Sampling equipment

Abstract

A sample probe (10) for adsorptive sampling includes an elongated body (22) having a longitudinal axis defined along its length and a radial axis extending transversely to the longitudinal axis. A sorbent element (24) formed of a sorbent material is secured to the body. The elongated body has an outer surface and a recess (52) positioned along the length of the body, the recess extending radially into the outer surface. The sorbent element is at least partially received within the recess of the body, the recess mechanically locking the sorbent element to the body to prevent relative longitudinal movement of the sorbent element relative to the body.

Description

[0001] The present invention relates to a sampling probe, and in particular to a sampling probe including a sorbent matrix for sorbent sampling of liquids and gases.

[0002] Sampling techniques are often used to identify components within liquids, such as contaminants in drinking water, fragrance allergens in cosmetics, or the flavor profile of beverages. Analysis of these samples can involve liquid-liquid extraction (LLE) or solid-phase extraction (SPE).

[0003] Solid phase extraction can be achieved using polydimethylsiloxane (PDMS). PDMS extraction is based on adsorption, an equilibrium technique based on the partitioning of analytes between silicone and an aqueous phase. An adsorbent material is placed in a liquid sample and absorbs the compound of interest contained therein. The amount of analyte extracted is proportional to its concentration in the sample, thus reaching equilibrium. The amount of analyte extracted also depends on the size of the analyte material and therefore on its maximum absorption volume. Extraction into PDMS can be estimated based on the octanol-water partition coefficient (kO / W) of the analyte. The ratio of PDMS to sample (called the phase ratio) becomes an important factor in analyte recovery. The extraction efficiency depends on the quality of the solid phase.

[0004] PDMS can be used in solid phase microextraction (SPME), a known solid phase extraction sampling technique for extracting organic compounds from a sample. SPME involves the use of a fiber coated with a thin layer of an adsorbent material, such as PDMS, which forms the extraction phase. The adsorbent material can be a solid adsorbent selected for extracting different types of analytes from a range of sample media, including both liquid and gas phases. SPME has been widely used because it is easily automated.

[0005] The adsorbent-coated fiber is sized to fit within the body of a needle used to pierce a sample vial. Once the needle has been inserted into the vial, the fiber is extended beyond the needle and introduced into the sample matrix. The needle is then removed and the sample retained on the fiber is subsequently desorbed for analysis in a gas chromatograph.

[0006] However, the necessity of fitting within a needle limits SPME to very thin PDMS layers (approximately 7-100 cm). Consequently, the total volume of compound recovered is limited, typically to approximately 0.5 CL, with a K₂ / W value below 1000 (log K₂ / W 3). Thus, a disadvantage of SPME is the limitation on the amount of adsorbent that can be loaded onto the fiber.

[0007] In order to address the low capacity limitations of SPME sampling, higher capacity adsorptive extraction samplers have been developed. This high capacity sampler includes a metal probe with a sleeve (cannula) of PDMS material, which is provided around the probe, which is significantly larger than the probe used in SPME. The large size of the sleeve and its exposed position on the outer surface of the probe have made this probe susceptible to wear and damage. In use, the probe is typically inserted into a sample container with a septum seal, and the probe is required to pierce the septum and / or penetrate the septum in a tight fit. The frictional engagement between the sample probe and the septum seal can cause damage to the adsorbent material and remove material from the surface. It is also necessary to constantly replace or maintain the probe, which can also cause the sampling process to be impaired.

[0008] It would therefore be desirable to provide an improved sampling probe for sorbent sampling that addresses the above-mentioned problems and / or generally provides improvements.

[0009] According to the present invention, there is provided a sampling device and a sampling method as described in the accompanying claims.

