Patent Grant
10077139
Historically, isotope analysis originated as a major tool for the field of geochemistry. However, as mass spectrometers and other equipment for taking isotopic measurements improve and advance, so does the utility of isotopic data in other areas. These have come to include oil and gas exploration, and gas identification and differentiation. In addition, isotope data has also become a useful tool in other fields, such as ecology, forensics, food adulteration, and others where isotope data can often provide a means of differentiating two otherwise chemically indistinguishable or undifferentiated substances.
As our world's energy supplies diminish, increasing attention is being given to recovering sources of oil and gas that were previously considered uneconomical and/or unconventional. These sources may be identified through “geochemical prospecting” of surface soils. A bag for containing a sample of soil and its associated gases, without altering its isotopic “signature” would be extremely valuable in helping to identify these sources. However, isotopic differences can arise in a sample during storage. Accordingly, it would be beneficial to control for mechanisms that might alter the isotopic signature of a sample substance. Geological sampling often requires specialized sampling containers and equipment, as described in various of the following published US applications: 20100083771 (Gas sampling apparatus); 20090260416 (Low dead-volume core-degassing apparatus); 20080282814 (Gas sampling apparatus); 20070056394 (Pressurized gas sampling container); 20040123679 (Gas sampling apparatus); the disclosures of which are incorporated herein by reference. Such devices can be used to contain a substance without altering or “fractionating” the sample's isotopic signature.
Traditional means of collecting soil samples utilize jars or other rigid containers which are quite bulky and relatively expensive to ship, especially to remote regions of the world where such prospecting often occurs. A rigid container (such as a jar) is always contaminated and/or its contents “diluted” by the atmospheric gases that occupy the container, and which constitute the headspace after the sample is introduced and the container sealed. This gaseous contamination (including atmospherically-borne contaminants) makes subsequent isotopic analysis difficult if not impossible. Additionally, techniques have been developed for sourcing groundwater from core samples using stable isotope analysis. In order to use such techniques, however, it is essential that samples be stored in such a way that prevents isotopic fractionation of the water vapor inside (i.e., no leakage on a molecular level).
In light of the foregoing, this invention provides a sample collection pouch having a sample collection bag in the form of a pouch having an opening to an interior portion and a closed end, the pouch is comprised of opposing facing films sealed along opposing edges, a portion of the film defining the interior portion and adjacent said opening comprising a heat sealable material, corresponding protrusions formed in said facing films to create a closure for sealing the bag, a self-sealing port disposed in one of said films between said closure and said closed end, and a removable funnel disposed in and extending from said opening to and beyond said closure.
More generally, this invention provides a collapsible bag or pouch for sample collecting having an internal mechanical seal and a heat sealable area near the opening that is protected during sample loading, preferably by a funnel detachable from the pouch. After loading and prior to heat sealing the pouch is secured from the outside by mechanical interlocking seal. The bag also has an air-tight port for sampling the gaseous headspace after the bag is sealed.
The invention also provides a clip for sealing the pouch, comprising a channel formed of a relatively rigid but flexible material, a softer, compressible material within the channel mostly surrounding a rigid rod inserted into and removable from the channel.
In use, the portion of the pouch adjacent the opening is heat sealable and is shielded from contamination by the funnel, which is removed after the sample is introduced. Thereafter, the closure is sealed, the clip is then secured between the closure and the opening, and one or more heat seals are formed from the facing films of the pouch between the clip and the opening to produce a sample contained within a pouch having two mechanical seals and at least one heat seal.
This invention advantageously provides a compressible container, a bag or pouch, that addresses the need to reduce dilution of a sample substrate that outgases and/or desorbs gases over time. The ability to squeeze out excess air prior to sealing means the headspace will have in a higher concentration of gases targeted for analysis (e.g., isotopic analysis). This is important because some testing (such as isotopic testing) requires a sufficient concentration of the gaseous compound to provide data other than its mere presence. The compressible wall of the container allows removal of air from the air head space, which reduces both air contamination and dilution of the sample gases.
As shown in
The pouch or gas bag portion 103 has an open end in which a funnel 105 is positioned. The funnel includes a wider mouth portion 107 defining an opening 109 that is essentially coextensive with the opening of the pouch, and continues to a narrower end opening 111 which is disposed within the pouch. The base 112 of the pouch defines the closed end, and the adjacent portion of the pouch defines an interior portion 113 in which a sample is retained.
Between the sample-retaining portion 113 of the interior and the opening of the pouch 109A is a mechanical seal closure 115. Preferably, this closure is a profile extrusion in the opposing films to provide an interlocking closure, such as described in U.S. Pat. No. 4,561,109 and Re. 28,969 (e.g., a re-sealable zip type closure), the disclosures of which are incorporated herein by reference.
The funnel is preferably tacked to the pouch (e.g., glued, heat-sealed, or tack-welded) at small areas, 117, adjacent the opposing seams where the pouch films meet, the areas being sufficient to keep the funnel in place during transport, but small enough to allow the funnel to be torn out without significant (and preferably without any) damage to the pouch. The funnel then can be tacked to the pouch only at the portion near the opening. By virtue of this structure, the user may tear the funnel away from the bag.
