System and method of trace-level analysis of chemical compounds

Techniques disclosed herein can be used to perform a rapid, splitless injection of a sample including SVOCs and VOCs. In some embodiments, a system includes two focusing traps combined in series, one inside of a GC oven and one in a separate oven to concentrate the SVOCs inside of the GC oven and concentrate the VOCs outside of the GC oven. Heating the VOC focusing trap and reversing the flow through both focusers allows splitless injection of compounds boiling from as low as −100° C. to as high as 600° C. in a single analysis, with a narrow injection bandwidth to optimize both sensitivity and the resolving power of the analyzer.

FIELD OF THE DISCLOSURE

The disclosure relates to chemical analysis and, more particularly, the analysis of SVOCs and VOCs in a single, splitless injection.

BACKGROUND OF THE DISCLOSURE

Most analytical techniques for analysis of compounds by GCMS target either the volatile or the semi-volatile fraction of the sample, and typically not both. That is, the low boiling compounds (e.g., −50° C. to 230° C.) are analyzed using a different sample preparation and introduction technique than is typically used for higher boiling compounds (e.g., 120° C. to 550+° C.). The lower boiling compounds are generally referred to as Volatile Organic Compounds (VOCs) while the heavier compounds are call Semi-Volatile Organic Compounds (SVOCs). When SVOCs are injected onto a column, either from a solvent extract via the heated expansion of a 1 microliter liquid injection, or by thermal desorption from a collection/enrichment device, the SVOCs will “stick” to the analytical capillary column in the GC, allowing the sample to be deposited over a period of 0.5-4 minutes while maintaining a narrow deposition band on the GC column. However, lighter VOC compounds do not “stick” to the column at the typical GC starting temperature (e.g., 30-40° C.), but will move through the GC column when injected onto a typical WCOT capillary column (Wall Coated Open Tubular) column. Since optimal capillary column GC peak widths are about 2-6 seconds wide, techniques that introduce the sample onto the column over 1-4 minutes would not yield the desired, narrow peaks for lighter VOC compounds that have increased mobility through WCOT columns compared to SVOC compounds.

As an example, one approach for reducing the bandwidth upon injection is to split the sample so that only part of the sample goes onto the column and the rest exits through a vent. For example, if 2 cc of gas phase sample is delivered to the GC column at a flow rate of 1 cc/min, a splitless injection would take 2 minutes to introduce the sample, causing substantial band broadening and loss of resolution for lighter compounds that are mobile on the GC column at the GC oven's starting temperature. However, if the sample was split 20:1 between the GC column and an outlet vent, then injection would instead take 6 seconds (e.g., 120 seconds divided by 20), thereby providing acceptable peak width for capillary chromatography, but at the expense of throwing away 95% of the sample through the outlet vent in this example.

As another example, it is possible to reduce the VOC bandwidth by increasing the retention (e.g., chemical affinity to the sample) or “strength” of the GC column. Porous Layer Open Tubular (PLOT) GC columns have a layer of adsorbent material on the walls, and tend to be much stronger (e.g., have higher chemical affinity to the sample) than the WCOT columns that use a polymer wall coating. For example, PLOT columns cause the VOCs to “stick” to the column during injection, but these columns will not allow the heavier SVOCs to elute at reasonable GC oven temperatures, so PLOT columns cannot be used when both VOCs and SVOCs are to be analyzed in a single analysis.

Another approach includes using a focusing trap to reduce the volume of the injected VOCs to allow them to be delivered without splitting to the GC WCOT column. Focusing has been done either using a micro packed trap, or by using a liquid nitrogen focusing trap. Micro-Packed traps will reduce the volume of the sample, but typically will not deliver the sample fast enough to a capillary trap without at least a small split operation (e.g., 3:1) which doesn't allow sensitivity to be maximized. Using liquid nitrogen to focus the VOCs is an option, but this kind of trap will also focus all of the water vapor in the original sample, and excess water can affect both GC performance and the sensitivity of the detector, such as a mass spectrometer (MS). In addition, focusing traps may not be compatible with SVOC analysis, as they typically do not achieve high enough temperatures to release the heavier SVOC compounds (e.g., during desorption).

SUMMARY OF THE DISCLOSURE

The disclosure relates to chemical analysis and, more particularly, the analysis of SVOCs and VOCs in a single, splitless injection. Embodiments of the present disclosure focus both VOCs and SVOCs in a single injection, allow a splitless delivery to the GC column of both fractions, and eliminate excess water vapor. This approach includes a SVOC trap in the GC oven for retaining heavy compounds, followed by a multi-capillary column VOC trap with a separate heating source to focus the more volatile compounds in a sample delivered from a thermal desorber or other sample introduction system. In some embodiments, focusing the SVOCs inside of the GC oven can reduce or eliminate losses or inferior chromatographic performance caused by thermal gradients or “cold spots” in the focused sample during delivery to the GC column. The multi-capillary column VOC trap downstream of the SVOC capillary trap can concentrate the VOCs while allowing the water vapor to continue through the trap. Once the sample has been injected and the water sufficiently removed through both the SVOC and VOC traps by a short flush with an inert gas, the VOC trap is desorbed and backflushed through the SVOC trap to the GC separation column (also called the analytical column) while starting to heat the GC oven. Finally, the SVOC focusing column can be backflushed to a vent after all compounds of interest have been transferred to the analytical column to remove the heaviest compounds that may not be desirable in the analysis. In some embodiments, the analytical column is chosen to allow the VOCs and SVOCs to separate while the oven temperature is increased during the analysis. Rapidly injected VOCs will retain a narrow peak width, requiring less separation on the analytical column to fully resolve compounds from one another (4 second wide peaks need to only separate by 4 seconds, whereas 8 second wide peaks must separate by 8 seconds), thereby allowing a thinner film, less retentive column to be used (0.5 um) for the analytical column, for example. Retaining the narrow peak widths of the injected VOCs can be important because typical thick film VOC columns (1-3 um) may not allow heavier SVOCs to elute without using oven temperatures that could cause thermal breakdown of the column and compounds (e.g., above 300-350° C.). Due to these challenges, rapid injection of the VOCs with prior water removal has been one of the primary barriers in allowing both VOCs and SVOCs to be analyzed in the same analysis

