Systems and methods for diffusion gas sampling for the collection of VOCs, SVOCs, and / or PFAS chemicals in the air.

Abstract

Diffusion sampling devices are used for quantitative measurements of chemicals in indoor and outdoor air. The sampling device includes a vial containing a sorbent in the inside bottom of the vial. The sampling device can be thermal vacuum cleaned before transport to the sampling location, and the sorbent is selected to collect either volatile or semi-volatile compounds (VOCs or SVOCs). After the diffusive sampling period (1 hour to 1 month), the vial is closed and the collected sample is transported to a laboratory for analysis. Using thermal vacuum extraction focusing technology, the collected sample is rapidly delivered to a GCMS-compatible preconcentrator containing a second sorbent for split or splitless injection into a capillary-based GCMS. No solvents are used during sampler preparation or analysis, and detection limits required for ambient or indoor air monitoring for thousands of chemicals can be achieved.

Description

Technical Field

[0001] (Cross - Reference to Related Applications) This application claims the benefit of U.S. Provisional Patent Application No. 63 / 264,651, filed on November 29, 2021, the disclosure of which is hereby incorporated by reference in its entirety for all purposes.

[0002] (Field of the Invention) This disclosure relates to the collection of gas samples, and more particularly, to the sampling of air using diffusion vial samplers in indoor and outdoor environments.

Background Art

[0003] Organic chemicals, ranging from light volatile compounds to heavy semi-volatile compounds, can be collected by actively aspirating samples through tubes or cartridges containing adsorbents, or by opening the shut-off valve of a vacuum vessel and aspirating the sample into the vessel by vacuum. In both cases, the equipment required to perform sampling is expensive, and the ability to perform long-term integrated sampling, where the chemicals accumulate over time to determine the average concentration, can be complex and costly. Vacuum canisters are popular for collecting compounds in the volatile range, but are ineffective for recovering compounds in the heavier semi-volatile (SVOC) range, and the cost of these canisters and the time required to integrate the inlets can also be high. PFAS compounds (perfluoroalkyl substances) are toxic and carcinogenic compounds with a volatility range spanning from light VOCs to heavy SVOCs, and many can be analyzed using the same sampling and analytical techniques used for VOCs and SVOCs; therefore, for the purposes of this explanation, when VOCs and SVOCs are mentioned in the specification, PFAS compounds are understood to be included as well. Like SVOCs, they can be acidic, basic, or neutral, and can be ionic at standard pH 7.0. SVOCs and PFAS (perfluoroalkyl substances) compounds not recovered by vacuum canister sampling may be even more toxic than VOCs, often adversely affecting the human endocrine system, impacting health, and potentially leading to life-threatening diseases such as cancer. SVOC / PFAS sampling devices that draw air through cartridges containing polyurethane foam (PUF) or XAD-2 resin do not retain lighter VOC compounds and require solvent extraction followed by blowdown to concentrate the extract, which is time-consuming, expensive, and may require solvents that are dangerous if inhaled over long periods.Finally, while thermal desorption (TD) tubes containing one or more adsorbent beds are used to collect various chemicals from the air, consistency between samplers can be low due to volumetric measurement errors caused by the pumps used to measure the amount of air passing through the tubes in the field. Furthermore, TD tubes during active sampling can be affected by a "channeling effect," which allows air to pass more quickly through gaps created in the adsorbent as it cools since the last thermal desorption and baking event. Again, these tubes and their field sampling components can be expensive and require advanced expertise to be used properly. [Overview of the project]

[0004] This disclosure relates to the collection of gas samples, more specifically, to the sampling of air using a diffusion vial sampler in indoor and outdoor environments. The glass vials are prepared to have a thin, thermally stable polymer material coated on the bottom surface, and any number of adsorbents can be applied to this material to modify the adsorption properties of the bottom surface. Solid adsorbents of 15 to 200 mesh readily adhere to many polymer films, and these films, composed of siloxanes (e.g., polydimethylsiloxane-PDMS), do not decompose to produce organic or PFAS chemicals, and therefore do not add to the chemical background even when exposed to oxygen or ozone. The vials, including the polymer base and applied adsorbents, are washed using a thermal vacuum cleaning process to remove the background of VOC / SVOC / PFAS chemicals within the vials, and then the vials are capped until they can be moved to a sampling location to collect air samples for analysis. At the sampling location, the vials are opened, and air diffuses into the vials for a certain period of time, and the diffusion / collection rates of a very wide range of compounds can be measured using vials of the same size (ID and height). After on-site collection, the "diffusion vial sampler" or DVS is returned to the laboratory for analysis using a thermal vacuum extraction process into a tube containing a secondary adsorbent that can be easily connected to a GC-MS or GC-MS-MS for quantitative analysis of the collected compounds. This technique significantly simplifies the sampling process, eliminates the use of solvents during sampler preparation and analysis, eliminates inconsistencies caused by dynamic sampling techniques, and increases the number of GC-compatible compounds that can be collected and analyzed in air, including toxic chemicals, endocrine disruptors, and compounds known to be carcinogenic. [Brief explanation of the drawing]

[0005] [Figure 1A] Figures 1A to 1B show examples of DVS samplers according to some embodiments of the present disclosure. [Figure 1B] Figures 1A to 1B show examples of DVS samplers according to some embodiments of the present disclosure.

[0006] [Figure 2] Figure 2 illustrates a cleanup technique used to remove chemicals from a DVS sampler according to some embodiments of the present disclosure.

[0007] [Figure 3A] Figures 3A to 3C show examples of methods for collecting air at a sampling location using a DVS sampler, according to several embodiments. [Figure 3B] Figures 3A to 3C show examples of methods for collecting air at a sampling location using a DVS sampler, according to several embodiments. [Figure 3C] Figures 3A to 3C show examples of methods for collecting air at a sampling location using a DVS sampler, according to several embodiments.

