Patent Application
20130276555
The present invention relates generally to surface sampling and methods for detection of analytes. More particularly, the invention relates to an enhanced surface sampler, method of making, and process for collection and release of selected analytes.
Current state of the art for trace detection of explosives, chemical and biological threat agents, and other threat agent signatures often requires physical swipes of surfaces to be collected for further on-site or remote instrumental analysis. Collection and subsequent assays of minute amounts of analytes such as explosive residues from surfaces is a primary method for detection of hidden explosives or discovery of residues on persons who have had contact with explosives. For example, collection of trace residues from surfaces is typically conducted by physically sampling surfaces with cotton or muslin swipe materials and swabs. Muslin is a woven cotton cloth that is a widely used surface sampling material for collection of trace explosives and other analyte samples. Explosives detection depends on the effectiveness of the measurement as well as the collection efficacy. Performance of the sampling material is fundamental to the analytical process upon which the entire detection and decision sequence depends.
Presence of trace explosives on swipes can be analyzed by various instruments. Ion mobility spectrometry (IMS) is a principle method presently employed in the field. Recovery of the analyte from the sampling media can be accomplished by rinsing with solvents or by heating the sampling media to introduce the analyte into the instrument for subsequent assay. IMS enables rapid analysis, has low detection limits for many analytes of interest, has a low operating cost, and requires no sample preparation. Consequently, IMS is one of the most widely used analytical methods for explosives detection throughout the world. However, IMS can produce erroneous results due to its lack of selectivity, susceptibility to interference, as well as nonlinear behaviors including, e.g., sample reproducibility issues, and human error. Thus, improving sample collection and analyte introduction into the IMS (and similar systems) should improve sensitivity; stability, and potentially selectivity, thereby resolving many fundamental problems presently plaguing field-deployed instruments that are tasked with trace detection of organics.
While effective, muslin sampling cloths made of cellulosic fibers are not ideal sampling materials. Cellulose fibers include a range of chemical moieties that result in heterogeneous binding of analytes, which can result in distributed or incomplete analyte release. Further, unprocessed muslin sampling swabs contain non-cellulosic compounds found in native cellulosic fibers (i.e. waxes, natural oils and starches) as well as sizing agents and lubricants added during and after textile processing. Processes typically, used to remove these impurities in industry such as mechanical scouring, chemical scouring agents, and enzymatic methods can weaken the cellulosic fibers and render them unsuitable for repeated use due to degradation. The decomposition and degradation of an unstable swab material can release contaminants into a detection instrument and therefore interfere with the sample analysis and negatively impact the detection process. Additionally, cellulosic fibers have a limited thermal stability as they decompose at the relatively low temperature of 150° C. And, the high specific heats (>1.3 J/g ° C.) and low thermal conductivity (˜0.24 W/m-K) of cellulosic fiber materials combined with the chemical heterogeneity of the surface result in less than optimal release of analytes from the surface, which can limit the detection performance.
Recently, different materials have been evaluated as candidates for surface sampling including, e.g., raw glass fibers, polytetrafluoroethylene (PTFE) fibers, and aromatic polyamide polymer fibers. These materials have a high thermal stability that allows thermal desorption of an analyte into an IMS. They are also resistant to mechanical and shredding stresses, and offer a high desorption efficiency for several explosive compounds. However, while PTFE has some suitable properties (e.g., is not wetted by water), PTFE has a lower efficiency for collection of explosives than muslin or cotton swabs. And, tests on simple glass fiber materials show they do not retain sufficient structural integrity and degrade during use.
Accordingly new swipe samplers and preparation processes are needed that are physically and thermally stable, enhance analyte adsorption and collection, and provide excellent desorption of analytes for detection, e.g., of explosives and other threat agents. The present invention addresses these needs.
An enhanced swipe, sampler and processes of making and using are described that improve collection and enhance sensitivity for trace level detection of target analytes including explosives and other threat agents. The swipe sampler may include a fabric of a selected thickness composed of selected glass and/or metal fibers (with an oxide coated surface). The fibers can have silane ligands covalently attached to the fibers, which yields a functionalized surface on the surface of the fabric. The fabric collects and retains an analyte(s) thereon upon contact with same.
A method of making is also described. The method may include: silanizing a fabric of a selected thickness comprising selected glass and/or metal fibers (with an oxide coated surface) therein by directly (e.g., covalently) attaching selected silane ligands to the surface of the fibers to functionalize the surface of the fabric. The fabric may be configured to collect and retain an analyte(s) on the surface of the fabric upon contact with the analyte(s).
A method of use is also described. The method may include: collecting an analyte(s) on a fabric that includes glass and/or metal fibers (with an oxide coated surface) therein having silane ligand(s) with terminal group(s) directly (e.g., covalently) attached to surfaces of the fibers. The method may also include releasing the analyte(s) from the surface of the fabric for detection of the analyte(s).
In some embodiments, the fabric of the enhanced sampler includes glass fibers. In some embodiments, the fibers are composed of or include a glass selected from: A-type glasses (e.g., alkali-lime glass with little or no boron oxide); E-type glasses; E-CR-type glasses (e.g., alumino-lime silicate with less than 1% w/w alkali oxides with high acid resistance); C-type glasses (e.g., alkali-lime glass with high boron oxide content); D-glass (borosilicate glass with high dielectric constant); R-glass (alumino silicate glass with no MgO or CaO); S-type glasses (e.g., alumino silicate glass without CaO but with high MgO content with a high tensile strength), including combinations of these various glasses. In some embodiments, the sampler includes pure silica fibers, E-glass fibers, S-glass fibers, or combinations of these fibers.
In some embodiments, the sampler may include metal-containing fibers such as those with an oxide coating on the surface of the fibers. In some embodiments, the fabric, may include fibers that include, or are composed of, e.g., a metal oxide.
In some embodiments, the fabric of the sampler includes fibers with a thickness between about 0.01 mm and about 1 mm; or between about 0.05 and about 0.15; or between about 0.01 mm and 0.20 mm; or between about 0.01 mm and about 0.10 mm.
In some embodiments, the fibers in the fabric include a weave or pattern. Fabric weaves include, but are not limited to, e.g., duraweaves, intraweaves, twill weaves, satin weaves, hybrid weaves, plain weaves, warp weaves, drape weaves, weft weaves, real weight weaves, braid weaves, and combinations of these various weaves. In some embodiments, the fibers are spunlaced fibers. In some embodiments, the fibers are woven fibers or patterned fibers.