Embodiments of the disclosure improve the trace level analysis by GCMS of chemicals encompassing a wide boiling point range. Pre-focusing the sample allows narrow peak widths on-column to improve compound separation and sensitivity. The disclosed configuration allows for a much larger boiling point range to be analyzed in a single analysis, at concentrations lower than previously possible by eliminating the need to perform a split injection. Pre-focusing the VOCs of the sample with multiple capillary columns of increasing strength followed by preheating the multiple capillary columns under zero flow allows all compounds to achieve a fast, splitless injection rate onto the GC analytical column to lower detection limits when using a detector such as a Mass Spectrometer (MS). Embodiments of the disclosure allow the sample to be focused and redirected onto the primary analytical GC column without requiring rotary valves, simply by using a pressure switch. The elimination of packed traps and rotary valves significantly improves the system performance relative to prior technology.

DETAILED DESCRIPTION

The disclosure relates to chemical analysis and, more particularly, the analysis of SVOCs and VOCs in a single, splitless injection. Embodiments of the present disclosure focus both VOCs and SVOCs in a single injection, allow a splitless delivery to the GC column of both fractions, and eliminate excess water vapor. This approach includes a SVOC trap in the GC oven for retaining heavy compounds, followed by a multi-capillary column VOC trap with a separate heating source to focus the more volatile compounds in a sample delivered from a thermal desorber or other sample introduction system. In some embodiments, focusing the SVOCs inside of the GC oven can reduce or eliminate losses or inferior chromatographic performance caused by thermal gradients or “cold spots” in the focused sample during delivery to the GC column. The multi-capillary column VOC trap downstream of the SVOC capillary trap can concentrate the VOCs while allowing the water vapor to continue through the trap. Once the sample has been injected and the water sufficiently removed through both the SVOC and VOC traps by a short flush with an inert gas, the VOC trap is desorbed and backflushed through the SVOC trap to the GC separation column (also called the analytical column) while starting to heat the GC oven. Finally, the SVOC focusing column can be backflushed to a vent after all compounds of interest have been transferred to the analytical column to remove the heaviest compounds that may not be desirable in the analysis. In some embodiments, the analytical column is chosen to allow the VOCs and SVOCs to separate while the oven temperature is increased during the analysis. Rapidly injected VOCs will retain a narrow peak width, requiring less separation on the analytical column to fully resolve compounds from one another (4 second wide peaks need to only separate by 4 seconds, whereas 8 second wide peaks must separate by 8 seconds), thereby allowing a thinner film, less retentive column to be used (0.5 um) for the analytical column, for example. Retaining the narrow peak widths of the injected VOCs can be important because typical thick film VOC columns (1-3 um) may not allow heavier SVOCs to elute without using oven temperatures that could cause thermal breakdown of the column and compounds (e.g., above 300-350° C.). Due to these challenges, rapid injection of the VOCs with prior water removal has been one of the primary barriers in allowing both VOCs and SVOCs to be analyzed in the same analysis

Embodiments of the disclosure improve the trace level analysis by GCMS of chemicals encompassing a wide boiling point range. Pre-focusing the sample allows narrow peak widths on-column to improve compound separation and sensitivity. The disclosed configuration allows for a much larger boiling point range to be analyzed in a single analysis, at concentrations lower than previously possible by eliminating the need to perform a split injection. Pre-focusing the VOCs of the sample with multiple capillary columns of increasing strength followed by preheating the multiple capillary columns under zero flow allows all compounds to achieve a fast, splitless injection rate onto the GC analytical column to lower detection limits when using a detector such as a Mass Spectrometer (MS). Embodiments of the disclosure allow the sample to be focused and redirected onto the primary analytical GC column without requiring rotary valves, simply by using a pressure switch. The elimination of packed traps and rotary valves significantly improves the system performance relative to prior technology.

FIGS.1A and1Billustrate examples of sample extraction devices100and150that can enrich a sample containing both VOCs and SVOCs prior to thermal desorption into a GC or GCMS according to some embodiments of the disclosure. Referring toFIG.1A, sample extraction device100includes a body110, external seals102a-c, a cavity104containing a sorbent106, a port108, and an internal seal112. In some embodiments, cavity104is disposed inside of the body110and is fluidly coupled to port108and internal seal112. In some embodiments, the external seals102a-care disposed around the outside of the body110of the sample extraction device100. In some embodiments, port108fluidly couples the inside of body110to the environment of the sample extraction device100and is disposed between two of the external seals102aand102b. In some embodiments, positioning port108between external seals102aand102benables selectively sealing the port108by inserting the sample extraction device100into a container (e.g., a sample vial) sized such that seals102a-care in contact with a surface of the container (e.g., an inner surface of the sample vial). In some embodiments, port108can be fluidly coupled to a system by inserting the sample extraction device100into, for example, a desorption device such that port108is coupled to a carrier fluid supply and/or an inlet of a chemical analysis system. In some embodiments, external seals102a-ccan prevent air from being introduced into the system (e.g., while the sample extraction device100is inserted into a desorption device), while directing a desorb gas flow through the internal sorbent106during thermal desorption to an analyzer (e.g., a GC or GCMS).

