The present invention relates to devices and techniques used to distinguish particular types of hydrocarbons from one another in a matrix that may be a fluid. More particularly, the present invention relates to systems and methods for capturing hydrocarbons on a test bed for subsequent analysis in a test device. More specifically, the present invention relates to devices and methods for determining particular hydrocarbons in a matrix, including polar and nonpolar hydrocarbons.
There is a range of situations in which it is desirable to determine the composition of a matrix. For purposes of describing the present invention, a matrix may be a fluid, such as a solvent including water, a mixture, a gaseous material, or a loose solid such as soil but not limited thereto. In particular, there are situations in which it is of interest to determine whether one or more hydrocarbons exist in the matrix. That interest includes being able to identify the specific hydrocarbon or hydrocarbons that exist in a sample. Such analyses are conducted for many samples and so there is a need for a fast, safe, accurate, precise, more environmentally friendly (“green”), and economical hydrocarbon measurement system and technique used to measure the hydrocarbon content of the matrix. An aspect of such systems and techniques that exist is that one or more solvents are used to separate components of the sample composition. It is desirable to minimize the use of solvents while providing an effective and reliable analysis platform.
Infrared absorption measurements have been the preferred basis of measurement of hydrocarbon existence in a matrix, such as a water sample in particular, for many years. Generally, these measurement techniques require first performing a liquid-liquid extraction to remove the hydrocarbon from the matrix. Those solvents that have been considered effective for performing hydrocarbon extraction also raise environmental, health, and safety concerns. The sensing and detection industry response to this challenge has been to introduce new methods and systems for effective hydrocarbon separation and detection in a sample.
As used herein, “hydrocarbon” means all molecules containing hydrogen and carbon; examples include aliphatic and aromatic molecules as well as carboxyl groups in carboxylic acids or ester groups. As used herein, “oil” means a mixture of aliphatic hydrocarbons with generally between seven and 40 carbons in the chain, aromatic species, and other hydrocarbons. It includes crude oil, refined oil, heating oil, and any other form of carbon-based oil. As used herein, “TPH” means Total Petroleum Hydrocarbons, generally including non-volatile aliphatic molecules of varying chemical structure with up to 40 carbons. As used herein, “Grease” refers to long chain hydrocarbon molecules containing carbonyls such as carboxylic acid and/or ester functional group or groups. As used herein, “TOG” means Total Oil and Grease; that is, the total of TPH and Grease. As used herein, “HEM” means Hexane Extractable Material.
The current US standard method approved by the Environmental Protection Agency (“EPA”) for measuring TOG and TPH in a water sample is to take a liter sample of the composition to be analyzed, add a substantial volume of hexane, in the range of 90 to 130 milliliters (mls) and sometimes more, for TOG, and 90 to 130 mls for TPH, shake the sample, and let the water and solvent phase separate. The solvent phase is dried, and the remainder is weighed, with that dried mass remainder identified as the TOG. Next, the nonpolar portion of the TOG is identified by reconstituting the dried solvent phase remainder with hexane, passing that reconstituted remainder through a silica gel matrix, or adding silica gel to the reconstituted solvent followed by stirring and filtration of the silica gel, heating the reconstituted remainder to remove the hexane solvent, and the dried reconstituted remainder is weighed. That dried reconstituted remainder is the nonpolar portion of the TOG composition from the sample.
The existing EPA-approved extraction method requires the use of a large quantity, on the order of 180 mls or more, of hexane solvent. It also requires the use of highly accurate balances to measure as accurately as possible the weight of the dried solvent phase TOG remainder that is the TOG content of the sample, and the dried reconstituted remainder that is the nonpolar portion of the TOG. The existing method produces substantial hexane off gassing. This method is also labor intensive, and the measurement process can take a long time. It must be ensured that there is no water present, and all the hexane is evaporated, as the presence of either will result in over-reporting the TOG content of the sample.