In some embodiments, the silane ligands are selected from silanes, alkoxysilanes, silanols, or combinations of these various ligands. The silane ligands may include a terminal group that enhances the affinity of the fabric to collect and retain analytes on the fabric surface. In some embodiments, the silane ligands with a terminal group attached provides an affinity for the analyte(s) greater than the affinity provided absent the terminal group. In some embodiments, the terminal group attached to the silane ligand is an amide group, an ester group, an alkyl group containing 1-18 linear or branched carbons, or a combination thereof. In some embodiments, the terminal group attached to the silane ligand is a fluoroalcohol or fluoroalkyl containing 1 to 18 linear or branched carbons. In some embodiments, the terminal group attached to the silane ligand is a perfluoroalkane, an oligomeric imide, or a combination of these two terminal groups. In some embodiments, the terminal group is selected from the group consisting of: methyl, phenyl, hydroxyphenyl, alkoxyphenyl, aminophenyl, nitrophenyl, thiophenyl, alkylthiophenyl, furanyl, alkylfuranyl, cyano, isocyanato, fluoroalkyl, amines, alkyl amines, and combinations thereof. In some embodiments, the terminal group attached to the silane ligand is an alkyl amine that includes 1 to 6 carbons. In some embodiments, the terminal group attached to the silane ligand includes: ethylenediamine tetraacetate (EDTA); ethylene diamine (EDA); diethylenetriamine (DETA); 1,10-phenanthralene; a beta-diketone; a 2,2′-bipyridyl; or a combination thereof. In some embodiments, the terminal group attached to the silane ligand is a beta-diketone including, but not limited to, e.g., 2-thenoyltrifluoroacetone; 2,4-pentanedione; 1,1,1-trifluoro-2,4-pentanedione, including combinations thereof. In some of these embodiments, the terminal group may further include a cation selected from: Cerium (Ce), Samarium (Sm), Europium (Eu), Tellurbium (Tb), Copper (Cu), Zinc (Zn), Chromium (Cr), Manganese (Mn), Iron (Fe), or a combination thereof. In some embodiments, the terminal group attached to the silane ligand is selected from: 1,2-hydroxypyridinone (HOPO), iminodiacetic acid (IDAA), diphosphene (diphos), an analogue thereof, or a combination thereof.
In some embodiments, the fabric of the sampler has a thermal conductivity greater than about 0.5 W/m-K.
In some embodiments, the fabric of the sampler has a specific heat below about 1.3 J/g ° C.; or between about 1 J/g ° C. and about 1.3 J/g ° C.; or between about 0.5 J/g ° C. and about 1.2 J/g ° C.; or between about 0.1 J/g ° C. and 0.5 J/g ° C.
In some embodiments, the method of making further includes stabilizing the fabric to prepare the fabric for collection of the analyte(s). In some embodiments, the stabilizing includes heating the fabric at a temperature of at least about 180° C. under vacuum for a time up to about 18 hours or greater.
In some embodiments, the method of making further includes pretreating the fibers of the fabric prior to silanizing to increase the density of silanols on the surface of the fibers that are reactive with the silane ligands. In some embodiments, the pretreating includes a method such as calcining, refluxing in a solvent(s), contacting with alkaline solution, contacting with acid solution, heating, or combinations of these pretreating methods. In some embodiments, the contacting may include a concentration of base or acid up to about 10M and a contacting time of up to about 4 hours.
In some embodiments, the silanizing includes covalently attaching silane ligands that include a selected terminal group chemically attached to the silane ligands. In some embodiments, the silanizing includes covalently attaching silane ligands without a selected terminal group directly attached to the silane ligands. In some embodiments, the silanizing includes covalently attaching silane ligands absent a terminal group chemically attached to the silane ligands. In some embodiments, the terminal group is chemically attached subsequent to the attachment of the silane ligands. In some embodiments, the silanizing is performed one or more times with the same or different silane ligands. In some embodiments, the silanizing includes refluxing the fabric in a solution containing at least one solvent and at least one silane ligand. In some embodiments, the silanizing with at least one solvent includes at least one organic solvent or at least one aqueous solvent. In some embodiments, the refluxing includes a time up to about 18 hours or greater and a temperature of at least about 180° C. In some embodiments, the silanizing includes an aqueous solution deposition method or a gas-phase deposition method. In some embodiments, the silanizing includes refluxing the fabric in a solvent containing a selected silane for a time sufficient to chemically bind the silane to the fibers to functionalize the surface. The functionalized surface may then be dried to condition the fabric for collection of one or more target analytes. In some embodiments, the silane has a concentration of about 10 wt % in toluene. In some embodiments, the refluxing is performed for a time of at least about 18 hours. In some embodiments, drying is performed at a temperature of at least about 180° C. for about 18 hours under vacuum. In some embodiments, the method can include rinsing the refluxed fabric with one or more aliquots of toluene to remove unbound silane from the functionalized surface. In some embodiments, the method can include rinsing the refluxed fabric with one or more aliquots of methanol to remove contaminants from the surface of the fabric.
In some embodiments, the method of making may further include post-treating the fabric following silanizing with a selected solvent(s) to remove unbound silane ligands or impurities from the surface of the fabric.
In some embodiments, the sampler has a sampling surface with a shape selected from: round, oval, rectangular, square, triangular, or combinations of these various shapes. In some embodiments, the sampling surface may have the form of a finger glove or a sampling glove. In some embodiments, the sampling surface may be attached to, or separate from, the finger glove or sampling glove.
In some embodiments, collecting the analyte(s) includes contacting a sampling surface to collect the analyte(s) on the surface of the fabric.
In some embodiments, the surface of the swipe sampler fabric retains the analytes until thermally released at a release temperature greater than the collection temperature into a downstream analytical instrument. In some embodiments, the releasing includes thermally desorbing the analyte(s) at a temperature between about 100° C. and about 500° C. In some embodiments, the releasing includes a concentration of the analyte(s) equal to or greater than the concentration released from a muslin-containing material of equal thickness. In some embodiments, the releasing includes detecting the analyte(s) in an ion mobility instrument with a signal intensity for the analyte(s) at least equal to, or greater than, the signal intensity of the analyte(s) obtained from a muslin-containing material at an equivalent analyte(s) mass. In some embodiments, the releasing includes detecting the analyte(s) in a thermal desorption instrument such as a thermal desorption gas chromatograph (GC) or a thermal desorption ion mobility spectrometer (IMS).
In some embodiments, the releasing includes releasing the analyte(s) from the surface of the fabric by contacting the surface with a solvent or a mixture of solvents. In some embodiments, the releasing includes cleaning the surface of the fabric to prepare the fabric for re-use or collection of another analyte(s) from a selected surface.
In some embodiments, the decomposition temperature of the functionalized fiber surface is greater than about 400° C.
The enhanced swipe sampler addresses previously unsolved issues with physical sampling known in the art including, e.g., high consumable costs, sample reproducibility issues, human error, and enhanced sensitivity for analytes that enable practical use of automated technologies.
The purpose of the foregoing abstract is to enable the United States Patent and Trademark Office and the public generally, especially the scientists, engineers, and practitioners in the art who are not familiar with patent or legal terms or phraseology, to determine quickly from a cursory inspection the nature and essence of the technical disclosure of the application. The abstract is neither intended to define the invention of the application, which is measured by the claims, nor is it intended to be limiting as to the scope of the invention in any way.
a-1d show different embodiments of enhanced surface samplers for collection and retention of selected analytes.
a shows a pretreatment process that increases density of reactive groups on the surface of the sampler.
b shows an exemplary reaction for direct attachment of silane ligands to fabric fibers.
a-6c show other analytes collected by samplers of the present invention.
Enhanced swipe samplers and a method of making are described that improve collection and sensitivity improvements for trace level detection of target agents including explosives, threat agents, and other materials known to be associated with criminal or terror-related activities. While preferred embodiments of the present invention will now be described, the invention is not intended to be limited thereto. From the description, it will be apparent that various modifications, alterations, and substitutions may also be made without departing from the scope of the invention as set forth in the claims listed hereafter. For example, while the invention will be described in reference to detection of explosives, the invention is intended to cover various illicit drugs, chemical weapons, and other threat agents. Accordingly, the description of the preferred embodiments should be seen as illustrative only and not limiting.
a-1d show enhanced surface samplers 100 that provide for collection, retention, and release of selected analytes. In
The fabric of enhanced samplers may be constructed of fibers that include, or are composed of, various types of glass, silica, non-metal oxides, oxide-coated metals, metal oxides, and/or metals coated with metal-oxides described further herein.
