Application of carbon microbeads for column packing for high-performance liquid chromatography

Abstract

Carbon microbeads have been recognized as an advanced carbonaceous material with exciting possibilities just like carbon fibre. Among their potential applications are high-density, high-strength, isotropic carbon solids [1] and bulking agents for liquid chromatography [2]. The microbeads have usually been obtained by carbonizing pitch, separating them from each other with solvent or in a high-temperature centrifuge. To name a few advantages of carbon microbeads, they offer (a) high resistance to very acidic and very basic reagents, (b) low expansion and shrinkage coefficients and (c) the ability to withstand an operating temperature of 250 °C. Recently we have developed a method for obtaining carbon microbeads from n-paraffin or a mixture of n-paraffin and coal tar pitch (CTP) under mild conditions at 873 K under a nitrogen pressure of 2 MPa [3, 4]. In this letter a study is made on the application of carbon microbeads for column packing for highperformance liquid chromatography (HPLC) for the separation of aromatic and polar compounds. n-Paraffin (melting point 341 to 343 K) was used as the starting material for production of carbon microbeads. Carbonization of paraffin was performed in a 15 ml autoclave. The autoclave charged with an 0.8 g sample was pressurized with nitrogen at an initial pressure of 5 MPa and put into an image furnace for carbonization at 873 K (the yield of carbon microbeads was 18 wt %). The rate of heating was 5 K min-~. The carbon microbeads formed in the autoclave were taken out and were heat-treated further at 973, 1073 and 1173 K for I h under nitrogen gas flow. Heat-treated carbon microbeads thus obtained were tested as a Figure 1 SEM micrographs of carbon microbeads from n-paraffin used for HPLC column packing.