FIG.1Billustrates a sample extraction device150similar to sample extraction device100. In some embodiments, sample extraction device150includes a body160, external seals152a-c, a cavity154containing a plurality of sorbents156a-c, a port158, and an internal seal162. In some embodiments, cavity154is disposed inside of the body160and is fluidly coupled to port158and internal seal162. In some embodiments, the external seals152a-care disposed around the outside of the body160of the sample extraction device100. In some embodiments, port158fluidly couples the inside of body160to the environment of the sample extraction device150and is disposed between two of the external seals152aand152b. In some embodiments, positioning port158between external seals152aand152benables selectively sealing the port158by inserting the sample extraction device150into a container (e.g., a sample vial) sized such that seals152a-care in contact with a surface of the container (e.g., an inner surface of the sample vial). In some embodiments, port158can be fluidly coupled to a system by inserting the sample extraction device150into, for example, a desorption device such that port158is coupled to a carrier fluid supply and/or an inlet of a chemical analysis system. In some embodiments, external seals152a-ccan prevent air from being introduced into the system (e.g., while the sample extraction device150is inserted into a desorption device), while directing a desorb gas flow through the internal sorbents156a-cduring thermal desorption to an analyzer (e.g., a GC or GCMS). In some embodiments, sorbents156a-ccan be arranged in order of increasing chemical affinity to one or more compounds of interest in a sample. For example, sorbent156acan have a relatively low chemical affinity, sorbent156bcan have a higher chemical affinity than sorbent156a, and sorbent156ccan have the highest chemical affinity of the sorbents.

Sample extraction devices100and/or150can collect the sample using an active flow of gas, a static diffusive flow, or by sealing the sample extraction devices100and/or150inside of a vial under vacuum. In some embodiments, pulling a vacuum on the sample while the sample extraction device100and/or150is sealed in the sample vial containing the sample can improve the rate of extraction, especially for the extraction of the higher boiling point compounds. In some situations, sample extraction device100and/or150has the capacity to collect a large amount of sample but may not release the collected sample fast enough to achieve narrow peak widths for VOCs. In some situations, sample can be released more quickly from sample extraction devices100and/or150using a split injection. However, as described previously, split injections cause a subsequent loss in sensitivity relative to splitless injections where 100% of the sample is directed to the analytical column and then to the detector, for example. Thus, in some embodiments, rapid injection of a sample collected using sample extraction device100or sample extraction device150can be performed using a system200that includes an SVOC focuser234and a VOC focuser240, as will now be described with reference toFIG.2.

FIG.2illustrates an exemplary chemical analysis system200according to some embodiments of the disclosure. In some embodiments, system200can include a GC oven202containing a thermal desorber220, SVOC focuser234, analytical column238, connections232and237, and restrictor236. that is fluidly coupled to a VOC focuser240, an analyzer250, a pressure control system204, GC split control system206, and a plurality of valves222,224,226,228, and246. In some embodiments, the VOC focuser240includes a plurality of capillary columns241a-cdisposed within a heater242, a backflush desorb gas valve246, and a fan244. Placing the VOC focuser240in a dedicated heater242can allow the system200to control the temperatures of the SVOC focuser234and the VOC focuser240independently from each other.

The inside of the GC oven202can be heated convectively to achieve a consistent temperature throughout, for example. The GC has a pressure control system204that can achieve a predetermined flow rate through the analytical GC column238based on the dimensions of the column238, the temperature of the GC oven202, and the makeup of the carrier gas (e.g., Helium, Hydrogen, etc.). The GC also includes a split controller206that can maintain a flow rate of carrier gas out through a split point to a vent. Therefore, pressure control system204can control the flow rate through the GC column via pressure, which can be adjusted based on the column dimensions and GC oven202temperature, while the split control206can control the flow rate out of a split port. In some embodiments, the pressure control system204and split control206can achieve a consistent split ratio. In some embodiments, the split control206can be used to control the desorb flow through both an SVOC focuser234and a VOC focuser240, without splitting the sample, as will be explained below. Thus, although system200includes GC split control system206, the system200can perform a splitless injection of the sample, including both the SVOCs and VOCs of interest.

In some embodiments, the (e.g., direction of the) flow of gas (e.g., carrier gas, sample, water, air, etc.) in the system200is controlled by valves222,224, and226. Valve222can allow carrier gas flow to bypass the sample extraction device210while sample extraction device210is inserted into the thermal desorber220, so that the flow of gas can be maintained through the analytical column238. Valve224can allow the carrier gas to be delivered through the sample extraction device210for delivering into the GC oven202. Valve226can facilitate a final bakeout of the sample extraction device210and can also facilitate a final backflush of the system200to eliminate very heavy, unwanted compounds, as will be described later. In some embodiments, valves228and246can control the flow of gas through the VOC focuser240and/or SVOC focuser234. Thus, in some embodiments, flow of gas in the system200can be controlled by valves222,224,226,228, and246and restrictor236without the use of rotary valves.

