Flow control device

Abstract

To provide a flow control device for delivering an aerosolized sample in an inductively coupled plasma (ICP) analysis system.SOLUTION: A device includes a main body which at least partially defines a sample flow separation region, and the sample flow separation region has a longitudinal flow direction and has an upstream end through which an aerosolized sample enters and a downstream end through which the modified aerosolized sample exits. The main body further includes an injection duct having an opening proximate to the sample flow separation region, and the injection duct is configured to direct a stream of gas in an injection direction to the sample flow separation region. The injection direction is angled with respect to the longitudinal flow direction such that a vortex flow is generated within the sample flow separation region upon introduction of the gas stream through the opening, and the vortex flow has a direction opposite to the flow direction of the aerosolized sample to control the size of droplets inside the modified aerosolized sample.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001]

[0001] The present invention relates to a flow control device, and more particularly to a droplet separation device for use in an inductively coupled plasma (ICP) analysis system for performing mass spectrometry (MS) or optical emission spectroscopy (OES).

Background Art

[0002]

[0002] In inductively coupled plasma mass spectrometry (ICP-MS) or inductively coupled plasma optical emission spectroscopy (ICP-OES), when using current radio frequency generator designs, argon plasmas generally have an aerosol loading rate of about 20 to 50 μL / min and are resistant to droplets with a size of less than about 10 μm before the plasma becomes unstable or completely extinguishes. In the sample introduction stage of an ICP-MS or ICP-OES system, a spray chamber is often used, and the transfer efficiency is typically less than 5%, i.e., less than 5% of the sample aerosol is transferred to the plasma. Thus, the typical uptake rate of liquid samples is in the range of 300 μL / min to 1000 μL / min. The spray chamber can also separate larger droplets created in the spraying process, and the efficiency of such separation depends on the specific spray chamber design. This is relevant for samples of both aqueous and organic bases.

[0003]

[0003] Generally, it is desirable to separate larger droplets from the aerosolized stream, thus enabling smoother introduction of the sample into the plasma by providing more consistent droplet sizes and more uniform mixing of the spray sample. It should also be noted that ICP-MS systems using an interface cone with a small (between 250 and 1000 μm in diameter) machined orifice between the plasma and the mass spectrometer to support the strong vacuum in the mass spectrometer chamber can tend to block when samples containing high (greater than 0.1% wt / wt) total dissolved solids are sprayed.

[0004]

[0004] A spray chamber may provide only specific performance characteristics to adjust transfer efficiency and droplet size rejection based on the specific design of the spray chamber system. In situations where the complexity of the sample matrix or sensitivity requirements vary, multiple spray chamber designs may be required, or significant compromises in analytical performance, such as short-term precision, matrix effects, spectral interference, and long-term stability, should be expected. In light of this, spray chamber systems used in ICP-MS and ICP-OES include single-pass spray chambers, double-pass spray chambers, and cyclone spray chambers.

[0005]

[0005] An example of a prior art spray chamber is disclosed in U.S. Patent Application No. 2017 / 0338092A1. This disclosure primarily relates to reducing droplet deposition on the surface of one or more parts of a spray chamber assembly. This reduction can be achieved by injecting a tangential flow of compositional gas into the spray chamber through an inlet formed within the spray chamber. This gas flow, combined with a microchannel structure arrangement formed within the spray chamber, can help protect the chamber and the surface of internal tubes disposed within the chamber from droplet formation.

[0006]

[0006] The present invention seeks to address at least partially one or more drawbacks of the prior art, or to provide an alternative method.

