MASS-TRANSFER IN THE MOBILE AND STATIONARY PHASES IN MICELLAR LIQUID-CHROMATOGRAPHY

The retention behaviors of a series of solutes having a wide range of polarity were evaluated for normal retention behavior in micellar chromatography and then used to measure column efficiencies as a function of the concentration of sodium dodecyl sulfate (0-0.3 mol L-1), both in the presence and absence of small concentrations of 1-propanol (0-0.8 mol L-1). Column efficiencies showed distinct maxima in the micellar region of SDS at a concentration near 0.01 mol L-1, which became broad in the presence of 1-propanol. In the absence of SDS maxima were observed when the 1-propanol concentration was near 0.1 mol L-1, but this maxima did not correspond to effects seen in the micellar region of SDS. The influence of ionic strength was also studied. A comparison of results obtained above and below the critical micelle concentration clearly showed that the low efficiencies observed in micellar chromatography are not due mass-transfer effects related to surfactant loading on the reversed phase. Improvements in mass transfer on the addition of alcohol appear to be related to effects taking place in the mobile phase. Some of these effects can be correlated with information available on the dynamics of SDS micelles, but more fundamental studies at higher concentrations of SDS are required for proper explanation of the results observed,