In some embodiments, thermal desorber220can desorb the sample from the sample extraction device210while the sample extraction device210is inserted into the thermal desorber220. As the sample is desorbed from the sample extraction device210, it can first pass through a connection232, then through the SVOC focuser234, and then—for the lighter VOC sample compounds that are unretained within SVOC focuser234—into the VOC focuser240.

In some embodiments, when preparing to desorb a sample from sample extraction device210, the previous sample extraction device210or blank tube can be removed from thermal desorber220, and the new sample extraction device210is inserted. During this time, for example, valve222can be on, allowing flow of carrier gas to the analytical column238, and some backflow of carrier gas out through thermal desorber220. In some embodiments, the flow of carrier gas can prevent air from entering the system200, which could cause contamination of the system200and/or introduction of water into the system200. After the sample extraction device210is inserted into thermal desorber220, and the carrier gas stabilizes, the sample extraction device210can either be preheated under zero flow (only valve222open), or desorption can occur without pre-heating.

During desorption, for example, valves222,224, and228can be open and valves226and246can be closed. By opening both valves222and224simultaneously, the pressure at connections232and237can be substantially the same, as the pressure drop across the sorbent of the sample extraction device210in the thermal desorber220and the pressure drop across the delivery line from valve222to connection237can be substantially the same, thereby reducing or substantially eliminating the pressure drop across restrictor236between connection232and connection237. For example, while the pressures at connection232and connection237are the same, then (e.g., substantially) no flow occurs across restrictor236. Thus, (e.g., substantially) all of the desorbed sample from the sample extraction device210will be directed through thermal desorber220and connection232towards SVOC focusing column234, VOC focuser240, and valve228.

In some embodiments, during and/or following desorption, a portion of the sample (e.g., SVOC target compounds) can be retained by the SVOC focuser234, a portion of the sample (e.g., VOC target compounds) can be retained by the VOC focuser240, and a portion of the sample (e.g., water vapor, air) and carrier gas can exit the system200through valve228. For example, gas can flow from the thermal desorber220, through the SVOC focuser234where one or more SVOC compounds can be deposited, through the VOC focuser240where one or more VOC compounds can be deposited, and out of the system through valve228, including allowing air, water, and carrier gas to exit the system200. In some embodiments, while gas flows from the thermal desorber220to valve228, the temperature of oven242can be warmer than the temperature of the GC oven202(e.g., by 5° C.) to prevent condensation of water vapor, thereby facilitating removal of water from the system200. The flow through the SVOC focusing trap234and the VOC focusing trap240can be controlled by the GC split control206and/or by a simple orifice, and flow can start or stop based on whether valve228is opened (e.g., to facilitate flow) or closed (e.g., to prevent flow) while valves222and224can remain open, for example.

In some embodiments, after a sufficient amount of gas is desorbed through sorbent device210in thermal desorber220to deliver the sample into SVOC focuser234and VOC focuser240, valve224can be turned off while valves222and228can remain on, allowing bypass gas introduced at connection237to flow both to the analytical column238and through restrictor236to the SVOC focuser234and the VOC focuser240in a direction from connections237and232towards valve228. This additional flow can purge out air and water vapor still remaining in the focusing traps234and240after sample delivery to the traps234and240. For example, the water and air can traverse focusing traps234and240and exit the system through valve228. Then, valve228can be closed to stop the flow of gas through the SVOC focuser234and the VOC focuser, for example.

In some embodiments, to perform a rapid, splitless injection, the VOC focuser242can be preheated under zero flow (e.g., while valve228is off), and then valve222can be turned off and valve246can be turned on while valve224is off to cause a flow of gas from the VOC focuser242towards the SVOC focuser234and towards the analytical column238. Valve246can provide carrier gas to backflush the sample from the VOC focusing trap240to deliver it quickly to the analytical column238by flowing through VOC trap234, connection232, restrictor236, and connection237.

In some embodiments, once the compounds of interest reach the analytical column238from the VOC focuser240and SVOC focuser234, the chemical analysis (e.g., GC or GCMS) can be started, including data collection from the analyzer250(e.g., an MS or other detector). Carrier gas flow from valve246, through focusers240and234, to the analytical column238can continue until all compounds of interest have been delivered from VOC focuser240and SVOC focuser234onto analytical column238, for example. For example, during transfer, valve246can be on and valves222,224,226, and228can be off. In some embodiments, “strength” (e.g., chemical affinity to one or more compounds of interest in the sample) of SVOC focuser234can be chosen to be less than that of the analytical column238to ensure that the SVOC compounds of interest further focus into narrow peaks upon delivery to analytical column238(e.g., through dynamic focusing). In some embodiments, the “strength” of the SVOC focuser234and analytical column238can be controlled by selecting the film or sorbent type or thickness, inner diameter, length, etc. of the SVOC focuser234and analytical column238.

In some embodiments, once all compounds of interest have been backflushed from SVOC trap234to analytical column238, valve222can be turned on, while valve246remains on and valves224,226, and228remain off, to elute all compounds through the analytical column238to the analyzer250. While valve222is turned on and once the compounds of interest have reached the analytical column238, valve226can also be opened, while valves246and222remain on and valves224and228remain off, to allow continued backflushing of VOC focuser240and SVOC focuser234, with delivery out through the GC split control206. In this way, very heavy compounds that were delivered to and remain retained by SVOC focuser234that are of no interest, or which are so heavy that they would require too high a GC oven temperature, or too much time, to elute to the analyzer250can be removed more effectively and in a shorter period of time.

