Surface swab for sampling of an unknown chemical

Abstract

A surface sampling swab that effectively de-couples the process of sample collection on a porous material (such as cellulose / paper), the dissolution of the chemical compound in suitable solvent and an ionization of compounds from the swab area by electrospray on a sharp corner of the swab – but not from the porous material itself – is described. This design shows improved robustness against mechanical impact on the tip side of the swab making it more suitable for swabbing / collecting from irregular or rough surfaces, an important aspect for ease of use for example in airport screening or threat detection scenarios.

Description

SURFACE SWAB FOR SAMPLING OF AN UNKNOWN CHEMICALField of the Invention

[0001] The present disclosure is directed to a chemical sampling technique, and more specifically to an improved surface sampling swab for use in chemical sampling and analysis.Background

[0002] Conventional systems and methods for the sampling and analysis of unknown chemical substances from surfaces include swabs made from porous materials, for example, Teflon coated fiberglass or cellulose paper. Sampled chemicals on the swab surface can then be analyzed by methods including, for example, thermal desorption ion mobility mass spectrometers or by solvent dissolution and electrospray mass spectrometry.

[0003] Electrospray ionization is a technique used in mass spectrometry that applies a high voltage to a liquid in order to produce an aerosol (as should be known and appreciated by those of ordinary skill in the art in review of this disclosure). In the case of a sample introduction to mass spectrometry by way of electrospray (atmospheric desorption ionization, ADI 2022 / 0229017 Al), the respective cellulose / paper is usually wetted with an elution / electrospray solvent and connected to a high voltage power source. Because of the high voltage at the edge of the porous material (sharp edge or single fibrous material at the end of the swab), high electrical field lines form to the nearest ground surface and an electrospray commences that provides evaporation of solvent into the gas phase and ionization of the analyte of interest. Such an approach is usually summarized under the term paperspray and shown and generally described, for example, in the following US Pat. Nos. 8,859,956 B2; 8,816,275 B2 and 10,761 ,083 B2, incorporated by reference herein.

[0004] To the extent that specific patents / publications / products are discussed in this disclosure, these discussions should not be taken as an admission that the discussed patents / publications / products are prior art for patent law purposes. For example, some or all of the discussed patents / publications / products may not be sufficiently early in time, may not reflect subject matter developed early enough in time and / or may not be sufficiently enabling so as to amount to prior art for patent law purposes. To the extent that specific patents / publications / products are discussed throughout the application, the descriptions / disclosures of which are all hereby incorporated by reference into this document in their respective entirety(ies).Summary

[0005] The inventors recognize that the material of conventional paper sampling swabs (e.g., cellulose) can create resistance as a liquid to be tested is pulled out of the paper during the electrospray process, which can lead to the consumption of large amounts of solvent and less stable electrospray. The inventors further recognize that collecting samples to be tested from irregular or rough surfaces can be difficult, as the tip side of the swab can be vulnerable to mechanical impact.

[0006] It is therefore a principal object and advantage of embodiments of the present disclosure to provide a surface sampling swab that is configured to effectively de-couple the process of sample collection on a porous material (such as cellulose / paper), the dissolution of the chemical compound in suitable solvent, and an ionization of compounds from the swab area by electrospray on a sharp corner of the swab - instead of the porous material itself. Such a structural configuration and associated process described herein and below increases the stability of test results and sensitivity of the testing system as compared with conventional technology and methods.

[0007] These and other aspects of the invention will be apparent from the embodiments described below.Brief Description of the Drawings

[0008] The present invention will be more fully understood and appreciated by reading the following Detailed Description in conjunction with the accompanying drawings, in which:

[0009] FIG. 1A is a chemical sampling swab according to an aspect of the present disclosure.

[0010] FIG. I B is a cross-sectional view of the chemical sampling swab shown in FIG. 1A according to an aspect of the present disclosure.

[0011] FIG. 2 is a chemical sampling swab in use with a system to dissolve the respective compounds according to an aspect of the present disclosure.

