JP2003510605A - Chemical sensing system - Google Patents

Abstract

The present invention relates to a chemical sensing system for gas or vapor analysis of a sample, and more particularly to an array-based chemical sensing system for gas or vapor headspace analysis of food packaging materials.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a gas or chemical sensing system for the above analysis of a sample, and more particularly to an array chemical sensing system for a gas or vapor headspace of food contact packaging materials.

[0002]

[Prior Art and Problems to be Solved by the Invention]

According to the current law, in terms of quality, it may endanger the health, or spoil (contaminate) food or give off odor. It is required that the ingredients (chemicals) should not be transferred to food. For example, chemical components that cause the packaging material (wrapping paper, packaging container) to become contaminated or smell may be diffused into the foodstuffs placed within the packaging material. Foods such as chocolate and tea are particularly sensitive to contamination and odor. In the manufacture of food contact packaging, it is required to perform "dirt and odor" tests in order to observe the stringent quality control procedures defined by current legislation and to meet customer requirements.

Analytical chemists have the scope to extend conventional equipment, but quality control techniques are usually limited to remote laboratories under the direction of trained personnel. Current food contact packaging manufacturers typically use human sensor panels (HSPs) for quality control.
) And / or gas chromatography / mass spectrometry (GC / MS). HSPs have been the industry standard for "dirt and odor" testing for over 20 years, but have two major drawbacks: (1) HSPs are individual and calibrate to other panels. It is not possible. (2) HSP is an off-line technology that provides post production for 36 hours or more. While an accepted analytical technique, GC / MS remains remote, GC / MS equipment is expensive to install and operate, and can only be operated by trained operators.

There is an increasing demand to improve quality control procedures and reduce costs due to manufacturing errors. Bringing quality control technology into the factory using techniques for unskilled operators is a very large goal for many manufacturing industries. For example, if analytical technology adds value to the quality control procedures of carton makers, it is possible to provide reliable quality control information in the manufacturing environment.

[0005]

[Means for Solving the Problems]

The present invention seeks to meet the need for improved quality control by providing an array-based chemical sensing system. More specifically, the present invention exposes a majority of the surface area of a sample to a continuous flow of carrier gas (eg, air) and sampling dead connected to an array-based chemical sensing assembly that improves sensitivity. A chemical sensing system with a modular sampling unit adapted to minimize space is provided. With little or no sample preparation prior to use, chemical sensing systems are capable of providing faster in-line (at-line) results than post-production (post-production). is there.

In one aspect, the invention is a chemical sensing system for analyzing headspace of a sample comprising a modular sampling unit operably connected to a chemical sensor assembly: (1) wherein the modular sampling unit is A mount having an inlet channel and an outlet channel; a base member having a hollow interior defined by one or more internal side walls and a base wall, one or more of which is at least a part of a connecting point of the base wall; The two or more inner walls include a base member having a support collar that supports all or part of the lower surface edge of the sample; one or more outer walls and a base wall defining the body portion. A closing member, wherein the body portion has a shape complementary to the hollow inside of the base member, The outer edge of the base wall is provided with a closure member having an upright portion capable of engaging the edge of the upper surface of the sample; and, in use, the base member is inserted into the mount and the body of the closure member is The section engages the hollow interior of the base member, thereby defining a headspace below the lower surface of the sample and a headspace above the upper surface of the bubble, such that the inlet channel causes the headspace below the lower surface of the sample ( Or the headspace above the top surface), and the outlet channel communicates with the headspace above the top surface of the sample (or below the bottom surface), thereby providing an inlet over most of the surface area of the sample. Defining a continuous flow path between the channel and the outlet channel, (2) wherein the chemical sensor assembly comprises: one or more One or more chemical sensors, wherein each chemical sensor has a chemical sensing component capable of providing a measurable and characteristic response to a chemical stimulant; and a carrier gas A solid body having an inlet end for permitting entry, an outlet end for exhausting a carrier gas, and one or more compartments between them containing one or more chemical sensors, respectively. , One or more compartments are in continuous fluid communication to define a continuous flow path between the inlet end and the outlet end of the solid body where the chemical sensing component of each chemical sensor is exposed to the carrier gas. It has a solid body.

