Dual stacking of unbuffered saline samples, transient isotachophoresis plus induced pH junction focusing

Sang-Hee Shim, Asif Riaz, Kihwan Choi, Doo Soo Chung

Research output: Contribution to journalArticle

26 Citations (Scopus)

Abstract

A dual stacking mechanism based on transient isotachophoresis (TITP) and induced pH junction focusing is demonstrated as a means to increase the concentration sensitivity in capillary electrophoresis of highly saline samples. When stacking was carried out with an unbuffered saline sample of fluorescein between two zones of low mobility background electrolyte at high pH under an electric field of reverse polarity, two transient peaks at both boundaries of the sample zone were observed. One peak at the rear boundary could be inferred as a transient isotachophoretic stacked zone. Through computer simulations of an unbuffered sample with a high concentration of sodium chloride, we showed that the fast moving zones of sodium and chloride ions induced pH changes at both boundaries to satisfy the electroneutrality condition and that the peak at the front boundary was due to the induced pH junction. To verify the pH changes, an indicator, thymol blue, was added to an NaCl solution and the color changes under an electric field were observed. The proposed mechanism was supported by observing the dual stacking procedure for an unbuffered sample of 4-nitrophenol and measuring additional sensitivity enhancements by dual stacking for ten weakly acidic compounds. For the ten analytes including nucleoside phosphates, every dual stacking of an unbuffered sample exhibited an additional enhancement up to 86% larger than that of usual transient isotachophoresis of the corresponding buffered sample without loss of separation efficiency and reproducibility. Therefore, it would be useful to skip over buffering in sample preparation for TITP, contrary to the general recommendation.

Original languageEnglish
Pages (from-to)1603-1611
Number of pages9
JournalElectrophoresis
Volume24
Issue number10
DOIs
Publication statusPublished - 2003 May 1
Externally publishedYes

Fingerprint

Isotachophoresis
Sodium Chloride
Electric fields
Capillary electrophoresis
Capillary Electrophoresis
Fluorescein
Nucleosides
Computer Simulation
Electrolytes
Color
Phosphates
Ions
Computer simulation

Keywords

  • Capillary electrophoresis
  • pH junction
  • Simulation
  • Stacking
  • Transient isotachophoresis

ASJC Scopus subject areas

  • Analytical Chemistry
  • Biochemistry
  • Clinical Biochemistry

Cite this

Dual stacking of unbuffered saline samples, transient isotachophoresis plus induced pH junction focusing. / Shim, Sang-Hee; Riaz, Asif; Choi, Kihwan; Chung, Doo Soo.

In: Electrophoresis, Vol. 24, No. 10, 01.05.2003, p. 1603-1611.

Research output: Contribution to journalArticle

Shim, Sang-Hee ; Riaz, Asif ; Choi, Kihwan ; Chung, Doo Soo. / Dual stacking of unbuffered saline samples, transient isotachophoresis plus induced pH junction focusing. In: Electrophoresis. 2003 ; Vol. 24, No. 10. pp. 1603-1611.
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