[0012] FIG. 3 is a chemical sampling swab (right) according to an aspect of the present disclosure compared to a chemical sampling swab (left) that is to be improved upon.Detailed Description of Embodiments

[0013] Aspects of the present embodiments and certain features, advantages, and details thereof, are explained more fully below with reference to the non-limiting examples illustratedin the accompanying drawings. Descriptions of well-known structures are omitted so as not to unnecessarily obscure the invention in detail. It should be understood, however, that the detailed description and the specific non-limiting examples, while indicating aspects of the invention, are given by way of illustration only, and are not by way of limitation. Various substitutions, modifications, additions, and / or arrangements, within the spirit and / or scope of the underlying inventive concepts will be apparent to those skilled in the art from this disclosure.

[0014] While embodiments of the present invention have been particularly shown and described with reference to certain exemplary embodiments, it will be understood by one skilled in the art that various changes in detail may be effected therein without departing from the spirit and scope of the invention as defined by claims that can be supported by the written description and drawings. Further, where exemplary embodiments are described with reference to a certain number of elements it will be understood that the exemplary embodiments can be practiced utilizing either less than or more than the certain number of elements. If elements shown in a particular Figure discussed below are not specifically identified with respect to that Figure, the elements should be sufficiently identified with respect to at least one other Figure.

[0015] The present disclosure describes embodiments of a surface sampling swab. Referring to FIGS. 1A-1 B, the exemplary sampling swab in accordance with an embodiment is shown. The exemplary sampling swab 100 can include a sampling area 102 (e.g., filter paper), a conductive aluminum layer 104, and a hard polymer area (e.g., plastic laminate sheet) 106. The polymer area 106 can have a sharp point (i.e., the length of the distal end of the swab is shorter than the proximal end length) at its distal end that provides a center for the electrospray (i.e., the electrospray area 108). In accordance with an embodiment, the electrospray area 108 can include only a portion of the plastic laminate sheet / layer 106 (and potentially also an aluminum layer portion 104) and can include a reservoir 1 10 at its proximal end (opposite the distal tip 108). In some embodiments, between at least some of the layers, a thermal bonding material sheet 1 12 can be included (see, e.g. FIG. IB showing a crosssectioned view taken from A-A) (but does not have to be). According to this embodiment, the sample collection area 102 is spatially separated from the electrospray area 108 (e.g., by approximately 1 -5 mm) such that the reservoir 1 10 in between said space can fill up with solvent used to dissolve and move the chemical compound from the sampling area 102 to the electrospray area 108 by gravity and surface tension (as the surface energy of paper is greater than the surface energy of a hard polymer or plastic). In other words, this open space creates a small solvent reservoir 1 10 and fills itself as a function of the surface tension differencesbetween the sampling area 102, the underlying swab structure, and the solvent used. The reservoir allows the electrospray process to more easily pull the chemical compound being tested away from the sampling area 102 and from the reservoir 1 10, as conventional sampling areas require more pulling force from the paper and can lead to less consistent results. Thus, when applying a high voltage power supply to the swab 100, the electrospray process forms at the edge of the hard polymer (e.g., plastic laminate, instead of the porous material) and consumes small amounts of solvent over time, a volume of which is replenished from the reservoir area. This creates a more stable and robust electrospray at voltages of around 500- 5000V, for example. In some embodiments, the reservoir 1 10 can be flush (i.e., level) with and formed of the same material as the electrospray area 108.

[0016] In accordance with an embodiment, the swab 100 surface can be formed of materials including but not limited to Whatman 3001-614 Grade 1 Chr Cellulose Chromatography Paper, the hard plastic can be formed of Scotch Thermal Laminating Pouches, Letter Size, 5 Mil (TP5854-100), and the bonding material can be formed of HeatnBond® 17” x 23” Ultra Hold Iron On Adhesive. While a hard plastic or polymer is described, it should be understood that other materials can be used and are contemplated herein (as should be understood by a person of ordinary skill in the art in conjunction with a review of this disclosure). In a preferred embodiment, the electrospray area can be of a material having a sharp point which is able to have the resulting ions be accepted by an entrance cone component of a mass spectrometer following ionization from electrospraying.