FIG.3illustrates an exemplary process300for conducting a chemical analysis according to some embodiments. In some embodiments, the chemical analysis process300includes collecting302a sample, such as by performing an extraction of organic compounds with a sample extraction device100,150, or210, or another sample delivery system. In some embodiments, pre-collection of a sample on a sorbent bed can be done by diffusive sampling at atmospheric pressure, diffusive sampling under vacuum conditions, or active sampling by drawing a known volume of gas to be analyzed through the sorbent.

In some embodiments, when the analyzer250(e.g., a GC or other detector) is ready304for the next analysis, the sample extraction device210can be placed306into thermal desorber220as shown inFIG.2while carrier gas is being supplied in and out of the system through valves222and226while valves224and228are closed, the GC oven202is at a temperature in the range of 35-50° C., the heater242of the VOC focuser240is 5° C. hotter than the GC oven202, and the thermal desorber220is at a temperature in the range of 40-80° C.

In some embodiments, while the sample extraction device210is disposed in the thermal desorber220, valve226can be turned off and valve228can be turned on during preheat308of the sample in the sample extraction device210in the thermal desorber220. In some embodiments, during preheating, the thermal desorber220can be heated to a desorption temperature in the range of 100-250° C. (e.g., while the GC oven202remains at a temperature in the range of 35-50° C. and the heater242of the VOC focuser240is 5° C. hotter than the GC oven202).

In some embodiments, the sample can be desorbed310from the sample extraction device210in the thermal desorber220by leaving valves222and228on, and also turning on valve224to start the desorption flow through thermal desorber220, connection232, SVOC focuser234, and VOC focuser240towards valve228while valve246and226are closed. In some embodiments, during desorption, the thermal desorber can be at a temperature in the range of 150-320° C. (e.g., while the GC oven202remains at a temperature in the range of 35-50° C. and the heater242of the VOC focuser240is 5° C. hotter than the GC oven202). During this 1-6-minute desorption, the heavier SVOCs from the sample can be transferred312to the SVOC focuser234and the VOCs from the sample can be transferred314to the VOC focuser240.

After the desorption is completed and while the SVOCs and VOCs of interest are retained by the SVOC focuser234and VOC focuser240, respectively, valve224can be turned off while valves222and228are on. In some embodiments, this configuration can allow carrier gas to flow through restrictor236, connection232, SVOC focuser234, and VOC focuser240to remove316any remaining air and water vapor out through vent228. In some embodiments, the process can be performed for 1-5 minutes. In some embodiments, while the air and/or water are being dry-purged from the system200, the GC oven202remains at a temperature in the range of 35-50° C. and the heater242of the VOC focuser240is 5° C. hotter than the GC oven202. At this time, for example, the heater of the thermal desorber220can be turned off to cool down the thermal desorber220, sample extraction device210, and connection232. Turning off the heater of the thermal desorber220in this way can reduce or eliminate thermal disturbances, such as thermal expansion of gases, for example, that can otherwise affect the proper, rapid transfer of compounds from the VOC focuser240and SVOC focuser234to analytical column238through connections232and237and restrictor236(e.g., later in the process).

In some embodiments, after removing (e.g., all of, substantially all of) the water and air from the system200, valve228can be turned off to stop the flow through the SVOC focuser234and VOC focuser240, and the VOC focuser240can be preheated318(e.g., with heater242) to a desorption temperature in the range of 80-300° C. (e.g., 80-200° C.), for example. In some embodiments, while the VOC focuser240is being preheated, the GC oven202can remain at the temperature in the range of 35 to 50° C.

In some embodiments, during or after preheating the VOC focuser240(e.g., and while the VOC focuser240is at a temperature in the range of 80-300° C. (e.g., 120-200° C.)), valves246and228can be turned on and valves222,224, and226can be turned off. This configuration can transfer320the sample to the analytical column250by directing the sample from the VOC focuser240through the SVOC focuser234, through restrictor236, and to the analytical column238while the GC oven202is at the temperature in the range of 35-50° C., for example.

In some embodiments, after preheating the VOC focuser240(e.g., and before, after, or during transfer of the VOCs from the VOC focuser240to the SVOC focuser234and/or analytical column238), the GC oven202can be heated319from the temperature in the range of 35-50° C. to a temperature in the range of 240-340° C. In some embodiments, the GC oven202can be heated at a rate of 2 to 20° C. per minute. While heating the GC oven202, valves246and228can remain on and valves222,224, and226can remain off. In some embodiments, this configuration of valves and the heating of the GC oven202can cause the SVOCs to (e.g., start to) transfer from the SVOC trap234towards the analytical column238.

In some embodiments, after transferring the sample to the analytical column238, the chemical (e.g., GC or GCMS) analysis can be conducted322. The GC oven202can increase in temperature to complete the transfer of all compounds of interest through SVOC focuser234and restrictor236onto analytical column238.