In use, the carrier gas is introduced into the inlet channel of the modular sampling unit where it sweeps the headspace of the sample.
The carrier gas (comprising one or more stimulants from the headspace) is then drawn to each chemical sensor in the array, and to varying degrees to obtain a time-dependent response profile specific to the chemical stimulant. While reacting with each chemical sensor.
Statistical methods defining X% confidence intervals in a multivariate sample population associated with data reduction methods may also be used to draw conclusions regarding the identification of unknown chemical stimuli. Analysis results may be as simple or complex as desired (eg, simple pass / fail answers with or without certainty values or conclusions, chemical stimuli). It may also be derived with regard to the possible identification of an object.)

In a preferred embodiment, the hollow interior of the base member and the body portion of the closure member are substantially cylindrical. In this embodiment, the support collar and / or the uprights are substantially annular. The annular support collar may include one or more cutouts. The annular upright may be a solid ring.

In a preferred embodiment, the inlet channel is connected to the headspace below the lower surface of the sample by a base conduit in the base wall of the base member. The base member is inserted into the mount such that the inlet channel and the base conduit are in fluid communication. The base member is inserted into the mount such that the inlet channel and the base conduit are in fluid communication.

In a preferred embodiment, the outlet channel is connected to the headspace above the upper surface of the sample by a lateral conduit in the side wall of the base member. The base member is
An outlet channel and a side conduit are inserted into the mount for fluid communication. Particularly preferably, the headspace above the sample and above the side conduits is in fluid communication by means of a radially arranged linear tube in the upright of the closure member. The upright may include more than one linear tube to accommodate a sample of varying thickness due to the variable extent of the body portion of the closure member operatively engaging the hollow interior of the base member.

In a preferred embodiment, the headspace below the lower surface of the sample is in fluid communication with the headspace above the upper surface of the sample via one or more substantially U-shaped tubes. The first arm of the U-tube (or each U-tube) is radially deployed in the support collar of the base member, and the second arm of the U-tube (or each U-tube) is a closure member. It is particularly preferable that the first arm and the second arm are arranged in a radial direction in the upright portion, and the first arm and the second arm are connected in fluid communication by the connection portion on the side wall of the base member. The support collar of the base member has two or more first arms, and the sidewalls provide a sample of varying thickness due to the variable extent to which the body portion of the closure member operatively engages the hollow interior of the base member. Two or more connections may be included to accommodate.

In a preferred embodiment, the base wall of the base member has a protrusion that supports the underside of the sample. The protrusions can preferably support a substantially central region of the lower surface of the sample. The protrusions preferably converge at a reduced contact edge (eg, to a point) to maximize the exposure of the lower surface of the sample to the carrier gas. The protrusions are preferably substantially cone-shaped.

In a preferred embodiment, the base wall of the closure member is provided with protrusions to assist in positioning and holding the sample. The protrusions preferably converge at a reduced contact edge (eg to a point) to maximize the exposure of the top surface of the sample to the carrier gas. The protrusions are preferably substantially cone-shaped.

The body portion of the closure member is preferably threadedly engaged within the hollow interior of the base member. The base member is preferably press fit into the mount.

The outer surface of the base wall of the base member and the mount are preferably provided with positioning features to allow proper placement and insertion of the base member in the mount. For example, the locating arrangement includes locating pins on the mount that can cooperate with locating apertures on the outer surface of the base wall of the base member.

The inlet and outlet channels are preferably sealed (eg, using one or more O-ring seals in the mount) and separated from each other. The inlet channels are preferably sealed from the environment (eg, using one or more O-ring seals in the mount) and separated from each other. The sample headspace and environment are preferably sealed (eg, using one or more O-ring seals in the closure member) and separated from each other.

The sampling chamber, defined when the base member is inserted into the mount and the body portion of the closure member engages the hollow interior of the base member, defines the desired sample (eg, solid) properties, sample size and It may be tailored to suit requirements such as / or shape and destructive or non-destructive sampling. The sampling unit is preferably adapted to define a sampling chamber for using the solid sample.

Each compartment of the solid body is arranged such that the chemical sensing components (including the chemical stimulus from the headspace) are exposed to the carrier gas in the form of wall jets. The "wall jet effect" is commonly known from the prior art of liquid dynamics, which studies the effect of liquid impinging on an extended solid surface.

