ABSTRACT
The resolution (R(s)) of hydrophobic analytes in microemulsion EKC (MEEKC) and MEKC with suppressed electroosmosis was investigated using bisphenol-A-diglycidyl ether and its derivatives (BADGEs) as test analytes. Separation scales were compared using our equation for the resolution, R(s)= (square rootN/4)(alpha-1)/(1+K(2)),where k is the retention factor, alpha the selectivity (alpha = k(2)/k(1) for k(2) > or = k(1)>0), and N the average efficiency. At given concentrations of SDS and organic cosolvent in the buffer, in comparison with MEKC, MEEKC was found to provide better resolution of BADGEs, mainly due to the significantly smaller k in MEEKC, but not the greater alpha in MEEKC, while a comparable range of N. Significantly improved resolution of BADGEs was obtained with increase in the concentration of organic cosolvent in the MEEKC and MEKC buffers, while small change in R(s) with the SDS concentration in a range of 100-180 mM. In addition, a decrease in temperature or voltage resulted in slightly better R(s).
Subject(s)
Chromatography, Micellar Electrokinetic Capillary/methods , Electroosmosis/methods , Electrophoresis, Capillary/methods , Epoxy Compounds/isolation & purification , Micelles , Algorithms , Benzhydryl Compounds , Buffers , Chromatography, Micellar Electrokinetic Capillary/instrumentation , Electrophoresis, Capillary/instrumentation , Emulsions , Epoxy Compounds/chemistry , Organic Chemicals/chemistry , Sensitivity and Specificity , Sodium Dodecyl Sulfate , Solvents/chemistry , TemperatureABSTRACT
The retention factor (k) and retention index (I) of homologous series compounds such as alkylbenzenes (BZ), alkylaryl ketones, alkylbenzoates, and alkylparabens in microemulsion electrokinetic chromatography (MEEKC) with suppressed electroosmosis were investigated in a wide range of SDS concentrations ([SDS]), temperatures, and concentrations of organic cosolvents (phi). Using BZ as standards, the retention indices of other homologous series compounds were determined and they were found to be independent of [SDS] and temperature, while are dependent on the types and concentrations of organic cosolvents. The retention factor linearly increases with increasing [SDS], while linearly decreases with increasing temperature. The value of log k linearly decreases with increasing phi for methanol, ethanol, or ACN, while decreases by a second-degree polynomial with increasing phi for 2-propanol. Excellent agreement was found between the observed and predicted values of log k of analytes in MEEKC at given [SDS] and phi, where the predicted values were obtained from modified equations of the linear relationship of log k as functions of [SDS], the number of carbons, and phi. Therefore, both k and I can be used for peak identification of homologous series compounds.