[0008] [Figure 4A] Figures 4A to 4D show examples of transferring samples collected using a DVS sampler to a secondary focus device for introduction into a capillary GCMS for analysis, according to several embodiments. [Figure 4B] Figures 4A to 4D show examples of transferring samples collected using a DVS sampler to a secondary focus device for introduction into a capillary GCMS for analysis, according to several embodiments. [Figure 4C] Figures 4A to 4D show examples of transferring samples collected using a DVS sampler to a secondary focus device for introduction into a capillary GCMS for analysis, according to several embodiments. [Figure 4D] Figures 4A to 4D show examples of transferring samples collected using a DVS sampler to a secondary focus device for introduction into a capillary GCMS for analysis, according to several embodiments.

[0009] [Figure 5]Figure 5 shows an example of how the adsorption pen is ultimately desorbed onto a capillary-based GCMS or GCMSMS chemical analyzer for analysis, according to some embodiments of the present disclosure. [Modes for carrying out the invention]

[0010] The following description refers to the accompanying drawings, which are shown by illustrating specific examples that form part of this specification and may be implemented. It should be understood that other examples may be used and structural modifications may be made without departing from the scope of the examples in this disclosure.

[0011] This disclosure relates to the collection of gas samples, more specifically, to the sampling of air using a diffusion vial sampler in indoor and outdoor environments. The glass vials are prepared to have a thin, thermally stable polymer material coated on the bottom surface, and any number of adsorbents can be applied to this material to modify the adsorption properties of the bottom surface. Solid adsorbents of 15 to 200 mesh readily adhere to many polymer films, and these films, composed of siloxanes (e.g., polydimethylsiloxane-PDMS), do not decompose to produce organic or PFAS chemicals, and therefore do not add to the chemical background even when exposed to oxygen or ozone. The vials, including the polymer base and applied adsorbents, are washed using a thermal vacuum cleaning process to remove the background of VOC / SVOC / PFAS chemicals within the vials, and then the vials are capped until they can be moved to a sampling location to collect air samples for analysis. At the sampling location, the vials are opened, and air diffuses into the vials for a certain period of time, and the diffusion / collection rates of a very wide range of compounds can be measured using vials of the same size (ID and height). After on-site collection, the "diffusion vial sampler" or DVS is returned to the laboratory for analysis using a thermal vacuum extraction process into a tube containing a secondary adsorbent that can be easily connected to a GC-MS or GC-MS-MS for quantitative analysis of the collected compounds. This technique significantly simplifies the sampling process, eliminates the use of solvents during sampler preparation and analysis, eliminates inconsistencies caused by dynamic sampling techniques, and increases the number of GC-compatible compounds that can be collected and analyzed in air, including toxic chemicals, endocrine disruptors, and compounds known to be carcinogenic.

[0012] Diffusion air sampling is a process that passively exposes an adsorbent to an indoor or outdoor air sample, without the use of pumps or vacuum equipment, allowing compounds to diffuse onto the adsorbent. In some embodiments, if the shape of the sampling device is appropriately selected and substantially consistent between devices, the collection rate is substantially constant for any target compound. Diffusion samplers are significantly less expensive than dynamic samplers and require less expertise for field use. US EPA Method 325 uses a 1 / 4-inch OD x 5 mm tube positioned vertically with the inlet facing downwards during sampling to allow compounds to diffuse into the adsorbent. However, the small inlet of the tube can limit the rate at which larger SVOC compounds migrate into the tube, potentially reducing sensitivity. Also, many SVOC and PFAS compounds tend to settle due to gravity because they adhere to airborne particles with diffusion rates thousands of times lower, and may not be collected during sampling, while individual molecules are not significantly affected by gravity on relatively short air columns. Using these thermal desorption devices upside down to collect falling dust can contaminate the collection tube, and these dust particles may transfer to the GC-MS or GC-MS-MS analyzer during desorption, contaminating these analyzers which are designed to accept only gaseous chemicals. Using samplers with larger cross-sectional areas can make it difficult to recover captured compounds in the laboratory, as these sampling devices typically require "flow-through" thermal desorption, which requires a specific linear velocity that is not maintained in devices with larger cross-sectional areas. Diffusion samplers with large cross-sections, such as badge or radial samplers, are usually solvent-extracted to recover the collected compounds. However, when the collected adsorbent is solvent-extracted, often only a small portion of the sample is injected into the GC or GC-MS for analysis. The resulting dilution can reach as high as 50,000:1, significantly limiting sensitivity to compounds in the ppm range.However, in many cases, ppb range measurements, and often ppt range measurements, are necessary, especially when monitoring chemicals that may increase long-term cancer risk or disrupt the body's normal hormonal system.

[0013] Embodiments of the present disclosure include sampling devices that are inexpensive, easy to use, capable of performing long-term time-integrated sampling to determine average concentrations (determining true risk factors), and capable of maximizing sensitivity to VOC / SVOC / PFAS compounds even if they are pre-adsorbed on airborne particles. For example, a diffusion vial sampler (DVS) includes a glass vial with a polymer layer or additional adsorbent at the bottom of the vial. Rather than preparing the adsorbent with a solvent or flow-through gas before sampling, the DVS sampler is connected to a vacuum to heat the adsorbent to a high temperature (e.g., 100 to 300°C) to release the compounds within the adsorbent, and the compounds are transferred to a vacuum pump that continuously pumps down the sampler during thermal adjustment.

[0014] In some embodiments, to collect compounds from the air, a pre-cleaned DVS sampler is brought to the sampling site, the cap is removed for a certain period, and then the cap is reattached before returning it to the laboratory for analysis. If the DVS sampler is installed in a windy location, a screen can be installed on top of the DVS sampler to prevent convective sampling, ensuring that, for example, compounds diffuse at a standard rate from the vial inlet to the adsorbent. To further simplify sampling in windy or turbulent air environments, a permanent screen can also be added to the top of the DVS, which is held under an isolation lid. Alternatively, the DVS sampler can be placed in a box or location that serves to eliminate turbulent air movement when installed outdoors. For indoor air, the DVS sampler can be installed away from windows or forced airflow (vents, fans, etc.), thus eliminating the need for intake screens or other convection prevention measures. By using a consistent vial shape (e.g., 20 mL × 1.08 inch OD, 2 inch height), the diffusion rate can be kept constant between different DVS samplers.

