High volume sampling trap thermal extraction device

In an example, a thermal extraction apparatus includes: a housing having a gas inlet and a gas outlet to receive a gas flow through the housing from the gas inlet to the gas outlet, and a side opening to receive a sample collector, having a sample collector adsorbent containing a vapor sample, into a sample collector location; a pump to generate the gas flow; a heater to heat the sample collector adsorbent of the sample collector to a temperature sufficient to release the vapor sample; a thermal desorption (TD) tube connected with the gas outlet of the housing to receive the gas flow downstream of the sample collector and collect the vapor sample released from the sample collector adsorbent of the sample collector; and a cooling member in heat exchange with the TD tube to cool the TD tube.

FIELD

The discussion below relates generally to systems and methods for high-volume sampling and, more specifically, to a thermal extraction device (TED) to thermally extract materials collected by a particle and vapor collection device such as a high volume sampling trap (HVST).

BACKGROUND

Sampling devices, specifically those used to screen large number of people or items, have been used for some time. These devices can be found almost anywhere, including government-run office buildings and airports. For example, airports use body scanners, utilizing machines that allow security officers an unobstructed view of a person's body to determine the presence of weapons. Other methods test for less visible items or substances, such as explosive residue or narcotics. Specifically, much focus has been put towards detection methods for these less visible substances as terrorism has risen, inasmuch as explosives, biochemical weapons, and the like threaten the security of the United States.

Liquid preparations have been used in detection methodologies. For example, a liquid is first applied to a surface to solvate or otherwise place into liquid phase the substance of interest which may be residing on the surface. Then, that mixture is tested. While such sampling devices are reliable, they suffer from many disadvantages, one of which is efficiency. Generally, in high volume situations it would take too much time to prepare liquid samples for every surface requiring testing.

Some detection systems require encapsulating the entire object, the surfaces of which require sampling. These systems involve large chambers, and therefore require a large footprint in which to operate. Handheld sampling wands also exist. However, many of these wands are tethered to stationary detection units, thereby hindering an operator's movement when climbing over parcels and crates. Other detection systems include vapor deposition systems whereby adsorbents sequester vapors containing target moieties. Such systems often do not allow for simultaneous extraction and sequestration of solid phase and/or liquid phase samples.

U.S. Pat. No. 8,578,796 to Cho discloses a device for sampling surfaces for the presence of compounds, including a housing having a proximal end adapted to receive a negative pressure gradient and a distal end adapted to contact the surfaces; a heating element spaced from the distal end; a primary filter spaced from the heating element; and a secondary filter spaced from the primary filter, the secondary filter removably received by the housing. A method for sampling a surface for the presence of compounds includes contacting the surface to dislodge the compounds from the surface; capturing first fractions of the compounds with a primary filter while allowing second fractions of the compounds to pass through the primary filter; heating the primary filter to volatilize the first fractions; capturing the volatized first fractions and the second fractions with a secondary filter; and analyzing the secondary filter to identify the compounds. The detection system is portable or stationary, light weight, and low cost. It utilizes off the shelf componentry, is capable of simultaneous sequestration of multi-phases of target compounds, and allows continued sequestration of target compounds in the field by facilitating in situ replacement of full sample carriers with empty ones.

SUMMARY

Embodiments of the present invention are directed to apparatuses and methods for thermally extracting vapor samples collected with a sample trap using a thermal desorption (TD) collector such as a TD tube, which can then be inserted into a mass spectrometer for direct sample analysis. One example of the sample trap is the secondary filter disclosed in U.S. Pat. No. 8,578,796 which also employs a primary filter to capture relatively large particles and a heater to heat and vaporize the captured particles. An adsorbent resin, as a sample collector adsorbent in the sample trap, collects the vaporized sample. See, e.g., U.S. Pat. No. 8,578,796 at column 7, line 18 to column 8, line 67 and in FIGS. 5 and 6, which is incorporated herein by reference. In another embodiment, the sample trap including an adsorbent resin is used to collect vapor-phase particle sample and potentially micrometer-sized particle sample, by adapting it to a vacuum device, without using the primary filter and heater. The sample trap may be referred to as a high volume sampling trap (HVST), which can be used to collect a large volume of the air samples from cargo container freight, palletized cargo, and security checkpoint to trap illicit organic volatile materials. The vacuum device is light-weight and portable, and can be used in other applications, such as sample collection at airports or other checkpoints, which involve smaller volumes of air sample collection.

