Extraction articles and methods

Details Extraction articles and methods Extraction articles and methods

2001-03-13

2002-12-10

Drodge, Joseph W. (Department: 1723)

Chemistry: analytical and immunological testing

Including sample preparation

Liberation or purification of sample or separation of...

C073S863230, C210S490000, C210S496000, C210S500360, C210S505000, C422S105000, C436S177000, C156S073500, C156S060000

Reexamination Certificate

active

06492183

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to extraction articles, particularly to a one-piece multilayer article for use in solid phase extraction in isolation, separation, and analysis techniques. The invention also relates to methods of separation and analysis using the articles, as well as to methods of making the one-piece multilayer article.
BACKGROUND OF THE INVENTION
Generally, the art of separation science, which involves extraction and chromatography, has two main objectives. One is high yield extraction and recovery of a targeted analyte and the other is a rapid rate of extraction and elution. A specific type of extraction used for separation is solid phase extraction, also known as SPE. SPE is a method of sample preparation that removes and concentrates an analyte from a liquid sample by absorption or adsorption onto a disposable solid phase medium. This is followed by elution of the analyte with a solvent appropriate for analysis. In SPE two devices commercialized to balance the two competing objectives described above are cartridges (such as those available under the trade designation BAKERBOND SPEEDISK from J. T. Baker, Phillipsburg, N.J.) and disks (such as those available under the trade designation DFP disks from Whatman, inc., Clifton, N.J.).
Solid phase extraction cartridges typically consist of a column of loose sorbent material as the extraction medium. This sorbent material has a sufficient surface area to reduce the problems of sample processing using gravity or vacuum. This design has certain inherent disadvantages. For example, such cartridges may typically have a small cross-sectional area of extraction media, which results in slow processing, as well as channeling, which reduces analyte retention. Solid phase extraction disks eliminate these disadvantages.
Commercial solid phase extraction disks include particle loaded membranes of various diameters as the extraction medium. For example, one such disk comprises a membrane that includes sorbent particles (e.g., C8- and C18-bonded silica particles) immobilized in a web of poly(tetrafluoroethylene) (PTFE) microfibrils. Another such disk includes a web of glass microfibers impregnated with chemically bonded silica sorbents such as C18 aliphatics. For general use, SPE disks can be supported on a glass or polymer frit disk in a standard filtration apparatus, using vacuum to generate the desired flow of sample through the disk.
Most commercial SPE products are designed to be used with a separate prefilter if the sample of interest (e.g., wastewater) contains a significant amount of solid material (e.g., suspended solids) that could plug the SPE medium. Commercial prefilters are typically constructed of natural fibers such as celluloses. glass fibers, or synthetic thermoplastic fibers such as polypropylene, polyester, and polyethyleneterephthalate. Typically, these prefilters are designed to prevent the SPE medium from becoming plugged. The prefilters are typically supplied separately from the SPE products.
SPE products are still needed that are capable of achieving high recoveries of analytes from a liquid sample while maintaining high sample flow-rates with little or no plugging of the disk during use. The latter problem can hinder effective analysis. This is particularly true for the extraction of nonpolar hydrocarbon extractable analytes from water. Ease of use and simplicity in procedure are also important considerations for the end user. Other factors the user may consider in choosing extraction media include the capability of being used with a variety of equipment and glassware including automatic analysis apparatus. The present invention provides an extraction disk that has one or more of these characteristics.
SUMMARY OF THE INVENTION
This invention provides a one-piece multilayer article for use in extraction, isolation, separation, and analysis techniques. In one aspect, the invention provides an article that includes a first porous support layer thermo-mechanically attached to a second porous support layer (preferably, welded together) at at least one attachment site, and therebetween, a solid phase extraction medium comprising a fluoropolymer (preferably, in the form of a membrane) is disposed. Preferably, at least one of the porous support layers is made from thermoplastic material.
Although the extraction articles specifically described herein include three layers, more than three layers can be incorporated into the articles if desired as long as at least one each of the three layers (first porous support layer, second porous support layer, and SPE medium) described herein are present. The multilayer articles specifically described herein may come in a variety of shapes and forms including circular disks, squares, ovals, etc.
The fluoropolymer solid phase extraction (SPE) medium can be in a variety of forms, such as fibers, particulate material, a membrane, other porous material having a high surface area, or combinations thereof. Preferably, the SPE medium is in the form of a membrane that includes a fibril matrix and sorptive particles enmeshed therein. The fibril matrix is typically an open-structured entangled mass of microfibers. The sorptive particles typically form the active material. By “active” it is meant that the material is capable of capturing an analyte of interest and holding it either by adsorption or absorption. The fibril matrix itself may also form the active material, although typically it does not. Furthermore, the fibril matrix may also include inactive particles such as glass beads or other materials for enhanced flow rates.
The porous support layers can be made of a wide variety of porous materials that do not substantially hinder flow of the liquid of the sample of interest. Typically these materials are those that are capable of protecting the solid phase extraction medium from abrasion and wear during handling and use. The material should be sufficiently porous to allow the liquid sample to flow through it, and preferably, able to retain particles contained within the SPE medium. Preferably, the support layers are made of a nonwoven material. It is also preferred that both the first and second porous support layers are very similar in composition (as opposed to structure), and more preferably, they are the same.
In a preferred embodiment, one of the porous support layers is a prefilter layer, preferably made of a nonwoven material. (For ease of description, as used herein the first porous support layer will be designated as the preferred porous support layer that is a prefilter; however, either the first or second porous support layer can be a prefilter). More preferably, the first porous support layer is a nonwoven web of blown microfibers, most preferably melt blown microfibers. Such “melt blown microfibers” or “BMF” are discrete, fine, fibers prepared by extruding fluid, fiber-forming material through fine orifices in a die, directing the extruded material into a high-velocity gaseous stream to attenuate it, and then solidifying and collecting the mass of fibers. In preferred embodiments, the prefilter layer includes a nonwoven web of melt blown polyolefin fibers, particularly polypropylene fibers.
In embodiments where one of the porous support layers is a prefilter, it is preferred that the prefilter have the following characteristics: a solidity of no greater than about 20%; a thickness of at least about 0.5 millimeters (mm); and a basis weight of at least about 70 grams per square meter (g/m
2
). As used herein, solidity refers to the amount of solid material in a given volume and is calculated by using the relationship between weight and thickness measurements of webs. That is, solidity equals the mass of a web divided by the polymer density divided by the volume of the web and is reported as a percentage of the volume. The thickness refers to the dimension of the prefilter through which the sample of interest flows and is reported in mm. The basis weight refers to mass of the material per unit area and is reported in g/m
2
.
The one-piece multilayer ext

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