[0015] In some embodiments, DVS samplers can include various adsorbents depending on the compound to be captured. For example, a strong adsorbent can be used in a DVS sampler to collect VOCs in the air, and a weak adsorbent can be used in a DVS sampler to collect SVOCs. For example, since the columns used in most US EPA methods are based on the boiling point range of the compound being analyzed, typically thin-film columns are used to analyze heavier SVOC (PFAS) compounds, and thicker-film GC columns are selected to separate and analyze lighter VOC (PFAS) compounds. Therefore, using two or three separate DVS samplers to cover from VOCs to SVOCs makes sense from a laboratory analysis standpoint and achieves consistency with current environmental GCMS methods. As with other adsorbent collection methods, the recovery of VVOCs (highly volatile organic compounds) can be difficult, and a vacuum canister or other technique may be required for the lightest compounds, but DVS samplers can be considered for compounds ranging from the heaviest GC-compatible compounds to those in the room temperature to boiling point range. Unlike other samplers that can perform thermal extraction or desorption, the DVS can also be used as an LC-MS / LC-MS-MS collection device by adding a small amount of solvent to the vial after sample collection and transferring aliquots of solvent to the vial for LC injection. The very thin layer of adsorbent at the bottom of the vial allows for rapid and efficient transfer of compounds into the solvent, and the pH can also be adjusted with the solvent to recover acids or bases in the DVS sampler.

[0016] When performing GC analysis (e.g., GCMS, GCMSMS), DVS sampling systems utilize a novel laboratory sample preparation technique called "Flash-VASE" or flash vacuum-assisted adsorbent extraction. Flash-VASE is a technique that transfers chemicals from VOCs to SVOCs in a solid matrix to an adsorbent-containing tube by placing an adsorbent-containing tube (e.g., an adsorbent pen) on top of a vial, vacuuming the pen / vial assembly, and then heating the vial, "flashing" the compound into the gas phase and the adsorbent pen. The Flash-VASE process can be performed manually or with an automated sampler, in some embodiments of the automated sampler, allowing analysis of an entire DVS sampler tray with only two adsorption pens. In an example of automated sampler operation, one adsorption pen performs Flash-VASE extraction on the next DVS sampler while the other pen desorbs the previous DVS sample onto the GCMS for analysis. In some embodiments, sample desorbing onto the GCMS can be performed in either split mode or splitless mode, depending on the required sensitivity. Since both sample collection to the DVS sampler and Flash-VASE transfer with the adsorption pen utilize a diffusion process, channeling effects are avoided, resulting in significantly improved consistency compared to heat-desorbing tubes collected individually in situ.

[0017] In particular, DVS samplers offer the simplest, and perhaps most accurate, method for analyzing the thousands of semi-volatile compounds present in ambient and indoor air. The inability to reliably and cost-effectively collect these compounds limits the ability of agencies to monitor these hazardous chemicals in indoor and outdoor air. Furthermore, the ability to perform long-term sampling with a single DVS sampler, such as over a week or a month, allows for the determination of average concentrations of these SVOCs and the assessment of the potential for disease resulting from long-term chronic exposure. DVS samplers possess all the advantages of other sampling devices currently in use, without any drawbacks, and when combined with Flash-VASE extraction and GC-MS analysis, this could all change in the future.

[0018] Figures 1A through 1B are an example of a DVS sampler 100 according to some embodiments of the present disclosure. The exemplary DVS sampler 100 includes a vial 102, a lid 104, a cap 105, an O-ring 207, a first adsorbent 106, and a second adsorbent 108. In some embodiments, the DVS sampler 100 omits the second adsorbent 108 shown in Figures 1A through 1B and includes the vial 102, the lid 104, the cap 105, and the first adsorbent 106. In some embodiments, the second adsorbent 108 is a stronger adsorbent than the first adsorbent 106, and the first adsorbent 106 may act as a weaker adsorbent depending on the situation. In some embodiments, the stronger second adsorbent 108 is used when collecting VOCs and / or SVOCs lighter than C14. In some embodiments, the stronger adsorbent 108 may be omitted when collecting VOCs and / or SVOCs of C14 or higher, as well as particles containing SVOCs and PFAS. Adding the second adsorbent 108 helps collect lighter VOCs, but omitting 108 enables collection of heavier SVOCs / PFASs and makes it easier to wash away dust before the next heat conditioning after thermal extraction and before reuse.

[0019] As shown in Figures 1A to 1B, the adsorbents 106 and / or 108 are placed on the inner surface of the bottom of the vial 102. If a second adsorbent 108 is used, the second adsorbent 108 is made to "adhere" to the first adsorbent 106 on the vial. For example, the first adsorbent 106 contains a polymer layer (e.g., PDMS, polydimethylsiloxane). For example, the first adsorbent 106 is coated on the bottom inside the vial 102. In some embodiments, the first adsorbent 106 may be pre-coated on the bottom inside the vial 102 and then exposed to the adsorbent material of the second adsorbent 108. In some embodiments, the second adsorbent 108 is mixed into a solvent-diluted coating material (polymer) layer added to the vial containing the first adsorbent 106 at the bottom of the vial 102, and the solvent evaporates, leaving the second adsorbent 108 bound to the bottom of the vial 102 via the first adsorbent 106. In any case, the second adsorbent 10 is positioned in the bottom layer of the vial 102, so that, for example, the diffusion pathway from the top to the bottom of the vial 102 is consistent from one sampler to the next. Thus, various vial shapes can be used, but selecting a shape and determining the relative sampling rate (diffusion absorption rate) of a particular vial shape is advantageous for consistent sampling and analysis. In some cases, a “package” containing multiple small vials is separated and opened as a group, and the pH of one or more vials is adjusted to contain acid and base compounds before extraction, collecting compounds from light to heavy to create a universal sample pack.

