Effects of organic mobile phase modifiers in micellar electrokinetic capillary chromatography

Abstract

SummaryThe addition of 1-20% (v/v) of methanol or acetonitrile as organic modifier to the mobile phase in a micellar electrokinetic capillary chromatographic (MECC) system, containing sodium dodecyl sulfate and a buffer, is shown to extend the elution range and thus increase the peak capacity of a given system. Although thenet changein theelution rangeparameter, tO/tmc,is essentially the same for both modifiers, the acetonitrile-modified system exhibits much faster elution times for the polar and non-polar test solutes employed in this study. Retention, as measured by thecapacity factor, is generally decreased with the increaseof anorganic modifier, just as in conventional reversedphase chromatography. However, changes in selectivity as a function of the added modifiers are noted among polar and nonpolar solutes as well. The efficiency of these MECC systems is increased with the addition of either organic modifier.

Application of micellar electrokinetic chromatography and indirect UV detection for the analysis of fatty acids

“…In our study the behaviour of acetonitrile on the migration agrees, up to 20% of acetonitrile, with the findings as mentioned in Ref. [12]. The elution order of C 8<C9... < Cz0 indicates that still micelles are present (see Fig.…”

“…2. The improvement of the baseline stability at larger organic solvent concentrations was found earlier by Gorse et al [12]. In 40% acetonitrile the larger fatty acids dissolve considerably better and under these conditions C8-C17 fatty acids (0.1-0.25 mM of each) could be completely separated except the C16 and C17 acids which coelute.…”

“…The effect of addition of organic solvents, like methanol and acetonitrile, to micellar systems has been studied before [12]. These studies showed that the addition of organic solvent (up to 20%) changes the partition of solutes (e.g.…”

Centrifuge microextraction coupled with sweeping–MEKC to analyze trace steroid hormones in urine samples

“…1). This is because organic additives in the BGS can alter hydrophobic analyte/micelle interactions by displacing the analytes from the micelle, by offering alternative hydrophobic binding sites, or by decreasing the surface tension of the separation buffer [36]. The resolution between methyltestosterone and testosterone is higher than 1.5 when the volume fraction of methanol was above 15%.…”

Pressure‐assisted field‐amplified sample injection with reverse migrating micelles for analyzing trace steroids in MEKC

“…The resolution was very poor because these analytes showed similar affinity for the micellar phase. Organic additives can alter hydrophobic analyte/ micelle interactions by displacing the analytes from the micelle, by offering alternative hydrophobic binding sites, or by decreasing the surface tension of the separation buffer [39]. Methanol was added to the separation buffer to improve the resolution.…”