[0010] In one embodiment of the invention, a sampling probe for adsorptive sampling is provided, comprising an elongated body having a longitudinal axis defined along its length and a radial axis extending transversely to the longitudinal axis. An adsorbent element formed of an adsorbent material is fixed to the body. The elongated body has an outer surface and a recess positioned along the length of the body, the recess extending radially into the outer surface. The adsorbent element is at least partially received within the recess of the body. Positioning at least a portion of the adsorbent element within the radial recess mechanically locks the adsorbent element to the body to prevent relative longitudinal movement of the adsorbent element relative to the body. This advantageously avoids the need to rely solely on chemical bonding to fix the adsorbent element to the body (which has been found difficult to achieve) and ensures that the adsorbent element cannot be dragged away from the body by a diaphragm or other means during use. The term "adsorbent" refers to any substance that has the property of collecting molecules of another substance by sorption. The term sorption includes both absorption and adsorption.

[0011] Preferably, the sorbent element is received within the recess such that the sorbent material does not extend radially beyond the recess. This ensures that the sorbent element is flush with or recessed below the outer surface, which prevents the sealing element from contacting the sorbent material during insertion and / or retraction of the probe from the sample container.

[0012] The body of the sampling probe may include a shaft and a first portion and a second portion having a larger diameter than the shaft at either end. The adsorbent element is a sleeve received around the shaft. The term "sleeve" generally refers to a layer of adsorbent material surrounding the shaft. The sleeve may be a separate component that can be inserted onto the shaft. Alternatively, the sleeve may be a layer of material deposited on or otherwise formed on and / or bonded to the shaft.

[0013] The enlarged diameter section has opposing inner ends that face the shaft in a longitudinal direction. Each inner face includes a longitudinally extending recess that is arranged to receive an end of an adsorbent sleeve such that the sleeve is constrained both radially and longitudinally by the enlarged diameter section. The stepped diameter between the shaft and the enlarged diameter section defines a recess in which the adsorbent element is housed.

[0014] The recess of each enlarged diameter section includes an inner wall and an outer wall in the radial direction, and the end of the sleeve is located between the inner wall and the outer wall of each recess, thereby radially constraining the sleeve at both ends.

[0015] Preferably, the sleeve is longitudinally clamped between the first and second enlarged diameter sections.

[0016] The sleeve preferably has an outer diameter that is equal to or smaller than the diameter of the enlarged diameter section. In this way, the outer surface of the sleeve is positioned flush with the outer surface of the enlarged diameter section or recessed radially inwardly, which protects the sleeve.

[0017] The recesses of the enlarged diameter section are preferably annular, so that they receive the ends of the sleeve around their entire circumference.

[0018] Each longitudinally extending recess of the expanded diameter section tapers radially inwardly away from an inner face of the expanded diameter section in the longitudinal direction. The tapering of the recess provides for radial constriction of the end portion of the sleeve between the radially inner and outer walls of the recess, thereby clamping the end portion and forming a seal between the expanded diameter section and the sleeve. The sealing of the sleeve at either end advantageously prevents liquid from entering the sleeve between the sleeve and the shaft, which could cause a sample to carry over into the next sample and thereby affect the results.

[0019] Preferably, the inner wall of the recess has a diameter that is continuous with the diameter of the shaft so that the shaft can be received in the bore of the sleeve.The outer wall tapers radially inwardly towards the inner wall in the longitudinal direction to a base of the recess.

[0020] Preferably, at least one of the enlarged diameter end sections is releasably connectable to the shaft.

[0021] Preferably, one of the expanded diameter end sections is secured to the shaft via a threaded connection. The end section includes a threaded bore, and the end of the shaft includes a threaded connector section having mating threads on its radially outer surface. The threaded connection allows the shaft to be disconnected from one of the expanded diameter end sections. This enables the sleeve to be inserted onto the shaft before the shaft is reconnected to the expanded diameter end section.

[0022] The sleeve's length is selected to correspond to the length of the shaft and the two recesses of the end section, excluding the length of the threaded connector section. When the shaft is screwed back into the end section, the sleeve is longitudinally received within the recesses. As the threaded connection continues, the end sections move toward each other, and the sleeve's end is clamped longitudinally between the two end sections and radially between the inner and outer walls of the recesses.

[0023] The first enlarged diameter end section preferably includes a tapered tip at its outer, distal end to assist in inserting the probe into the sample container.The first enlarged diameter end section and the shaft are preferably integrally formed as a unitary component.

