title: Chromatographic shape selectivity with carbon dioxide-acetonitrile mobile phases. Effect of mobile phase composition and density.
abstract: Trends in chromatographic shape selectivity with mobile phases consisting of mixtures of carbon dioxide and acetonitrile are investigated. Selectivity is evaluated as a function of mobile phase composition, temperature, and column bonding chemistry. SRM (standard reference material) 869a is used as a probe of shape selectivity, while the selectivity between triphenylene and o-terphenyl is used to investigate planarity selectivity. Four molecular mass 228 polyaromatic hydrocarbon isomers are used to investigate shape selectivity based on differences in length-to-breadth ratio. Shape selectivity trends as a function of temperature and column type are found to be similar to what is seen in reversed-phase liquid chromatography, while the trend seen as the amount of acetonitrile in the mobile phase increases is found to be different than in reversed-phase liquid chromatography. In addition, the effect of mobile phase density, i.e., solvent strength, on shape selectivity is investigated by examining shape selectivity as a function of density with neat carbon dioxide as the mobile phase.
mesh_terms: D000097:Acetonitriles / Q000737:chemistry*; D002245:Carbon Dioxide / Q000737:chemistry*; D002853:Chromatography, Liquid / Q000379:methods*; D012680:Sensitivity and Specificity
chemical_list: D000097:Acetonitriles; D002245:Carbon Dioxide; C032159:acetonitrile