The sample trap is placed into a TED, which may be referred to as an HVST-TED. The device may include a heater to heat the sample trap to about 200° C. and a gas flow is used to move the heated vapor-phase sample and any semi-volatile organic compound sample to a TD collector such as a TD tube disposed downstream. The TD tube may be cooled to about 0-10° C. for collecting the vapors and analytes. The use of the TD tube facilitates direct analysis on a mass spectrometer to identify the chemical species released from the sample trap, by removing the TD tube from the TED and inserting it directly into a Thermal Desorption-Gas Chromatography/Mass Spectrometer (TD-GC/MS) for sample analysis. As such, the HVST desorber has been modified for better sample recovery on a TD tube. The use of the TD tube provides a one-step analysis of the trapped sample.

In accordance with one aspect, a thermal extraction apparatus comprises: a housing having a gas inlet and a gas outlet to receive a gas flow through the housing from the gas inlet to the gas outlet, and a side opening to receive a sample collector into a sample collector location, the sample collector having a sample collector adsorbent containing a vapor sample; a pump to generate the gas flow; a heater to heat the sample collector adsorbent of the sample collector to a temperature sufficient to release the vapor sample; a TD tube connected with the gas outlet of the housing to receive the gas flow downstream of the sample collector and collect the vapor sample released from the sample collector adsorbent of the sample collector; and a cooling member in heat exchange with the TD tube to cool the TD tube.

In accordance with another aspect, a thermal extraction apparatus comprises: a housing having a gas inlet and a gas outlet to receive a gas flow through the housing from the gas inlet to the gas outlet, and an insertion port to receive a sample collector having a sample collector adsorbent containing a vapor sample; a pump to generate the gas flow; a heating mechanism for heating the sample collector adsorbent of the sample collector to a temperature sufficiently high to facilitate release of the vapor sample from the sample collector adsorbent of the sample collector; and a TD tube connected with the gas outlet of the housing to receive the gas flow downstream of the sample collector and collect the vapor sample released from the sample collector adsorbent of the sample collector.

In accordance with yet another aspect, a thermal extraction method comprises: placing a sample collector, which has a sample collector adsorbent containing a vapor sample, inside a housing via a side opening; heating the sample collector adsorbent of the sample collector to a temperature sufficiently high to facilitate release of the vapor sample from the sample collector adsorbent and directing a gas flow through a gas inlet of the housing through the sample collector adsorbent of the sample collector through a gas outlet of the housing to a TD tube connected with the gas outlet of the housing to receive the gas flow downstream of the sample collector and collect the vapor sample released from the sample collector adsorbent of the sample collector inside the TD tube.

Other features and aspects of various examples and embodiments will become apparent to those of ordinary skill in the art from the following detailed description which discloses, in conjunction with the accompanying drawings, examples that explain features in accordance with embodiments. This summary is not intended to identify key or essential features, nor is it intended to limit the scope of the invention, which is defined solely by the claims.

DETAILED DESCRIPTION

A number of examples or embodiments of the present invention are described, and it should be appreciated that the present invention provides many applicable inventive concepts that can be embodied in a variety of ways. The embodiments discussed herein are merely illustrative of ways to make and use the invention and are not intended to limit the scope of the invention. Rather, as will be appreciated by one of skill in the art, the teachings and disclosures herein can be combined or rearranged with other portions of this disclosure along with the knowledge of one of ordinary skill in the art.

In large volume sampling, a high volume sampling (HVS) device is adapted to be in fluid communication with a target such as a ventilation port of a cargo container such that, for example, the device is placed upstream or downstream of the ventilation port, or perhaps within and coaxial to the port. In one example, the HVS device is a vacuum device, which may be portable, for directing a flow of sample through a sample trap containing an adsorbent for trapping vapor-phase sample and any semi-volatile organic compound sample. The sample trap, which may be referred to as an HVS trap or H-trap, is then placed into a thermal extraction device (TED). The HVS device can be applied to the break bulk, pelletized or containerized air/sea cargo. Also, the device can be utilized on chemical and biological warfare agent samples, industrial toxic chemicals, explosives particle samples, and drugs or hazardous waste sampling. The HVS device facilitates large volume of air sample collection from a large screening area. The military explosive, Composition C-4, can be used as a standard explosive for the device particle sample testing. Vapor Sample C-4 includes Triacetone triperoxide (TATP) and Ethylene glycol dinitrate (EGDN).