What is needed is a reliable system and method to enable the detection of TOG in a matrix sample, as well as any polar and nonpolar hydrocarbons in the sample. The system and method must be relatively easy to use, and it must minimize solvent usage. Moreover, the system and method must be cost effective and reduce the importance of using highly accurate balances.
It is an object of the present invention to provide a reliable apparatus and method to enable the detection of TOG in a matrix sample, as well as any polar and nonpolar hydrocarbons in the sample. It is also an object of the invention to provide such an apparatus and method that is relatively easy to use and that minimizes solvent usage, particularly in comparison to the amount of solvent needed under existing EPA-approved extraction methods. It is further an object of the invention to provide such an apparatus and method that is cost effective and reduces the need to use highly accurate balances.
These and other objects are achieved with the present invention, which is a hydrocarbon separation apparatus capable of obtaining test specimens suitable for use in detecting hydrocarbons in a matrix sample, and a related method for using that apparatus. The apparatus includes a first container, a second container, and a connector between the first container and the second container. The separation apparatus can be used to transfer captured hydrocarbon material to a specimen extractor apparatus and then to an analyzer for the analysis of hydrocarbons capture from a fluid sample.
The first container is used to collect a sample of a matrix such as a fluid to be analyzed. The matrix may be water but not limited thereto. The connector is used to transfer contents of the first container into the second container. The connector includes means for capturing a portion of the contents of the first container. The second container is used to reconstitute nonpolar elements of the contents transferred through the connector. Alternatively, the nonpolar constituents can be transferred to an additional sample container where reconstitution steps can be carried out. The second container may then be coupled to the specimen extractor apparatus, which includes a membrane for retaining analyte thereto. Specifically, the extractor apparatus is used to capture on the membrane the nonpolar hydrocarbon of the second container. The extractor apparatus may then be coupled to an analyzer, which analyzer is configured to identify the nonpolar hydrocarbon or hydrocarbons retained on the membrane. The analyzer may be a spectrometer, a radiometer or other detection tool configured with analysis software to enable hydrocarbon determination.
The membrane used in the extractor apparatus is preferably the type that contains minimal or no amount of the analyte of interest or minimal amounts or zero chemical bonds similar to the chemical bonds in the analyte of interest, which bonds may interfere with the wavelength detection range or ranges of interest. If the membrane contains the analyte or chemical bonds similar to the analyte, it must be such that they can be accounted for in the analysis of the tested membrane. For the purpose of determining hydrocarbon content in water, for example, the membrane contains minimal or zero hydrocarbon bonds which interfere with the wavelength detection range or ranges of interest. Such a membrane can be used to determine the type of hydrocarbon molecule present, and thus can differentiate TPH from TOG, without any separate sample preparation. The ClearShot™ Extractor system available from Orono Spectral Solutions of Hermon, Maine, US is suitable for this application. The OSS ClearShot method measures TOG by liquid-liquid extraction in syringe. In this process, after separating TOG in the separating container, fluid is removed, and solvent is evaporated. The remaining material is reconstituted using a solvent and that sample is processed through the extractor. In this case, the extracted TOG will not be passed through the connector to the second container.
The apparatus described is used to carry out the method for isolating TOG from the matrix, which may be a fluid such as water, and isolating nonpolar hydrocarbons of the TOG. The method includes the steps of directing a sample of the fluid to be analyzed into the first container and adding a small amount of hexane to the fluid in the first container. The combination is mixed and allowed to separate before removing the water phase from the first container to leave a hexane-based non-aqueous fluid in the first container. The connector includes a first end and a second end. The first end is removably connected to the first container and the second end is removably connected to the second container. The connector is a conduit with an interior through which fluid passes. The interior of the connector includes a selective fluid retainer chosen to capture within the connector at least a substantial portion of the polar portion of the TOG. That retainer may be an adsorbent selected to adsorb expected hydrocarbon components of the matrix under analysis. The retainer may be held in the connector with a mesh containment, for example. The adsorbent may be a powdered magnesium silicate or Silica Gel but not limited thereto.