In a preferred embodiment, the inlet end for admitting the carrier gas and the outlet end for exhausting the carrier gas are connected by a substantially linear conduit. The substantially linear conduit preferably defines a spine that connects each compartment in series. It is particularly preferable that the sections are spaced apart and arranged in parallel and connected. It is particularly preferred that each compartment is substantially orthogonal to its protrusion. Thus, the carrier gas passes in a repeatable manner through each compartment where it impinges on the chemical sensing component in the form of a wall jet (eg, to allow the carrier gas to traverse the surface area of the chemical sensing component). Then, a converging channel is formed in each section).

In a preferred embodiment, each compartment is adapted to house a chemical sensing component in a substantially free space. In this embodiment, the chamber is sized and shaped to correspond to the size and shape of the chemical sensing component and to minimize dead space.

The chemical sensor assembly preferably comprises a plurality of chemical sensors (eg, an array). Array-based sensing systems have been the subject of intense research over the last 15 years (eg, Sensors and Actua by Gardner et al.
tors B, 18-19, 211 (1994); Grate et al., Anal. Chem., 60, 2801 (1988)), their properties are generally well known to those skilled in the art.

The chemical sensing component is preferably a planar chemical sensing component. The planar chemical sensing component may be any convenient shape and any convenient type, as desired for the stimulus of interest. For example, each chemical sensing component may be bulk or surface acoustic wave type, metal oxide type, conductive polymer type, or optical type. Such chemical sensing components (eg WO98 / 22807) are widely reported and well known. It is preferably a quartz chemical sensor (eg, a bulk acoustic wave sensor).

Although normal, but not essential, the planar chemical sensing component is coated with a material capable of exhibiting or inducing a measurable response to the stimulus of interest. Materials and methods for coating sensor components are familiar to those skilled in the art and are widely reported (eg King, Anal. Chem., 36, 1735 (1964)).

The material of the chemical sensor assembly is adapted to suppress carrier gas absorption and minimize cross-contamination. For example, the solid body may conveniently consist of an inert material (eg PTFE). The chemical sensor assembly may be directly mounted on the electronic circuit board. This has the added advantage of eliminating the conductors between the sensor assembly and the electronics and enhancing sensitivity (eg, signal to noise ratio).

The chemical sensor assembly is new and improves the sensitivity of gas and vapor analysis by more effectively exposing the chemical sensor to a carrier gas.

[0026]   In another aspect of the invention, a chemical sensor assembly as specified above is provided.

The modular sampling unit is novel and improves the sampling operation by exposing most of the surface area of the sample to a substantially unobstructed flow of carrier gas (eg air) in the low dead space. The advantage of this is that the concentration of the stimulant in question in the carrier gas is optimized, which enhances the overall sensitivity.

Another aspect of the invention provides a modular sampling unit as specified above.

The chemical sensing component of the present invention is suitable for use in any application where a gas or vapor phase of a sample is desired. For example, the present invention may be used to screen volatile components in food contact packaging (eg, printed cardboard cartons, paper or related materials) or fibers. For this reason, the chemical sensing system preferably comprises a template for adjusting the sample to the size and configuration of the sampling unit.

In another aspect of the invention, a method of detecting the presence of one or more chemical stimulants in the headspace of a food packaging material using a chemical sensing system as specified above: base Inserting the member into the mount; placing the sample of food packaging material within the hollow interior of the base member such that the sample is supported on the support collar; engaging the body portion of the closure member within the hollow interior of the base member. Sweeping the headspace of the sample with a carrier gas; passing a carrier gas containing one or more chemical stimulants from the headspace to the inlet end of the chemical sensor assembly; Measuring the response of the chemical sensor to a carrier gas containing one or more chemical stimulants; And a step of associating the presence of the above chemical irritants.

Chemical stimulants of interest are (for example) diisopropylnaphthalene (DIPN)
The method may be cardboard (paperboard) at the level of current interest in the industry
May be used to rapidly detect the DIPN in.

The chemical stimulant of interest may be (for example) hexanal, and the method rapidly detects hexanal contained in cardboard at levels that indicate potential problems with food packaging. It may be used for.

