Peak focusing based on stationary phase thickness gradient

Maxwell Wei-Hao Li; Hongbo Zhu; Menglian Zhou; Jinyan She; Ziqi Li; Katsuo Kurabayashi; Xudong Fan

doi:10.1016/j.chroma.2019.460737

Peak focusing based on stationary phase thickness gradient

J Chromatogr A. 2020 Mar 15:1614:460737. doi: 10.1016/j.chroma.2019.460737. Epub 2019 Nov 26.

Authors

Maxwell Wei-Hao Li¹, Hongbo Zhu², Menglian Zhou², Jinyan She², Ziqi Li³, Katsuo Kurabayashi⁴, Xudong Fan⁵

Affiliations

¹ Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA; Center for Wireless Integrated MicroSensing and Systems (WIMS2), University of Michigan, Ann Arbor, MI 48109, USA; Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109, USA.
² Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA; Center for Wireless Integrated MicroSensing and Systems (WIMS2), University of Michigan, Ann Arbor, MI 48109, USA.
³ Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA; School of Precision Instruments and Opto-electronics Engineering, Tianjin University, PR China.
⁴ Center for Wireless Integrated MicroSensing and Systems (WIMS2), University of Michigan, Ann Arbor, MI 48109, USA; Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109, USA.
⁵ Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA; Center for Wireless Integrated MicroSensing and Systems (WIMS2), University of Michigan, Ann Arbor, MI 48109, USA. Electronic address: xsfan@umich.edu.

PMID: 31831145
DOI: 10.1016/j.chroma.2019.460737

Abstract

This paper reports the development of a stationary phase thickness gradient gas chromatography (GC) column that enables analyte peak focusing and improves separation resolution. Theoretical analysis and simulation demonstrate focusing via a positive thickness gradient, i.e., the stationary phase thickness increases along the column. This effect was experimentally verified by coating a 5 m long capillary column with a film thickness varying from 34 nm at the column inlet to 241 nm at the column outlet. The column was analyzed in forward (thin to thick) and backward (thick to thin) modes and compared to a uniform thickness column with a thickness of 131 nm, using alkanes ranging from C₅ to C₁₆ and aromatics. Comparison of resolutions between forward mode and the uniform thickness column demonstrated an overall focusing rate (i.e., improvement in peak capacity) of 11.7% on alkanes and 28.2% on aromatics. The focusing effect was also demonstrated for isothermal room temperature separation of highly volatile compounds and temperature programmed separation with different ramping rates. In all cases, peak capacities from forward mode separations are higher than those from other modes, indicating the ability of a positive thickness gradient to focus analyte peaks. This thickness gradient technique can therefore be broadly applied to various stationary phases and column types as a general method for improving GC separation performance.

Keywords: Gas chromatography; Peak capacity; Peak focusing; Resolution; Stationary phase gradient; Thickness gradient.

MeSH terms

Alkanes / chemistry
Chemistry Techniques, Analytical / methods*
Chromatography, Gas / instrumentation*
Temperature

Substances

Alkanes