Chemical apparatus and process disinfecting – deodorizing – preser – Analyzer – structured indicator – or manipulative laboratory... – Means for analyzing gas sample
Reexamination Certificate
2001-03-02
2004-01-27
Soderquist, Arlen (Department: 1743)
Chemical apparatus and process disinfecting, deodorizing, preser
Analyzer, structured indicator, or manipulative laboratory...
Means for analyzing gas sample
C096S104000, C096S106000, C422S090000, C422S091000, C422S092000
Reexamination Certificate
active
06682699
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to gas chromatography systems for generally continuously sampling chemical samples and detecting desired compounds therefrom. In particular, the subject invention is directed to gas chromatographic column assemblies for temperature programmed analyses. More in particular, the subject invention relates to gas chromatograph column assemblies where power savings are achieved through optimized packing of capillary gas chromatograph column members with temperature sensors and heating wires which substantially increases the internal contact of such components with themselves and each other while reducing the amount of surface area of these components in contact with the surroundings. Still further, this invention relates to gas chromatograph systems which include assemblies of capillary gas chromatograph column members, temperature sensing mechanisms and heating mechanisms formed into a gas chromatograph column assembly which is positionally located in a manner to optimize thermal effects and produce an overall low power consumption system.
2. Prior Art
High performance gas chromatography has typically required the use of large laboratory instruments using large amounts of electrical power in their operation. This is especially the case for the standard practice of temperature programming a chromatographic separation in which the temperature of the oven containing the gas chromatography column is steadily increased to extend the range of gas chromatography separation capability. The large power required to heat and temperature program gas chromatography ovens has limited the capability of gas chromatography for use in portable instrumentation and especially in hand-portable instrumentation used in the field. Without large external power sources or large batteries, gas chromatography design and operations have been limited largely to non-temperature programming applications in small, lightweight portable instruments.
Additional requirements for gas chromatography technology to be practical in small portable instruments is for the technology to be compatible with and use commercially available gas chromatography capillary column technology. Since the use of capillary columns has become standard practice in laboratory gas chromatography instrumentation, a large number of capillary columns are now commercially available which offer a wide range of separation capabilities. The wide range of separation capabilities has been made possible through variation of the chemical compositions of the polymers which coat the inner walls of the capillary gas chromatography columns. Choice may now be had from many polymer coatings that are commercially available in capillary gas chromatography columns having standard thicknesses, column lengths, and column inner diameters to optimize the chemical separations required of the gas chromatography. The ability to readily use this commercially available gas chromatography column technology in small portable gas chromatography instruments is desirable for the practical realization of similar analytical capabilities in portable or small gas chromatography instruments.
The temperature programming of capillary gas chromatography columns is standardly practiced by electronic control of the temperature of an oven containing the gas chromatography column. To achieve rapid and uniform temperature response of the gas chromatography column assembly to temperature changes in the oven, capillary gas chromatography columns are standardly packaged by winding the columns on a wire frame support. The winding of the columns on the wire frame support provides extensive surface contact of the capillary gas chromatography column with the heated air in the oven for rapid temperature equilibration of the capillary gas chromatography column with the oven air. In laboratory gas chromatography ovens, the air within the oven is typically mixed with a fan to achieve temperature uniformity within the oven. Laboratory gas chromatography instruments typically consume power on the order of kilowatts for temperature programming and are power limited to temperature ramping rates approximating 10's of ° C./min or less, especially at higher operating temperatures. While smaller, more portable gas chromatography instruments have been manufactured which have smaller ovens, such still require powers on the order of 1 kW or more for temperature programming, especially when ramping rates of 10's of ° C./min are required for fast analysis times.
Reductions in gas chromatography oven size to that of a small heated compartment large enough to contain a short length of gas chromatography column have been made for the purposes of reducing power consumption and reducing instrument size. The resulting gas chromatography instruments are typically operated isothermally to avoid the power consumption associated with temperature programming, but this greatly constrains the analytical capabilities of such gas chromatography instrumentation. One case in which low power temperature programming has been implemented is described by Maswadeh et al. in “New Generation of Hand-Held, Compact, Disposable Gas Chromatography Devices,” Field-Portable Chromatography and Spectrometry workshop, Jun. 3-5, 1996, Snowbird, Utah, pp. P56-P59. In this case a palm-size gas chromatography module was demonstrated which consumes 15W of power for temperature programming at a 0.75° C./s ramp rate. A short ramp with a maximum temperature of 60° C. served to limit power consumption by the module.
The need for fast temperature programming of miniature chromatographic analysis instrumentation is described by Sides and Cates in U.S. Pat. No. 5,014,541. They describe the requirement to raise the temperature of the capillary gas chromatography column from 50° C. to 120° C. within 20 seconds to achieve their analysis objectives. They accomplish this with a miniature gas chromatography column assembly in which the standard gas chromatography oven is replaced by a tubular heat conductor support on which the gas chromatography column is wound. A heating element within the tubular support is used for temperature programming. While this instrument achieves a gas chromatograph of small size, the power consumption is on the order of 1 kW and a portable power generator is a recommended option for portable operation of this commercial instrument.
The importance of reducing the thermal mass of gas chromatography column assemblies for the rapid heating was recognized by Norem in U.S. Pat. No. 3,159,996. This invention consisted of a glass tube with three parallel bores and sufficient length to contain a heater wire, a resistance thermometer wire (a type of temperature sensor), with the remaining bore coated on the inside to function as a gas chromatography column. While such a device could have a smaller thermal mass than a small, conventional gas chromatography oven, a large amount of power will still be required to heat the sizable mass of glass tubing.
Another way to significantly reduce power consumption with a miniature gas chromatography is by reducing the electrical heating and sensing elements of gas chromatography ovens to miniature forms and integrate them with a capillary gas chromatography column. U.S. Pat. No. 5,005,399 achieves this by using a thin-film coated capillary gas chromatography column wound on a mandrill consisting of an insulating material. Electrical current passed through the thin film surrounding the gas chromatography column is used to resistively heat the column. While this approach uses far less power than heating a conventional gas chromatography oven, it still requires significant power to heat the gas chromatography column because of the large surface area of the gas chromatography column in contact with the mandrill material since this insulating support is also heated through contact with the heating element. A serious shortcoming of this approach is the difficulty of fabricating annular thin film coatings of substantial l
Everson James F.
Mustacich Robert V.
RVM Scientific, Inc.
Soderquist Arlen
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