Abstract
A new bonded liquid crystal stationary phase (2OC 12) for high-performance liquid chromatography was studied. It resulted from coupling of LiChrospher Si 100 NH 2 and a mesogenic carboxylic acid, 4-(4-(4-(3,4-didoceyloxy-styrenyl)phenyl-diazenyl)phenyloxy-methylene) benzoic acid (ILC). ILC was characterized with proton NMR and differential scanning calorimetry, while 2OC 12 was characterized by solid state 13C NMR and elemental analysis. 2OC 12 surface area was determined by the BET method. The chromatographic behaviour of 2OC 12 was investigated under both normal- and reversed-phase conditions. The plots of ln k against 1/ T showed transition temperatures at 325 and 337 K. Polyaromatic hydrocarbons (PAHs) were separated using hexane, isooctane or hexane-chloroform. Above the transition temperatures, the bonded material exhibited a liquid crystal-like behaviour: (i) the plate number N was always highest possible, and (ii) the more retained the solute the more elongated it was (anthracene is eluted after phenanthrene, chrysene before tetracene, pentacene after dibenzo-a,h-anthracene). Using acetonitrile/water (60/40), reversed-phase data of aromatic hydrocarbons are similar (highest values of N, better resolution below than during the transitions).
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