In some embodiments, once the compounds of interest have been transferred to the analytical column238(e.g., from the SVOC focuser234and the VOC focuser240), one or more heavy compounds remaining in the SVOC focuser234that are not of interest for analysis can be removed324from the system200. In some embodiments, removing these compounds can include leaving valve246on and turning on valves222and226. This configuration can facilitate flow of the remaining, undesirable compounds from the SVOC focuser234to the split port226, while valve222flushes the compounds of interest in the analytical column238to the analyzer250. The system can remain in this configuration with valves246,222, and226on and the remaining valves off until the analysis is complete. In some embodiments, valve224can be turned on during this time to facilitate bakeout of the sample extraction device210(e.g., through valve226) to clean the sample extraction device210to prepare it for reuse. In some embodiments, the sample extraction device210and the thermal desorber220are at a temperature higher than (e.g., 20° C. higher than) the temperature of the sample extraction device210and thermal desorber220during desorption310of the sample from the sample extraction device210.

In some embodiments, after analyzing the compounds of interest, the system can be cooled down326, including cooling the GC oven202and the heater242of the VOC focuser240. During cooling, valves222and226can remain on and valve246can be turned off, for example, which can stop the flow of gas through the VOC focuser240. In some embodiments, once the analyzer250is cool and ready for the next analysis, the process can be repeated with a subsequent sample (e.g., provided in a new sample collection device210).

FIG.4illustrates an exemplary chemical analysis system400according to some embodiments of the disclosure. System400can include a number of components that are the same as or similar to the components of system200described above with reference toFIG.2. For example, system400can include a GC oven402(e.g., similar to GC oven202described above with reference toFIG.2) containing a thermal desorber420(e.g., similar to thermal desorber220described above with reference toFIG.2), SVOC focuser434(e.g., similar to SVOC focuser234) described above with reference toFIG.2), analytical column438(e.g., similar to analytical column238described above with reference toFIG.2), connections432and437(e.g., similar to connections232and237described above with reference toFIG.2), non-coated, non-retentive column439, and restrictor436(e.g., similar to restrictor236described above with reference toFIG.2). In some embodiments, the GC oven402and one or more components therein are fluidly coupled to a VOC focuser440(e.g., similar to VOC focuser240described above with reference toFIG.2), an analyzer450(e.g., similar to analyzer250described above with reference toFIG.2), a pressure control system404(e.g., similar to pressure control system204described above with reference toFIG.2), GC split control system406(e.g., similar to GC split control system206described above with reference toFIG.2), and a plurality of valves422,424,426,428, and446(e.g., similar to valves222,224,226,228, and246described above with reference toFIG.2). In some embodiments, the VOC focuser440includes a plurality of capillary columns441a-c(e.g., similar to capillary columns241a-cdescribed above with reference toFIG.2) disposed within a heater442(e.g., similar to heater242described above with reference toFIG.2), a backflush desorb gas valve446(e.g., similar to backflush desorb gas valve246described above with reference toFIG.2), and a fan444(e.g., similar to fan244described above with reference toFIG.2).

In some embodiments, system400can operate similarly to system200described above with reference toFIG.2, such as the operation of valves422,424,426,446, and428being similar to the operation of valves222,224,226,246, and228described above with reference toFIG.2. Unlike system200, however, system400includes SVOC focuser434coupled between thermal desorber420and connection432, for example. In some embodiments, during desorption, the compounds of the sample (e.g., collected using sample extraction device410) can flow from the sample extraction device410in the thermal desorber420towards the SVOC focuser434, with the SVOC and heavier compounds being retained by the SVOC focuser434and the lighter VOC compounds and any air or water included in the system traversing the SVOC focuser434and proceeding through non-retentive column439towards VOC focuser440. In some embodiments, when the VOC focuser440is desorbed (e.g., after air and water have been removed from the system through valve428), flow of the VOC compounds from the sample can be facilitated from the VOC focuser440, through non-retentive column439, connection432, restrictor436, and connection437and into analytical column438. In some embodiments, when the SVOC focuser434is desorbed, flow of the SVOCs proceeds in the same direction as the direction of flow of the SVOC compounds during desorption of the sample extraction device410(e.g., from the end of the SVOC focuser434coupled to thermal desorber420towards the end of the SVOC focuser434coupled to connection432), through connection432, restrictor436, and connection437, and into analytical column438. In some embodiments, the SVOC compounds dynamically re-focus while traversing analytical column438, thereby reducing the bandwidth of these compounds. In some embodiments, after the VOC focuser434is desorbed in this manner, valves424and426can be opened to continue the elution of the SVOCs through the SVOC focuser434and bake out the sample extraction device420and sample extraction device420.

FIG.5illustrates an exemplary process500for conducting a chemical analysis according to some embodiments. In some embodiments, the chemical analysis process500includes collecting502a sample, such as by performing an extraction of organic compounds with a sample extraction device100,150, or210, or another sample delivery system. In some embodiments, pre-collection of a sample on a sorbent bed can be done by diffusive sampling at atmospheric pressure, diffusive sampling under vacuum conditions, or active sampling by drawing a known volume of gas to be analyzed through the sorbent.

In some embodiments, when the analyzer450(e.g., a MS or other detector) and oven402are ready504for the next analysis, the sample extraction device410can be placed506into thermal desorber420as shown inFIG.4while carrier gas is being supplied in and out of the system through valves422and426while valves424and428are closed, the GC oven402is at a temperature in the range of 35-50° C., the heater442of the VOC focuser440is 5° C. hotter than the GC oven402, and the thermal desorber420is at a temperature in the range of 40-80° C.