The chemical sensing system of the present invention and its component parts may be controlled using suitable expert software. Expert software
It may be suitable for simultaneous control of the process and analysis of the data to allow use by non-technical workers. Similarly, a chemical sensing system may reliably track chemical sensors and components and support an automated check process to perform calibration of chemical sensor components.

[0034]

DETAILED DESCRIPTION OF THE INVENTION

  Hereinafter, the present invention will be described in a non-limiting manner with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view of an embodiment of a chemical sensor assembly of the present invention designated by the reference numeral 1. The chemical sensor assembly comprises eight quartz gas sensors 2 for bulk acoustic wave sensing, each sensor being a planar chemical sensing component 2a.
With an array of. Each sensor 2 is housed in one of a group of solid sensor blocks made of an inert material such as PTFE. The sensor block 1a defines parallel carrier gas flows arranged to allow each planar chemical sensing component 2a to cover and allow gas flow over the surface in a unique manner (see FIG. 2). A linear conduit 51 between an inlet end and an outlet end interconnecting a series of compartments 50 spaced apart in relation to each other.

FIG. 2 shows in detail the carrier gas flow path X on the surface of the planar chemical sensing component 2 a of the quartz sensor 2. "Chemical Sensing Component 2a
The "wall jet" incidence on the top leads to branch channels around and over the entire surface, which contributes to the overall improvement in sensitivity.

FIG. 3 is a side view of the sensor block 1 a (the coupling unit is referred to as a sensor board 4) directly connected to the electronic circuit 3.

The sensor board 4 is controlled by the microcontroller 6 which receives a command directly from the personal computer C downstream of the RS232 line 9. The microcontroller 6 feeds back the temperature of each sensor converter 5, the driving output and the sensor block to the feedback mechanism 7, 8
Control using. The temperature control 7 enables heating and cooling of the sensor block.

As shown in FIG. 5, the control board 10 of the sampling unit 14 is
It is controlled by the microcontroller 13 from the personal computer C downstream of the 32nd line 9. The instructions may be issued from the personal computer C to the microcontroller 13 during use, or using a full sampling routine executed after downloading. The control board 10 controls the switching of the pump 11 and the valve group 12 and the temperature of the sampling chamber 14. The control board 10 may also support LEDs or LCD panels to indicate the status of the device.

In FIG. 6, during use, a carrier gas such as air (or steam) is drawn from inlet I to outlet O via flow path X via sampling unit 14 and sensor block 1 a. The flow is carried out using a pump 11 and a group of valves 12 with a connecting pipe 16. The valve 12 and the pump 11 are capable of directing a carrier gas or vapor around the system, and the filtered air can be withdrawn through the filter 15 and via a chemical sensor after use for cleaning purposes after cleaning (see FIG. 3). 5)). The wet material of the pump 11, the group of valves 12 and the connecting pipe 16 is chemically inert. The sampling unit 14 includes a temperature controller T.

7a, 7b and 7c are sectional views of exploded compartments of the modular sampling unit of the present invention. FIG. 7a shows a mount 17 to which the base member of the sampling unit is connected by push fit (described below).
The channel 18a partially defines the flow path X of the carrier gas. Correct positioning of the mount 17 with the base member of the sampling unit is aided by the positioning pins 20. Gas sealing between the mount 17 and the base member and separation of the gas inlet and the gas outlet are realized by three O-rings 19.

As shown in FIG. 7B, the base member 21 has positioning pin holes 22 for connecting the positioning pins 20 of the mount 17 into which the sampling base 21 is inserted by being pressed and fitted. A sample (for example, cardboard) is cut into a predetermined size using a template (template) and placed on a base member supported on the inner wall 24a. The channel 18b is aligned with the channel 18a of the mount 17.

FIG. 7c shows the closure member. The closing member 25 is fixed to the base member 21 by the screw 23b on the body portion 54 that is connected to the internal screw 23a on the base member. O
The ring 26 functions as a gas seal between the base member 21 and the closing member 25. The base wall of the closure member 25 comprises an upright portion 24b that engages the top surface of the sample.

Each of the base member 21 and the closure member 25 is manufactured from an inert material and / or from a material that allows the chamber to be disposable or to be cleaned and reused.

