Determination of ionic mobilities and dissociation constants of monovalent acids and bases by micropreparative capillary isotachophoresis with off-line measurement of the pH of zones

Pospı́chal, Jan; Deml, Mirko; Boček, Petr

doi:10.1016/s0021-9673(01)94356-0

Cited by 26 publications

(13 citation statements)

References 17 publications

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“…ITP is attractive as it can easily identify and quantify the mobility of multiple samples simultaneously, allows for low analyte Denitsa Milanova Robert D. Chambers Supreet S. Bahga Juan G. Santiago concentrations (order of nmol), and can be robust to trace impurities [25,26]. Hirokawa et al [21,22] and Pospichal et al [23,24] used ITP to quantify the absolute mobilities (mobility of chemical species when it is fully ionized under infinite dilution) and acid dissociation constant (pK a ) for a number of compounds with sufficiently high accuracy and good reproducibility.…”

Section: Introductionmentioning

confidence: 99%

Electrophoretic mobility measurements of fluorescent dyes using on‐chip capillary electrophoresis

et al. 2011

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We present an experimental study of the effect of pH, ionic strength, and concentrations of the electroosmotic flow (EOF)-suppressing polymer polyvinylpyrrolidone (PVP) on the electrophoretic mobilities of commonly used fluorescent dyes (fluorescein, Rhodamine 6G, and Alexa Fluor 488). We performed on-chip capillary zone electrophoresis experiments to directly quantify the effective electrophoretic mobility. We use Rhodamine B as a fluorescent neutral marker (to quantify EOF) and CCD detection. We also report relevant acid dissociation constants and analyte diffusivities based on our absolute estimate (as per Nernst-Einstein diffusion). We perform well-controlled experiments in a pH range of 3-11 and ionic strengths ranging from 30 to 90 mM. We account for the influence of ionic strength on the electrophoretic transport of sample analytes through the Onsager and Fuoss theory extended for finite radii ions to obtain the absolute mobility of the fluorophores. Lastly, we briefly explore the effect of PVP on adsorption-desorption dynamics of all three analytes, with particular attention to cationic R6G.

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Section: Introductionmentioning

confidence: 99%

Electrophoretic mobility measurements of fluorescent dyes using on‐chip capillary electrophoresis

et al. 2011

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“…ITP used for the determination of dissociation constants was based on the measurement of the observed R E values (R E = R S /R L ), where R S is the resistance of the sample zone and R L is the resistance of the leading electrolyte with different leading electrolyte pH values [12]. Calculation of mobilities and pK a values is laborious because in ITP individual zones have different values of concentration, conductivity, resistance or temperature, and the data have to be calculated iteratively [13][14][15][16]. ITP was used for pK a determination of some local anesthetics [12], amino acids and peptides [17].…”

Section: General Aspectsmentioning

confidence: 99%

Determination of dissociation constants of compounds with potential cognition enhancing activity by capillary zone electrophoresis

Lišková

Křivánková

2005

Electrophoresis

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Accurate determination of pK(a) values is important for proper characterization of newly synthesized molecules. In this work we have used CZE for determination of pK(a) values of new compounds prepared from intermediates, 2, 3 and 4-(2-chloro-acetylamino)-phenoxyacetic acids, by substituting chloride for 2-oxo-pyrrolidine, 2-oxo-piperidine or 2-oxo-azepane. These substances are expected to have a cognition enhancing activity and free radicals scavenging effect. Measurements were performed in a polyacrylamide-coated fused-silica capillary of 0.075 mm ID using direct UV detection at 254 nm. Three electrolyte systems were used for measurements to eliminate effects of potential interactions between tested compounds and components of the BGE. In the pH range 2.7-5.4, chloride, formate, acetate and phosphate were used as BGE co-ions, and sodium, beta-alanine and epsilon-aminocaproate as counterions. Mobility standards were measured simultaneously with the tested compounds for calculations of correct electrophoretic mobilities. Several approaches for the calculation of the pK(a) values were used. The values of pK(a) were determined by standard point-to-point calculation using Henderson-Hasselbach equation. Mobility and pH data were also evaluated by using nonlinear regression. Three parameter sigmoidal function fitted the experimental data with correlation coefficients higher than 0.99. Results from CZE measurements were compared with spectrophotometric measurements performed in sodium formate buffer solutions and evaluated at wavelength where the highest absorbance difference for varying pH was recorded. The experimental pK(a) values were compared with corresponding values calculated by the SPARC online calculator. Results of all three used methods were in good correlation.

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“…This program includes a computer program for calculating peptide pK a values, an equation that relates the peptide sequence to its electrophoretic mobility [28], and a coupled program for the prediction of electropherograms [37]. As input data in the computer program [37], pK a and electrophoretic mobilities of the different buffer ions of the running buffer have to be introduced, being easily obtained from the literature [38][39][40]. The SPPM also needs as input data on injection time, capillary dimensions and voltage (or injected plug length), separation voltage, electroosmotic mobility and sample concentration; these parameters can be freely chosen if different separation conditions have to be tested or are known if a given experiment has to be simulated.…”

Section: Computer Programsmentioning

confidence: 99%

Capillary electrophoresis‐mass spectrometry of peptides from enzymatic protein hydrolysis: Simulation and optimization

Simó

Cifuentes

2003

Electrophoresis

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Two important limitations still exist for the characterization of protein digests by capillary electrophoresis-mass spectrometry (CE-MS): (i) the buffer choice (i.e., the buffer must provide an adequate CE separation without ruining the MS signal), and (ii) the frequent generation of "unexpected" peptidic fragments during the enzymatic protein hydrolysis. In this work, a new approach is used to solve these difficulties, namely a theoretical model that relates the electrophoretic behavior of peptides to their sequence. The effectiveness of this procedure is demonstrated by the fast attainment of good CE-MS conditions for analyzing the peptides obtained from an enzymatic protein hydrolysate in a single run. This strategy can provide useful information for helping to characterize "unexpected" fragments from protein digests.

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Determination of ionic mobilities and dissociation constants of monovalent acids and bases by micropreparative capillary isotachophoresis with off-line measurement of the pH of zones

Cited by 26 publications

References 17 publications

Electrophoretic mobility measurements of fluorescent dyes using on‐chip capillary electrophoresis

Electrophoretic mobility measurements of fluorescent dyes using on‐chip capillary electrophoresis

Determination of dissociation constants of compounds with potential cognition enhancing activity by capillary zone electrophoresis

Capillary electrophoresis‐mass spectrometry of peptides from enzymatic protein hydrolysis: Simulation and optimization

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