Leland Stanford Junior University

Xiaohua Huang

Richard Neil Zare

Stephen L Pentoney, Jr

Andrew G Ewing

Jack I Ohms

Raymond T Huckaby

Sandra E Sloss

A cross or T-shaped device is disclosed for use in capillary electrophoresis or capillary chromatography. The device includes a first capillary tube and a second capillary tube connected to the first tube at a point between the two ends of the first tube so that the contents flowing in the second tube will mix with a fluid flowing in the first tube. The two tubes enclose spaces with cross-sectional dimensions less than about 200 microns. The two tubes are connected so that there is substantially no dead space at the connection. The device is made by boring a hole at a selected location in the first tube, introducing an elongated guide member into the hole, threading the member into the second tube until the second tube contacts the first tube. The second tube is then permanently connected to the first tube and the guide member is then removed to form a T-shaped device. To form the cross-shaped device, a second hole is drilled at a location opposite to the first hole and a guide member is introduced into the second hole as well. A third tube is threaded onto the guide member on the opposite side of the second tube until it contacts the first tube. The third tube is also permanently connected to the first tube and the guide member is removed to yield a device with a cross-shaped configuration.

Capillary device

An end-column conductivity detector is described. A sensing electrode is placed in the outlet end of a capillary that has a hole in its side wall through which electrolyte moves past the sensing electrode into a reservoir that contains the ground electrode. This structure is simple to construct, has almost no dead volume, and minimizes electrolyte contact with adhesives used to mount the sensing electrode. The end-column conductivity detector is operated in conjunction with a commercial capillary zone electrophoresis system that has a capillary cartridge and a UV absorption detector. This design thus permits sequential measurement of the absorption and conductivity characteristics of separated analyte zones. When a species can be detected by both conductivity and UV absorption, then the absorption coefficient can be determined from the relation between the conductivity signal and the concentration of the species.

End-column conductivity detector for capillary zone electrophoresis

Electrical and electrochemical end-column detectors are provided in which the sensing microelectrode is placed at the outlet of the separation capillary. The novel design minimizes the electrical interference caused by the applied high voltage during CZE separations, and provides for detectors that are easy to construct, sensitive, reliable, and easy to operate.

End-column electrical and electrochemical detector for capillary zone

The electroosmotic velocity of an electrolyte is determined by displacing the electrolyte which fills a capillary tube by a second electrolyte which has the same composition as the first electrolyte but of a different concentration. The current flowing through the electrolyte is monitored until the current value becomes constant, indicating that all of the first electrolyte has been replaced by the second electrolyte. The time required for the first electrolyte to be entirely replaced by the second electrolyte is therefore measured to yield the electroosmotic velocity. Any components of samples in the electrolyte can also be detected by a detector to measure its actual velocity. Such actual velocity and the electroosmotic velocity of the electrolyte as a whole enables the electrophoretic mobility of the sample component to be determined. This method also enables the measurement of migration rates of micelles. If the constant current flowing when only the second electrolyte is in the tube is measured when the same voltage is applied as an additional data point, one need not wait until all of the first electrolyte has been replaced by the second electrolyte. The current value of only a short time interval needs to be monitored. The straight line curve plotted for such short time interval can be simply extended until the current value falls or rises to the constant current value when the tube is filled by the second electrolyte to find the time needed for the first electrolyte to be entirely replaced by the second electrolyte.

System for measuring electrokinetic properties and for characterizing

A capillary tube has a structure in its wall that permits ions to flow but no substantial amount of electrolyte to move therethrough. The structure therefore permits electrical contact between the electrolyte inside the tube and the outside environment without diluting the electrolyte. The structure forms only a small part of the side wall so that the tube retains its structural integrity and can be used in electrophoresis without requiring structural support. In the preferred embodiment, the structure is formed by drilling a hole in the side wall, filling the hole with glass powder and fused silica and heating the mixture to form a frit structure to plug the hole. The frit structure permits ions to flow but substantially no electrolyte to move therethrough. Electrophoretic samples exiting from the end of the tube are not diluted and can be continuously collected, such as on top of a moving plate.

Growing community of inventors

Mountain View, CA, United States of America

Xiaohua Huang