Measuring and testing – Sampler – sample handling – etc. – With heating or cooling
Reexamination Certificate
1999-04-27
2001-09-11
Williams, Hezron (Department: 2856)
Measuring and testing
Sampler, sample handling, etc.
With heating or cooling
C073S019090, C073S023410, C073S863810
Reexamination Certificate
active
06286375
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to headspace sampling apparatus and, more particularly, to a field usable apparatus for facilitating the extraction of vapor from the headspace of a vial containing a sample of water or soil to be analyzed for volatile contamination.
BACKGROUND OF THE INVENTION
Volatile organic compounds (VOC) in water and soil are routinely analyzed by headspace analysis. A sample of water or soil mixed with water partially fills a closed septum vial and is heated, driving dissolved volatile organics out of solution and into the vapor headspace and establishing an equilibrium between the sample and the vapor. A portion of this vapor is then extracted for analysis by, typically, a form of gas chromatography. Sufficient vapor is extracted from the headspace to purge connecting lines to the gas chromotagraph with a representative sample. Sampling vapor avoids the introduction of non-volatile or solid particles into the inlet of the gas chromatograph, which is not desirable.
Known in the art are field-portable gas chromatograph/mass spectrometers (GC/MS) engineered specifically for on-site VOC analysis. These self-contained devices typically comprise a vacuum system, analytical components and power components within one compact unit and are capable of acquiring and analyzing VOC samples in the field, thus eliminating the problems associated with conventional collecting, shipping, storing, and analyzing of samples. The ability of such portable devices to provide confirmatory test results immediately on site make them particularly useful for hazardous-waste site investigations, and emergency response situations.
Unfortunately, these portable GC/MS devices do not work well in headspace analysis. Their sample vacuum pumping systems are not powerful enough to extract vapors from a headspace. In order to make the portable devices suitable for headspace analysis, portable device manufacturers have developed auxiliary equipment. Such equipment generally operates to replace the headspace vapor with a VOC-free make up gas as the vapor is extracted by the sample pumping system. This additional equipment is complex in operation and expensive.
It is therefore a feature of the present invention to provide a compact portable, apparatus which facilitates the extraction of vapor from the headspace of a sample vial for accurate VOC analysis. An advantage of the invention is the provision of a relatively simple and inexpensive apparatus for facilitating vapor extraction.
A further advantage of the present invention is that it facilitates the extraction of the entire headspace from sample vial, thus increasing the sensitivity of the analysis.
Other aspects and advantages of the invention are set forth in part herein and in part will be obvious herefrom, or may be attained by means of instrumentalities and combinations pointed out in the appended claims.
SUMMARY OF THE INVENTION
In accordance with the foregoing principles and objects of the invention, an apparatus for facilitating vapor extraction from the headspace of a closed septum vial containing a sample to be analyzed is described. The sample vial is exposed to a heat source, thus driving dissolved volatile organics out of solution and into the vapor headspace. The sample vial may be substantially submerged in a heated water bath or sand bath or inserted into the well of a block heater. A first end of a hollow probe penetrates the septum of the sample vial and is submerged within the sample. The second end of the probe is connected to the first port of a two-port gas-tight valve. A first end of a flexible tube is connected to the second port of the valve. The second end of the tube is submerged in a heated liquid reservoir. The liquid is exposed to atmospheric pressure. If the sample vial is submerged in a heated water bath, the second end of the tube is submerged in the water bath. If the sample vial is inserted into a heated sand bath or block heater, the second end of the tube is submerged in heated liquid contained in a second vial. The vapor is extracted from the vial through the septum by a vapor extraction means.
In a first embodiment, vapor is extracted from the headspace, thereby lowering the pressure within the vial and creating a vacuum therein. During such vapor extraction, the valve is opened, thereby connecting the sample in the vial to the liquid, that is, the water from the water bath or liquid in the second vial, via the tube. The liquid thereby replaces the vapor as it is extracted for analysis from the otherwise closed headspace volume. The apparatus thus allows liquid displacement to relieve the vacuum in the headspace of the sample vial during vapor extraction without diluting the vapor.
In an alternate embodiment, the sample vial is inserted into the well of a block heater. As before, a first end of a hollow probe penetrates the septum of the sample vial and is submerged within the sample. The second end of the probe is connected to the first port of a two-port gas-tight valve. A first end of a flexible tube is connected to the second port of the valve. The second end of the tube penetrates the septum of a septum-sealed second vial containing a heated liquid and is submerged in the liquid. A source of pressurized VOC-free gas supplies the gas to the second vial through the septum. During such pressurization, the valve is opened, thereby connecting the vial to the heated liquid via the tube. The heated liquid thereby expels the headspace vapors, which may then be analyzed.
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Cole Tony Y
Garber Charles D.
Kundert Thomas L.
Scearce Bobby D.
The United States of America as represented by the Secretary of
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