these two semi-packed columns, SC HECP and SC CP were fabricated. A 10-nm thick alumina film was deposited as the stationary phase by atomic layer deposition technique to ensure the uniformity and repeatability of the stationary-phase film. A contrast experiment was conducted, and the results showed that compared with SC CP, better separation performance was realized in SC HECP due to the increase in surface area and aspect ratio. The number of theoretical plates of nonane was increased by 541.84%, and the tailing factor was decreased by 54.31%.
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