Generally, the TED includes a heating device such as a heating cartridge for heating the sample trap and a thermal desorption collector such as a TD tube positioned downstream of the sample trap. The TD tube may include a polymer adsorbent to trap vapor samples. The heating cartridge and sample trap are supported by a housing so as to be substantially encased by the housing.

In an embodiment, the sample trap is heated to evaporate the target compounds that are trapped. The vaporized compounds are directed by a gas flow from the sample trap to the TD tube to be re-trapped in the TD tube. During the process, about 1 to 4 L/min of flow, for example, will be applied to the sample trap for carrying target moieties from the sample trap to the TD tube.

In an embodiment, an aluminum housing holds a removable sample trap and a heater to heat the sample trap. A TD tube is spaced from and disposed downstream of the sample trap along a gas flow to collect vapor-phase sample and any semi-volatile organic compound sample. In one example, heating members such as heating cartridges are provided upstream and downstream of the sample trap to generate a temperature gradient that is higher upstream of the sample trap and lower downstream of the sample trap.

In one example, the TD tube, comprised of a polymer adsorbent material such as Tenax, collects vapors and analytes from the sample trap after the sample trap is heated up to about 200° C. within about 60-120 seconds to vaporize some of the particles and analytes collected from the sample trap. The TD tube is cooled to about 0-10° C. for collecting the vapors and analytes. The TD tube is then easily removed and inserted directly into a Thermal Desorption-Gas Chromatography/Mass Spectrometer (TD-GC/MS) for sample analysis.

FIG. 1is a cross-sectional view of a high volume sampling trap thermal extraction device (HVST-TED)100according to an embodiment of the present invention. The device100includes a main housing104and a secondary housing106connected to a proximal end of the main housing104. In some embodiments, the secondary housing106is disposed at least partially or completely inside the main housing104. Along the direction of gas flow from an inlet at the distal end108toward a proximal end146of the secondary housing106, disposed inside the main housing104are a heater110(including a hot plate112in the embodiment shown), a right holder118, a sample trap or collector120, and a left holder122. The gas can be air. The right holder118, sample trap120, and left holder122form a sample trap assembly124that can be inserted into and removed from the main housing104. Downstream of the left holder122is a frustoconical cavity130of the secondary housing106which contracts in cross-sectional area in the downstream direction and leads to a TD collector140connected to the proximal end146of the secondary housing106via a proximal connector150. One example of the TD collector140is a TD tube140wrapped around by a cooling coil or tubing160having a flow of cooling fluid such as liquid nitrogen (LN2) for cooling the TD tube140by heat exchange. The gas flow exits at a proximal end170of the device100, which in one embodiment is connected to a vacuum pump. This is one means for cooling the TD tube. Other cooling means or mechanisms may be used for cooling the TD tube in other embodiments.

High volume sampling encompasses sample volumes as high as approximately 400 liters per minute of air using a 1-inch inner diameter input aperture such as a 1″ ID sample tube connected at the distal end108. Higher sample volumes are attainable if input diameters increase. Either the distal end108of the device100may be adapted to receive pressurized effluent or the proximal end170of the device100may be adapted to establish fluid communication with negative pressure (i.e., a vacuum pull). In one example, a vacuum pull is established between the proximal end170and a vacuum line via a snap fit assembly or threaded connectors. The proximal end146of the secondary housing106defines a ¼″ Teflon ferrule with a compression fitting nut to effectuate a negative pressure pull with a vacuum hose.

Prior to thermal extraction, the sample trap assembly124may be attached to a commercial vacuum system with some modifications to collect target sample. For instance, the vacuum system may be adapted to be in fluid communication with a target such as a ventilation port of a cargo container. Examples of the vacuum system include the Dayton Backpack Vacuum system (Model 4TRI0) and the Dyson handheld vacuum system (Model V6).

