Estimation of logP(ow) values for neutral and basic compounds by microchip microemulsion electrokinetic...

Microchip microemulsion electrokinetic chromatography with indirect fluorimetric detection (muMEEKC-IFD) was used to obtain logP octanol/water (logP(ow)) values for neutral and basic compounds. Six compounds, with logP(ow) values between 0.38 and 5.03, were used to create a calibration curve relating the log of retention factors (logk) obtained from muMEEKC-IFD with the known logP(ow) values. The logP(ow) values for six additional compounds were determined using the logk values obtained by muMEEKC-IFD and the linear relationship between logP(ow) and logk established for the standard compounds. The muMEEKC-IFD buffer was composed of 50 mM 3-[cyclohexylamino]-1-propane-sulfonic acid (CAPS) buffer (pH 10.4) containing 1.2% n-heptane (v/v), 2% sodium dodecylsulfate (w/v), 8% 1-butanol (v/v) and 4 microM 5-carboxytetramethyl-rhodamine (TAMRA) as the fluorophore probe for indirect detection. The muMEEKC-IFD provided an accurate method for estimating logP(ow) values and also a means for analyzing compounds that are non-fluorescent.