ALKYLBENZENES AS A RETENTION-INDEX SCALE IN REVERSED-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

Retention in high-performance liquid chromatography is very susceptibl e to small changes in the stationary- and mobile-phase composition and in the operating conditions. One of the methods to minimise these eff ects is by using a retention index. In this study, alkylbenzene homolo gs from toluene to decylbenzene have been used as a retention-index sc ale in reversed-phase high-performance liquid chromatography. Three di fferent stationary phases, octylsilyl(RP-8)-silica, octadecylsilyl(ODS )-silica and PLRP-S poly(styrene-divinylbenzene) (PS-DVB) polymer have been used with aqueous methanol and acetonitrile as the liquid phase. The application of this retention-index scale was studied using a num ber of model compounds of different polarities. The alkylbenzenes are readily detected with a UV detector and give linear relationships betw een log k' and the number of carbon atoms. On RP-8, ODS, and PLRP-S co lumns, a retention scale based on alkylbenzenes showed poor coverage o f the less retained polar compounds but it can potentially be used as an alternative method for measuring the retention of relatively non-po lar compounds.