FIG. 2shows an elevational view of a main housing of the HVST-TED according to another embodiment.FIG. 2Ashows a side view A-A of the main housing ofFIG. 2.FIG. 2Bshows a side view B-B of the main housing ofFIG. 2. The main housing204includes a proximal internally threaded section210for receiving a secondary housing similar to the secondary housing106ofFIG. 1on the proximal side. The main housing204includes a distal internally threaded section220for connecting to an air intake at the distal end208. The main housing204has a side opening or slot230which is a complementary aperture or insertion port formed along a longitudinally extending surface of the main housing204for receiving the sample trap assembly124into a sample collector location in the main housing204. The side opening230defines a plane which is positioned transverse to the longitudinal axis of the main housing204. The main housing204has a frustoconical cavity234that expands in cross-sectional area from the distal internally threaded section220near the distal end208in a downstream direction toward the proximal internally threaded section210near the proximal end of the main housing204.

In the embodiment shown inFIG. 2, instead of a hot plate112inFIG. 1, heating cartridges242,244may be provided in the main housing204for heating and RTD (resistance temperature detector) probes252,254may be provided in the main housing204for measuring temperature. These components are commercially available and are cylindrical in shape. The upstream heating cartridge244and upstream RTD probe254are disposed upstream of the sample trap assembly124that is inserted into the side opening230. The downstream heating cartridge242and downstream RTD probe252are disposed downstream of the sample trap assembly124. In one example, the upstream heating cartridge244and upstream RTD probe254each have a dimension of about 2″ in length X ¼″ in OD and the downstream heating cartridge242and downstream RTD probe252each have a dimension of about 1″ in length X ¼″ in OD. Also, thermometers other than RTD probes are used in other embodiments. The hot plate112and heating cartridges242,244are example means for heating the sample collector adsorbent in the sample trap assembly124. Other heating means or mechanisms for heating the sample collector adsorbent may be used instead of the examples described herein.

The heating cartridges242,244and RTD probes252,254are seen as being reversibly or releasably attached to the main housing204. However, heating cartridges and RTD probes are integrally molded to the main housing204in another embodiment. The main housing204is heated at the start of the thermal extraction process.

FIG. 3shows an exploded perspective view of the main housing204ofFIG. 2and a secondary housing306coupled to the proximal side of the main housing204. The main housing204includes the side opening230for receiving the sample trap assembly124. It is cylindrical so as to allow for easy manipulation by a single hand of a user. Other shapes are also envisioned. The secondary housing306has a proximal end346and includes a distal externally threaded section320for engaging with the proximal internally threaded section210of the main housing204shown inFIG. 2.

FIG. 4shows an elevational view of the secondary housing306ofFIG. 3.FIG. 4Ashows a side view A-A of the secondary housing ofFIG. 4. The secondary housing306may include frustoconical cavity430, similar to the frustoconical cavity130ofFIG. 1, which contracts in cross-sectional area from the distal end of the secondary housing306toward the proximal end446. It may include a proximal internally threaded section420for receiving a proximal connector similar to the proximal connector150ofFIG. 1for connecting to a TD tube. It may have a distal externally threaded section410for engaging the proximal internally threaded section210of the main housing204ofFIG. 2.

FIG. 5Ashows a side view of the left holder122according to an embodiment.FIG. 5Bshows a front elevational view of the left holder122.FIG. 5Cshows a front elevational view of the right holder118according to an embodiment.FIG. 5Dshows a side view of the right holder118.

FIG. 6shows an example of the sample trap120, the left holder122, and the right holder118of the sample trap assembly124. The left holder122is matingly received by the right holder118to form an interior space to receive the sample trap120. The interior space has a depth measuring approximately the thickness of the sample trap120. The left holder122and the right holder118may at least substantially completely encase the sample trap120. The sample trap120may include an adsorbent resin used to collect vapor-phase sample and any micrometer-sized particle sample prior to being inserted into the main housing206via the side opening230for thermal extraction.

FIG. 8shows an example of an assembled HVST-TED. The main housing204is connected to the secondary housing306, and sample trap assembly124is inserted into the main housing204via the side opening230. Air enters via the distal end of the main housing204, flow through the sample trap assembly124, and exits via the proximal end of the secondary housing306.

FIG. 9shows an example of an assembled HVST-TED illustrating connection to a TD tube. The side opening230in the main housing204for receiving the sample trap assembly124is more clearly shown. The TD tube140is connected to the secondary housing306via a proximal connector950similar to the proximal connector150ofFIG. 1. In this example, a graphite ferrule910and a thumb wheel920are used to tighten the connection between the proximal connector950and an inlet end of the TD tube140. The outlet end of the TD tube may be connected to a vacuum pump.

