Chemical apparatus and process disinfecting – deodorizing – preser – Analyzer – structured indicator – or manipulative laboratory... – Means for analyzing gas sample
Reexamination Certificate
1999-04-30
2001-02-20
Ludlow, Jan (Department: 1743)
Chemical apparatus and process disinfecting, deodorizing, preser
Analyzer, structured indicator, or manipulative laboratory...
Means for analyzing gas sample
C422S089000, C422S105000, C073S023410, C095S087000, C095S089000, C096S103000, C096S104000, C096S105000
Reexamination Certificate
active
06190613
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a gaseous sample concentration device that, upon analyzing a gaseous or liquid sample composed of multiple components using an apparatus such as a gas chromatograph, concentrates the gaseous sample at a certain position in the gas transfer line that transfers the gas into the apparatus.
Description of the Related Art
Apparatus, such as gas chromatographs, are available for analyzing gaseous or liquid samples composed of multiple components by introduction of such gas or liquid samples into a detector via a gas transfer line.
The gas chromatograph unit analyzes a gaseous sample composed of multiple components, first by injecting the sample using a micro-syringe or the like into a sample injection port located at one end of a separation column such as a capillary column or the like housed in a constant temperature chamber, then by separating the sample into each component in the separation column, and by detecting each separated component using a detector located at the other end of the separation column. The detector that is typically employed is a mass spectrometer or hydrogen flame ionization detector. Using the gas chromatograph, a gas chromatogram showing peaks to indicate the detection intensity (concentration) of each component along with corresponding retention times can be obtained as a result of this analysis.
For improving accuracy of the analysis, it is desirable when using the gas chromatograph that a single component be detected by a single isolated peak, and not be broken into multiple peaks. For this, it is required that the gaseous sample be introduced at the narrowest volume possible at the end of the separation column. In order for the gaseous sample injected into the separation column in the gas chromatograph to be concentrated within the narrowest possible volume, a conceivable method is to inject a required amount of the sample with a micro-syringe or the like. However, in the case that the concentration of the sample is very low, a large amount of sample, for example a few ml, needs to be injected. This is time-consuming and, therefore, is not at all a practical process to be implemented. Another conceivable method is to cool the entire column to a temperature below the ambient temperature so that the sample injected in the column becomes condensed and concentrated. This method, on the other hand, requires a large amount of refrigerant. Also, as the minimum attainable temperature is only −80° C., trapping of low boiling-point compounds, such a hydrocarbons with carbon numbers less than 10, is almost impossible.
There is a conventionally known method wherein a portion of one side of the separation column to which the sample is introduced is wound in a coil and is cooled by dipping it into liquid nitrogen placed in a Dewar vessel. In this method, after the gas sample is condensed within that portion, the separation column is taken out of the Dewar vessel and is placed in a constant temperature chamber. By these processes, the temperature inside of the separation column is raised and the condensed sample desorbs thermally, and the components of the sample are further separated from each other by the separation column.
This method can almost perfectly condense and trap a sample consisting of multiple components having carbon numbers of greater than 3 or 4 (i.e., propane or butane in the case of hydrocarbon) at the cooled portion. As a result, each component that is trapped thereby is detected by a single peak.
The above-described method can be practiced in the laboratory. However, implementing it is still cumbersome due to the fact that all the steps usually have to be carried out manually, since it has proven difficult to automate the method.
In order to solve the aforementioned problem, a method can be considered in which a nozzle for spraying liquid nitrogen is placed facing a portion of the separation column in the neighborhood of the sample injection port, whereby the portion of the separation column is directly cooled with liquid nitrogen that is sprayed from the nozzle. By this method, the portion of the separation column can be locally cooled to the temperature of liquid nitrogen (−196° C. ) within a constant temperature chamber which is otherwise kept at a desired temperature, 40° C. for example. It is therefore expected that the sample injected into the sample injection port can be condensed at the cooled portion of the column and that each component can be detected as a corresponding single peak.
However, upon cooling by liquid nitrogen using this method, moisture in the air condenses and freezes around the cooled portion of the separation column, and after the nitrogen spray stops, the air inside the constant temperature chamber enters into the nozzle and moisture existing in the air freezes into ice inside of the nozzle. This will create a problem in that the open end of the nozzle becomes plugged up with ice, making subsequent sprays of the liquid nitrogen difficult.
SUMMARY OF THE INVENTION
The present invention provides a device which concentrates a gaseous sample without causing plugging of the nozzle with ice when the gaseous sample is concentrated by cooling with a coolant spray at a portion of the gas transfer line in which the sample is introduced.
The sample concentration device of the present invention concentrates a sample in the vicinity of the sample injection port, wherein a sample consisting of multiple components can then be analyzed by introducing the sample via the sample injection port, and by transferring the sample to a detector through the gas transfer line which is housed in a constant temperature chamber. The device is characterized by a cooling means for cooling a portion of the gas transfer line by spraying coolant from a nozzle facing the portion near the gas injection port, and by a gas flow means for creating a substantially dry gas flow through the nozzle to prevent the nozzle from becoming plugged with ice which is formed by freezing of moisture in the air when the coolant spray is ceased. Also, according to the present invention, the gas transfer line may be either a separation column, such as a capillary separation column used to separate a gas mixture having multiple components into each respective component thereof, or a simple conduit which operates without separation capability.
According to the present invention, the gas transfer line can be locally cooled to the temperature of the coolant by cooling a portion of the gas transfer line by spraying the coolant onto that portion. Thus, using the present invention, the sample introduced from the sample injection port can be condensed at the cooled portion of the gas transfer line. As a result, a single component is shown by a single peak when detecting each component of the sample with the detector.
The present invention provides an arrangement whereby a dry gas flows through the nozzle by the gas flow means, and therefore, the dry gas flows through the nozzle after the coolant spray in the cooling means has ceased. By the provision of flowing such a dry gas, moisturized air is prevented from entering inside the nozzle through its open end. Because the gas that flows through the nozzle owing to the gas flow means is a substantially dry gas which does not contain moisture, formation of ice caused by freezing of water existing in air, and thus plugging of the nozzle, can be prevented.
The sample concentration device of the present invention can condense the injected sample at the portion of the gas transfer line which is cooled by the coolant spray. However, if the humidity of the environment where the sample concentration device is employed is extremely high, a single component within the sample might be detected by plural split peaks.
This is considered to be due <6> to an ice formation at the cooled portion following the condensation of the water in highly humid air. As a result, a non-uniform thermal desorption takes place following a non-uniform melting of ice when external heating is late
Hosaka Akihiko
Morikawa Masami
Sato Kunitaka
Tsuge Shin
Watanabe Chuichi
Frontier Laboratories Ltd.
Guss Paul A.
Ludlow Jan
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