[0024] The second enlarged diameter end section includes a connecting portion at a distal end thereof, the distal end being the opposite end to the inner face, the connecting portion being configured to allow the probe to be connected by an actuator, such as a robotic arm, or for manual use.

[0025] In another embodiment of the invention, the elongated body preferably includes at least one channel formed in a surface thereof, the channel defining the recess. The adsorbent material is disposed within the channel such that an outer surface of the adsorbent material is exposed. The adsorbent material may be molded, adhered, or secured into the channel by any suitable means.

[0026] The body of the sample probe has an outer surface, and the sorbent material is preferably recessed within the body such that an exposed outer surface of the sorbent material does not extend radially outward beyond the outer surface of the body. The sorbent material is maintained flush with or recessed below the outer surface of the probe to prevent significant contact with the sorbent material.

[0027] The body may comprise at least two longitudinally extending channels, the channels being arranged on radially opposite sides of the body, each channel containing adsorbent material.

[0028] The channels are preferably longitudinally extending and longitudinally aligned.

[0029] The body of the probe may comprise a tip section and a stem section which are detachably connected and the adsorbent material is provided on the tip section. This enables the adsorbent material to be periodically replaced by replacing the tip section without requiring replacement of the entire probe.

[0030] The distal end of the tip segment can have a first diameter, and the proximal end can have a second diameter that is preferably larger than the first diameter. The tapered segment interconnects the first and second diameter segments, with the adsorbent material located on the first diameter segment. Thus, most of the force required to penetrate and seal the septum is borne by the wider diameter segment, limiting shear forces on the tip segment.

[0031] The shaft may include a further recess arranged to receive an identification element carrying a barcode or other indicia. The recess includes an area of ​​reduced diameter which ensures that the indicia, which is preferably an adhesive strip affixed around the circumference of the shaft, does not extend through the outer surface of the shaft, preventing the strip from being damaged or removed in use.

[0032] The present invention will now be described, by way of example only, with reference to the following illustrative drawings, in which:

[0033] Figure 1 shows a sampling probe according to an embodiment of the invention;

[0034] Figure 2 Shown Figure 1 A cross-sectional view of a sampling probe;

[0035] Figure 3 shows a cross-sectional view of a sampling probe according to another embodiment of the invention; and

[0036] Figure 4 yes Figure 3 Magnified view of the lower section of the probe.

[0037] Reference Figure 1 , the sampling probe 10 includes a rod 18 having an upper rod section 20 and a lower rod section 22. The upper rod section 20 is cylindrical and includes a connector portion 26 at its upper end 24, which has a larger diameter than the main axis of the upper rod section 20. The connector portion 26 includes a circumferentially extending chamfered engagement channel 28 of reduced diameter that is configured to receive a corresponding latch element of the z-axis actuator of the robotic arm. The latch element can be a spring-loaded ball lock or any other suitable element that is configured to extend into the channel 28 and engage the channel to vertically hold the probe 10.

[0038] The upper stem section 20 includes a locking section 31. The locking section 31 includes a radially extending shoulder section 36 having a larger diameter than the main body of the upper stem section 20. The shoulder 36 is configured to receive a latch plate or similar locking element. In use, the latch plate is arranged so that when the probe 10 is received in a position where it is desired to vertically lock the probe 10 in place, the latch plate is vertically aligned such that the lower surface of the latch plate is vertically aligned with the upper surface of the shoulder 36.

[0039] The probe 10 can be received in the latch plate through the aperture. The latch plate can slide horizontally to a locked position in which at least a portion of the plate is positioned above the shoulder 36. When the latch plate is in the locked position, the probe 10 is prevented from being removed vertically by engaging the shoulder 36 with the latch plate.

