Highly sensitive analysis of catecholamines by counter‐flow electrokinetic supercharging in the constant voltage mode

Abstract

Electrokinetic supercharging is one of the most powerful sample-stacking methods that combines field amplified sample injection and transient ITP. In counter-flow electrokinetic supercharging, a constant counter pressure is applied during sample injection in order to counterbalance the movement of the injected sample zone. As a result, there will be a pronounced increase in the amount of sample injected and the portion of the capillary available for electrophoresis. In this report, counter-flow electrokinetic supercharging optimization factors such as the electric field application in the constant voltage and constant current modes, the magnitude of counter pressure, and the terminating electrolyte concentrations were investigated. The enrichments obtained with a 30 min injection of 10 nM catecholamines in 5 mM terminating electrolyte solution in the constant voltage mode applying a counter pressure of 1.3 psi were 41,000-fold for dopamine, 50,000-fold for norepinephrine, and 32,000-fold for epinephrine, yielding detection limits of 1.3, 1.4, and 1.2 nM, respectively, with absorbance detection at 200 nm.

Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2016–2018)

“…Another limitation of the electrokinetic injection of sample is the movement of the stacking boundary during the long FASI step. Many approaches in the last 10 years were proposed for the immobilization of the stacking boundary through application of a counterflow (CF‐EKS) or employing the EOF to cease the movement of the stacking boundary . Recently, the Chung's group revisited CF‐EKS for the sensitive speciation of arsenic in water samples .…”

Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2014–2016)

“…This boundary movement could be detrimental to the performance of the EKS system. There have been several reports over the past decade aimed to enhancing the performance of EKS via manipulation of EOF or hydrodynamic pressure for the control of boundary movement . Breadmore et al.…”

Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2012–2014)

“…Since the application of FESI is fairly straightforward, it can be combined with different detection methods such as inductively coupled plasma MS , electrochemiluminescence , UV , quadrupole, IT, and TOF‐MS , amperometric , and laser‐induced fluorescence . It can also be combined with different CE techniques such as open‐tubular CEC and chiral EKC .…”