[0017] Additionally, this design shows improved robustness against mechanical impact on the sampling side of the swab making it more suitable for swabbing / collecting from irregular or rough surfaces, an important aspect for ease of use for example in airport screening or threat detection scenarios. Thus, it can be preferred that a durable and hard material reinforces the swab 100.

[0018] Referring to FIG. 2, the general components of a system that uses a swab 100 of an embodiment to dissolve the respective compounds from the swab area 102 by way of an applied solvent 200, the electrospray ionization of said compounds, and their entrance into a mass spectrometer 1 14 for detection are shown. Optical inspection of the drop, travel, and electrospray ionization indicates a more stable and consistent electrospray when having a reservoir of about 1-5 mm distance between the electrospray area 108 and the sampling area of the swab 102, as detailed above. In this example, to use the sampling swab 100, the swab containing the contaminant to be tested (i.e., by contacting the swab with the contaminant) is inserted into the special ion source housing component 116 of a mass spectrometer 1 14. Asshould be understood by a person of ordinary skill in the art in conjunction with a review of this disclosure, the housing functions to position the swab 100 correctly and move the edge / tip of the swab 106’ in a specific location relative to the cone of the mass spectrometer 1 14 (e.g., 1 -10 mm above the plane of the cone and 1-5 mm sideways of the cone), as well as apply the high voltage. Once the swab 100 is connected to the housing / high voltage machine 116, the liquid solvent 200 is added (e.g., dripped) to the swab 100 at the sampling area 102 where it dissolves the material to be analyzed. The gap or reservoir area 1 10 is shown adjacent to the sharp edge 108 that forms the electrospray for ionization of analytes and adjacent the sampling area 102 (i.e., the space between the two areas). Due to the force of gravity and surface tension of the liquid, the applied solvent travels from the sampling area 102, through the reservoir 110, and to the sharp edge 108 of the swab where the electrospray will occur. Upon application of high voltage, the electrospray forms and creates a very fine mist of solvent droplets from the tip / edge 108 of the swab toward the entrance cone component 1 14’ of the mass spectrometer 1 14. This process includes evaporation and ionization, generating ions in the electrospray region (between the tip / edge 108 and the cone 1 14’) that will be inhaled into the cone 1 14’ of the mass spectrometer 1 14 for testing (as should be understood by a person of ordinary skill in the relevant art in conjunction with this disclosure).

[0019] Referring to FIG. 3, a swab construction with a gap (i.e.. reservoir area 1 10) between the sampling area 102 and the electrospray area 108 at the bottom of the swab - compared to a swab construction where the sampling area 102 is extended to the end of the tip 108 - are shown as cases B and A, respectively. In case A, the electrospray would form from the sampling material itself (e.g., its edge or protruding fibers of the cellulose / paper), whereas in case B (current embodiment example), the electrospray forms at the sharp edge 108 of the hard polymer used in the swab construction. Due to gravity and surface tension (as should be understood by a person of ordinary skill in the art in conjunction with this disclosure), the reservoir area 1 10 allows for less force required to pull the chemical to be tested from the reservoir 1 10 to the end of the tip 108 as compared to the use of a fully paper sw ab seen in A (i.e., the reservoir can be easier to access for electrospray rather than the spray pulling the liquid out of paper, equaling less resistance). This additionally allows for a more consistent spray and signal, as well as increased stability.

