Development and Evaluation of a New Fluorinated Double-Wall Carbon Nanotube HPLC Stationary Phase

A novel column based on silica-containing immobilized fluorinated double-wall carbon nanotubes (F-DWCNTs) was developed. This F-DWCNT stationary phase was synthesized to combine the analytical performance of carbon nanotubes and the fluorine-based unique selectivity for polar compounds. First, the chromatographic support was coated with DWCNTs in a noncovalent way to preserve the sp² internal nanotube structure. Second, the DWCNT silica particles were functionalized with fluorine atoms via a solution of Br₂ and BrF₃ at room temperature. This F-DWCNT stationary phase was applied for a variety of separations. The solute retention behaviour was particularly studied under isocratic conditions with a high fraction of ACN in the ACN/water (v/v) mobile phase. The retention factors of the solute molecule do not depend linearly on the ACN fraction, but follow a quadratic relationship. This fluorinated stationary phase separated compounds based upon a combination of hydrophobic and polar selective stationary phase interactions. This F-DWCNT appeared to work best when fluorinated or halogenated compounds were encountered. They have longer retention time, better selectivity and work well with high fraction of organic modifiers. This novel stationary phase could thus be a good choice for LC–MS experiments.