FIG. 10shows a view illustrating the insertion of the sample trap assembly124into the sample collector location1010of the main housing204via the side opening230.FIG. 11shows another view illustrating the insertion of the sample trap assembly124into the sample collector location1010of the main housing204via the side opening230. The sample collector location1010of the main housing204may be configured with the shape and size to receive the sample trap assembly124and align it automatically to the gas flow path in the main housing204. Inserting and removing the sample trap assembly124can be done quickly and precisely.

Sample Trap

An embodiment utilizes stainless steel mesh as a constituent of the sample trap120. The sample trap120is a filter made of a mesh stainless steel screen and can be heated to about 200° C. or higher to vaporize materials on its surface. The thermal desorption process may occur within about 20 seconds, or between about 5 and 15 seconds, or between about 5 and 10 seconds. The thermal desorption may be accompanied with a gas flow through the device100so as to direct desorbed moieties from the sample trap120to the TD collector140. The gas flow rates may range from approximately 50 cc/minute for about four minutes to about 100 cc/minute for about two minutes.

An embodiment of the sorbent entity comprises 200 mesh (approximately 74 microns) stainless steel with between 75 and 200 milligrams of Tenax-GR backed therein. The trap materials (i.e., resin) are placed in between the two stainless steel wire cloth or fiberglass substrates; then, a tap welding machine is utilized to weld the edges of the cloth together, thereby substantially encapsulating the trap materials within the wire cloth. Generally, when Tenax-GR resin is utilized, its mesh size may be between 80 and 100 or particle sizes having diameters of between about 180 microns and 145 microns. When Tenax TA resin is used, its mesh size may be between about 60 and 80.

A specific embodiment of the sample trap120includes a stainless steel 200 mesh. Particle sizes of the adsorbent resin may be about 150 to 250 μm. The sample trap120can utilize a mesh portion composed of alternative materials that are inert or non-reactive with the target compounds. For any sample trap120, in order to accommodate the adsorbent resin particles, the stainless steel mesh is typically smaller than the adsorbent particles.

Thermal Desorption Collector

The TD collector140is capable of collecting vapor and any micrometer-sized particles simultaneously. In an embodiment, the TD collector140includes an adsorbent such as porous polymer resin. An example is diphenylene-oxide on a heat-resistant substrate such as graphite. Tenax-GR and Tenax-TA resins are available through Scientific Instrument Services of Ringoes, N.J. Other suitable resins include Supelco (Sigma-Aldrich), Restek, Perkin-Elmer, Agilent, and combinations thereof.

FIG. 12is a schematic view of an example of a TD tube140. From the sampling inlet1210to the sampling outlet1212are disposed a glass frit1220, Tenax-TA1230, glass wool1240, Carboxen-10031250, glass wool1260, and a stainless-steel screen1270(e.g., having a mesh size between about 60 and 80). Tenax-TA1230is a porous material based on 2,6-diphenylene oxide polymer. It is used to trap volatile and semi-volatile compounds with an upper temperature limit of about 320° C. It has a low affinity for water or methanol. Water has a very low breakthrough value on Tenax adsorbent. Typically, a carbon molecular sieve is used as a backup adsorbent when sampling for very volatile analytes for example, smaller than dichloromethane. Carboxon1003is a carbon molecular sieve1250with a large surface area and hydrophobic surface characteristics, which provide a combination of efficient absorption/desorption and good hydrophobicity.

Thermal Extraction System

FIG. 13shows an example of an external housing1310for the HVST-TED having a gas flow inlet at the distal end208. A temperature control unit1320is provided to control the temperature of the main housing204in which the sample trap124is removably placed. For example, the temperature control unit1320is coupled with the downstream heating cartridge242and the upstream heating cartridge244of the main housing204inFIG. 2for heating and the downstream RTD probe252and the upstream RTD probe254for measuring the temperature. The temperature control unit1320uses the temperature measurement from the RTD probes as feedback for controlling thermal outputs of the heating cartridges to achieve the desired temperatures. Various temperature control units (TCUs) are commercially available. Any suitable unit can be used or adapted to be used as means or a mechanism for controlling the temperature of the heating members.

