Effect of Organic Modifier on the Retention of Low-Molecular-Weight Organic Compounds in Low-Temperature HPLC Using a Liquid CO<sub>2</sub> Mobile Phase and an Octadecyl Stationary Phase

The retention behaviors of various low-molecular-weight compounds in low-temperature HPLC with an ODS (octadecyl silica) column and liquid CO2 mobile phase containing methanol or acetonitrile as modifiers were investigated. addition methanol/acetonitrile reduced the xanthone, which was dominated by content, independent modifier. Additionally, polycyclic aromatic hydrocarbons (PAHs) methanol/acetonitrile. Because resulted a rapid reduction compared methanol, it suggested that CH- interactions have important role PAHs C18 stationary phase. Notably, alkylbenzenes only slightly affected Acetonitrile increased longer alkyl chains than those shorter chains. It is interaction phenyl moiety increase enhanced case chain moieties. retentions benzenes approximately compensated, when length relatively short.