Electrophoretic Behavior in Nonaqueous Capillary Zone Electrophoresis Using Tetrahydrofuran-Based Ternary Nonaqueous Solutions

Abstract

Nonaqueous capillary electrophoresis has the potential to separate water-insoluble analytes. Previously, we reported the separation of water-insoluble and neutral synthetic polymers in nonaqueous capillary zone electrophoresis using tetrahydrofuran (THF)-based ternary nonaqueous solutions. In this paper, the effect of the composition of a THF-based ternary solution (THF, acetonitrile, and methanol) containing cetyltrimethylammonium chloride (CTAC) on electrophoretic behavior is investigated using small organic compounds as prove analytes. In addition to general electrophoretic parameters such as electrophoretic mobility, analytical stability was also evaluated. The electric current, electrophoretic mobility of the benzyltriethylammonium cation (ion pair formation with chloride anion), and electrophoretic mobility of coronene (solvophobic interaction with the CTA cation) were dominated mainly by the THF content, and lower THF content resulted in higher values. In contrast, electroosmotic mobility was enhanced by an increase in THF content and was affected mainly by methanol content. Interestingly, in addition to stable electropherograms, we observed instable (fluctuation of baseline or zero current) electropherograms, which were obtained irregularly. Although a notable relation between the composition and the instable behavior was not observed, it is suggested that this "discontinuous instability" is related with the composition distribution (heterogeneous composition) of the ternary solvents in a capillary. Increasing the temperature effectively suppressed the composition distribution and has the potential to decrease the risk of instable behavior.

Nonaqueous Capillary Zone Electrophoresis for Polyesters and Polyamides Using Hexafluoroisopropyl Alcohol as Electrophoretic Medium

“…In our previous study with THF-based electrophoretic media, we found that small compounds without high hydrophobicity was not interact with the cetyltrimethylammonium (CTA) cation [15]. In this study, as the neutral marker soluble in HFIP, phenol was employed as EOF marker which less interacts with CTA cation in HFIP.…”

“…In subsequent studies, we investigated the effect of surfactant species and electrophoretic medium compositions on electrophoretic behaviors using THF-based electrophoretic media [13][14][15]. Specifically, synthetic polymers soluble in THF were used as test analytes for these investigations.…”

Development of Novel Analytical Methods Based on Liquid Chromatography and Electrophoresis

“…In the aforementioned studies, THF-soluble polymers were used as test analytes. Therefore, tetrahydrofuran-based ternary nonaqueous solutions were used for the investigation [57]. However, there are many linear polymers insoluble in THF-based solutions.…”

Capillary and Microchip Electrophoresis

“…Uchida et al reported on the effect of the composition of a THF-based ternary solution containing CTAC on the electrophoretic behavior of small organic compounds. 6 They found that the THF content has an important role in the electrophoretic behavior in NACE. The same research group also reported on an evaluation of interactions between the anionic complex of palladium(II) and the extraction reagent in the presence of SDS or polyoxyethylene alkylphenyl ether by CE, demonstrating that the Pd complex is rapidly captured by the polyoxyethylene micelles compared with the SDS micelles.…”