Counter‐flow gradient electrofocusing

Shackman, Jonathan G.; Ross, David

doi:10.1002/elps.200600592

Cited by 73 publications

(97 citation statements)

References 91 publications

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“…In this regime, electrophoresis is countered by the bulk solution flow, which can be applied through external pressure, hydrodynamic force, or electroosmotic force [23][24][25][26][27][28][29][30][31][32]. A species will then come to rest where its electrophoretic velocity is equal to the counterflow [33].…”

Section: Introductionmentioning

confidence: 99%

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Electrophoretic exclusion for the selective transport of small molecules

et al. 2009

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A novel method capable of differentiating and concentrating small molecules in bulk solution termed "electrophoretic exclusion" is described and experimentally investigated. In this technique, the hydrodynamic flow of the system is countered by the electrophoretic velocity to prevent a species from entering into the channel. The separation can be controlled by changing the flow rate or applied electric field in order to exclude certain species selectively while allowing others to pass through the capillary. Proof of principle studies employed a flow injection regime of the method and examined the exclusion of Methyl Violet dye in the presence of a neutral species. Methyl Violet was concentrated almost 40 times the background concentration in 30 s using 6 kV. Additionally, a threshold voltage necessary for exclusion was determined. The establishment of a threshold voltage enabled the differentiation of two similar cationic species: Methyl Green and Neutral Red.

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Section: Introductionmentioning

confidence: 99%

“…One separations technique, capillary electrophoresis (CE), has been used for numerous biochemical applications [1][2][3][4][5][6][7][8]. However, one of the major disadvantages of CE is its poor concentration limits.…”

Section: Introductionmentioning

confidence: 99%

Electrophoretic exclusion for the selective transport of small molecules

et al. 2009

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“…Recently, interest in EFGF has increased with the focus of research being placed on the development of systems that use alternative methods to generate the electric field gradient (for reviews see [15,[18][19][20]). Some of the major advances have been: (i) the use of dialysis membranes to form a conductivity gradient which gives rise to an electric field gradient [21][22][23], (ii) the use of shaped, ionically conductive polymers [24], (iii) the use of buffers with temperature dependent ionic strengths [25], and (iv) the use of a computer-controlled electrode array to generate the electric field gradient [26][27][28].…”

Section: Introductionmentioning

confidence: 99%

Characterization of voltage degradation in dynamic field gradient focusing

Burke

Ivory

2008

Electrophoresis

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Dynamic field gradient focusing (DFGF) is an equilibrium gradient method that utilizes an electric field gradient to simultaneously separate and concentrate charged analytes based on their individual electrophoretic mobilities. This work describes the use of a 2-D nonlinear, numerical simulation to examine the impact of voltage loss from the electrodes to the separation channel, termed voltage degradation, and distortions in the electric field on the performance of DFGF. One of the design parameters that has a large impact on the degree of voltage degradation is the placement of the electrodes in relation to the separation channel. The simulation shows that a distance of about 3 mm from the electrodes to the separation channel gives the electric field profile with least amount of voltage degradation. The simulation was also used to describe the elution of focused protein peaks. The simulation shows that elution under constant electric field gradient gives better performance than elution through shallowing of the electric field. Qualitative agreement between the numerical simulation and experimental results is shown. The simulation also illustrates that the presence of a defocusing region at the cathodic end of the separation channel causes peak dispersion during elution. The numerical model is then used to design a system that does not suffer from a defocusing region. Peaks eluted under this design experienced no band broadening in our simulations. Preliminary experimental results using the redesigned chamber are shown.

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“…The advantages of the TGF method that make it promising for application to in situ extraterrestrial biomarker analysis are: (i) the fabrication and operation of the TGF microfluidic devices are simple and robust [13]. Only simple, short, nonintersecting separation channels are required.…”

Section: Discussionmentioning

confidence: 99%

“…Counterflow gradient electrofocusing methods [11][12][13] are a family of electrophoretic separation methods in which the electrophoretic motion of analyte ions is counterbalanced by a bulk flow of solution. Through the use of electrodes, membranes, or other techniques, the electrophoretic velocity is made to vary along the length of the separation column, so that the total velocity (the sum of the electrophoretic and bulk velocities) is equal to zero at a unique point in the column (see Fig.…”

Section: Introductionmentioning

confidence: 99%

Development of a temperature gradient focusing method for in situ extraterrestrial biomarker analysis

Danger¹,

Ross²

2008

Electrophoresis

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Development of a temperature gradient focusing method for in situ extraterrestrial biomarker analysisScanning temperature gradient focusing (TGF) is a recently described technique for the simultaneous concentration and separation of charged analytes. It allows for high analyte peak capacities and low LODs in microcolumn electrophoretic separations. In this paper, we present the application of scanning TGF for chiral separations of amino acids. Using a mixture of seven carboxyfluorescein succinimidyl ester-labeled amino acids (including five chiral amino acids) which constitute the Mars7 standard, we show that scanning TGF is a very simple and efficient method for chiral separations. The modulation of TGF separation parameters (temperature window, pressure scan rate, temperature range, and chiral selector concentration) allows optimization of peak efficiencies and analyte resolutions. The use of hydroxypropyl-b-CD at low concentration (1-5 mmol/L) as a chiral selector, with an appropriate pressure scan rate ( 20.25 Pa/s) and with a low temperature range (3-257C over 1 cm) provided high resolution between enantiomers (R s .1.5 for each pair of enantiomers) using a short, 4 cm long capillary. With these new results, the scanning TGF method appears to be a viable method for in situ trace biomarker analysis for future missions to Mars or other solar system bodies.

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Counter‐flow gradient electrofocusing

Cited by 73 publications

References 91 publications

Electrophoretic exclusion for the selective transport of small molecules

Electrophoretic exclusion for the selective transport of small molecules

Characterization of voltage degradation in dynamic field gradient focusing

Development of a temperature gradient focusing method for in situ extraterrestrial biomarker analysis

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