Low-Cost Liquid Chromatography (LC-LC). IV. “Pulsed Open Tube Gradient Generation”, A New Approach for Generating Nanoliter Volume Linear and Tailored Gradients for Capillary Electrophoresis and Micro-LC

Berry, V.; Rohwer, Egmont Richard

doi:10.1080/01483919008048974

Journal of Liquid Chromatography

1990

DOI: 10.1080/01483919008048974

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Low-Cost Liquid Chromatography (LC-LC). IV. “Pulsed Open Tube Gradient Generation”, A New Approach for Generating Nanoliter Volume Linear and Tailored Gradients for Capillary Electrophoresis and Micro-LC

V. Berry¹,

Egmont Richard Rohwer²

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1992

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Cited by 4 publications

(2 citation statements)

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“…To reduce the delay time of a gradient with the new method, part of the gradient is formed and delivered at a relatively higher flow rate to the column inlet. Forming a gradient at a relatively higher flow rate than used for delivery has previously been used by others, mostly to form a more accurate gradient that could not otherwise be possibly formed at the flow rates used for separations. − In any of these previous studies, however, a dedicated gradient storage device was added to the LC system, along with separate pumping systems for gradient formation and delivery. In addition, the entire gradient had to be formed at the higher flow rate.…”

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confidence: 99%

A Method To Reduce Gradient Delay Time of NanoLC

2007

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A novel method to dramatically reduce the delay time of a nanoLC gradient is described. The gradient is divided into two parts, and each part is formed at different flow rates. The beginning part is formed and delivered to the inlet of the column at a higher-than-normal flow rate. With the formation of the rest of the gradient at a normal flow rate, the whole gradient is further delivered through the column at the same normal flow rate. To form the gradient with the desired slope, the volumetric gradient slope was kept constant, independent of the flow rate. A gradient delay time reduction of 12.5-16 min was observed with the reported method. The resulting gradient profiles and chromatograms were very similar to those obtained with a conventional method. Comparable retention time reproducibility was observed between the two methods.

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A Method To Reduce Gradient Delay Time of NanoLC

2007

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“…To realize the full potential of CEC, it is necessary to develop the capability of gradient elution, as in HPLC and micro-HPLC, , for successfully separating a wide variety of complex samples. So far, there appears to be no report on solvent gradient elution in CEC using direct, electroosmotically driven flow in packed capillary columns in an automated manner.…”

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Gradient Elution in Capillary Electrochromatography

Yan¹,

Dadoo²,

Zare³

et al. 1996

Anal. Chem.

143

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In analogy to pressure-driven gradient techniques in high-performance liquid chromatography, a system has been developed for delivering electroosmotically driven solvent gradients for capillary electrochromatography (CEC). Dynamic gradients with submicroliter per minute flow rates are generated by merging two electroosmotic flows that are regulated by computer-controlled voltages. These flows are delivered by two fused-silica capillary arms attached to a T-connector, where they mix and then flow into a capillary column that has been electrokinetically packed with 3-μm reversed-phase particles. The inlet of one capillary arm is placed in a solution reservoir containing one mobile phase, and the inlet of the other is placed in a second reservoir containing a second mobile phase. Two independent computer-controlled, programmable, high-voltage power supplies (0−50 kV)one providing an increasing ramp and the other providing a decreasing rampare used to apply variable high-voltage potentials to the mobile phase reservoirs to regulate the electroosmotic flow in each arm. The ratio of the electroosmotic flow rates between the two arms is changed with time according to the computer-controlled voltages to deliver the required gradient profile to the separation column. Experiments were performed to confirm the composition of the mobile phase during a gradient run and to determine the change of the composition in response to the programmed voltage profile. To demonstrate the performance of electroosmotically driven gradient elution in CEC, a mixture of 16 polycyclic aromatic hydrocarbons was separated in less than 90 min. This gradient technique is expected to be well-suited for generating not only solvent gradients in CEC but also other types of gradients, such as pH and ionic strength gradients, in capillary electrokinetic separations and analyses.

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Computer-controlled generation of pH gradients in capillary zone electrophoresis

Purghart

Games

1992

Journal of Chromatography A

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Low-Cost Liquid Chromatography (LC-LC). IV. “Pulsed Open Tube Gradient Generation”, A New Approach for Generating Nanoliter Volume Linear and Tailored Gradients for Capillary Electrophoresis and Micro-LC

Cited by 4 publications

References 5 publications

A Method To Reduce Gradient Delay Time of NanoLC

A Method To Reduce Gradient Delay Time of NanoLC

Gradient Elution in Capillary Electrochromatography

Computer-controlled generation of pH gradients in capillary zone electrophoresis

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