[0040] like Figure 2As shown, the upper stem segment 20 includes an internal passage 39 that includes internal threads 40 at the base end. The lower stem segment 22 includes a corresponding threaded portion 42 that engages the threaded portion 40 of the upper stem segment 20 to connect the lower stem segment 22 to the upper stem segment 20. The upper end 44 of the lower stem segment 22 has a diameter that corresponds to the diameter of the upper stem segment 20. The diameter of the lower stem segment 22 decreases along its length at a tapered section 46 to a reduced diameter lower end 48. At its distal end, the lower stem segment 22 includes a protruding tip 50 for providing a tapered leading edge to facilitate insertion through the orifice of the septum of a sample container.

[0041] The reduced diameter of lower section 48 allows for easy initial insertion of probe 10 through the septum. The diameter of lower section 48 is selected so that, during use, it slides relatively easily through the opening of the septum, with some seal between the edge of the opening and lower section 48. As probe 10 is further inserted, the tapering section 46 reaches the septum. The expanded diameter of tapering section 46 allows for a transition to a larger diameter section 44, which forms a positive seal with the septum as probe 10 is further inserted. This enables probe 10 to seal against sample container 2 in a very simple manner, without requiring more complex additional seal arrangements on the sample container and / or probe 10. The larger diameter section 44 can also be used to seal probe 10 within a probe reservoir and within an oven by engaging the larger diameter section 44 with an O-ring seal or similar sealing arrangement.

[0042] The lower shaft section 22 includes a pair of longitudinally aligned and diametrically opposed grooved adsorbent channels 52. The adsorbent channels 52 extend longitudinally and are recessed radially inwardly into the body of the lower shaft section 22. The adsorbent channels 52 are of equal length and have a first lower end that is longitudinally inwardly spaced from the tapered protruding tip 50. The upper end of each channel 2 is longitudinally downwardly spaced from the tapered section 46. The adsorbent channels 52 contain an adsorbent material 54 suitable for performing adsorptive sampling. Preferably, the adsorbent material 54 is polydimethylsiloxane (PDMS), but other materials detailed in the claims are foreseeable. The dimensions of each channel 52, including length, depth, and width, are selected to define the volume of adsorbent material 54 contained therein.

[0043] The adsorbent material 54 is preferably injected into the channels 52 in a liquid state, wherein the channels 52 are filled with a set volume of the adsorbent material 54, which is molded to the form of the channels 52. The adsorbent material 54 is arranged within the channels 52, wherein the outer surface of the adsorbent material 54 is flush with the outer edge 56 of each channel 52. In this way, the surface of the adsorbent material 54 is flush with the surface of the rod 22 or slightly recessed therein. In this way, the surface of the adsorbent material 54 is protected from wear when the lower rod section 22 is inserted through the septum of the sampling container 2 and when it is retracted therefrom. Alternatively, the adsorbent material can be applied to the outer surface in a cylindrical manner, similar to the prior art, but with a greater surface thickness and, therefore, a greater material volume, which greatly improves sampling performance.

[0044] Because the lower stem section 22 is detachable from the stem 20 , if there is any degradation in the integrity of the sorbent material 54 over time, the lower stem section 22 can be replaced without replacing the entire probe 10 .

[0045] The upper stem section 20 includes a recess 30 for bar coding by printing, engraving or other means. The recessed bar code minimizes wear on the bar code during use.

[0046] exist Figure 3 In the illustrated alternative embodiment, the sampling probe 60 includes an upper rod section 20 and a lower rod section 64. The upper rod section 20 is configured identically to the upper rod section 20 described above. The lower rod section 64 includes a threaded portion 66 that engages with the corresponding threaded portion 40 of the upper rod section 20 to connect the lower rod section 64 to the upper rod section 20. An upper end 70 of the lower rod section 64 has a diameter that corresponds to the diameter of the upper rod section 20. The diameter of the lower rod section 64 decreases along its length at a tapered section 72 to a reduced diameter lower end 74.

[0047] The lower end 74 includes a detachable tip section 76. The tip section 76 includes a shaft 78 and a tip 80 that tapers at its distal end. A sleeve 82 is provided that is formed of an adsorbent material. Figure 4 As shown, sleeve 82 is substantially cylindrical having a wall section 84 with a bore 86 extending therethrough. Bore 84 has a diameter substantially equal to the diameter of shaft section 76. Thus, sleeve 82 is configured to fit and receive shaft 78 with a close tolerance fit such that substantially no gap exists between the inner surface of bore 84 and the outer surface of shaft 78.