FIG. 7 d shows the assembled modular sampling unit of the present invention with the base member 21 inserted into the mount 17 and the closure member 25 screwed into the base member 21. The sample is supported on the inner wall 24a of the base member and the upper surface is sealingly engaged by the upright 24b. The U-tube 56 is shaped to complete a continuous path X for carrier flow across most of the exposed surface area of the sample during assembly. Thus, the carrier gas may be used to effectively sweep the headspace of the sample into the lower dead space.

Example 1 -Demonstration Experiment of "at-line" Analysis Various carton samples of a single manufacturing run were analyzed using an embodiment of the chemical sensing system of the present invention. Sample at different post-production times (14-hour post-production and many intervals in between).
A 50x60 mm rectangle was cut from the board and no further sample preparation was done.

Results The response of a coupled chemical sensor for folding a carton sample in a dual manufacturing run was used to define a qualitative calibration. "Calibration" cartons have been previously proven "in specification" using alternative analytical methods. Various manufactured carton samples were compared to this calibrator.

[Table 1]

Discussion Carton samples coming directly from the press (0 hours / 1-6) show a gradual increase in certainty belonging to the “standard” population. Samples analyzed immediately 0 hours /
1 was rejected from the "standard" population and accepted as belonging to the "standard" population at sample 0 hours / 5 analyzed in the 10-minute post-production. This is mostly due to the rapid loss of residual solvent from the carton.

Conclusion These results exclude the latest 14 hours "air exposure" period and 24 hours incubation period before the carton is analyzed in post-production almost immediately before the carton sample can be checked for quality. In addition, manufacturing can be monitored during implementation, adding additional values to the manufacturer's quality procedures.

Example 2- Detection of Hexanal in Cardboard The presence of hexanal in the raw cardboard is often recognized as a marker of potential quality problems in possible packaging.

Experimental Cardboard packaging samples were analyzed using an embodiment of the chemical sensing system according to the present invention. By HSP, one sample was a "pass" package and the other sample was a "fail". A 50x60 mm rectangle was cut from the package and no other sample preparation was done.

Results The response of a coupled chemical sensor for folding back samples of “pass” packaging was used to define a qualitative calibration. This calibration was used to compare to the "fail" packaging.

Discussion FIG. 8 shows that an embodiment of a chemical sensing system according to the present invention clearly separates low levels (less than 0.8 ppm) contained in cardboard from higher levels (1.6 ppm) of hexanol. be able to. The level of hexanol contained in the cardboard was independently determined using conventional analytical methods. Testing for other contaminants found in cardboard can provide a wide range of reliable quantitative information with embodiments of the chemical sensing system according to the present invention.

Conclusion Embodiments of the chemical sensing system according to the present invention provide a rapid (less than 2 minutes) method for determining effective cardboard hexanal content for both cardboard manufacturers and packaging manufacturers.

Example 3- Experimental Detection of Contaminated Food Contact Cartons "Rotten" food contact carton samples were analyzed using an embodiment of the chemical sensing system according to the present invention. Samples of various cartons in the "Design Specification" were also analyzed using an embodiment of the chemical sensing system according to the invention to calibrate the device. A 50x60 mm rectangle was cut from the package and no other sample preparation was done.

Results The response of the coupled chemical sensor to the “design specification” carton sample was used to define a qualitative calibration. A "dirty" food contact carton was compared to this calibration and the results are shown in Table 2.

[Table 2]

The results of the comparison of the discussion sample with the “standard” calibration are shown as the percent probability of belonging to the “standard” population. The normal 5% risk rate (significance level) was applied as pass / fail. This result identified the "dirty" carton (T) as dirty. This carton (T) was previously analyzed using HSP and "passed". It was later identified as "dirty" by the second HSP. This discrepancy in the results is due to HS
Attention is drawn to the subjective nature of the P method. The "dirty" carton (T) is part 2
It is divided into two component layers and re-analyzed. The results suggested that the source of contamination came from the cardboard (Sample U). The fouling chemicals are either attributed to the cardboard or the result of chemical reactions in the cardboard during manufacturing (probably initiated by UV light). It was confirmed by GC-MS that the results obtained by the embodiment of the chemical sensing system according to the present invention were indeed correct and that it was the cardboard that was the source of contamination.