The pouch is preferably made from opposing films. The films are preferably multilayer films to provide both strength and durability to the pouch and to protect the sample from isotopic signature changes. In addition, the use of films allows the pouch to be collapsed and the air forced out prior to sealing, in contrast to the rigid containers used presently. Still further, the portion of the films defining the interior space are preferably upper heat-seable in the area between the closure 115 and the bag opening 109A. As described, the funnel spans the same extent, thereby protecting preferably both the heat-sealable material 119 and the mechanical closure 115 and the port 201 from contamination by sample materials, which are directed by the funnel to the sample retaining portion (113) of the pouch.
The portions of the films defining the heat-sealable area 119 and 119A preferably comprise a polyolefin that is heat sealable. Commercial and home-use heat-sealing systems for storing food are well-known. In this invention, polyethylene (PE), especially low density, is preferred. Depending on the sample material collected, one or more layers may be treated, and/or layers may be provided, to secure the chemical signature of the sample contents remains unchanged. For example, an ethylene vinyl alcohol (EVOH) copolymer can be used as the heat sealable material to reduce oxygen penetration through the bag to the sample. For samples containing carbon dioxide, a higher density (HDPE) and/or a more crystalline polyolefin, and/or a metal foil, can be used to provide a hermetically sealed interior. The outer layer is preferably relatively tough, such as a polyamide (e.g., a nylon), a polyethylene terephthalate (PET), or polypropylene, or combinations thereof. Various ways of making multilayer film materials are well-known, including co-extrusion, lamination, and combinations thereof. Exemplary multilayer films include a two layer film (outside to inside) with nylon and EVOH/PE, and a five layer film with PET, HDPE, foil, regular density PE, and low density PE. Such films are commercial available as, for example, a 5 mil clear biaxially oriented nylon and EVOH/LLDPE laminated barrier film, and a 4 mil white laminated PET/PE/foil/PE/LLDPE film. The collected samples will produce gasses, termed “off gasses.” The films are substantially impermeable to off gasses and thus the gasses are retained. The films are also substantially impermeable to ambient atmosphere and gasses generally existing in the environment to prevent dilution of off gasses within the bag. Further more the films are non-reactive with the gathered sample and the sample off gases to preserve the isotopic fractions of the off gasses.
Disposed in one of the films is a self-sealing port 201, which is shown in more detail in
The side wall of the pouch 103A is disposed between the cap and bottom portion when the two are snapped together. The bottom also has a flange 215 extending about the perimeter which forms a surface on which the foot of the cap lies flush, and for added sealing includes a groove 217 in which is disposed a seal (e.g., an O-ring or synthetic washer) 219 secured between the cap foot and the flange. Axially, the bottom has a bore 221 that aligns with the tapered hole in the cap and opens into a center cavity 223 in the bottom portion. The cavity accepts a penetrable, self-sealing plug or septum 225 that blocks the bore and is positioned between the tapered hole in the cap and the bore. When assembled, a hypodermic needle can be inserted through the port (the first insertion thus penetrating the film) to remove material for analysis without compromising the chemical signature of the sample contents, or to add material (e.g., a liquid or gaseous reagent, or an inert gas or liquid). As shown, the upper or outermost portion of the cap preferably is separated from the foot by a groove to provide improved tactile sensation while grasping the cap. This can be an important consideration for avoiding puncturing the opposing film of the pouch when the plug is penetrated by the hypodermic needle. The groove also provides a means by which the pouch can be suspended and the head space sampled through the port.
In field use, for example, a hand spade or garden trowel is used to collect soil and then inserted through the funnel to place a sample of the material collected into the closed end portion of the sample container. Preferably, the outside of the pouch in the area in which the sample is retained (113) includes printed indicia with desired information such as, for example, a fill line, instructions for use, a form for indicating sample information (e.g., date, location, sample identification (such as a unique sample number or name), location from which the sample was taken, by whom the sample was taken, sampling conditions), or other notes or comments. After the sample is introduced, the bag is held vertically, the funnel, is removed, the bag compressed to remove the head space air and the re-sealable zip closure is secured, to retain the sample in the bag during the remaining manipulation.
It is preferred then to place a clip onto the bag because the closure does not form a gas tight seal, so leakage or reaction with incoming gas would fractionate or otherwise change the sample. The clip is secured onto the outside of the pouch. A preferred clip 301 is shown in
The clip is capable of creating a vacuum tight seal. By virtue of the difference in rigidity of the two parts of the clip and the conformable nature of the soft inner portion, soft inner section of the clip conforms to irregularities in the films and can ‘surround’ these inconsistencies, providing consistent pressure along the length of the clip, and therefore providing a reliable means of sealing gases inside the pouch. Without these properties, the pressure on the inner rod tends to be inconsistent and incapable of providing a vacuum tight seal.
As noted, the closure is capable of being opened. Accordingly, it is preferable to heat-seal the sample pouch, and multiple seals are more preferred. As noted above, the funnel protects the heat-sealable material during introduction of the sample. After the funnel is removed, a commercially-available heat sealing machine can be used to add additional, permanent seals. It may be impractical, or impossible, to have such a device at the point of sampling, or even on location. Accordingly, the aforementioned clip is used to secure the pouch until the pouch can be heat-sealed. As shown in
The foregoing description is meant to be illustrative and not limiting. Various changes, modifications, and additions may become apparent to the skilled artisan upon a perusal of this specification, and such are meant to be within the scope and spirit of the invention as defined by the claims.
This application claims the benefit of U.S. Provisional Application No. 61/217,944, filed 5 Jun. 2009, and is also the United States national stage application of PCT/US2010/001626 filed 5 Jun. 2010.
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