Dionex Corporation

Agilent Technologies, Inc.

The Dow Chemical Company

Roy D Rocklin

Christopher A Pohl

Hongfeng Yin

Kevin P Killeen

John R Stillian

Daniel Sobek

Nebojsa Avdalovic

Randy M McCormick

Neboisa Avdalovic

The subject invention includes constituent separation apparatuses that include a fluid pathway and a pair of spaced-apart electrodes positioned within the pathway for detecting current flow within a mobile phase present in the pathway. Coupled to the pair of spaced-apart electrodes is a mix ratio determinator for determining the mix ratio of the mobile phase from the detected current flow. Also provided are methods that include contacting a mobile phase with an apparatus for separating constituents of a mobile phase, detecting the current flow of the mobile phase when the mobile phase is in contact with the apparatus and determining the mix ratio of the mobile phase from the detected current flow. The mix ratio may be adjusted based on the determined mix ratio. Algorithms for practicing the subject methods are also provided on computer readable mediums. Systems and kits for practicing the subject methods are also provided.

Devices and methods for separating constituents

The fluid flow rate within a microfluidic passageway of a microfabricated device is determined by measuring the time-of-flight of a heat pulse coupled into the fluid. Since the propagation velocity of the heat trace is generally slower than the mean flow rate of the flow, additional processing provides the appropriate scaling needed to obtain an accurate fluid flow rate measurement. The scaling factor is based on the geometry of the structure and the thermal properties of the fluid and the materials used for the device.

Microfluidic bulk flow determinations based on converting heat tracer measurements

Apparatus and methods are provided for increasing the sensitivity of detection of ionic species separated by capillary electrophoresis. The apparatus includes capillary electrophoretic separating means, suppressor means and detector means.

Method and apparatus for improved detection of ionic species by

In capillary electrophoresis systems, real-time monitoring and measurement of the electroosmotic flow through a separation capillary is accomplished by coupling the outlet of the separation capillary to an electrically-conductive junction. In one embodiment, this junction is an ion-impermeable or an ion-exchange membrane unit that preferentially exchanges ions having a charge opposite to analyte ions of interest. Within a downstream region of the junction, all axial incremental voltage from the electroosmotic voltage source is terminated, which ensures that downstream electrolyte ion movement is passive, due to active flow created upstream when an incremental axial voltage existed. Upstream electrolyte ion flux is proportional to C.sub.1 .multidot.(.mu..sub.e +.mu..sub.eo), where C.sub.1 is the upstream concentration of the electrolyte ion of interest, .mu..sub.e is the electrolyte electrophoretic mobility, and .mu..sub.eo is the electroosmotic mobility. Downstream, the flux is proportional to C.sub.2 .multidot..mu..sub.eo, where C.sub.2 is the downstream concentration of the electrolyte ion of interest. The fluxes are equal, whereupon .mu..sub.eo .apprxeq.C.sub.1 .multidot..mu..sub.e /(C.sub.2 -C.sub.1). Since .mu..sub.e is known, .mu..sub.eo can be determined in real-time by measuring C.sub.2 and C.sub.1. In a second embodiment, the electrically-conductive junction preferably is a grounding capillary that converts plug-like electroosmotic flow to parabolic flow. A parabolic flow characteristic such as streaming potential, streaming current, or pressure differential is measured in real-time to ascertain electroosmotic flow rate. In each embodiment, the realtime measured flow information is feedback-coupled to preferably alter zeta-potential to regulate electrolyte solution flow in the separation capillary.

Methods and apparatus for real-time monitoring, measurement and control

A method of ion chromatography in which the sample passes through a chromatographic column, a suppressor, and a conductivity detector, using a gradient electrolyte eluent. A non-ionic polyhydroxy compound is added with the eluent to the chromatographic column at a concentration inversely related to the concentration of the electrolyte which increases with time. The effluent is passed through a membrane suppressor for the conductivity of the electrolyte. The regenerant stream in the suppressor includes a complexing agent (boric acid) which passes through the membrane into the effluent to form highly ionized complex which counterbalances the increased background conductivity of the electrolyte to stabilize the background conductivity in the conductor.

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Sunnyvale, CA, United States of America

Roy D Rocklin