[0048] Tip 80 tapers to a point at its distal end to provide a tapered leading edge to aid insertion through the orifice of the septum of a sample container. At inner end 88, tip 80 includes an annular recess 90 extending longitudinally toward the distal end. Recess 90 has an inner wall 92 that abuts the outer wall of shaft 78, and an outer wall 94. At the opening of recess 90, outer wall 94 is radially spaced outward from inner wall 92. Outer wall 94 is angled radially inward toward the base of recess 90, such that recess 90 tapers to the base where outer wall 94 meets inner wall 92.

Claims

1. A sample probe for adsorptive sampling, comprising: an elongated body having a longitudinal axis defined along its length and a radial axis extending transverse to the longitudinal axis, the elongated body having an outer surface having a shaft section having a first outer diameter and a second reduced diameter shaft section having a smaller outer diameter than the first outer diameter, the reduced diameter shaft section defining a recess along the length of the body, the recess extending radially inwardly of the outer surface, the recess being longitudinally positioned between a first expanded diameter section and a second expanded diameter section, the first expanded diameter section and the second expanded diameter section being positioned at first and second ends of the recess, respectively; and a sleeve formed of an adsorbent material; wherein the sleeve is disposed about the outer surface of the elongated body and is received within the recess defined by the reduced diameter shaft section.

2. The sample probe according to claim 1, wherein The sleeve is received within the recess, and the recess and sleeve are configured such that the sleeve does not extend radially out of the recess.

3. The sample probe according to claim 1 or 2, wherein: The first and second enlarged diameter sections have outer diameters defining the first outer diameter. The sample probe according to claim 3 , wherein: The first and second expanded diameter sections have inner ends, the inner ends of the first and second expanded diameter sections are opposite to each other, the inner end of the first expanded diameter section has a first inner surface and the inner end of the second expanded diameter section has a second inner surface, the first and second inner surfaces face the reduced diameter shaft section in a longitudinal direction, the first inner surface includes a first recess extending longitudinally into the first inner surface and the second inner surface includes a second recess extending longitudinally into the second inner surface, the first and second recesses are arranged to receive the ends of the sleeve so that when the ends of the sleeve are received in the first and second recesses, the ends of the sleeve are radially and longitudinally constrained. The sample probe according to claim 4 , wherein: Each inner facing recess includes an inner wall and an outer wall, and the end of the sleeve is positioned between the inner and outer walls of the corresponding inner facing recess. The sample probe according to claim 1 or 2, wherein: The sleeve is longitudinally sandwiched between the first and second enlarged diameter sections.

7. The sample probe according to claim 1 or 2, wherein: The sleeve has an outer diameter that is equal to or smaller than the first outer diameter.

8. The sample probe according to claim 4, wherein The first and second recesses are annular and have an outer diameter and the outer diameter of the sleeve is substantially equal to the outer diameter of the first and second recesses, and the ends of the sleeve are received in the respective first and second recesses around their entire circumferences.

9. The sample probe according to claim 8, wherein The annular first and second recesses each have an opening and a base and taper radially inwardly away from the opening in a longitudinal direction to the base to clamp and seal with the sleeve.

10. The sample probe according to claim 1 or 2, wherein At least one of the first and second expanded diameter sections is releasably connected to the reduced diameter shaft section. The sample probe according to claim 10 , wherein: One of the first and second enlarged diameter sections is secured to the reduced diameter shaft section by a threaded connection, the first and second enlarged diameter sections comprising threaded holes and respective ends of the reduced diameter shaft section comprising respective threaded connector sections.

12. The sample probe according to claim 11, wherein The length of the sleeve is selected so that when one of the first and second expanded diameter sections is threadedly connected to the reduced diameter shaft section, the sleeve is longitudinally clamped by the first and second expanded diameter sections at either end of the reduced diameter shaft section.

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