Carbon nanomaterials have been used as gas solid chromatography stationary phases in recent years

————Excerpted from "Evolution of Carbon Stationary Phase in Gas Chromatography" by Fu Ruolong

Since Japanese scholar Sumo Iijima discovered carbon nano-tubes (CNTs) in 1991，This event changed people's previous understanding of the three forms of carbon (diamond, graphite, and amorphous carbon), and led to continuous research on carbon nano-tubes, competing to use this novel material in various fields. In 2004, another interesting carbon substance emerged - graphene (G), CNTs and G are two allotropes of carbon. They have sp2 hybrid networks, but with different structures, CNTs have tubular nano-structures formed by rolling graphene sheets into tubular structures, forming quasi one-dimensional structures, but G is a flat two-dimensional sheet formed by opening nano-tubes. CNTs can be divided into single-walled carbon nano-tubes (SWCNTs) and multi walled carbon nano-tubes (MWCNTs), symmetric chromatographic peaks can be obtained, but currently their applications are mainly limited to standard mixtures such as alkanes, aromatic compounds, alcohols, esters, and ketones.

Because of the special properties of CNTs, such as large surface area, multiple activation points, and strong π - π bonding forces, Yuan Dongxing and others from Xiamen University used relatively pure carbon nanotubes to make filling columns for research as early as 2002, and compared with activated carbon and graphitized carbon black (CarbopackB) columns, comparing their performance in separating alcohols, ketones, ethers, esters, and organic acids. In 2005, Mitra et al. first coated self-assembled carbon nanotubes onto long capillary chromatography columns using chemical vapor deposition (CVD) method, achieving high column efficiency, changing CVD conditions can alter the thickness and morphology of CNT films, thus adjusting the selectivity of chromatography. In 2006, Mitra et al. used chemical vapor deposition catalyzed by cobalt and molybdenum salts to coat single-walled CNTs onto a capillary chromatography column, with a thickness of 300nm and a column efficiency of up to 1000 theoretical plates per meter. Their Maxwell's constant was tested to be non-polar stationary phase. In the same year, Yuan Liming's research group in China composed a mixed gas chromatography stationary phase of single-walled CNTs and ionic liquids, and made it into a capillary chromatography column, CNTs can improve the separation performance of ionic liquids. After two years of stagnation, some research reports appeared in 2008. In the past five years, there have been more studies on the use of CNTs as gas chromatography stationary phases. At the same time, there are many review articles on the application of nanomaterials in analytical chemistry. After the emergence of graphene, in 2012, Qu Qishu's research team chose oxidized graphene as a gas chromatography stationary phase, they chose 3-Aminopropyl diethoxymethylsilaneas a crosslinking agent to bond graphene oxide to the quartz capillary wall, creating a capillary gas chromatography column. However, due to the short column length, the separation was not ideal.