In some embodiments, fabric may include glass fibers composed of pure silica (e.g., ASTROQUARTZ®, JPS Composites Materials, Anderson, S.C., USA), or glass of various types. In some embodiments, fabric may include S-glass fibers, E-glass fibers (BGF Industries, Inc., Greensboro, N.C., USA), or a combination of these glass types. In other embodiments, the fabric may include glass fibers that include, or that are coated with, metal oxides and/or non-metal oxides.
Metals include, but are not limited to, e.g., iron (Fe), aluminum (Al), copper (Cu), nickel (Ni), silver (Ag), including alloys thereof. In some embodiments, metal fibers may be treated with acid or base to clean and activate the surface of the fibers prior to silanization. In some embodiments, metal fibers may include a native oxide coating prior to silanization or installation of silane ligands on the surface of the metal fibers.
In some embodiments, the fabric may include fibers that are composed of, or that include, metal oxides, oxide coated metals, or metals that include a metal oxide coating of the same or different metal provided that refractory properties of the metal oxide coating are compatible with the underlying metal in the fiber. Metal oxides and non-metal oxides include, but are not limited to, e.g., Ag2O, Al2O3, As2O3, As4O6, BaO, B2O3, BeO, Bi2O3, CO, CaO, CdO, CeO2, CoO, CrO3, Cr2O3, CuO, Cu2O, Dy2O3, Er2O3, Eu2O3, FeO, Fe2O3, Ga2O3, GdO3, GeO2, Ho2O3, HfO2, In2O3, IrO2, K2O, KNaO, La2O3, Li2O, Lu2O3, MgO, MnO, MnO2, Mn2O3, MoO3, N2O5, Na2O, Nb2O3, Nb2O5, Nd2O3, NiO, Ni2O3, PO4, PbO, PdO, PmO3, PrO2, Pr2O3, PtO2, Rb2O, Re2O7, RhO3, SO3, SO4, Sb2O3, Sb2O5, Sc2O3, SeO2, SiO2, Sm2O3, SnO2, Ta2O5, Tb2O3, ThO2, TiO2, Tl2O, Tm2O3, V2O5, WO3, Y2O3, Yb2O3, ZnO, ZrO, ZrO2, including combinations of these various oxides. Other minor constituents commonly found in glasses may also be found therein which are unlikely to influence the properties of the overall material including, e.g., alkali metal oxides, alkaline earth oxides, and impurities.
Enhanced samplers have a selectable thickness (height dimension). In some embodiments, thickness of the samplers may be between about 0.01 mm and about 1 mm. In some embodiments, thickness of the samplers may be between about 0.05 mm and about 0.15 mm. In some embodiments, thickness of the samplers may be between about 0.05 mm and about 0.20 mm. In some embodiments, thicknesses of the samplers may be between about 0.01 mm and about 0.10 mm. No limitations to selected thicknesses are intended. “Thick” as used herein refers to a thickness of about 2 mm. “Medium” as used herein refers to a thickness of about 0.2 mm to about 2 mm. “Thin” means a thickness of about 0.01 mm to about 0.2 mm. No limitations are intended.
Fibers in the sampler fabric can include various weaves, patterns, and thicknesses that optimize the collection, retention, and release of analyte(s) from the sampling surface. For example, patterns and weaves of the sampler may be selected that provide a suitable surface roughness and flexibility that optimize collection and retention of analytes from surfaces. Weaves and patterns may also be selected that provide for gas permeation, desorption (e.g., thermal desorption), solvent extraction, and/or uniform release of analytes from the sampler. In addition, weaves and patterns of fibers within the fabric can increase the strength and the durability of the fabric. Weaves include, but are not limited to, e.g., duraweaves, intraweaves, twill weaves, satin weaves, harness satin weaves (e.g., 4HS, 8HS, and the like), hybrid weaves, plain weaves, warp weaves, drape weaves, weft weaves, real weight weaves, braid weaves, other weaves, including combinations of these various weaves. No limitations are intended.
Samplers include a sampling surface that is chemically-modified or chemically functionalized to provide enhanced physical, chemical properties compared with cellulose-based materials such as muslin cloth and cotton. Physical properties include, but are not limited to, e.g., fiber composition, fiber strength, fiber length, fiber diameter, metal oxide composition; affinity for collection, retention, and release of analytes; surface homogeneity; thermal conductivity; specific heat; thickness, weave or pattern, durability, number of surface hydroxyls available for functionalization; and combinations of these various properties. Surface-modified fabrics may also include an engineered structure with selectable features. Engineered features include, but are not limited to, e.g., weave, surface roughness, fiber thickness, fiber length, fiber density, gas permeability, and other properties that enable preferred physical properties of the fabric to be selected. Surface-modified fabrics can also be made to resist repeated mechanical stresses and thermal treatment, which allows for repeated reuse.
TABLE 1 compares selected physical properties of glass, silica, and metal-containing fibers to those of conventional (0.26-0.32 mm thickness) cotton and muslin materials.
AHarris, M., Harris's Handbook of Textile Fibers, Harris Res. Lab., Inc., Washington, D.C., 1954.
BCurtis, L. J., Miller, D. J., Transport Model with Radiative Heat Transfer for Rapid Cellulose Pyrolysis. Ind. Eng. Chem. Res., 1988, 27, 1783-1788.
CMartienssen, W. and Warliment, H (Eds). Springer Handbook of Condensed Matter and Material data, Springer Berlin Heidelberg.: Germany, 2005.
Dhttp://www.tekna.com/powder/spherical-powder/silica.html
EJPS Composite Materials databook. http://ipsglass.com/
FLubin, G. Handbook of fiberglass and advanced plastics composites, Robert E. Krieger Pub. Co.: Huntington, N.Y, 1969.
GMatWeb Material Property Data. http://www.matweb.com/index.aspx
Hhttp://www.lenntech.com/stainless-steel-316l.htm
As shown in TABLE 1, glass and silica fibers have better thermal properties including a thermal conductivity ˜5 times greater, and a specific heat ˜½ times lower than cellulosic fiber materials such as muslin or cotton cloth. In some embodiments, glass and/or silica fibers have a specific heat below about 1.3 J/g ° C. In some embodiments, specific heat is between about 1 J/g ° C. and about 1.3 J/g ° C. In some embodiments, specific heat is between about 0.5 J/g ° C. and about 1.2 J/g ° C. Metal-containing fibers have specific heats below about 0.5 J/g ° C. with superior thermal conductivity values relative to cellulosic materials.