[0007]

[0007] Any reference to prior art in this specification is not an affirmation or suggestion that the prior art forms part of the common general knowledge in any jurisdiction, or that a person skilled in the art would reasonably expect to understand, consider the prior art relevant, and / or combine it with other prior art. [Overview of the project]

[0008]

[0008] In a first embodiment, the present invention provides a flow control device for aerosolized sample delivery in an inductively coupled plasma (ICP) analysis system, the device is A body that at least partially defines a sample flow separation region, the sample flow separation region having a longitudinal flow direction and comprising a body having an upstream end through which the aerosolized sample enters and a downstream end through which the modified aerosolized sample exits, The main body includes an injection duct having an opening adjacent to a sample flow separation region, the injection duct is configured to guide a stream of gas in the injection direction into the sample flow separation region, the injection direction is angled with respect to the longitudinal flow direction so that a vortex flow is generated within the sample flow separation region upon introduction of the gas stream through the opening, and the vortex flow is oriented opposite to the direction of the aerosolized sample flow to provide control over droplet size within the modified aerosolized sample.

[0009]

[0009] Advantageously, the flow control device of the present invention can have the effect of reducing the proportion of large droplets contained in the modified aerosolized sample compared to what would otherwise be achieved by the flow toward the plasma. The present invention achieves this effect by slowing down or preventing the passage of larger droplets in the aerosolized sample flow, while allowing smaller droplets in the modified aerosolized sample flow to pass through. The larger droplets can then be removed from the sample flow. This removal of larger droplets is facilitated by inducing vortices in the opposite direction to the flow of the aerosolized sample, and the larger droplets are guided away from the separation region (e.g., toward the drain) to prevent or reduce the restriction or fluctuation of the aerosolized flow passing through the device.

[0010]

[0010] According to the present invention, the modified aerosolized sample flow moving toward the plasma has a relatively increased proportion of smaller droplets, enabling smoother introduction of the sample into the plasma and more uniform mixing of the aerosolized sample reaching the plasma. The flow control device may also have a pulverizing effect (i.e., a secondary spray effect) on larger droplets contained in the aerosolized sample flow, resulting in a modified aerosolized sample flow that again has a higher proportion of smaller droplets than in other cases.

[0011]

[0011] Therefore, the present invention can provide better control over the composition of the aerosolized sample and the amount of sample that travels beyond the separation region (and thus directly affect the issues of transport efficiency and matrix effects). Varying the flow rate (and / or other properties) of the gas stream into the sample flow separation region has the effect of varying the proportion of larger droplets that travel through the modified aerosolized sample and the amount of aerosolized sample that travels through the modified aerosolized sample. Thus, the flow control device can effectively provide an aerosol filtration function.

[0012]

[0012] The present invention is particularly suitable for use in inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma emission spectroscopy (ICP-OES). However, it will be understood that the present invention may be suitable for use in other applications, in particular in analytical systems where flow control is available.

[0013]

[0013] In one embodiment, the device is configured to be positioned between the atomizer and the plasma in an ICP analysis system. Preferably, the device is configured to be positioned between the spray chamber and the plasma in an ICP analysis system. In one embodiment, the device is configured to receive the primary aerosolized sample flow from the spray chamber in order to generate a secondary aerosolized sample flow (i.e., a modified aerosolized sample flow).

[0014]

[0014] In one embodiment, the injection direction is substantially offset from the radial direction of the sample flow separation region, and the degree of offset determines the characteristics of the vortex flow.

[0015]

[0015] Preferably, the injection direction is substantially tangential to the sample flow separation region. Therefore, in the case of a tubular body, for example, the injection duct is positioned tangential to, or near tangential to, the arc of the inner diameter of the body.

[0016]

[0016] Preferably, the injection direction component is located upstream of the sample flow, thereby generating a vortex flow (i.e., upstream) that has a direction opposite to the flow of the aerosolized sample.

[0017]

[0017] In a preferred form, the injection duct generates a gas jet flow into the sample flow separation region. In one embodiment, the injection duct has a shortened diameter portion near the opening, thereby accelerating the stream of gas into the gas jet flow. The generated gas jet flow may be configured to further spray larger droplets in the aerosolized sample flow into smaller droplets. The generated gas jet flow may be configured to slow down the progress of larger droplets in the aerosolized sample flow or prevent them from passing through. Preferably, the generated gas jet flow is configured to further spray larger droplets in the aerosolized sample flow into smaller droplets, and to slow down the progress of larger droplets in the aerosolized sample flow or prevent them from passing through. The diameter of the shortened diameter portion may be between 0.1 mm and 0.5 mm. The injection duct may be configured to generate a gas jet flow within the sample flow separation region having a velocity of about 4 m / s to about 320 m / s, or about 4 m / s to about 300 m / s, or about 10 m / s to about 20 m / s to about 240 m / s, or about 10 m / s to about 150 m / s. Preferably, the injection duct may be configured to generate a gas jet flow within the sample flow separation region having a velocity of about 4 m / s to about 265 m / s, or about 17 m / s to about 265 m / s, or about 26 m / s to about 66 m / s.

