Non-aqueous Capillary Electrophoresis of p-Quinone Anion Radicals

Esaka, Yukihiro; Okumura, Noriko; Uno, Bunji; Goto, Masashi

doi:10.2116/analsci.17.99

Cited by 29 publications

(25 citation statements)

References 24 publications

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“…However, most coatings have been developed for aqueous buffers. There have only been few reports of stable coatings for mixed organic-water buffers or pure organic solvents [12][13][14][15][16]. All of these are based on covalent bonding of the coating to the capillary surface.…”

Section: Introductionmentioning

confidence: 99%

Semipermanent capillary coatings in mixed organic–water solvents for CE

2007

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This report describes the creation of semipermanent capillary coatings that are compatible with organic-water solvent systems in CE. The coatings are created by simply rinsing the fused-silica capillary with long double-chain cationic surfactants, such as dimethyl-ditetradecyl ammonium bromide (2C(14)DAB), dihexadecyldimethyl ammonium bromide (2C(16)DAB), and dimethyldioctadecyl ammonium bromide (2C(18)DAB). These surfactants generate semipermanent bilayer coatings on the capillary surface, which display a high degree of stability in buffers containing up to 60% v/v of organic solvents, such as methanol and ACN. The coating stability increases with increasing hydrophobicity of the surfactant, i.e., with increasing chain length. For instance, the EOF changes by only 1.2% in a 2C(18)DAB-coated capillary after 130 capillary volumes of rinsing with 60% v/v methanol containing buffer. The bilayer coatings allow separations to be performed without the need to regenerate the coating between runs or to maintain the EOF modifier in the run buffer. Rapid separations (<2 min) of anions and basic drugs with migration time reproducibility of less than 0.5% RSD and efficiencies of 0.4-0.6 million plates/m are obtained. In addition, selectivity changes for small anions and cationic drugs are also observed when the organic solvent content is adjusted.

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Section: Introductionmentioning

confidence: 99%

Semipermanent capillary coatings in mixed organic–water solvents for CE

2007

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“…For the separation of water-insoluble or sparingly soluble pharmaceuticals, NACE, which employs electrolytes composed of organic solvents, has been used successfully [3][4][5][6][7]. NACE is also useful for the resolution of watersoluble charged solutes as the selectivity obtained can be different to aqueous-based separations.…”

Section: Electrophoretic Modesmentioning

confidence: 99%

“…[3][4][5][6]11]. NACE electrolytes do not contain water, with organic solvents such as methanol and ACN being used instead.…”

Section: Nacementioning

confidence: 99%

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Capillary electrophoresis for the analysis of small‐molecule pharmaceuticals

2006

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This paper reviews the application of CE to the analysis of small-molecule pharmaceuticals. The areas of pharmaceutical analysis covered are enantiomer separation, the analysis of small molecules such as amino acids or drug counter-ions, pharmaceutical assay, determination of related substances and physicochemical measurements such as log P and pK(a) of compounds. The different electrophoretic modes available and their advantages for pharmaceutical analysis are described. Recent applications of CE for each subject area are tabulated with electrolyte details.

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“…Capillary coatings are also highly desirable in organic solventsinvolved CE because they are very useful for the control of EOF and wall adsorption of analytes [23][24][25]. Unfortunately, only few reports focused on developing stable coatings for aqueous-organic buffers or pure organic solvents [26][27][28][29][30]. Most of the coatings were covalently bonded onto the capillary surface to obtain a satisfactory stability.…”

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confidence: 99%

Use of gemini surfactants as semipermanent capillary coatings in aqueous‐organic solvents for capillary electrophoretic separation of inorganic anions

Liu

Yao

et al. 2009

J of Separation Science

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This paper proposes a new method for CE separation of inorganic anions based on the use of gemini surfactants as capillary coatings in mixed aqueous-organic solvents. The semipermanent gemini surfactant coatings were facilely prepared by rinsing the capillary with 18-s-18 solutions; they can keep be stable during the electrophoretic runs without surfactants in buffer. The coatings showed a good tolerance of methanol (MeOH) or ACN, e.g. at pH 8.0 and with 40% v/v MeOH or ACN, the EOF magnitude after 60 min of continuous electrokinetic rinsing only decreased by 2.9 or 6.0%, respectively. The coatings were successfully applied to the separation of inorganic anions. Adding organic solvents in buffer can effectively improve the resolution and efficiencies; however, it remarkably prolonged the analysis time due to the suppression of EOF. Interestingly, varying the spacer length of the gemini surfactants can also modulate (improve) the resolution but without any sacrifice of analysis time. This benefit was resulted from the unique chemical structures of gemini surfactants because it introduced a new variable, i.e. the spacer length, to the separation mechanism. IntroductionGemini surfactants are a relatively new type of surfactants, which have two hydrophobic chains and two polar headgroups linked by a spacer group [1][2][3]. Compared with the corresponding conventional (monomeric) single-chained surfactants, the gemini surfactants show better water solubility, lower critical micelle concentration, lower Krafft point, and better surface activity in aqueous solutions [2][3][4]. These features make the gemini surfactants very attractive in both academic and industrial worlds. In particular, the spacer group that can be hydrophilic or hydrophobic, flexible or rigid, heteroatomic, aromatic, etc., plays an important role in determining the solution properties of gemini surfactants [5][6][7][8][9]. In principle, the spacer group can connect any two identical or different surfactants among the available ones. Therefore, gemini surfactants are thought to be designable with an enormous variety of structures [3].Although gemini surfactants have recently generated much research interest, their applications in CE are still rare. Gemini surfactants can be good alternatives to other micelle-forming reagents, buffer additives and capillary coatings, thus it is rational to anticipate a bright prospect of application of gemini surfactants in CE. A few earlier reports described the use of gemini surfactants as micelleforming reagents in MEKC, and found that the gemini surfactants exhibit better resolution or wider migration time windows than the commonly used single-chained surfactants [10][11][12]. Warner and coworkers [13][14] and systematically studied the use of anionic gemini surfactants as pseudostationary phases in MEKC, and presented some advantages of anionic gemini surfactants compared with conventionally used SDS. Due to their lower critical micelle concentrations, the gemini surfactants can be used at much lower concentrat...

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Non-aqueous Capillary Electrophoresis of p-Quinone Anion Radicals

Cited by 29 publications

References 24 publications

Semipermanent capillary coatings in mixed organic–water solvents for CE

Semipermanent capillary coatings in mixed organic–water solvents for CE

Capillary electrophoresis for the analysis of small‐molecule pharmaceuticals

Use of gemini surfactants as semipermanent capillary coatings in aqueous‐organic solvents for capillary electrophoretic separation of inorganic anions

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