In some embodiments, while the sample extraction device410is disposed in the thermal desorber420, valve426can be turned off and valve428can be turned on during preheat508of the sample in the sample extraction device410in the thermal desorber420. In some embodiments, during preheating, the thermal desorber420can be heated to a desorption temperature in the range of 100-250° C. (e.g., while the GC oven402remains at a temperature in the range of 35-50° C. and the heater442of the VOC focuser240is 5° C. hotter than the GC oven402).

In some embodiments, the sample can be desorbed510from the sample extraction device410in the thermal desorber420by leaving valves422and428on, and also turning on valve424to start the desorption flow through thermal desorber420, connection432, SVOC focuser434, and VOC focuser440towards valve428while valve446and426are closed. In some embodiments, during desorption, the thermal desorber can be at a temperature in the range of 150-320° C. (e.g., while the GC oven402remains at a temperature in the range of 35-50° C. and the heater442of the VOC focuser440is 5° C. hotter than the GC oven402). During this 1-6-minute desorption, the heavier SVOCs from the sample can be transferred512to the SVOC focuser434and the VOCs from the sample can be transferred514to the VOC focuser440.

After the desorption is completed and while the SVOCs and VOCs of interest are retained by the SVOC focuser434and VOC focuser440, respectively, valve424can be turned off while valves422and428are on. In some embodiments, this configuration can allow carrier gas to flow through restrictor436, connection432, SVOC focuser434, non-retentive column439, and VOC focuser440to remove516any remaining air and water vapor out through vent428. In some embodiments, the process can be performed for 1-5 minutes. In some embodiments, while the air and/or water are being dry-purged from the system400, the GC oven402remains at a temperature in the range of 35-50° C. and the heater442of the VOC focuser440is 5° C. hotter than the GC oven402. At this time, for example, the heater of the thermal desorber420can be turned off to cool down the thermal desorber420, sample extraction device410, and connection432.

In some embodiments, after removing (e.g., all of, substantially all of) the water and air from the system400, valve428can be turned off to stop the flow through the SVOC focuser434and VOC focuser440, and the VOC focuser440can be preheated518(e.g., with heater442) to a desorption temperature in the range of 80-300° C. (e.g., 80-200° C.), for example. In some embodiments, while the VOC focuser440is being preheated, the GC oven402can remain at the temperature in the range of 35 to 50° C.

In some embodiments, during or after preheating the VOC focuser440(e.g., and while the VOC focuser440is at a temperature in the range of 80-300° C. (e.g., 120-200° C.)), valves446and428can be turned on and valves422,424, and426can be turned off. This configuration can transfer520the sample to the analytical column450by directing the sample from the VOC focuser440through non-retentive column439, through restrictor436, and to the analytical column438while the GC oven402is at the temperature in the range of 35-50° C., for example.

In some embodiments, after preheating the VOC focuser440(e.g., and before, after, or during transfer of the VOCs from the VOC focuser440to the analytical column438), the GC oven402can be heated519from the temperature in the range of 35-50° C. to a temperature in the range of 240-340° C. In some embodiments, the GC oven402can be heated at a rate of 2 to 20° C. per minute. In some embodiments, after desorbing the VOCs from VOC focuser440, valves446and428can be turned off and valves424and426can be turned on to flush the SVOCs from SVOC focuser434towards the analytical column438while heating the GC oven402.

In some embodiments, after transferring the sample to the analytical column438, the chemical (e.g., GC or GCMS) analysis can be conducted522. The GC oven402can increase in temperature to complete the transfer of all compounds of interest from SVOC focuser434, through restrictor436onto analytical column238.

In some embodiments, once the compounds of interest have been transferred to the analytical column438(e.g., from the SVOC focuser434and the VOC focuser440), one or more heavy compounds remaining in the SVOC focuser434that are not of interest for analysis can be removed524from the system400. In some embodiments, removing these compounds can include leaving valve446on and turning on valves422and426. This configuration can facilitate flow of the remaining, undesirable compounds from the SVOC focuser434to the split port426, while valve422flushes the compounds of interest in the analytical column438to the analyzer450. The system can remain in this configuration with valves446,422, and426on and the remaining valves off until the analysis is complete. In some embodiments, valve424can be turned on during this time to facilitate bakeout of the sample extraction device410(e.g., through valve426) to clean the sample extraction device410to prepare it for reuse. In some embodiments, the sample extraction device410and the thermal desorber420are at a temperature higher than (e.g., 20° C. higher than) the temperature of the sample extraction device410and thermal desorber420during desorption510of the sample from the sample extraction device410.

In some embodiments, after analyzing the compounds of interest, the system can be cooled down526, including cooling the GC oven402and the heater442of the VOC focuser440. During cooling, valves422and426can remain on and valve446can be turned off, for example, which can stop the flow of gas through the VOC focuser440. In some embodiments, once the analyzer450is cool and ready for the next analysis, the process can be repeated with a subsequent sample (e.g., provided in a new sample collection device410).