Conclusion This embodiment of the chemical sensing system according to the invention could be successfully identified by the carton as "dirty" which the human sensor panel cannot detect.

Example 4- Detection of DIPN in food contact cardboard Diisopropylnaphthalene (DIPN) was found in both food contact cardboard and cardboard packaging (wrapping cardboard). It has been demonstrated that DIPN can diffuse into the food products they package. The overall toxicological effects of DIPN are currently unknown, and until the time that the manufacturers of cardboard and cardboard packaging can use more information about the toxicological effects of DIPN, DI in packaging
I have been advised to keep PN levels as low as practical.

Six samples of experimental cardboard were analyzed using an embodiment of the chemical sensing system according to the present invention. A 50x60 mm rectangle was cut from the package and no other sample preparation was done. Embodiments of the chemical sensing system according to the present invention were used in a method that included a 25 second sampling time after a 60 second cleaning cycle.

Results The response of the bound chemosensor to 6 samples (determined by folding) was
Comparisons were made using the qualitative data reduction (reduction) method. The results are shown in Fig. 9.

Embodiments of the chemical sensing system according to the present invention have demonstrated a clear correlation between the response of coupled chemical sensors and the concentration of DIPN in cardboard. The concentration of DIPN was independently verified using conventional analytical methods. For DIPN, the embodiment of the chemical sensing system according to the present invention has a wide dynamic range of about 3 mg / kg.
To more than 70 mg / kg. 4 if the tolerance limit for DIPN is set
It is estimated to be in the mg / kg range. The reproducibility of the obtained measurement is about 5%,
It is comparable to other methods used to determine PN.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an array based chemical sensor assembly of the present invention.

FIG. 2 shows details of individual sensors of the array-based chemical sensor assembly shown in FIG.

FIG. 3 is a side view of an array-based chemical sensor assembly of the present invention.

FIG. 4 is a schematic diagram of a control system for an array-based chemical sensor assembly of the present invention.

FIG. 5 is a schematic diagram of a control system of an embodiment of a modular sampling unit of the present invention.

FIG. 6 is a diagram schematically showing a gas flow through an embodiment of the chemical sensing system of the present invention.

FIG. 7 is an exploded view of the embodiment of the module sampling unit of the present invention, showing (a) mount, (b) base member, and (c) closing member; and (d) assembly of the module sampling unit of the present invention. It is the figure which showed the form.

FIG. 8 is a diagram showing results of a test example of the embodiment of the chemical sensing system of the present invention.

FIG. 9 is a diagram showing a result of a test example of the embodiment of the chemical sensing system of the present invention.

[Explanation of symbols]

  1 Chemical sensor assembly   2 sensors   7 Temperature controller   14 Sampling unit   17 mount   18a channel   21 Base member   24a inner wall   24b upright   25 Closure member   54 Body   56 U type tube

─────────────────────────────────────────────────── ─── Continued front page    (81) Designated countries EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, I T, LU, MC, NL, PT, SE), OA (BF, BJ , CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, K E, LS, MW, MZ, SD, SL, SZ, TZ, UG , ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AG, AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, BZ, C A, CH, CN, CR, CU, CZ, DE, DK, DM , DZ, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL, IN, IS, JP, K E, KG, KP, KR, KZ, LC, LK, LR, LS , LT, LU, LV, MA, MD, MG, MK, MN, MW, MX, MZ, NO, NZ, PL, PT, RO, R U, SD, SE, SG, SI, SK, SL, TJ, TM , TR, TT, TZ, UA, UG, US, UZ, VN, YU, ZA, ZW

Claims (22)

