High-performance liquid chromatography of alkylbenzenes on alumina

Retention characteristics of aromatic hydrocarbons on silica and aminopropyl‐modified monolithic columns in normal‐phase HPLC

“…Comprehensive studies of normalphase retention characteristics for alkylbenzenes using such columns have been reported previously, e.g. alumina [3][4][5], and silica [4,6], but less comprehensively for amino- [7][8][9][10], cyano-or diol- [10,11] bonded phases. Studies using silica demonstrated that benzene retention is influenced by the number, position and structure of alkyl substituents.…”

“…n-alkylbenzenes) extention of chain length leads to reduced retention, ortho-substituted compounds have increased retention (ortho effect) compared to non-ortho isomers, substituent chain branching reduces retention compared to n-alkylbenzenes of the same carbon number. Moisture control of the hexane eluent was found to be crucial for good reproducibility when using bare silica and alumina supports as build-up of water molecules adsorbed to polar sites on pellicular surfaces leads to changes in the adsorption properties of the column [5]. Bonded phases are less susceptible to retention variation due to water build-up as the bonded phase inhibits interaction between water molecules and vacant silanol groups [8].…”