| Abstract
| - One of the limitations that has restricted the applicabilityof micellar liquid chromatography (MLC) is the weakeluting power of micellar mobile phases compared toconventional hydro-organic mobile phases used in reversed-phase liquid chromatography. This may be theresult of Donnan or steric exclusion of the micelles fromthe pores of the stationary phase, within which nearly all(≥99%) of the stationary phase resides and the analytesspend most of their time. To determine whether wide-porestationary phases would overcome this limitation in MLC,several C8 and C18 stationary phases ranging from 100to 4000 Å were investigated using a diverse set of testsolutes and micellar solutions of anionic, neutral, andcationic surfactants as mobile phases. With the larger poresize stationary phases, the eluting power of the MLCmobile phases was enhanced with all surfactant types, thegreatest effect being with the neutral surfactant. Differences in retention behavior were observed between various solute types and between the C8 and C18 stationaryphases. These differences appear to be related to therelative hydrophobicity of the solutes and to differencesin the surfactant-modified stationary phases. Partitioningbehavior of representative solutes on the large-pore C8and C18 columns was shown to follow the three-phasepartitioning model for MLC. Methylene group selectivitydata showed only minor differences in the stationary-phase characteristics between the small- and large-poresize C18 columns. The true eluting power of micellarmobile phases was revealed with wide-pore stationaryphases and was demonstrated by the separation andelution of an extended series of alkylphenones on C18columns.
|