Sampling surface may also provide suitable desorption properties for release of collected analytes and organics. For example, fiberglass has physical properties that provide the fabric with its ability to withstand repeated mechanical stresses rendering it suitable for use as a sampling swipe material. Glass and silica fibers are also more durable compared with muslin or cellulosic fibers. Fiberglass fabrics made of these materials are also more physically and chemically stable at high temperatures. These thermal properties enable the enhanced sampling materials of the present invention to heat more quickly and evenly than muslin and cotton cloth, and can result in both uniform and faster thermal desorption of analytes to a detector. The modified fabric can also be thinner (i.e., thickness dimension) than conventional cotton and muslin materials. Thinner materials can provide reduced thermal mass and better gas permeability, which provide faster release and improved transport of desorbed analytes to the detector. Detectors include, but are not limited to, e.g., liquid chromatography (LC) instruments, gas chromatography (GC) instruments, mass spectrometry (MS) instruments, ion mobility spectrometry (IMS) instruments, and combinations of these various instruments including, e.g., thermal desorption gas chromatography mass spectrometers (TD-GCMS) and headspace analyzer gas chromatography mass spectrometers (HA-GCMS).
In addition, sampling surface can be tailored with a specified surface chemistry. The enhanced surface chemistry may provide greater homogeneity and analyte affinity that enables better analyte recovery when compared with the heterogeneous surface chemistry of conventional cellulosic materials. The enhanced surface chemistry can also provide enhanced analyte desorption into the detector or otherwise maximize performance relevant to collection, release, and detection (i.e., signal intensity) of analytes released from the surface of the swipe sampler materials.
Commercially available glass or silica fiber materials are typically coated with a variety of chemicals such as binders, oils, resins, and other compounds that facilitate uses in a variety of industrial applications. Removal of these compounds is preferred in order to install specific surface chemistries at densities that enhance the physical properties of the samplers described herein. For example, untreated glass and/or silica fibers can include many unavailable reactive surface sites because these surface sites are physically obstructed by a surface coating or undesirable contaminants, or are chemically unavailable because of a previous reaction between adjacent silanols (e.g., metal hydroxyl groups) that form, e.g., bridging oxo groups.
a illustrates an exemplary pretreatment process that activates and increases density of reactive groups such as silanols on the surfaces of fibers of the sampler or corrects unfavorable surface chemistry. For example, fibers treated with, e.g., bases or acids can increase the density of silanols on the surfaces of the fibers in the absence of added water. In some embodiments, hydrotreating the surface with an aqueous medium can increase the density of silanols or reactive (—OH containing) groups on the surfaces of the fibers. Reactions are not intended to be limited. As shown in the figure, pretreatment can also reverse unsuitable condensation reactions without damaging the underlying physical structure of the glass, silica, and/or metal-containing fibers thereby maximizing the number of reactive groups (e.g., surface silanols) at the surface of the fibers. In addition, pretreatment can remove unfavorable physical coatings present on as-received materials. Optimizing the number of active sites on the fibers also optimizes the number of silanes that can be subsequently directly (chemically) attached to surface of fibers functionalizing the sampling surface of fabric as detailed hereafter. Activation of surface sites to form reactive silanols is detailed, e.g., by Koyama et al. in U.S. Pat. No. 7,553,574, which reference is incorporated herein in its entirety.
b shows an exemplary condensation reaction for direct attachment of silane ligands or terminally functionalized silane ligands to activated anchor sites (e.g., silanols) on the surfaces of fabric fibers. Samplers including glass, metal oxide, and/or oxide coated glass or metal fibers are amenable to surface functionalization using a wide range of functional groups through Si—O—Si bonds [or metal (M)-O—Si bonds in the case of metal oxide and oxide-coated metal fibers] that form in concert with Anchor groups (Z) attached to a (Si) atom at the terminal attaching end of a Linking group (Y). Another terminal end of the Linking group (Y) may include other terminal groups (X), e.g., as shown in [1] hereafter:
In general, Si—OH groups on the surface of the fibers attach to a (Si) attached at the attaching end of a linking group (Y) via anchor groups (Z) at the attaching end of the (Si). In some embodiments, the silanization process may involve chemically attaching silanes to reactive Si—OH groups on the surface of the fibers. For example, Si—OH reactive sites on the surface of the fibers may attach to selected silane ligands via an anchor group (Z) positioned at the attaching end of the silane ligand. The reaction may form a Si—O—Si bond, e.g., via a condensation reaction. In some embodiments, silanes can attach directly to reactive Si—OH (anchor) groups in the absence of a linking group. Silanization can be performed in the presence of water or in the absence of water. For example, fibers treated with, e.g., bases or acids, can yield hydroxyl ions on the surfaces of the fibers in the absence of added water. Reactions are not intended to be limited.
Silane ligands suitable for selective collection of target analytes include, but are not limited to, e.g., phenyl silanes; organosilanes; alkoxysilanes, phenyl-trimethoxysilanes; silanols; multidentate organosilanes containing acidic and/or basic functional groups; multidentate organosilanes that are coordinated to selected metal cations; multidentate organosilanes which may or may not be coordinated through a cation to other organic molecules, including combinations of these various silanes, described further herein.
Passivation (functionalization) of any residual (e.g., unbound or free) reaction sites on the sampling, surface can yield further improvements in surface chemistry results. “Passivation” means that the surface of the fibers is functionalized additional times after an initial functionalization step with: 1) the same silane, 2) with a different silane having different Z-groups (e.g., to allow the different silanes to be positioned in-between the original silane molecules on the surface of the fibers, or 3) with smaller or larger silanes than the original silanes that have different X-groups (e.g., to provide a desirable mixed/non-homogeneous chemistry on the surface of the fibers. For example, passivation using a smaller silane may provide better access to residual surface sites. The term “smaller” refers to the actual volume that the Z-groups take up around the silane silicon (Si) while reacting with the surface of the fibers. For example, as an anchoring (Z) group, SiCl3 may take up a smaller volume than would a Si(OCH3)3 or similar alkoxysilane. A SiCl3 group could allow silanes containing this Z-group to insert between surrounding or existing silanes and thus to access the surface.
Installation of a typical surface chemistry will be described. While the process will be described with reference to a phenyl silane monolayer (i.e., 1st functionalization layer), the invention is not intended to be limited thereto. Various and numerous other suitable surface chemistries can be installed according to other embodiments of the invention. Thus, no limitations are intended.
Phenyl silanes represent an exemplary surface chemistry for modification and functionalization of glass, silica, metal oxide, and/or oxide-coated glass or metal fibers 12 within the sampling fabric 10 material for collection of a wide variety of organics. Phenyl silanes provide a thermally robust and thermally stable surface chemistry at temperatures in excess of 400° C. In addition, phenyl silanes can provide a lipophilic surface with a general affinity for various organic materials, and additionally, greater chemical selectivity for TNT and other nitroaromatics, as detailed further herein.
In some embodiments, installation may involve 1) pre-treating as-received glass and silica fibers 12 to remove commercial coatings or surface contaminants, 2) activating the fibers 12 in a base-containing or acid-containing bath to increase the density of active silanol sites on surfaces 14 of fibers 12, 3) silanizing fibers 12 by chemically attaching silanes (e.g., phenyl silanes) on the on surfaces 14 of fibers 12, 4) conditioning (i.e., cleaning) surfaces 14 of the surface-functionalized or modified fiber 12 fabric 10 material, and/or 5) post-treating the surface-modified fabric 10 to remove, e.g., unreacted (or oligomerized but unattached silanes) from fabric 10.