[0020] In some embodiments, the second adsorbent 108 is weaker than the first adsorbent 106. In this situation, a relatively strong adsorbent can be added to the polymer mixture to form the first adsorbent 106, which can be coated onto the inner surface of the bottom of the vial 102. Once the carrier solvent of the first adsorbent 106 is removed and the polymer and the added stronger adsorbent remain bound to the bottom of the vial 102, the second adsorbent 108 can be sprinkled on top of the first adsorbent 106. By arranging the adsorbents 106 and 108 in this way, heavier compounds can be separated significantly from the stronger first adsorbent 106, thereby allowing for the recovery of a wider range of VOCs, such as compounds that boil from 30 to 80°C and then from 80 to 240°C, and possibly even heavier compounds, in a single analysis.

[0021] Compared to a badge worn during personal hygiene monitoring, the uptake rate of the DVS sampler may be slower, for example, than that of a badge for personal hygiene monitoring, because the distance from the inlet of the vial to the adsorbent is long. However, since the analysis of the sample is performed by thermal desorption, the final amount reaching the GCMS is usually diluted from 2000:1 or up to 50,000:1 using splitting during solvent extraction and GC injection, so it can be 5 to 100% of the sampled amount compared to 0.002 to 0.05% of the amount sampled with a badge. Reducing the sampling rate of the DVS sampler has the advantage of not properly purging the local environment around the inlet and eliminating the starvation state where the concentration and pressure of the air around the inlet of the sampler decrease. In other words, if the air at the inlet of the sampler has already been extracted, it cannot be extracted a second time, so the extracted air needs to move at a rate 5 to 10 times the rate at which the chemical substance is adsorbed from the air by the sampler to avoid starvation. Therefore, the combination of a slower sampling rate and a much higher sample recovery rate during analysis is a solution far superior to that provided by conventional workplace monitoring badges, especially for the determination of indoor air quality (IAQ) where a sufficient air flow rate on the sampling device cannot be relied upon. Furthermore, due to the plastic enclosure on the badge preventing dust from reaching the collection medium, the badge cannot collect chemical substances bound to dust. Even for SVOCs not bound to particles, they may adhere to the plastic badge enclosure without diffusing into the collection medium and be lost. In the DVS sampler, when the lid / cap is removed to enable the sampling process, such a barrier between the air and the collection medium is eliminated.

[0022] The DVS sampler 100 includes an inert, non-adsorbent / non-absorbent lid 104 for isolating the sampler after cleaning and during transport to and from the laboratory. As shown in Figures 1A to 1B, the lid 104 and its sealing O-ring 107 are pressed firmly onto the top of the vial 102 using the threads of the cap 105, and this combination ensures a leak-free seal, preventing VOCs / SVOCs / PFAS from being collected during transport to and from the sampling site without organic compounds from the environment of the sampler 100 being collected on the second adsorbent 108 and / or the first adsorbent 106. In some embodiments, the cap 105 and vial 102 include threads to facilitate seal formation with the cap 105. The lid uses a small O-ring 107 for sealing, but is otherwise made of a non-absorbent, non-adsorbent material such as stainless steel or ceramic-coated stainless steel. Depending on the situation, the sampler 100 can be labeled with a barcode or other tracking technology to maintain the storage chain during field sampling and ensure proper data integrity. A multi-position vial carrier can also be used to hold vials during transport and sampling and to track each vial until it is heated or liquid extracted in the laboratory, for example, this may include positions 1 to 4.

[0023] Figure 2 illustrates a cleanup technique used to remove chemicals from a DVS sampler 100, according to some embodiments of the present disclosure. Figure 2 includes the DVS sampler 100, a heater 202, and a manifold 204. As shown in Figure 2, the manifold 204 includes a connection 212 to a vacuum pump 210.

[0024] Depending on the situation, cleanup techniques may be performed before deploying the sampler 100 in the field, or at any other point where it is desirable to remove residual chemicals from the sampler 100. Cleanup techniques are similar to those used to recover chemicals in the laboratory after sampling and are described in detail below with reference to Figures 4A to 4D. In the example in Figure 2, during cleanup, the DVS sampler 100 is exposed to a higher vacuum and temperature for a longer period than during sample recovery for analysis, so that virtually nothing remains in the sampler 100 except what will be added during the next field sampling event.

[0025] A heater 202 (e.g., an oven or block heater) is used to heat the adsorbent in the vial, and a non-heating manifold 204 creates an O-ring seal on top of the sampler 100. As shown in Figure 2, an O-ring 206 (e.g., silicone or FKM) can be used to seal the top of the sampler 100, allowing multiple DVS samplers 100 to be cleaned simultaneously. For example, 10, 20, 30, or more samplers 100 can be cleaned at the same time.

[0026] In some embodiments, the heater 202 can apply more heat to the lower portion of the sampler 100 than to the upper portion. In some embodiments, the heater 202 applies heat uniformly or substantially uniformly to the vial 102. By heating the sampler 100, particularly the bottom portion of the sampler 100 where the first adsorbent 106 and / or optional second adsorbent 108 are located (see Figures 1A to 1B), the affinity of the chemicals in the adsorbents 106 and / or 108 can be reduced to near zero, and the chemicals are gasified through the vacuum line 208 and discharged to the pump 210. A strong vacuum compared to ambient atmospheric pressure (e.g., 1 Torr or more) generates a sealing force, for example, several pounds, which keeps the DVS sampler 100 sealed to the manifold 204 during cleaning. In some embodiments, after cleaning the sampler 100, the manifold 204 can be lifted while the vacuum is still maintained, removing all the samplers 100 from the heater 202 and transferring them to a room temperature tray for rapid cooling. In some embodiments, nitrogen can be introduced into the sampler 100 via the manifold 204, allowing the sampler 100 to be released from the manifold 204. By introducing high-purity nitrogen into the manifold 204, the DVS sampler 100 can be discharged from the manifold 204 and quickly sealed with the cap 105 and inert liner. In some embodiments, the liner is made of silonite-coated stainless steel and an O-ring to form the seal. These liners and O-rings can be cleaned in a heated vacuum vial or chamber.