The method further includes the steps of directing solvent including the analyte to be detected from the first container through the connector to the second container and capturing polar hydrocarbons of the non-aqueous fluid in the connector. The solvent and non-polar hydrocarbon fluid that passes into the second container can be heated and/or exposed to an air flow sufficient to cause evaporation of the solvent. The remaining dried non-polar hydrocarbon content is then reconstituted, such as with Acetone, Methanol, Ethanol, water, or other suitable solvent, and then may be transferred to the extractor apparatus. The fluid may be passed through the membrane of the extractor apparatus, which is selected to retain thereon the non-polar hydrocarbon. The membrane may then be placed in the analyzer for non-polar hydrocarbon analysis.
The apparatus and method of the present invention significantly reduce the use of solvent for effective extraction by as much as 99% in comparison to existing extractor methods. It eliminates the need to use very accurate balances as the nonpolar hydrocarbon specimen goes directly to the membrane and then directly to the analyzer. All sample processing can be carried out in the containers and connector, all of which may be enclosed, thereby reducing off gassing concerns. That closed system established with the apparatus is used to push the solvent such as hexane portion from one end of the apparatus to the other, thereby reducing solvent transfer steps. The result is an apparatus and method that can be used to identify specific oils in a sample and in the nonpolar portion of the sample as well. These and other features and advantages of the present invention will become apparent upon review of the following detailed description, the accompanying drawings and the appended claims.
In general, the present invention relates to the determination of analytes in fluids and, more particularly, to the determination of hydrocarbons in a matrix such as a fluid. Hydrocarbons in a matrix such as water are known to be harmful to the environment and human health. ‘Water’ can indicate fresh water, sea water, municipal wastewater, petroleum industry produced water (as used herein, “produced water” means wastewater produced, for example, in crude oil pumping or during industrial processing), bilge water from ships, and other waters. Each source of water has a limit to the concentration of hydrocarbons that can be present before the water can be discharged to the environment. Regulatory agencies worldwide enforce these limits by requiring periodic testing at industrial sites and others where hydrocarbons may be present in the water. The present invention seeks to provide an accurate, economical, rapid, environmentally-friendly solution to the problem of measuring hydrocarbons in water.
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The connector 16 may be a non-hydrocarbon based and pressure-tight tube. It may be fabricated of a material suitable to continue its intended function while in contact with a matrix sample. For example, the connector 16 may be a metallic tube, a nonmetallic tube such as a plastic tube arranged or other type of material suitable to enable the passage of the matrix such as a fluid between the first container 12 and the second container 14 in either direction. The connector 16 may be chosen to select at least 50 psi of internal pressure. The connector 16 includes a first end 30 and a second end 32, wherein the first end 30 is removably connectable to the inlet port 22 of the first container 12 and the second end 32 is removably connectable to the inlet port 24 of the second container 14. The ends 30 and 32 of the connector 16 may be reversibly connected to the inlet 24 of the second container 14 and to the inlet 22 of the first container 12. The connector 16 includes an interior 36 through which fluid passes. In addition, when the apparatus 10 is in use for the purpose of separating hydrocarbons in a fluid, the interior 36 of the connector 16 is used to retain there in a hydrocarbon capture element 38, which may be Silica gel.
The apparatus 10 is used to perform steps of the method of the present invention to separate hydrocarbons in a matrix sample from one another for the purpose of subsequent use in an analyte analysis process. As illustrated in
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An example of an analysis system that can be used to determine hydrocarbon content of a fluid sample using the membrane 102 as a sample retention device is described in U.S. Pat. No. 8,613,214. The content of that patent is incorporated herein by reference.
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A portion of the contents of the container 230 is added to a TPH syringe 238 which may be a polypropylene syringe as shown in
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It is to be understood that various modifications of the apparatus 10 as expressly described may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the claims appended hereto.
Filing Document | Filing Date | Country | Kind |
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PCT/US2021/058487 | 11/8/2021 | WO |
Number | Date | Country | |
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63111076 | Nov 2020 | US |