[0020] Referring to TABLE 1 below, the signal intensity of two m / z monitored masses indicating RDX as a compound present on the respective swab is shown. The results show ten swabs and their respective signal intensity in case A, a swab with a paper collection area extended all the way to the front, forming an electrospray from the porous material directly;and B (current embodiment example), from swabs with a 1-5 mm gap between the sampling surface of the swab and the sharp edge of a polymer structure of the swab itself (with cases A and B referring to what is described above and shown in FIG. 3). In direct comparison, the results group is tighter with lower CV in case B, indicating a more stable and reproducible electrospray and mass spec detection of the generated ions.Table I: Signal Intensity of Monitored Masses

[0021] In accordance with an alternative embodiment, the reservoir 1 10 is recessed within the swab 100. In some embodiments, the solvent is added to both the sampling area 102 and the reservoir 1 10 (instead of just the sampling area 102). While a square portion with a triangle top is described and shown herein with respect to the swab 100, additional shape combinations are contemplated, such as square, diamond, etc. In one embodiment, the aluminum layer 104 does not extend behind the sampling area 102. In some embodiments, the reservoir and electrospray area are only formed of plastic laminate (or other hard polymer). In other embodiments, the reservoir and electrospray area are formed of different materials. In some embodiments, the sampling area 102 is removably coupled to the swab 100 such that a sample can be collected with the sampling area 102 and then secured to the swab 100 for testing.

[0022] It should be understood that any of the embodiments described herein can be combined in any way mechanically possible.

[0023] While various embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and / or structures for performing the function and / or obtaining the results and / or one or more of the advantagesdescribed herein, and each of such variations and / or modifications is deemed to be within the scope of the embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and / or configurations will depend upon the specific application or applications for which the teachings is / are used. Those skilled in the art will recognize or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, embodiments may be practiced otherwise than as specifically described and claimed. Embodiments of the present disclosure are directed to each individual feature, system, article, material, kit. and / or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and / or methods, if such features, systems, articles, materials, kits, and / or methods are not mutually inconsistent, is included within the scope of the present disclosure.

[0024] The above-described embodiments of the described subject matter can be implemented in any of numerous ways. For example, some embodiments may be implemented using hardware, software or a combination thereof. When any aspect of an embodiment is implemented at least in part in software, the software code can be executed on any suitable processor or collection of processors, whether provided in a single device or computer or distributed among multiple devices / computers.

Claims

ClaimsWhat is claimed is:

1. A surface sampling swab, comprising: a body having a top surface, a bottom surface, a first side and an opposing second side, a proximal end, and a distal tip, wherein: the top surface further comprises a paper layer extending from the proximal end to a position proximal to the distal tip, and a plastic layer extending distally from the paper layer and forming the distal tip.

2. The surface sampling swab of claim 1, further comprising an aluminum layer positioned underneath the top surface.

3. The surface sampling swab of claim 1, further comprising a reservoir positioned on the top surface and between the paper layer and the distal tip.

4. The surface sampling swab of claim 3, wherein the reservoir is configured to hold a solvent.

5. The surface sampling swab of claim 1, wherein a distance between the paper layer and the distal tip is between about 1-5 mm.

6. The surface sampling swab of claim 1, wherein the paper layer has a higher surface energy than the plastic layer.

7. The surface sampling swab of claim 1, wherein the paper layer comprises cellulose.

8. A method of using a surface sampling swab, comprising: providing a surface sampling swab, comprising: a body having a top surface, a bottom surface, a first side and an opposing second side, a proximal end, and a distal tip, wherein: the top surface further comprises a paper layer and a reservoir area, wherein the reservoir area extends distally from the paper layer; and connecting the surface sampling swab to a high voltage machine; adding a liquid solvent to the paper area of the surface sampling swab; and electrospraying the distal tip via a mass spectrometer.

9. The method of claim 8, wherein the sampling swab further comprises an aluminum layer positioned underneath the top surface.

10. The method of claim 8, wherein the sampling swab further comprising a reservoir positioned on the top surface and between the paper layer and the distal tip.

11. The method of claim 10, wherein the reservoir is configured to hold a solvent.

12. The method of claim 8, wherein a distance between the paper layer and the distal tip is between about 1-5 mm.

13. The method of claim 8, wherein the paper layer has a higher surface energy than the plastic layer.

14. The method of claim 8, wherein the paper layer comprises cellulose.

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