[0027] In some embodiments, the inert liner, O-ring, and / or DVS sampler 100 can be cleaned and reused using a thermal vacuum cleaning system. For example, a thermal vacuum cleaning system may include a vial, a water supply device, one or more heaters, a vacuum source, and multiple transfer lines for delivering various fluids (e.g., steam, nitrogen) to the parts to be cleaned. In some embodiments, cleaning using a vacuum cleaning system may include placing one or more parts in a vial, rinsing the parts with deionized water, steam cleaning the parts, vacuum cleaning the parts, and then releasing the vacuum by applying nitrogen while avoiding contamination by air in the cleaning system environment.

[0028] Figures 3A to 3C show examples of methods for collecting air at a sampling location using the DVS sampler 100, according to several embodiments. Depending on the rate and consistency of air movement in the sampler 100 environment and whether collection of dust and heavy compounds adsorbed on the dust is desired, the DVS sampler 100 can be positioned upright as shown in Figure 3A, upside down as shown in Figure 3B, or sideways as shown in Figure 3C, as will be explained in more detail below. In some embodiments, the DVS sampler 100 is used in a diffusion sampling process.

[0029] In situations where the air movement speed over the sampler 100 is quite slow, simply removing the isolation lid 104 and cap 105 shown in Figures 1A to 1B allows ambient air to enter the sampler 100, initiating the sampling process. For example, in the case of indoor air monitoring, if the sampling period is 1 to 30 days, a representative sample of the air at that location during the sampling period is provided. When sampling in areas with high air movement, convective sampling can be eliminated, for example, by adding a screen 302 to the top of the sampler 100, where the absorption rate increases to an unknown amount. For example, in the case of indoor air, this is not a problem if the DVS sampler 100 is placed away from forced ventilation openings or open windows. In some cases, it may be necessary to slow down the sampling rate, which can be done by adding a second lid at the location of the screen 302 in Figures 3A to 3C, or at the location of the lid 104 in Figures 1A to 1B, which has an opening smaller than the opening of the sampler 100. This may only be necessary when the sampling time is very long or in environments with a high organic matter content in the air. In other cases, using split injection of up to 200:1 can reduce the amount of sample sent to the GC / GCMS, making it another way to optimize the amount of sample that reaches the GC column or MS (MSMS) detector.

[0030] In some situations, the orientation of the sampler 100 may have little effect on the rate of gas-phase molecule ingestion because the diffusion of these compounds occurs randomly in all directions. However, if the sampler 100 is positioned with its opening 304 facing upwards, as shown in Figure 3A, the sampling rate of heavy chemicals attached to particles in the air will be much faster. For example, these chemicals are very likely to be easily inhaled and absorbed into the body, so when sampling and analyzing air, it is usually important to include chemicals bound to these particles. However, if the opening 304 of the sampler 100 is facing downwards, as shown in Figure 3B, i.e., if the DVS sampler is suspended from some support, perhaps near the ceiling, the introduction of particles will be much less, potentially 10 times or less. If you want to measure the concentration of these compounds on particles rather than in the gas phase, you can place two DVS samplers 100 at the sampling location, one facing upwards as shown in Figure 3A and the other facing downwards as shown in Figure 3B. However, depending on the situation, the objective may be to determine which compounds are present, and considering that indoor airborne dust may be statistically similar in location, collecting samples with the opening 304 of the sampler 100 facing upwards, as shown in Figure 3A, is important for identifying locations where the concentration of a particular chemical is higher than in other locations, and also for including airborne contaminants that can be easily inhaled and absorbed into the human body. As a collection direction for intermediate particles, the sampler 100 may be positioned horizontally, as shown in Figure 3C. After collecting samples over a period of time from one hour to one month, the sampler 100 is capped (for example, using the lid 104 and cap 105 shown in Figures 1A to 1B) for return to the laboratory for analysis.

[0031] Figures 4A to 4D show an example of transferring a sample collected using a DVS sampler 100 to a secondary focus device 400 for introduction into a capillary GCMS for analysis, according to several embodiments. As shown in Figures 4A to 4D, the focus device 400 includes a body 401 with an opening 403 to a cavity containing an adsorbent 406, a channel 405, a valve 408, a desorption port 410, and a seal 412. During the sample transfer process shown in Figures 4A to 4D, the DVS sampler 100 is positioned within a heater 414 and coupled to the focus device 400 by a vacuum sleeve 402, which will be described in more detail below.

[0032] For GC analysis, the DVS Sampler 100 workup differs significantly from polyurethane foam (PUF) cartridge or XAD-2 tube workups, which require solvent extraction and a blowdown process to concentrate the solvent extract before subsequent analysis. PUF cartridge or XAD-2 tube implementations can be very expensive, completely unsuitable for most indoor environments, and the use of large amounts of solvent during sample workup is considered a health concern for both chemists and the surrounding environment.

[0033] In Figures 4A to 4D, the DVS sampler 100 is mounted on a vacuum sleeve 402, to which an adsorption device 400 (adsorption pen) is attached, and a vacuum is generated through the upper part 404 of the adsorption pen 400. For example, during part of the sample transfer process (e.g., at the start), a vacuum can be applied to the system via a valve 408 located on the upper part of the adsorption pen 400 while the DVS sampler 100 is heated by a heater 414. In some embodiments, a vacuum source can be fluidly coupled to the DVS sampler 100 via the adsorption pen 400, including a channel 405, an adsorbent 406, and an opening 403. Once a vacuum is drawn into the DVS sampler and adsorption pen 400, the vacuum evacuation process can be stopped by removing or deactivating the vacuum source. For example, even if the vacuum source is removed, the seal 412 and valve 408 of the adsorption pen 400 can maintain the vacuum within the closed system. During or after vacuum evacuation, the heater 414 can apply heat to the DVS sampler 100, for example. In some embodiments, the position of the heater keeps the adsorbent 406 in the adsorbent pen 400 at a lower temperature than the adsorbent 106 and / or 108 in the DVS sampler 100, and the heater applies more heat to the adsorbent 106 and / or 108 in the DVS sampler 100 than to the adsorbent 406 in the adsorbent pen 400.