FIG. 14shows an example of a thermal extraction system1400including the external housing1310for the HVST-TED and the temperature control unit1320ofFIG. 13. The system1400includes an inlet flow line1404into and an outlet flow line1406out of the HVST-TED inside the external housing1310, and the cooling coil160wrapped around the TD tube140. The LN2 cooling temperature is below set point (10° C.) around the TD tube140. The outlet flow line1406is a low-flow TD sampling pump line (negative pressure) connected to the sampling outlet1212of the TD tube140inFIG. 12. In one example, the gas flow rate is set at about 50-100 cc/minute for about 2-4 minutes, while the temperature control unit1320is set at about 200° C. near the distal end208and about 190° C. near the proximal end of the main housing204inFIG. 2.

At the start of an example process, the sample trap120has collected therein gas phase moieties and potentially micrometer-sized particle samples from a target area. The sample trap120is placed inside the main housing204of the HVST-TED, heat is applied, and a gas flow is directed through the interior of the main housing204, for instance, by applying a negative pressure to the proximal end downstream of the main housing204and the secondary housing306. For example, the heater increases the temperature of the sample trap120to about 190-200° C. within about 10 seconds. Under the heating and gas flow, the gaseous moieties and any particle moieties are released from the sample trap120and collected by the TD tube140downstream. A LN2 cooling system provides the LN2 cooling coil160wrapped around the TD tube140. Once the cooling temperature reaches below about 10° C., a sample pump is activated to apply the negative pressure.

The adsorbent resin in the TD tube140disposed downstream of the secondary housing306collects vapor-phase sample and any particle sample collected in the sample trap120that are released by the heating and gas flow therethrough. In one embodiment, the TD tube140collects sample at a gas flow rate of about 50-100 mL/min for about 2-4 minutes. Vapor-phase and any micrometer-sized particle samples are collected using the TD collector140connected to the proximal end346of the secondary housing306. Some of the target analytes in explosive vapor sampling include high volatile organic compounds (e.g., MNT, NG, EGDN, and DMNB (taggant)).

The TD tube140is then separated from the TED and inserted directly into a TD-GC/MS. For a reusable TD tube, this desorption step serves also as a regeneration step for the TD tube140. As such, the TD tube140is subsequently reconnected to the housing104,106of the TED, and the device is ready for another round of sample taking.

Once the sample trap120is heated and analyte is collected in the TD collector140, the TD collector (e.g., TD tube)140can be then analyzed by inserting it directly into the thermal desorption-gas chromatography/mass spectrometer (TD-GC/MS) for analysis of the collected sample. A TDS (thermal desorption system) is coupled onto the GC injection port and the TD tube is inserted in the TDS. The vaporized analytes are re-tapped into a PTV (Programmed Temperature Vaporizer), which is set at about −40° C. The specified end temperature may be set at about 280° C. and the PTV is rapidly raised temperature ramp rate at 12° C./second. Once the PTV is reached at the end temperature at about 280° C. the operation system activates the MS to collect data.

The inventive concepts taught by way of the examples discussed above are amenable to modification, rearrangement, and embodiment in several ways. Accordingly, although the present disclosure has been described with reference to specific embodiments and examples, persons skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the disclosure.

The claims define the invention and form part of the specification. Limitations from the written description are not to be read into the claims.

An interpretation under 35 U.S.C. § 112(f) is desired only where this description and/or the claims use specific terminology historically recognized to invoke the benefit of interpretation, such as “means,” and the structure corresponding to a recited function, to include the equivalents thereof, as permitted to the fullest extent of the law and this written description, may include the disclosure, the accompanying claims, and the drawings, as they would be understood by one of skill in the art.

To the extent the subject matter has been described in language specific to structural features and/or methodological steps, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or steps described. Rather, the specific features and steps are disclosed as example forms of implementing the claimed subject matter. To the extent headings are used, they are provided for the convenience of the reader and are not be taken as limiting or restricting the systems, techniques, approaches, methods, devices to those appearing in any section. Rather, the teachings and disclosures herein can be combined, rearranged, with other portions of this disclosure and the knowledge of one of ordinary skill in the art. It is the intention of this disclosure to encompass and include such variation. The indication of any elements or steps as “optional” does not indicate that all other or any other elements or steps are mandatory.