In some embodiments, fiber fabric 10 may be silanized (functionalized) by refluxing the fabric in a fluid containing the selected silanes at a selected temperature, concentration, and time sufficient to chemically bind the silanes to the surface of the fibers. Concentrations are selected that balance 1) the rate at which silane ligands 16 react with silanols or other reactive sites on the surface of the fibers and 2) the rate at which cross-linking reactions between the silanes occurs to form oligomers In typical reactions, an excess quantity of silanes is used to ensure complete coverage at the surface of fibers 12 of the fabric 10. In some embodiments, silanes may have a concentration of about 10 wt % in toluene. No limitations are intended.
In some embodiments, the silanizing may include a condensation reaction. In some embodiments, the silanizing may be done in an aqueous medium using, e.g., an aqueous deposition method. In some embodiments, the silanizing may be done using, e.g., a gas-phase deposition method. In some embodiments, the fluid may be a boiling solvent, e.g., toluene or a mixed solvent. In some embodiments, the temperature for functionalization of the surface is a boiling temperature of the solvent (toluene=110.6° C.). Different and mixed solvents may be employed. Solvents and reflux temperatures may be selected that drive the desired surface reactions at a sufficient rate. For example, without the reflux, the condensation reaction may not occur, which may be undesirable. Times are not limited. In some embodiments, refluxing may be performed for a time of about 18 hours. No limitations are intended.
In some embodiments, the method may include rinsing the refluxed fabric with one or more aliquots of a solvent (e.g., toluene, methanol, and other solvents) or various mixed solvents to remove unsecured, oligomerized, and/or unreacted silanes from the fabric.
In some embodiments, the method can include rinsing the refluxed fabric with one or more aliquots of methanol to re-hydrate the surface of the fibers to secure some silane oligomers on the surface of the fabric.
Overall, results demonstrate that functionalized surfaces are particularly suited for collection of a wide range of chemicals, explosives, organics, and threat agents for assays thereof.
Anchor (Z) groups include, but are not limited to, e.g., H; OH; Cl; Br; I; F; siloxanes [e.g., O(CnH2n+1)] where n=1-3, including combinations of these anchor groups.
Linking (Y) groups include, but are not limited to, e.g., alkyl groups (CnH2n) of a linear or branched type, where n=1 to 17; esters [RC(O)OR′]; amides [RC(O)NOR′H]; ureas such as [HRNC(O)NR′H] or [RR′NC(O)NR″H]; carbonates [ROC(O)OR′]; carbamates [ROC(O)NR′]; imides [RC(NR′)R″]; ketals [RC(OR′)2R″]; and acetals [RC(OR′)2H]. Here, R, R′, and R″ are functional groups of like or different kind, and may further include various other linking groups, anchor groups, and terminal groups, or, simple alkyl groups of the form (CnH2n+1) where n=1-3. No limitations are intended.
In some embodiments, multidentate ligands of the form [(X2)m(Mn+)X2)] may be used including, e.g., beta-diketones, phenanthrolines, or bipyridyls where X=O or N (e.g., in Lewis Base ligand sites), (M) is a coordinated metal selected from, e.g., Ce, Sm, Eu, Tb, Cu, Zn, Cr, Mn, or Fe, where (n) is the charge of the metal ion from (n)=0 to 3; and where (m) is any number of mono-, bi-, or multidentate ligands required to satisfy the coordination of the metal in the coordination sphere. Ligands surrounding the metal may or may not be identical. Thus, no limitations are intended. As will be understood by those of ordinary skill in the art, the general formula takes into account number of available coordination sites (e.g., from about 6 to about 9); the “denticity” (e.g., number of atoms in a single ligand that directly bind to the central atom in a coordination complex) of each ligand (e.g., from about 1 to about 6); the number of ligands involved; and the number of different types of ligands (e.g., from about 1 to about 3). No limitations are intended to any one exemplary structure.
With terminal groups attached to the silanes, other and various terminal groups or ligands can be chemically attached to the terminal end of the silane ligands to provide enhanced affinity and selectivity towards selected analytes. The various surface chemistries represent an advantage as such enhancements do not occur in natural fibers. For example, in some embodiments, surface chemistries can be installed having a better uniformity, selectivity, and affinity that improve analytical performance. Enhancing the collection and subsequent assay of trace amounts of organic residues from surfaces has immediate and significant applications to explosive detection but also has broader utility in forensic, biomedical, and environmental analytical applications.
Once silanization is complete, sampling surface 14 may be further treated to ensure that silanes are completely bound to the surface and to remove unwanted reactants and side products. This stabilization process prepares the functionalized surface for collection of target analytes. “Stabilization” refers to the completion of surface chemistry reactions that prepare the functionalized surface for collection of target analytes. In some embodiments, the fabric may be thermally cured to stabilize the surface chemistry. When thermally cured, the fabric may be heated in an oven, e.g., a forced-air oven, but is not limited thereto. In one exemplary procedure, curing that finalizes the surface chemistry and prepares the swipe sampler includes heating the fabric to a temperature of between about 200° C. and about 250° C. for a time of between about 5 minutes to about 15 minutes. But, the process is not intended to be limited thereto. In some embodiments, the surface is vacuum dried to prevent further reactions on the surface of the functionalized fibers in the fabric, which readies the surface for collection of target analytes. In some embodiments, drying may be performed at a temperature of at least about 180° C. for about 18 hours under vacuum. Pre-conditioning does not need to be accomplished “just prior” to use of the sampler.
Temperatures for stabilization of the functionalized surface of the enhanced swipe sampler fabrics depend in part on the selected silanes, thermal stability of the silanes, size of the selected silanes, packing density of the selected silanes on the surface of the fibers, or combinations of the various factors. In various embodiments, temperatures are preferably selected that promote cross-linking of silanes positioned adjacent each other on the surface of the fibers in the fabric. In some embodiments, cross-linking between silanes of the functionalized fabric is performed at temperatures between about 120° C. and about 400° C. In some embodiments, the fabric is heated at an oven temperature of at least 120° C. In some embodiments, the fabric is heated at a temperature of at least about 140° C. In some embodiments, the fabric is heated at a temperature of at least about 250° C. In some embodiments, the fabric is heated at a temperature of at least about 300° C. In some embodiments, the fabric is heated at a temperature of at least about 350° C.
Time required for stabilization will vary depending on the surface chemistry. Suitable stabilization times are those that complete the functionalization of the surface. In some embodiments, stabilization times are in the range from about 1 to about 20 hours. In some embodiments, the fabric is heated for a time of at least about 30 minutes. In some embodiments, the fabric is heated for a time of at least about 60 minutes. In some embodiments, processing times are typically between about 60 minutes and 180 minutes. No limitations are intended.