[0034] Figure 4C is a close-up view of the DVS sampler 100 during sample transfer, according to several embodiments. As shown in Figure 4C, the DVS sampler 100 includes a first adsorbent 106 and a second adsorbent 108 on the inner surface of a vial 102. During sample transfer as shown in Figures 4A to 4B, in the example shown in Figure 4C, one or more compounds are transferred from the first adsorbent 106 and the second adsorbent 108 to the adsorbent 406 in the adsorbent pen 400.

[0035] Figure 4D is a close-up view of the DVS sampler 100 during sample transfer according to several embodiments. As shown in Figure 4D, the DVS sampler 100 contains a first adsorbent 106 on the inner surface of the vial 102 and does not contain a second adsorbent 108. During the sample transfer shown in Figures 4A to 4B, in the example shown in Figure 4D, one or more compounds are transferred from the first adsorbent 106 or from particles collected in the DVS sampler 100 to the adsorbent 406 in the adsorbent pen 400.

[0036] By creating a vacuum and then either removing the vacuum pump from the adsorbent pen 400, or turning off the vacuum pump without removing it from the adsorbent pen 400 to release the vacuum, a closed system is obtained that allows for the very rapid transfer of all or substantially all (e.g., >95%) of the thermally desorbable compounds from the DVS sampler 100 to the adsorbent pen 400 in a very short time of 3 to 10 minutes or 3 to 5 minutes, while keeping the adsorbent 406 in the adsorbent pen in a cooling state while heating the adsorbent 106 and / or 108 in the DVS sampler 100. For example, compounds held in the adsorbent 106 and / or 108 of the DVS sampler 100 can be diffusively transferred from the adsorbent 106 and / or 108 of the DVS sampler 100 to the adsorbent 406 of the adsorbent pen 400 under vacuum. In some embodiments, drawing a vacuum increases or maximizes the diffusion rate of compounds from the adsorbent 106 and / or 108 to the adsorbent 406. Thus, diffusively transferring compounds from the DVS sampler 100 to the adsorbent pen 400 is advantageous because it reduces channeling (e.g., the flow of the carrier fluid further "pushing" the compound into the adsorbent 406 during dynamic transfer of the compound), thereby improving the recovery rate of compounds during GCMS analysis and broadening the range of compounds that can be analyzed with this technique. For example, heating adsorbents 106 and / or 108 without heating adsorbent 406 allows for sampling of thermally unstable compounds that cannot be exposed to high-temperature adsorbents for extended periods. Since adsorbents 106 and / or 108 used in the DVS sampler 100 are primarily hydrophobic, moisture collection is minimized, and no attenuation of the response in GCMS is expected. After a short transfer period, the DVS sampler 100 / adsorbent pen 400 assembly is briefly moved to a room-temperature tray, where the adsorbent pen 400 is removed and isolated in a sleeve, awaiting GCMS analysis. Many SVOC / PFAS compounds are bound to particles as salts and are themselves completely non-volatile.However, the pH of the DVS medium can be adjusted to increase its acidity or basicity immediately before desorption, allowing for the recovery of compounds classified as acidic / neutral, and conversely, the deprotonation of basic compounds (amines, amides, etc.) into neutral nonionic forms, which can then be recovered and analyzed using thermal desorption. To achieve this pH change, it is sufficient to add just one microliter of a suitable solution, such as citric acid or NH4OH of appropriate strength, or another pH-adjusting solution.

[0037] Figure 5 shows an example of finally desorbing an adsorption pen 400 into a capillary-based GCMS or GCMSMS chemical analyzer 500 for analysis, according to some embodiments of the present disclosure. As shown in Figure 5, the chemical analyzer 500 includes a thermal desorption unit 501, a carrier fluid supply unit 506, a pressure controller 508, valves 510a to 510d, a split controller 512, a pre-column 504, a junction 514, a GC column 502, and a detector 516. The adsorption pen 400 is inserted into the thermal desorption unit 501 and heated to, for example, a desorption temperature (e.g., 100 to 500°C). In some embodiments, after preheating the adsorption pen 400, it can be desorbed using one or more of the valves 510a to 510d. For example, a carrier fluid can flow from the supply device 506 through valve 510b and into the adsorption pen 400 via the desorption port 410, and at least a portion of the compound can be transferred to the pre-column 504. In some embodiments, valves 510c and / or valve 510d can be opened to perform split injection. In some embodiments, valves 510c and 510d can be closed during transfer to the pre-column 504 to perform splitless injection. In some embodiments, the compound can be transferred from the pre-column 504 to the GC column 502 via junction 514. When performing split injection using valve 510d, in some embodiments, a portion of the sample is discharged from the system via valve 510d and split control 512, and a portion of the sample proceeds to the GC column 502. In some embodiments, once the sample has been transferred to the GC column 502, a carrier fluid can be introduced via valve 510a to control the flow of the sample and carrier fluid from the GC column 502 to the detector 502 for chemical analysis of the sample. In some embodiments, the detector 502 is a mass spectrometer. After analysis, in some embodiments, the adsorption pen 400 may be heated to a bake-out temperature (e.g., 100 to 500°C) to open valves 510a and 510c to remove any remaining compounds from the adsorption pen 400, allowing the adsorption pen 400 to be reused in subsequent analyses.

