Abstract:
A voltage alternating between a high value and a low value is applied across a separation capillary in an electrophoretic system and electrochemical detection is performed only during time periods when a low voltage or no voltage is applied to the tube to improve the sensitivity of detection.
Abstract:
The present invention features a method and apparatus with a rotatable central reservoir and radially extending support arms for packing chromatographic columns at a consistent gradient of particle impact by using centripetal forces to independently accelerate particles comprising a bed material through a filling opening at one end of the column and continuously as they move axially along the length of the column to their packed destination. The method and apparatus are particularly suitable for use in packing capillary columns having an interior diameter of about 500 microns or less.
Abstract:
The present invention relates to silica materials and particles having surfaces which define an interior. The interior includes interior silicon atoms at least a portion of which is bonded to a substituted or unsubstituted alkyl moiety. In a preferred aspect of the present invention, the silica material also has surface silicon atoms to which are bonded substituted or unsubstituted alkyl moieties. A capillary tube coated on its inner surface with the silica material of the present invention is also disclosed. The silica materials of the present invention are resistant to degradation at high or low pH and are particularly useful as chromatographic stationary phases, especially for use in open tubular liquid chromatography and open tubular electrochromatography.
Abstract:
An electrophoretic or chromatographic separation capillary containing a fluid defines a bore therein through which a sample travels and separates into components. The tube has a side wall defining a through hole therein which is surrounded by a medium including a substance. The substance is introduced into the capillary through the hole by means of gravity, pressure or electroosmosis. The substance introduced may be used to label sample components to enhance detection, or to enhance separation of sample components.
Abstract:
The present invention discloses methods of preparing a continuous, porous metal oxide monolith in a container. The method involves providing a reaction mixture containing a metal salt or metal alkoxide compound, a solvent, and a porogenic reagent. Next, an epoxide is added to the reaction mixture under conditions effective to initiate condensation and polymerization of the reaction mixture. Then, a container is filled with the reaction mixture after epoxide addition to obtain a continuous, porous metal oxide monolith in the container. The present invention also discloses columns including a tubular container and a continuous, porous Group IV metal oxide monolith in contact with the inner walls of the tubular container, where the Group IV metal oxide monolith is free of any support or matrix material, and other articles including a continuous, porous Group IV metal oxide monolith, where the metal oxide monolith is free of any support or matrix material.
Abstract:
A method of preparing a thermoplastic polycarbonate film having an optical retardation value of less than or equal to 20 nm, is described. The method includes: (a) forming a molten extrudate (20) of a thermoplastic polycarbonate polymer in an extruder (11) having a terminal die (17) through which the molten extrudate is passed, the molten extrudate having a temperature of 150° C. to 400° C. upon emerging from terminal die (17); and (b) passing molten extrudate (20), from die (17), between two counter-rotating rolls (23 and 26) each having an elastomeric polymer surface (35 and 38), the counter-rotating rolls having a roll speed ratio and a nip (41), the distance between the terminal die (17) and the nip (41) being a die-nip distance (47). The extrudate temperature, the roll speed ratio and the die-nip distance (47) are each selected such that a thermoplastic polycarbonate film (32) having an optical retardation value of less than or equal to 20 nm is formed.
Abstract:
A sensor having a substrate overlayed with a sol-gel layer, a chemical sensing species deposited upon the sol-gel layer, and a thin film of a second sol-gel layer overlaying and entrapping the species. The effect of this sensor is that the species exhibits a significant portion of its intrinsic function over a period of time. In yet another embodiment of the subject invention, a method is disclosed to form a thin sol-gel layer upon an ambient substrat. This method ensures the integrity, stability and functionality of the chemical sensing species within the sol-gel layers.
Abstract:
End-column detectors are provided in which either a sensing microelectrode or optical fiber is placed at the end of the separation capillary. Additionally, an alignment apparatus is provided to facilitate the manual or automated positioning of either type of sensing device relative to the end of the separation capillary. The invention provides detectors that are sensitive, reliable, and easy to construct and to operate.
Abstract:
An on-column derivatization scheme where a liquid or solid labeling reagent is provided in a capillary to react chemically with a sample in order to label the sample. Electrophoretic separation may be carried out immediately thereafter to simplify the derivatization, separation and detection process. By localizing the labeling process to a small area within the capillary, fast kinetics and high reaction yield are achieved.