Samplers of the present invention provide improved collection of analytes for detection of these various compounds and agents. Analytes include, but are not limited to, e.g., explosives, narcotics, pharmaceutical process contaminants, biological warfare agents, chemical warfare agents; nerve agents; pesticides, environmental toxins, including analogues and stimulants of these compounds.
a-6c show chemical structures of other analytes collected by enhanced samplers described herein including, but not limited to, e.g., drugs, illicit drugs, narcotics, chemical warfare agents, nerve agents, biological warfare agents, and pesticides.
b shows exemplary chemical warfare agents and stimulants including, but not limited to, e.g., adamsite; amiton; arsine; blood agents including, e.g., lewisite, lewisite oxide, and its analogues and simulates; CEES/HM; diphosgene; distilled mustard; chlorine; chloropicrin; cyanogen chloride; cyclohexyl methylphosphonofluoridate; dimethylmethyl phosphonate; diisopropylmethylphosphonate; ethyl N,N-dimethyl phosphoramicocyanidate; ethyldichloroarsine; hydrogen chloride; GB; GD; PFIB; phenyldichloroarsine; phosgene; phosgene oxime; isopropyl ester; isopropyl methyl phosphonofluoridate; pinacolyl methyl phosphonefluoridate; phosphonofluoridic acid; phosphonothioic acid; S-(2-(diethylamino)ethyl) O-ethyl ester; S-(2-(diethylamino)ethyl) O-ethyl ester; lewisite-1; lewisite-2; lewisite-3; methyldichloroarsine; mustard; sulfur-mustard; Demeton-S; including analogues) and its stimulants; mustard-lewisite mixtures; mustard-T mixtures; nitrogen mustard-1; nitrogen mustard-2; nitrogen mustard-3; phosgene oxime; sesqui mustard; methylphosphonothioic acid; S-(2-(bis(1-methylethyl)amino)ethyl) O-ethyl ester; VX (e.g., US and Russian VX); analogues thereof, variants thereof, including combinations of these various agents. Biological warfare agents (BWA) include, but are not limited to, e.g., anthrax; aflatoxin; botulinus toxin; ricin; saxitoxin; trichothecene mycotoxin; including combinations of these various agents.
c shows exemplary pesticides including, but not limited to, e.g., malathion, parathion, paraoxon, derivatives thereof, analogues thereof, including combinations of these compounds. Industrial chemicals include organophosphates such as detergents and foaming agents, hydrocarbons (e.g., gasoline, diesel fuel, or aviation fuel); anti-knock agents and similar compounds (e.g., methylcymantrene and methyl-t-butoxide).
In various embodiments, analyte(s) are released from the sampler in a solvent or a mixture of solvents for detection thereof. In some embodiments, analyte(s) are thermally desorbed from the sampler for detection thereof.
Impact of temperature on analyte desorption and release from surfaces of phenyl-functionalized glass fiber materials and their detection was investigated in a Thermal Desorption Ion Mobility Spectrometry (IMS) instrument (e.g., Smiths Detection, Inc., Morristown, N.J., USA).
Results show the phenyl-functionalized sampler (e.g., 2× Phenyl PPS F.G.) gave an IMS signal for TNT about 10-times greater than muslin. Signal decreases at temperatures above 200° C. when TNT begins to thermally decompose. Muslin did not provide a TNT signal above a desorption temperature of 260° C. However, enhanced samplers gave a signal (referenced to the muslin signal at 180° C.) that remained ˜8 times greater than that observed for muslin even at a temperature of 29.0° C.
The higher thermal conductivity and lower specific heats for glass and pure silica fibers compared to muslin result in a more rapid heating of enhanced samplers containing these selected fibers. And, as shown here, this rapid heating releases TNT from the sampler into the IMS at a faster rate than for muslin. Additionally, terminal phenyl groups directly attached to the fibers assist with the retention of TNT on the surface and facilitate rapid release of TNT. In addition, only small amounts of TNT are decomposed even at high desorption temperatures. In contrast, muslin samplers demonstrate lower utility for collection and desorption of TNT due to the higher specific heat and an unsuitable surface chemistry that interacts with TNT and results in slow release of the TNT. TNT also readily decomposes prior to release into the IMS instrument from the muslin sampling material.
Sampling materials of different thicknesses with the same surface chemistry were assembled and assayed to quantitatively evaluate impact of thickness on analyte release. TABLE 2 lists numerical results showing impact of swipe thickness on IMS signal response.
1IMS (e.g., Thermal Desorption IMS, Smiths Detection, Inc., Morristown, NJ, USA)
2PPE = Polymer Primer on E-glass, finish 497A; PSiSF—Pure Silica, Silane Functionalized; F.G. = Fiberglass cloth.
3Materials preconditioned at 180° C. overnight under vacuum. Response to 10 ng liquid TNT spike taken at 1 minute assay interval. Muslin not preconditioned.
Preconditioning may be a preliminary step prior to exposure of the samplers to the analyte that effectively cleans the sampler of unwanted contaminates. In some embodiments, preconditioning may involve heating the swipe material to 180° C. in a vacuum oven for a time of about 18 hours. Preconditioning also removes any remaining residues from the fabrication process so as not to interfere with swipe performance. Here, muslin cloth was not preconditioned because the manufacturer claimed the material to be field ready as-received. It was found to degrade at this temperature and time.
Results show that the thicker the sampling material, the lower the measured TNT signal. Relative IMS signal from a fixed mass of spiked TNT was strongly nonlinear as a function of swipe thickness. For example, a 0.06 mm increase in muslin thickness was observed to reduce IMS signal by over 50%. In general, IMS response data show that the measured signal material is in part impacted by thickness of the fabric material.
Other factors that influence results include, analyte collection efficiency, release of analytes from the sampling material, transfer of the desorbed analyte to the downstream instrument, and the durability of the sampling material. Results show IMS analytical accuracy and repeatability are due in part to the uniformity of the thickness of the sampling material. In addition, permeability of the swipe materials—a function of weave and morphology and thickness—may also impact recovery of desorbed analytes. In some embodiments, the thinner the swipe, the greater quantity of analyte recovered from the sampling materials upon thermal desorption. However, no limitations in thickness or weave are intended.
Enhanced surface samplers described herein may be used to collect, retain, and detect target analytes retrieved from various surfaces including, countertop surfaces, luggage surfaces, cargo surfaces, vehicle surfaces, building interior and exterior surfaces, clothing, skin surfaces, and other surfaces. Performance of chemically modified fiberglass cloth was compared with standard muslin.
Surface functionalization of pure silica fiber materials (PSiSF) with, e.g., phenyl silanes (i.e., PSiSF+Phenyl) impacts its performance as a sampling material. TNT spikes on the PSiSF+phenyl-functionalized surface at both a 5 ng and 10 ng level showed a large increase in relative IMS signal response compared with unmodified PSiSF. And, a single functionalization of the pure silica fiber surface with phenyl silane provided a significantly higher relative TNT signal than those from functionalized E-glass or functionalization S-glass. Results are attributed to a greater density of surface silanol sites of pure silica compared to E-glass or S-glass fibers, which can increase the density of organosilanes installed. However, unlike E-glass or S-glass fiber materials, a second functionalization step (i.e., PSiSF+2× Phenyl) and a reduction in thickness did not significantly enhance the performance. Results are attributed to a near-quantitative release of analyte at the 5 ng level and a saturation of the detector at the 10 ng level.
Analyte collection from surfaces is due in part to fiber size and weave of the selected sampler material. In one test, analyte collection with an enhanced sampler made of phenyl-functionalized glass fibers exceeded muslin by a factor of roughly 2-fold, although factors such as pressure on the swipe surface were not investigated. Because glass, pure silica, and/or metal fiber fabrics are engineered materials, fiber size, weave, and thickness can be adjusted to improve analyte collection, analyte release, and sampling material durability. Optimization of these features can be expected to improve analyte collection, release, and durability.
TABLE 3 compares relative IMS response for selected explosives and explosive compounds released from enhanced surface samplers compared to muslin cloth.
1IMS (e.g., Thermal Desorption IMS, Smiths Detection, Inc., Morristown, NJ, USA) operated in negative ion mode at a desorption temperature of 180° C.