[0038] The design of the analyzer 500 allows for either split injection, where perhaps only 1 to 10% of the sample is transferred to the GC column 502, or splitless technology, where a pre-column 504 is selected to hold the target compound during desorption of the adsorption pen 400. For short sampling periods (1 to 8 hours), splitless injection may be necessary in some cases, but for longer sampling times, splitless injection may overload the GCMS even with compounds in the ppt range, so in such cases split injection of 10:1 or up to 200:1 may be necessary. However, when using the DVS sampler for area or individual monitoring in industrial environments where concentrations may be in the ppm range, split injection may be necessary to prevent column overload even for 1 to 8 hour sampling, or, as mentioned above, the sampling rate can be slowed by using a lid with a small sampling hole at the opening of the DVS sampler 100. The delivery of the adsorption pens 400 to the system 500 shown in Figure 5 can be automated using a rail-based automated sampler, managing up to eight trays containing 30 adsorption pens 400 each (240 pens in total) to achieve significant lab throughput in a production lab environment. Alternatively, in some embodiments, the transfer time from DVS to adsorption pens is as short as 3 to 10 minutes, or 3 to 5 minutes, allowing more than 100 vials to be analyzed with just two adsorption pens. This can be automated by analyzing one pen for GC-MS analysis, collecting the next DVS sample with the other adsorption pen, and alternating until all samples have been analyzed using the two adsorption pen devices. Referring to Figures 4A to 4D, the diffusion characteristics of the transfer from the DVS sampler 100 to the adsorption pen 400 described above mean that the chemical substances do not "flow" deep into the adsorbent 406 of the adsorption pen 400 (channeling effect). Therefore, the level remaining in the adsorption pen 400 after desorption to the GCMS 500 is usually less than 1 / 10,000, and thus there is no need to separately bake out the adsorption pen 400 before reuse. For this reason, this technology is considered suitable for high-production laboratories where it is necessary to achieve high-quality instrument blanks to guarantee accurate results, for example.In some embodiments, the DVS sampler 100 can also collect samples for analysis by liquid chromatography separation and one or more-stage mass spectrometry detection (LCMS, LCMSMS). In such cases, a small amount of solvent is added to extract compounds from the polymer film, and since these compounds that are not GC-compatible generally have low vapor pressures, the DVS sampler 100 can be used with only the first adsorbent 106 and without the additional second adsorbent 108. In this case, the migration of LC-compatible compounds to the liquid phase occurs very easily, and since many LC-compatible solvents are too polar to dissolve the common (PDMS and other) polymers used to coat the bottom of the DVS sampler 100, the sampler can be used multiple times. Exposure of the polymer layer with a low pH, high pH, ​​or unpH-adjusted solvent allows the solvent to be transferred to a vial for automatic injection into the LCMS / LCMSMS system. The sampler is then washed with water, vacuum-heat-conditioned, and sent to site to collect new samples. This process can occur dozens of times before the DVS is replaced.

[0039] The new sampler can provide a simple yet quantitative and highly sensitive technique for measuring everything from VOCs to SVOCs during surveys of outdoor air, workplace air, and especially indoor air quality. The sampler can accurately measure the time-weighted average concentrations of many compounds that are carcinogenic and pose risk factors not only to the general public but also to pregnant women and children in their first few years of life. Many of the chemicals in indoor air are endocrine disruptors that can affect fetal and adolescent development and may cause autism and other disorders that have been increasing in recent decades, possibly due to rising levels of these endocrine disruptors in the environment. Many researchers believe that exposure to chemicals in food, air, water, and clothing is a cause of these developmental disorders, and using improved equipment for monitoring indoor air quality in combination with epidemiological studies may help identify chemicals that are likely to cause these and other disorders.

[0040] DVS samplers can also be used to determine other air quality, such as monitoring air in hospitals, office buildings, cars, schools, and other locations. These inexpensive samplers can be used to look for microbial VOCs that indicate the presence of mold growing inside a building, as well as spores that may have originated outdoors rather than growing inside the building. Mold spores can be trapped inside walls and are invisible with current measurement techniques, but microbial VOCs can penetrate walls and be detected using a DVS sampler placed anywhere in the indoor environment. This technology could also be used to monitor the air in submarines and in low-gravity or zero-gravity areas on space stations. With this low-cost yet highly effective device, air quality in the cabins of civilian and military aircraft could also be monitored.

[0041] Some embodiments relate to a method for collecting an air sample in a diffusion sampling process using a sampling device comprising a vial having a first adsorbent including an adhesive surface coated on the inner surface of the vial, wherein the first adsorbent is bonded to the inner surface of the vial and the sampling device is compatible with thermal desorption and solvent extraction; sealing the sampling device using an inert cap attached to the sampling device; and sending one or more compounds of the air sample to a gas chromatograph for chemical analysis using thermal desorption or solvent extraction. Furthermore, or alternatively, in some embodiments, the sampling device further comprises a second adsorbent bonded to the adhesive surface of the first adsorbent. Furthermore, or alternatively, in some embodiments, the method further includes coupling the sampling device to a pre-concentrator containing a third adsorbent located in a cavity, after collecting the air sample and sealing the sampling device, wherein the opening of the cavity is coupled to the opening of the sampling device; heating the first adsorbent using a heater so that more heat is applied to the first adsorbent than to the third adsorbent; and diffusing the one or more compounds of the air sample from the first adsorbent to the third adsorbent while applying the heat to the first adsorbent. Furthermore, or alternatively, in some embodiments, thermal desorption of the third adsorbent is included by using thermal desorption to send the one or more compounds of the air sample to the gas chromatograph for chemical analysis. Furthermore, or alternatively, in some embodiments, the method further includes sealing the sampling device and the pre-concentrator using a valve in the pre-concentrator to form a closed system. Furthermore, or alternatively, in some embodiments, the method further includes evacuating the pre-concentrator and the sampling device using a vacuum source coupled to the valve of the pre-concentrator while the pre-concentrator and the sampling device are coupled together.Furthermore, or alternatively, in some embodiments, coupling the sampling device to the pre-concentration device includes coupling the sampling device and the pre-concentration device using a vacuum sleeve around the pre-concentration device. Furthermore, or alternatively, in some embodiments, the heat is applied to the first adsorbent while the sampling device and the pre-concentration device form a closed system under vacuum. Furthermore, or alternatively, in some embodiments, the method includes coupling the sampling device to a manifold before collecting the air sample in the diffusion sampling process, and drawing a vacuum through the manifold to the sampling device while applying heat to the first adsorbent while the sampling device is coupled to the manifold.

