Chemistry: analytical and immunological testing – Including sample preparation – Gaseous sample or with change of physical state
Reexamination Certificate
1999-08-02
2001-08-21
Warden, Jill (Department: 1743)
Chemistry: analytical and immunological testing
Including sample preparation
Gaseous sample or with change of physical state
C436S157000, C422S098000
Reexamination Certificate
active
06277649
ABSTRACT:
TECHNICAL FIELD
This invention relates to analytical apparatus and methods. Particularly, this invention relates to a system which serves to pass sample vapors into operative relation with a sensor array of an analytical instrument.
BACKGROUND ART
Headspace technology is a relatively new technique which allows the sampling of the vapor of a material, so that the vapor may be analyzed using a gas chromatograph or other analytical instrument. The volatile (liquid or solid) material attains equilibrium with the vapor phase within a sealed vial. Equilibrium is established when the level of liquid or solid material in the vial no longer changes so that the total quantity of liquid or solid, and vapor remains constant. A syringe is then used to retrieve a small amount of vapor for analysis. Headspace technology is advantageous over conventional direct sample injection because it assures that only vapor enters the gas chromatograph. This is advantageous because it reduces the chance of contamination or destruction of the instrument due to introduction of unevaporated sample. Since the sample is in the vapor form, a larger sample size is possible. An increased sample size generally results in increased sensitivity.
The unique quality and character of many products are rooted in the chemical volatiles which comprise their odor. The ability to reliably measure and identify impurities, taints and adulteration is therefore valuable in many situations. Analytical techniques such as gas chromatography are sometimes used but data is often difficult to correlate with sensory information and is costly to produce. The Aromascan® technology produced by Aromascan Technologies allows odors to be measured electronically. Measurement of aromatic characteristics is very useful in certain applications.
A conventional Aromascan(& system is comprised of a sensory array and a gas sampling device that presents vapor of the sample material into connection with the array. The system is controlled and the data generated from array signals using an attached computer. The technology can recognize differences in the aroma, and hence the quality, of incoming raw materials. The ability to recognize or differentiate between a characterized product and an unknown imparts a wide range of potential applications for technology. The speed, sensitivity and accuracy of the technology translate into improved productivity and reduced costs.
Unfortunately, since this type of analysis is relatively new, there is still much needed improvement. Current Aromascan® sensors do not provide a means to control the rate of passage of sample materials before the sensor array. This lack of control translates into decreased sensitivity since the vapor for analysis travels too rapidly or slowly in front of the sensor array. An improper rate of travel in relation to the sensor array results in a lack of repeatability and potentially inaccurate results. Other types of analytical instruments may also benefit from better control of the flow of sample material thereto.
Thus, there exists a need for an apparatus and method to control the rate of travel of sample vapors in relation to a sensor array of an analytical instrument. There further exists a need for an apparatus which provides a controlled rate of flow of material collected from a sample into relation with the sensors of an analytical instrument.
DISCLOSURE OF INVENTION
It is an object of the present invention to provide a novel apparatus and method for passing headspace vapors in relation to a sensor array of an analytical instrument.
It is a further object of the present invention to provide a non-mechanical means of passing sample vapors in relation to a sensor array.
It is a further object of the present invention to provide an apparatus and method which improves sample data collection.
It is a further object of the present invention to provide an apparatus and method which improves accuracy of measurement.
It is a further object of the present invention to provide an apparatus and method which provides a controlled distribution of sample vapors.
It is a further object of the present invention to provide an apparatus which enables the sensor array to obtain a larger amount of data for a given amount of sample.
It is a further object of the present invention to provide a highly effective means for use with electronic aroma sensors.
It is a further object of the present invention to provide an apparatus which permits the passage of sample vapors past a sensor array multiple times.
It is a further object of the present invention to enable the process of thermal desorption of headspace vapors inside a chamber.
It is a further object of the present invention to provide a means for thermal desorption of headspace vapors between two traps located at opposite ends of a sample path.
The foregoing objects are accomplished in an exemplary apparatus and method which enables sample vapors to slowly pass a sensor of an analytical instrument, such as a sensor array of an electronic aroma sensor. The apparatus may include a gas sampling device. The gas sampling device extracts sample vapors from a vial containing a material to be analyzed and passes them into the apparatus. The apparatus further includes a purge gas source. The purge gas is preferably an inert gas such as helium. The purge gas may be used to move sample vapors in the system.
The apparatus further includes a valve mechanism which is in connection with a sensor loop. The pathways in the valve mechanism selectively direct the headspace vapors and the purge gas onto a first sample collection device which in the exemplary embodiment includes a first trap located at a first end of the sensor loop. The trap functions as a sample concentrator and consists of a collection vessel and a surrounding heater. Purge gas and other materials not collected in the first trap pass through the sample loop to a vent.
After the sample is collected in the first trap, the heater surrounding the first trap is turned on. Material in the sample thermally desorbs off the first trap and slowly travels through the sensor loop past the sensor mechanisms of the analytical instrument. The sensor mechanisms preferably include a sensor array of an electronic aroma sensor. The sensor array senses the material collected from the headspace and provides signals indicative of its chemical composition or other properties. After passing in front of the sensor array in the sensor loop, the sample material collects on a second sample collection device which in the exemplary embodiment includes a second trap located at the opposite end of the sensor loop from the first trap. The second trap again collects the sample material. The second trap includes a heater. When the heater is later turned on, the sample material thermally desorbs so that it may pass through the sensor loop in front of the sensor array again. The position of the valve mechanism is changed to enable reverse flow in the sensor loop. The first trap is cooled so that the material desorbed from the second trap is again collected in the first trap. The process is repeated until sample analysis is completed. Upon completion both traps may be heated. The sample vapors are vented to purge the sensor loop.
REFERENCES:
patent: 5441700 (1995-08-01), Markelov
patent: 5693538 (1997-12-01), Capuano et al.
Cole Monique T.
Jocke Ralph E.
Parmelee Christopher L.
Walker & Jocke
Warden Jill
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