Analytes listed in TABLE 3 had IMS signals that were superior to those obtained with muslin. Listed analytes represent a wide variety of structural characteristics common to explosives including, e.g., nitroaromatics, nitroalkanes, and peroxides found in, e.g., military, industrial, or homemade explosives. Results obtained for the various explosives indicate that the applied surface chemistry is uniform, since different explosives compounds may be expected to exhibit different affinities for the sampling surface of the enhanced swipe. Surface uniformity ensures that the fabric material behaves predictably and allows the advantages of the surface samplers to be extended to other explosive materials, as well as other general categories of chemicals. In addition, samplers enable detection of many analytes that have a sufficiently strong response signal (e.g., in an IMS) but do not produce a corresponding signal on muslin. Examples include analytes such as DNT and heroin, described hereafter. For example, thin samplers functionalized once (e.g., thin PPS+1× Phenyl) gave an absolute IMS response for DNT of 8.0±0.3. Thin samplers functionalized twice (e.g., thin PPS+2× Phenyl) gave an absolute IMS response for DNT of 9.3±0.1.
TABLE 4 compares IMS results for selected drugs released from enhanced samplers of the present invention compared with muslin.
1IMS (e.g., Thermal Desorption IMS, Smiths Detection, Inc., Morristown, NJ, USA) operated in positive ion mode at a desorption temperature of 200° C.
Thermal desorption is not typically applied to surface sampling for drugs, whether illicit or commercial. Surface samples are typically taken to a laboratory, where extraction of analytes is performed with solvent extraction. Then, samples are analyzed, e.g., with an LC or GC. IMS results in TABLE 4 for these analytes provide direct evidence of the versatility of the modified glass fiber materials for many and varied organic compounds. As shown here, modified glass fiber swipes or swabs can allow surface sampling techniques to be used to screen for drugs and other analytes in the field. Applications include rapid screening of, e.g., crime scenes to reduce the number of samples returned to a laboratory for analysis, and consequently to reduce costs associated with obtaining, and processing crime scene evidence. In addition, the enhanced surface samplers enable detection of many analytes that have a sufficiently strong response signal (e.g., in an IMS) but do not produce a corresponding signal when released from muslin. For example, 30 ng of heroin produces a signal that is unambiguous and provides a signal-to-noise ratio of at least 3.
TABLE 5 compares IMS results for selected CWA stimulants released from enhanced samplers of the present invention compared with muslin.
1IMS (e.g., Thermal Desorption IMS, Smiths Detection, Inc., Morristown, NJ, USA) operated in positive ion mode at a desorption temperature of 220° C.
IMS results in TABLE 5 provide direct evidence of the versatility of surface samplers made of modified glass fiber materials for many and varied organic compounds. Surface sampling with field analyses using thermal desorption is not typically applied in the art for detecting chemical warfare agents. However, as shown here, two nerve agent surrogates both exhibited IMS responses at least equal to, or greater than, those observed with muslin. Thus, modified glass fiber swipes or swabs can allow surface sampling techniques to be used to screen for chemical warfare agents and nerve agents in the field and allow rapid screening for suspect violations of various treaties, to reduce the number of samples returned to a laboratory for analysis, and to reduce the cost of obtaining and processing evidence on site.
In some embodiments, analytes may be recovered from the surface of the samplers by extraction in selected solvents. Any solvent that provides solubility for the selected analyte may be used. No limitations are intended. TABLE 6 compares recovery results for a nerve agent (i.e., CWA) stimulant di-methyl-methylphosphonate (DMMP) obtained with a phenyl-silane functionalized swipe sampler, compared against untreated fiberglass and commercial muslin. Data in column 2 (acetone) report relative signal intensity values for analytes (here DMMP) recovered from samplers by solvent extraction with acetone, and analyzed through a GC-MS. IMS signal data are also reported for comparison, although IMS testing is not a liquid extraction method. Results are normalized to muslin.
1Solvent = Acetone.
2IMS (e.g., Thermal Desorption IMS, Smiths Detection, Inc., Morristown, NJ, USA).
Data in TABLE 6 show that solvent washing is a viable method for extracting analytes captured from enhanced E-glass, S-glass, and pure silica fiber samplers functionalized with, e.g., phenyl silanes (e.g., 2×+Phenyl). Data further indicate that enhanced samplers can be used in applications that currently employ conventional muslin samplers. Results are important because many sampling procedures call for solvent extraction of analytes from a surface sampler. Results further show that enhanced samplers provide a superior signal intensity and performance compared with conventional muslin. Data indicate that modified glass fiber materials release a greater fraction of collected analytes from the sampler surface into the analyzing instrument (e.g., LC, GC, IMS, etc.) producing a greater instrument response, which increases the probability of detecting the analyte of interest:
Enhanced samplers are not limited to single-use applications. Enhanced samplers may be conditioned for re-use.
In some embodiments, surface samplers may be thermally conditioned to desorb analytes to ready the samplers for re-use.
In some embodiments, surface samplers may be preconditioned or conditioned by cleaning the surface of the sampler to remove residual analyte residues (conditioned) or to remove residues involved in surface functionalization. In some embodiments, conditioning may include washing or rinsing the surface of the sampler one or more times with a solvent or a mixture of solvents to clean the surface. Cleaning may include use of solvents that have affinity for analytes residues in the samplers and/or solvent/surfactant (detergent) combinations that remove residues from the samplers. Solvents may be chosen based on analyte solubility, or those that do not interfere with activity of the sampling surface. Solvents include, but are not limited to, e.g., toluene, methanol, methylene chloride, propanol, acetone, and including combinations of these various solvents. Various high volatility solvents may also be employed. For some applications, suitable vapor pressures may be between about 0.05 atm and about 0.032 atm at 25° C.
As detailed herein, conditioning or preconditioning may include drying the sampler after cleaning. In some embodiments, drying includes vacuum drying the sampler fabric. Drying temperatures may be selected above 100° C. In some embodiments, drying temperature may be greater than about 150° C. In some embodiments, drying temperature may be greater than about 250° C. In some embodiments, drying temperature may be between about 150° C. and 300° C. Drying times are selected such that no residual solvents or detergents used to remove analyte residues are detectable in the detector. In some embodiments, drying time may be selected above about 6 hours. In some embodiments, drying time may be between about 6 hours to about 24 hours. In some embodiments, drying time may be greater than 18 hours. In some embodiments, drying time may be below 24 hours. In some embodiments, drying time may be below 6 hours. In some embodiments, pre-conditioning is a step involved in the post-treatment of the surface samplers. Thus, pre-conditioning does not need to be accomplished “just prior” to use.
Longevity (i.e., lifetime) of the sampler is a function of the surface activity, integrity, and/or signal noise observed in the detection platform. Discoloration May also be used to assess the quality of the sampler. Standards may also be used to measure the viability of the sampler surface.
