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).