Determination of effective mobilities of EOF markers in BGE containing sulfated β‐cyclodextrin by a two‐detector method

Abstract

A neutral marker of the EOF can gain a nonzero effective mobility because of its possible interaction with a charged complexing agent, such as a chiral selector in CE. We determined effective mobilities of four compounds often used as EOF markers (dimethyl sulfoxide, mesityl oxide, nitromethane, and thiourea) in the BGE-containing sulfated β-CD (60 g/L). All the compounds studied were measurably mobilized by their interaction with the selector. The highest effective mobility (-3.0·10(-9) m(2) s(-1) V(-1)) was observed for thiourea and the lowest (-1.5·10(-9) m(2) s(-1) V(-1)) for dimethyl sulfoxide and nitromethane. The mobilities were determined by a new two-detector pressure mobilization method (2d method), which we propose, and the results were confirmed by standard CE measurements. In the 2d method, one marker zone is situated in the BGE containing the charged selector, while the second marker zone is surrounded with a selector-free BGE, which prevents its complexation. The initial distance between the two marker zones equals the capillary length from the inlet to the first detector. After a brief voltage application, the final distance between the marker zones is determined based on known capillary length from the first to the second detector. The difference between these two distances determines the effective mobility.

Evaluation of electroosmotic markers in aqueous and nonaqueous capillary electrophoresis

“…However, the RSD for the markers is somewhat higher (0.3–7%) compared to the phosphate‐based BGE without CD (0.07–2%). This is in contrast to the recently reported results by Müllerova et al that observed a difference in mobility between DMSO and mesityl oxide in a similar BGE (at a higher ionic strength) with sulphated CDs.…”

“…In a paper by Beckers et al mesityl oxide was considered to be the most appropriate marker in the aqueous BGE for EOF determinations since it had high absorbance and gave symmetric peaks, whereas Fuguet et al concluded that MeOH, ACN, and formamide were the best‐suited EOF markers for aqueous BGEs containing seven different types of (negatively or positively charged) micelles. Müllerova et al concluded that thiourea was inappropriate as an EOF marker in a chiral system (S‐β‐CD) studied.…”

“…They evaluated acetone, benzene, crotonaldehyde, mesityl oxide, and paracetamol and discovered that mesityl oxide was the best marker whereas Fuguet concluded that ACN, MeOH, and formamide provided migration times closest to the EOF. Recently, Müllerova et al studied DMSO, mesityl oxide, nitromethane, and thiourea in sulphated‐β‐CD (S‐β‐CD) at pH 5.5 and stated that thiourea is unappropriate as EOF marker in the studied system. Thus, the published comparative studies of EOF markers only report two aqueous system and some micellar systems and do not include different pH or nonaqueous BGEs.…”

Kinetic Study of Interaction between Solute Molecule and Surfactant Micelle

“…[23][24][25][26][27] Thymol was dissolved with the mixture at 2.0 mmol dm -3 to prepare a solute solution. Five microliters of DMSO was also dissolved in 1.5 mL of the solute solution.…”

Evaluation of three neutral capillary coatings for the determination of analyte-cyclodextrin binding constants by affinity capillary electrophoresis. Application to N , N ⿲-disubstituted piperazine derivatives.

“…The influence of ionic strength (which changes the -potential) is more problematic and can be significant using anionic SBE-␤-CD. Müllerova et al [39] have demonstrated that DMSO is a suitable neutral marker to determine the EOF in presence of CD in the BGE: the interaction between DMSO and CD is sufficiently weak to neglect the effect of their complexation on the mobility measurements. The EOF was evaluated for each coating in absence or presence of the neutral ␤-CD at various concentrations in the BGE.…”