[Claims] 1. A chemical sensing system for analyzing headspace of a sample, comprising a modular sampling unit operably connected to a chemical sensor assembly: (1) said modular sampling unit comprises: an inlet channel and an outlet. A mount having a channel; a base member having a hollow interior defined by one or more interior side walls and a base wall, at least a portion of a connection point of the base wall and one or more interior walls. Is a closure member having a base member having a support collar that supports all or part of the lower surface edge of the sample; one or more outer walls and a base wall defining a body portion. An outer edge of the base wall, the body portion having a shape complementary to the hollow inside of the base member, A closure member having an upright portion capable of engaging the edge of the upper surface of the sample; a base member is inserted into the mount in use, and the body portion of the closure member is a hollow interior of the base member. To define a head space below the lower surface of the sample and a head space above the upper surface of the bubble, whereby the inlet channel communicates with the head space below the lower surface of the sample and the outlet channel Communicate with a headspace above the top surface of the sample, thereby defining a continuous flow path between an inlet channel and an outlet channel over most of the surface area of the sample. The assembly is: one or more chemical sensors, each chemical sensor exhibiting a measurable and characteristic response to a chemical stimulant. One or more chemical sensors having a chemical sensing component capable of; and an inlet end that allows a carrier gas to enter, an outlet end that exhausts the carrier gas, and one or more between them. A solid body having one or more compartments containing each of the chemical sensors, the chemical sensing component of each chemical sensor being between an inlet end and an outlet end of the solid body exposed to a carrier gas. A solid sensing body having one or more compartments in continuous fluid communication to define a continuous flow path. 2. The chemical sensing system of claim 1, wherein the inlet channel is connected to the headspace below the lower surface of the sample by a base conduit in the base wall of the base member. 3. The outlet channel is connected to the headspace above the top surface of the sample by a side conduit in the side wall of the base member.
The chemical sensing system according to any one of 1. 4. The chemical sensing system of claim 3, wherein the headspace above the sample and above the side conduit is in fluid communication by a linear tube radially disposed at the upright of the closure member. 5. The headspace below the lower surface of the sample is in fluid communication with the headspace above the upper surface of the sample via one or more substantially U-shaped tubes. The chemical sensing system according to any one of 1. 6. A first arm of the U-tube is radially deployed in the support collar of the base member and a second arm of the U-tube is radially deployed in the upright portion of the closure member. The chemical sensing system according to claim 5, wherein the first arm and the second arm are connected in fluid communication by a connection portion on a side wall of the base member. 7. The chemical sensing system according to claim 1, wherein the base wall of the base member has a protrusion that supports the lower surface of the sample. 8. The chemical sensing system of claim 7, wherein the protrusion converges on the reduced contact end. 9. The chemical sensing system of claim 1, wherein the body portion of the closure member is threadably engaged within the hollow interior of the base member. 10. The chemical sensing system according to claim 1, wherein the base member is press fitted into the mount. 11. The base member outer wall surface of the base member and the mount comprises a locating arrangement for allowing correct placement and insertion of the base member in the mount. The chemical sensing system described in. 12. A chemical sensing system according to claim 1, wherein each compartment of the solid body is arranged such that the chemical sensing component is exposed to a carrier gas in the form of a wall jet. . 13. The inlet end for admitting the carrier gas and the outlet end for exhausting the carrier gas are connected by a substantially linear conduit.
To the chemical sensing system according to claim 12. 14. The chemical sensing system of claim 13, wherein the substantially linear conduit defines a protrusion that connects each compartment in series. 15. The chemical sensing system of claim 14, wherein each compartment houses a chemical sensing component in a substantially free space. 16. The chemical sensing system according to claim 1, wherein the chemical sensor assembly comprises a plurality of chemical sensors. 17. The chemical sensing system according to claim 1, wherein the chemical sensor is a crystal chemical sensor. 18. A chemical sensor assembly according to any one of claims 1 to 17. 19. A modular sampling unit according to any one of claims 1 to 17. 20. A method for detecting the presence of one or more chemical stimulants in the headspace of a food packaging material using the chemical sensing system according to claim 1. Description: Inserting the base member into the mount; placing the sample of food packaging material inside the hollow of the base member such that the sample is supported on the support collar; closing the body of the closure member into the hollow of the base member. Engaging the interior; sweeping the headspace of the sample with a carrier gas; passing a carrier gas containing one or more chemical stimulants from the headspace to the inlet end of the chemical sensor assembly; Measuring the response of the chemical sensor to a carrier gas containing one or more chemical stimulants from the headspace; Method and a step in correlating or to the presence of two or more chemical irritants. 21. The method of claim 20, wherein the chemical stimulator of interest is DIPN. 22. The method of claim 20, wherein the target chemical stimulant is hexanal.