Corrections to moving chemical reaction boundary equation for weak reactive electrolytes under the existence of background electrolyte KCl in large concentrations

The paper advanced the theoretical procedures for quantitative design on selective stacking of zwitterions in full capillary sample matrix by a cathodic-direction moving reaction boundary (MRB) in capillary electrophoresis (CE) under control of electroosmotic flow (EOF). With the procedures, we conducted the theoretical computations on the selective stacking of two test analytes of L-histidine (His) and L-tryptophan (Trp) by the MRB created with 30 mM pH 3.0 formic acid-NaOH buffer and 2-80 mM sodium formate. The results revealed the following three predictions. At first, the MRB cannot stack His and Trp plugs if less than 12.5 mM sodium formate is used to form the MRB and prepare the sample matrix. Second, the MRB can stack His and/or Trp sample plugs completely if higher than 50 mM sodium formate is chosen to form the MRB. Third, the MRB can only focus His plug completely, but stack Trp plug partially if 20-50 mM sodium formate is used; this implied the complete MRB-induced selective stacking to His rather than Trp. All the three predictions were quantitatively proved by the experiments. With great dilution of sample matrix and control of EOF, controllable, simultaneous and MRB-induced selective stacking and separation of zwitterions were achieved. The theoretical results hold evident significances to the quantitative design of selective stacking conditions and the increase of detection sensitivity of zwitterions in CE. In addition, the control of EOF by cetyltrimethylammonium bromide (CTAB) can evidently improve the stacking efficiency to both His and Trp.

show abstract

“…The validity of Eq. (5) has been quantitatively proved in our previous paper [41]. The physical-chemical mechanism why Eq.…”

Section: Velocity Of Mrbmentioning

confidence: 60%

“…(5), as well as Eq. (14), as has been verified in the previous papers [41]. The velocities of His and Trp in phase a are computed with Eq.…”

Section: Data and Computationsmentioning

confidence: 63%

See 1 more Smart Citation

Quantitative study on selective stacking of zwitterions in large‐volume sample matrix by moving reaction boundary in capillary electrophoresis

Qin

Cao

et al. 2005

Electrophoresis

Self Cite

View full text Add to dashboard Cite

show abstract

“…Cao et al [140][141][142][143][144][145][146][147][148][149][150][151] have made a significant contribution to the field with their work on moving reaction boundaries. Initial work in gels demonstrated controlled movement of the pH boundary and an inconsistency with the current theory for predicting the migration of this boundary.…”

Section: Dynamic Ph Junctionmentioning

confidence: 99%

Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips

2007

View full text Add to dashboard Cite

Poor sensitivity is considered to be one of the major limitations of electrophoretic separation methods, particularly when compared to traditional liquid chromatographic techniques. To address this issue, various in-line preconcentration techniques have been developed over the past 15 years, ranging in power and complexity, and there are now a number of well understood approaches routinely capable of providing a 10,000- to 100,000-fold increase in sensitivity, as well as several that can be pushed above a million. Furthermore, these have been achieved with particularly troublesome and often difficult samples, such as those having high salinity from a biological or environmental origin. This review will discuss the most common methods for improving the sensitivity of CE, CEC and microchip version of these, with particular attention to those approaches developed over the last five years.

show abstract

“…This method relies on a discontinuous buffer system to trap the analyte between differing electrolyte zones, creating an electric potential gradient. Several other methods take a similar approach to ITP using the chemical differences in discontinuous buffer zones to enhance peak efficiencies [22][23][24][25][26][27]. A counterflow transient ITP method was developed by Touissant and coworkers [28] that utilizes a counterpressure step to move the sample zone near the inlet of the capillary once ITP-focused so a larger amount of capillary is available for separation.…”

Section: Introductionmentioning

confidence: 99%

pH-mediated acid stacking with reverse pressure for the analysis of cationic pharmaceuticals in capillary electrophoresis

Gillogly

Lunte

2005

Electrophoresis

View full text Add to dashboard Cite

When using capillary electrophoresis (CE) for the analysis of biological samples, it is often necessary to employ techniques to overcome peak-broadening that results from having a high-conductivity sample matrix. To improve the concentration detection limits and separation efficiency of cationic pharmaceuticals in CE, pH-mediated acid stacking was performed to electrofocus the sample, improving separation sensitivity for the analyzed cations by 60-fold. However, this method introduces a large titrated acid plug into the capillary. To overcome the limitations this lowconductivity plug poses to stacking, the plug was removed prior to the separation step by applying reverse pressure to force it out of the anode of the capillary. Employing this technique allows for roughly twice the volume of sample to be injected. A maximum sample injection time of 240 s was attainable with baseline peak resolution compared to a maximum sample injection time of 120 s without reverse pressure, leading to a twofold decrease in the limits of detection of the analytes used. Separation efficiency overall is also improved when utilizing the reverse pressure step. For example, a 60 s sample injection time results in 94 000 theoretical plates as compared to 60 500 theoretical plates without reverse pressure. This reverse-pressure method was used for detection and quantitation of several cationic pharmaceuticals that were prepared in Ringer's solution to simulate microdialysis sampling conditions.

show abstract

Corrections to moving chemical reaction boundary equation for weak reactive electrolytes under the existence of background electrolyte KCl in large concentrations

Cited by 19 publications

References 22 publications

Quantitative study on selective stacking of zwitterions in large‐volume sample matrix by moving reaction boundary in capillary electrophoresis

Quantitative study on selective stacking of zwitterions in large‐volume sample matrix by moving reaction boundary in capillary electrophoresis

Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips

pH-mediated acid stacking with reverse pressure for the analysis of cationic pharmaceuticals in capillary electrophoresis

Contact Info

Product

Resources

About