Isotachophoretic focusing and mass spectrometry detection as tools for improving the determination of aromatic sulfonates in capillary electrophoresis

Abstract

We explored isotachophoresis-capillary zone electrophoresis (ITP-CZE) with diode array detection on a single capillary to find out how to increase the injection volume and decrease the detection limits of aromatic sulfonates in CZE. The ITP was performed by applying a negative voltage in conjunction with hydrodynamic backpressure programming, and the terminating buffer was removed before the CZE separation, which resulted in highly sensitive determinations. The ITP increased the signal response of conventional hydrodynamic injection by a factor of 100, whereas the separation efficiency was unaffected. The limits of detection of the method were between 3 and 5 nugL(-1). The method was successfully used to determine these compounds in water samples. Experimental conditions for capillary electrophoresis-mass spectrometry were optimized and applied to determine aromatic sulfonates in water samples. These techniques enables the 2-naphthalenesulfonate to be determined in water samples.

Optimization of Field-Amplified Sample Injection for Analysis of Peptides by Capillary Electrophoresis−Mass Spectrometry

“…On the other hand, ESI-MS functions as a concentration-sensitive detector under many conditions. 15 The intensity of analyte ions from electrospray ionization is dependent on ESI efficiency, ion sampling efficiency into the vacuum, and ion transmission efficiency through ion optics Many chromatographic and electrokinetic on-column and offcolumn sample stacking approaches, such as solid-phase extraction, 18 pH-mediated sample stacking, 19 on-column isotachophoresis, 20 and field-amplified sample injection (FASI) 10,[21][22][23][24] have been applied to increase the amount of polar analytes such as drug substances, which can be loaded into the capillary in order to improve the sensitivity of the detection. Of these, field-amplified sample injection is a robust approach that has been used with organic analytes to provide ∼1000-fold sensitivity enhancement, while maintaining the other advantages of CE, such as rapid separation and high efficiency.…”

“…Many chromatographic and electrokinetic on-column and off-column sample stacking approaches, such as solid-phase extraction, pH-mediated sample stacking, on-column isotachophoresis, and field-amplified sample injection (FASI) 10,21-24 have been applied to increase the amount of polar analytes such as drug substances, which can be loaded into the capillary in order to improve the sensitivity of the detection. Of these, field-amplified sample injection is a robust approach that has been used with organic analytes to provide ∼1000-fold sensitivity enhancement, while maintaining the other advantages of CE, such as rapid separation and high efficiency. ,, In this modified CE technique, charged solutes contained in a relatively large volume of sample can be effectively stacked at the head of a CE capillary prior to their separation. , After filling the capillary with buffer electrolyte, a short low-conductivity zone (usually a water plug) is introduced hydrodynamically at the inlet end prior to electrokinetic sample injection of a sample solution, also of low conductivity.…”

Sensitive profiling of biogenic amines in human urine by capillary electrophoresis with field amplified sample injection

“…Concerning pre-concentration techniques of biogenic amines, detection limits and sensitivity were improved by increasing the amount of polar analytes loaded into the capillary. Many contributions have focused on electrophoretic on-column and off-column sample stacking approaches, such as solid-phase extraction (Strausbauch et al, 1996), pH-mediated sample stacking (Neususs et al, 2002), on-column isotachophoresis (Cugat et al, 2002;Xu et al, 2009) and field-amplified sample injection (FASI; Zhang and Thormann, 1996;Chien and Burgi, 1991;Wey and Thormann, 2001;Monton and Terabe, 2004;Yang et al, 2006). Among these, FASI is a robust technique that has been used with organic analytes to provide 1000-fold or higher sensitivity enhancement, maintaining CE advantages such as rapid separation and high efficiency (Zhang and Thormann, 1996;Monton and Terabe, 2004;Hempel, 2000).…”