[0042] Some embodiments relate to a sampling device comprising a vial having a first adsorbent bonded to the inner surface of the vial, wherein the first adsorbent includes an adhesive surface, and the sampling device is configured to diffusely collect an air sample for chemical analysis by gas chromatography after thermal desorption or solvent extraction, and the sampling device is compatible with thermal desorption and solvent extraction, and an inert cap configured to be bonded to the sampling device to seal the sampling device. Further or alternatively, in some embodiments, the sampling device further comprises a second adsorbent bonded to the adhesive surface of the first adsorbent. Further or alternatively, in some embodiments, the system further comprises a pre-concentration device comprising a third adsorbent disposed in a cavity, and the pre-concentration device being bonded to the sampling device having an opening in the cavity located at the opening of the sampling device, and a heater configured to apply more heat to the first adsorbent than to the third adsorbent. Furthermore, or alternatively, in some embodiments, the pre-concentration device further comprises a valve, and the system is a closed system while the valve is closed and the sampling device is coupled to the pre-concentration device. Furthermore, or alternatively, in some embodiments, the system further comprises a vacuum source, and the pre-concentration device further comprises a valve, and the vacuum source is configured to create a vacuum within the pre-concentration device and the sampling device while the vacuum source is coupled to the valve of the pre-concentration device. Furthermore, or alternatively, in some embodiments, the system further comprises a vacuum sleeve, and the pre-concentration device is positioned inside the vacuum sleeve while the pre-concentration device is coupled to the sampling device.

[0043] While embodiments have been fully described with reference to the attached drawings, it should be noted that various changes and modifications will be apparent to those skilled in the art. Such changes and modifications should be understood to fall within the scope of embodiments of this disclosure as defined by the attached claims.

Claims

1. Collecting an air sample in a diffusion sampling process using a sampling apparatus comprising a vial equipped with a first adsorbent including an adhesive surface coated on the inner surface of the closed bottom of the vial, wherein the first adsorbent is bonded to the inner surface of the vial and the sampling apparatus is compatible with thermal desorption and solvent extraction. The sampling device is sealed using an inert cap attached to the sampling device, Using thermal desorption or solvent extraction, one or more compounds from the air sample are sent to a gas chromatograph for chemical analysis via a pre-concentration device. After collecting the air sample and sealing the sampling device, The inert cap is removed, and the sampling device is coupled to a pre-concentration device containing a third adsorbent placed in the cavity, via the opening of the sampling device. A method comprising heating one or more of the aforementioned compounds with a heat source and recovering the one or more compounds using a vacuum source.

2. The method according to claim 1, wherein the sampling device further comprises a second adsorbent bonded to the adhesive surface of the first adsorbent.

3. Heating the first adsorbent using a heater so that more heat is applied to the first adsorbent than to the third adsorbent, The method according to claim 1, further comprising applying the heat to the first adsorbent while diffusing one or more compounds of the air sample from the first adsorbent to the third adsorbent.

4. The method according to claim 3, wherein the process of using thermal desorption to deliver one or more of the air sample to the gas chromatograph for chemical analysis includes thermal desorption of the third adsorbent.

5. The method according to claim 3, further comprising sealing the sampling device and the pre-concentration device so as to form a closed system using the valve of the pre-concentration device.

6. The method according to claim 3, further comprising using a vacuum source connected to a valve of the pre-concentration device to create a vacuum between the pre-concentration device and the sampling device while the pre-concentration device and the sampling device are coupled together.

7. The method according to claim 3, wherein coupling the sampling device with the pre-concentration device includes coupling the sampling device and the pre-concentration device using a vacuum sleeve around the pre-concentration device.

8. The method according to claim 3, wherein the heat is added to the first adsorbent while the sampling device and the pre-concentration device form a closed system under vacuum.

9. Before collecting the air sample in the diffusion sampling process, The sampling device is coupled to the manifold, While the sampling device is coupled to the manifold, Applying heat to the first adsorbent while creating a vacuum inside the sampling device through the manifold, The method according to claim 1, further comprising:

10. A sampling apparatus comprising a vial having a first adsorbent bonded to the inner surface of the closed bottom of the vial, wherein the first adsorbent includes an adhesive surface, and the sampling apparatus is configured to diffusely collect an air sample for chemical analysis by gas chromatography after thermal desorption or solvent extraction, and the sampling apparatus is compatible with thermal desorption and solvent extraction, and the sampling apparatus, An inert cap configured to be coupled to the sampling device and seal the sampling device, A pre-concentration device comprising a third adsorbent disposed in a cavity and coupled to the sampling device via an opening in the sampling device located at the opening of the sampling device, A vacuum source coupled to the aforementioned pre-concentration device for recovering one or more compounds from the collected air sample, A system that includes this.

11. The system according to claim 10, wherein the sampling device further comprises a second adsorbent bonded to the adhesive surface of the first adsorbent.

12. The system according to claim 10, further comprising a heater configured to apply more heat to the first adsorbent than to the third adsorbent.

13. The system according to claim 12, wherein the pre-concentration device further comprises a valve, and the system is a closed system while the valve is closed and the sampling device is coupled to the pre-concentration device.

14. The system according to claim 12, wherein the pre-concentration device further comprises a valve, and the vacuum source is configured to create a vacuum in the pre-concentration device and the sampling device while the vacuum source is coupled to the valve of the pre-concentration device.

15. The system according to claim 12, further comprising a vacuum sleeve, wherein the pre-concentration device is positioned inside the vacuum sleeve while the pre-concentration device is coupled to the sampling device.

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