Enhanced surface-functionalized samplers including glass, silica, and/or metal fibers provide enhanced collection and subsequent assay of target analytes and trace organic residues from surfaces that find applications in, e.g., international treaty verification; military; forensic; security; transportation security (e.g., explosives detection); law enforcement (e.g., drug detection and forensic sampling); environmental sampling; industrial sampling (e.g., health and safety monitoring), and biomedical applications. These samplers provide benefits compared to muslin and cotton sampling materials that include, but are not limited to: 1) up to 50-times better analyte sensitivity, 2) improved surface homogeneity and analyte affinity that enables better analyte collection: 3) better analyte release that enhances analyte recovery from the sampler surface, 4) a flexible and tailored surface chemistry that enables selectivity and tuning to specific analytes of interest or for specific applications, 5) samplers can be thermally and/or chemically cleaned and reused without a change in performance, and 6) better repeatability for sequential and repeated usage.
The following Examples provide a further understanding of the invention.
In some embodiments, fabrics containing glass and fused silica fibers were pretreated with a base and/or an acid to expose a maximum number of silanol groups on the surface of the fibers. In cases where fabric was pretreated, fabrics were refluxed in acetone, e.g., for 3 hours and dipped, e.g., in 1.0 M NaOH for 1 hour. Excess base may be neutralized with 0.1 M HCl, e.g., for 30 minutes. Fabrics may then be washed with water. Concentrations of base and acid can be varied as needed. For example, in some thick (>0.25 mm) fabrics, fibers may be treated with 1.0 M NaOH, e.g., for 4 hours, rinsed with water, and followed by neutralizing excess NaOH with 0.1 M HCl, e.g., for 30 minutes. Thin (<0.14 mm) fabrics may be treated similarly, but may involve a reduced rinsing time in NaOH solution, e.g., from 4 hours to 1 hour. For thin glass-A fiber materials (e.g., ASTROQUARTZ®), a rinsing time of 1 hour in 2 M NaOH, and 30 minutes in 0.2 M HCl was sufficient. Longer exposures in basic solution (e.g., 4 hours) may be used, or higher concentrations of base (e.g., 2 M NaOH) and acid (e.g., 0.2 M HCl) may be used. When rinsed, fabrics treated with base or acid may be dried, e.g., at 120° C. and, e.g., for 3 hours. Pretreatment or preconditioning may be a function of fiber diameter, fiber weave, fiber density, permeability, and like parameters. In some embodiments, pretreatment is not necessary, e.g., when pretreatment may dissolve or weaken fibers of the fabric, or, e.g., when thinner fabrics are used.
In one exemplary process, fabrics containing pretreated glass and/or silica fibers were refluxed overnight (e.g., 18 hours) in a 10% phenyl trimethoxysilane solution in toluene solvent. The fabrics were then rinsed (e.g., twice) with 100 mL toluene, and then rinsed (e.g., twice) with 100 mL of methanol. Secondary treatments using the same process were carried out to enhance the density of silanes on the surface of the fibers.
Fabrics containing functionalized (e.g., silanized) glass and/or silica fibers were stabilized by drying at 180° C. under vacuum for 18 hours to remove excess solvent and finalize surface condensation reactions.
Swipe sampler thickness measurements were obtained with a digital caliper (e.g., a Absolute Digimatic Caliper Series 500, Mitutoyo, Aurora, Ill., USA). Ten measurements from each of five different pieces (locations) of each respective swipe were collected (minimum 50 points). Error was assessed by calculating standard deviation for all measurement points. Density measurements were also obtained by taking the mass of swipes and dividing by the dimensions of the fabric pieces. Values were reported as averages of five density measurements.
An IMS was configured with a sliding stage mount coupled to an ionizing source (e.g., a 63Ni β ionization source) that was further coupled to a drift tube equipped with an electric field generator. A thermal desorber was used to volatilize analytes (e.g., explosive compounds) from various locations on the samplers. A carrier gas directed the analyte(s) to a glass inlet liner that ended at an ionizing source (e.g., a 63Ni β ionization source), where analyte(s) were ionized. Hexachloroethane dopant gas controlled ion chemistry (e.g., preventing charge losses or charge transfer losses from the analytes) within the drift tube. Purified air, used as the drift gas, effected mobility of the ionized particles. Ionized particles were carried by electric field to a collector. Collection time, relative to the calibrant (4-nitrobenzyl nitrile), was used to identify explosive compounds. The IMS instrument was operated (e.g., in negative ion mode for detection of explosives) at a desorption temperature of 180° C. and a collection time of 10 seconds. Drift tube and inlet temperatures were set at 114° C. and 240° C., respectively. Dopant gas was set at 239 mL/min and the drift (carrier) gas was set at 351 mL/min or per standard instrument settings. Sample analysis consisted of first mounting an un-spiked sampler on the IMS thermal desorption stage to obtain a background spectrum. Sampler was then spiked using a 2 μL GC syringe with 1 μL of methanol solution containing, e.g., 10 ng/μL TNT. The solvent was evaporated (˜15-20 seconds), leaving the explosive residue. For consistency, spiked samplers were mounted on the thermal desorption stage one minute after completion of the baseline run, and assayed for one minute. Data for all samplers were collected similarly to avoid IMS instrument variations with time and conditions. Ion mobility spectra were analyzed to determine the maximum TNT signal and noise. The TNT peak selected had a reduced mobility (Ko) of 1.45 cm2 V−1s−1 in agreement with literature values. Background signal was subtracted from the TNT sample signal (at the TNT Ko). Noise was calculated by taking the root mean square (RMS) along the 16 ms drift region. Sampler data were all normalized to the muslin response.
Determination of dry analyte pickup from surfaces was measured by depositing 30 ng of a TNT standard dispersed in a methanol (4.4×10−5 M TNT) solution was placed onto the surface of a 2-inch (5.08 cm) diameter TEFLON® disk using a 10 microliter (μL) syringe. Methanol was evaporated leaving the 30 ng TNT deposition as a residue at the center on the surface of the TEFLON® disk. A 30 ng spike of analyte was selected to provide statistically sound instrumental signals after potential collection loses had been taken into account. Following deposition, the swipe material was used to sample TEFLON® surfaces. Swipe sampler material was then immediately transferred to the IMS for standard analysis. Each swipe sample was run in triplicate using fresh swipe material for each assay.
Repeatability tests were performed using muslin and a thin twice-treated (2×) phenyl-functionalized S-glass fiber material. Replicate cycles were run on the same swatch to quantify repeatability and reusability of the material. A single cycle consisted of running a background and then spiking the swipe with 10 ng TNT. Run was repeated ten times for each material. Thermal conditioning of muslin consisted of passing the material twice through the IMS and then cycling as described above. Functionalized glass fiber samplers showed superior analyte release and an IMS repeatability with less than 5% change over ten replicate cycles. Results showed a consistent noise output lower than that of muslin.
IMS instrument response and sensitivity of enhanced samplers of the present invention to quantitative liquid TNT spikes were tested against commercial muslin and commercial fiberglass materials. In one test, enhanced samplers containing phenyl functionalized thin S-glass fibers were compared with commercial muslin and commercial fiberglass (e.g., thin S-glass fibers with polymer primer finish, 497A). Analysis consisted of spiking samples with 1 μL of a known TNT concentration ranging from 0.1 ng to 50 ng TNT in methanol and conducting IMS assays of the samples. A one minute assay interval was used. All results were normalized to muslin.
While exemplary embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that many changes and modifications may be made without departing from the invention in its true scope and broader aspects. The appended claims are therefore intended to cover all such changes and modifications as fall within the spirit and scope of the invention.
This invention was made with Government support under Contract DE-AC05-76RLO1830 awarded by the U.S. Department of Energy. The Government has certain rights in the invention.