In some embodiments, the systems and methods described above can achieve the following goals:Both VOCs and SVOCs are 100% delivered to the analytical column238and to the analyzer250without splitting, thereby maximizing sensitivityVOCs are focused to optimize capillary column GC performance (maximized compound resolution)Excess water vapor is eliminated (e.g., through valve228) before it can affect chromatography, reducing hydrolysis of the analytical column238, and eliminating suppression within the analyzer250Elimination of cold spots or rotary valve rotors that would affect SVOC recoveryElimination of moving parts in the flow path (rotary valves, solenoid valves), that would reduce system longevityElimination of packed traps and liquid nitrogen, that can have negative effects on performance

Therefore, in some embodiments, techniques disclosed herein can use an SVOC focuser234disposed in a GC oven202and a VOC focuser240attached to the GC oven202to complete sample preparation processes, including eliminating residual water, air, and other undesirable fixed gases in a sample, reducing the sample volume, and rapidly injecting the compounds of interest into an analyzer250(e.g., a GC or GCMS). In some embodiments, both VOCs and SVOCs can be analyzed in a single analysis using a splitless injection to transfer 100% of the compounds of interest of the sample to the analyzer250in order to maximize the sensitivity of the analytical technique.

Techniques disclosed herein can be used in the analysis of chemicals in waste water, drinking water, sea water, soils, indoor and outdoor air, beverages such as wine and beer, spirits, consumer products, and many other applications where either trace level analysis is required, or where the volume of the original sample is limiting. Another application for this technique is the analysis of breath condensate in which an oral rinse is placed in a vial where it is extracted under vacuum using sample extraction device100,150, and/or210to recover volatile through semi-volatile compounds originating within the body where trace level analysis is required for detection of various diseases, for example. In some embodiments, other biological fluids and/or tissues can likewise be vacuum extracted to recover their volatile and semi volatile content for metabolomic research and for detection of disease markers. In addition, chemical warfare agents in air, water, or breath condensate can also be analyzed at ultra-trace levels (part per quadrillion), and sample extraction devices100,150, and/or210can be placed on drones to collect samples remotely in search of CWAs or signatures indicating illicit drug laboratory operations. Some embodiments can be used to analyze the widest range of boiling points, at the lowest detection limits possible, with the least amount of system contamination and carryover. Some embodiments of the disclosure relate to a system comprising a first oven containing an SVOC focuser and an analytical column; a thermal desorber fluidly coupled to the SVOC focuser and analytical column; a VOC focuser fluidly coupled to the SVOC focuser; a plurality of valves configured to: introduce a first flow of sample from the thermal desorber, through the SVOC focuser towards the VOC focuser, wherein the SVOC focuser is configured to retain first compounds and the VOC focuser is configured to retain second compounds; after the SVOC focuser retains the first compounds and the VOC focuser retains second compounds, introduce a second flow of the sample from the VOC focuser and the SVOC focuser to the analytical column, wherein the second flow transfers the first compounds and second compounds to the analytical column; and an analyzer fluidly coupled to the analytical column, wherein the analyzer is configured to conduct a chemical analysis of the first and second compounds after the first and second compounds traverse the analytical column. Additionally or alternatively, in some embodiments, the system further includes a first valve coupled to a GC split controller, wherein the first valve is open while the first flow of sample is introduced. Additionally or alternatively, in some embodiments, the system further includes a second oven different from the first oven, the second oven containing the VOC focuser. Additionally or alternatively, in some embodiments, while introducing the first flow of sample, the system heats the second oven to a higher temperature than the first oven. Additionally or alternatively, in some embodiments, the first flow includes removing one or more of water or air from the system through a valve coupled to the VOC focuser. Additionally or alternatively, in some embodiments, the chemical analysis is performed based on a single, splitless injection of the sample including SVOCs and VOCs. Additionally or alternatively, in some embodiments, the SVOC focuser is configured to retain third compounds, and the plurality of valves are further configured to, after the first compounds and second compounds are transferred to the analytical column, remove the third compounds from the system. Additionally or alternatively, in some embodiments, the system further includes a restrictor disposed between a connection of the thermal desorber and the SVOC focuser and the analytical column, the restrictor fluidly coupled to the thermal desorber, SVOC focuser, and analytical column.

Some embodiments are directed to a method comprising introducing, via a plurality of valves, a first flow of sample from a thermal desorber, through the SVOC focuser towards the VOC focuser; while introducing the first flow: retaining, with the SVOC focuser, first compounds; and retaining, via the VOC focuser, second compounds; after the SVOC focuser retains the first compounds and the VOC focuser retains second compounds: introduce, via the plurality of valves, a second flow of the sample from the VOC focuser and the SVOC focuser to an analytical column, wherein the second flow transfers the first compounds and second compounds to the analytical column; after the first and second compounds traverse the analytical column: conduct a chemical analysis, via an analyzer fluidly coupled to the analytical column, of the first and second compounds. Additionally or alternatively, in some embodiments, introducing the first flow of the sample includes opening a first valve coupled to a GC split controller. Additionally or alternatively, in some embodiments, the method further includes, while introducing the first flow, heating, via a first oven, the SVOC focuser to a first temperature; and heating, via a second oven, the VOC focuser to a second temperature higher than the first temperature. Additionally or alternatively, in some embodiments, introducing the first flow includes removing one or more of air or water from the sample through a valve of the plurality of valves, the valve coupled to the VOC focuser. Additionally or alternatively, in some embodiments, the chemical analysis is conducted based on a single, splitless injection of the sample, the sample including SVOCs and VOCs. Additionally or alternatively, in some embodiments, the method further includes, while introducing the first flow and while introducing the second flow: retaining, via the SVOC focuser, third compounds; and after introducing the second flow: introducing, via the plurality of valves, a third flow to remove the third compounds from a system including SVOC focuser and the analytical column.