[0018]

[0018] In one embodiment, the injection duct is angled between about 70° and about 88° with respect to the longitudinal flow direction, preferably between about 75° and about 85°, for example, about 80°.

[0019]

[0019] In one embodiment, the flow control device is a single unit adapted for installation between the atomizer and the plasma (e.g., between the spray chamber and the torch) in an ICP-MS or ICP-OES. In this form, the flow control device can be installed in an existing ICP-MS or ICP-OES instrument to assist in controlling the aerosolized sample flow. In one embodiment, the flow control device is part of the ICP-MS or ICP-OES instrument and is incorporated, for example, into other parts of the instrument.

[0020]

[0020] Preferably, the flow control device is generally elongated in shape. In one embodiment, the body is substantially tubular. In one embodiment, the flow control device includes a downstream portion, an upstream portion, and an intermediate portion between them. The intermediate portion may provide at least partially a sample flow separation region.

[0021]

[0021] The upstream portion may be adapted to connect to the upstream components of an ICP-MS or ICP-OES instrument. For example, the upstream portion may include threading (internal or external) to enable or facilitate connection to the upstream components. Alternatively, the upstream portion may be configured to press-fit for engagement with the upstream components. In one embodiment, the upstream portion may be provided in the form of a ball joint adapted to connect to a socket in the upstream components. The downstream portion may be adapted to connect to the downstream components of an ICP-MS or ICP-OES instrument. For example, the downstream portion may include threading (internal or external) to enable or facilitate connection to the downstream components. Alternatively, the downstream portion may be configured to press-fit for engagement with the downstream components. In one embodiment, the downstream portion may be provided in the form of a ball joint adapted to connect to a socket in the downstream components. Preferably, a fluid (i.e., gas and liquid) seal is established between the flow control device and the respective upstream and downstream components.

[0022]

[0022] The upstream portion can be adapted to connect directly or indirectly to the outlet of an ICP-MS or ICP-OES spray chamber. The spray chamber can be any form known in the art, such as a cyclone spray chamber, a single-pass spray chamber, or a double-pass spray chamber. Thus, in such embodiments, it will be understood that the flow control device has the effect of providing a secondary droplet size separation stage. In this configuration, the aerosolized sample generated by the sprayer is first subjected to a first droplet size separation stage by the spray chamber, and then the resulting stream is subjected to a second droplet size separation stage by the flow control device of the present invention, thereby generating a modified aerosolized stream.

[0023]

[0023] The downstream portion can be adapted to connect to the inlet of an ICP-MS or ICP-OES torch. The torch then receives the modified aerosolized sample.

[0024]

[0024] In one embodiment, the intermediate portion includes a collar portion that projects radially outward, and the injection duct extends through the collar. Preferably, the injection duct extends through the sidewall of the collar portion. The collar portion is preferably generally annular in shape with truncated sides, which form the sidewall through which the injection duct extends. The truncated sides preferably have angled planar facets, and the injection duct extends substantially perpendicular to these planar facets.

[0025] Preferably, the flow control device is configured to be substantially vertically oriented with an upward sample flow direction during use within an ICP-MS or ICP-OES system. In such a configuration, larger droplets that are retarded or removed by the generated vortex flow are induced upstream, assisted by gravity, towards a drain, such as the drain tube of an ICP-MS or ICP-OES spray chamber. In an alternative embodiment, the flow control device is configured to be generally substantially horizontally oriented during use within an ICP-MS or ICP-OES system. In such embodiments, the flow control device may have a dedicated drain for removing larger droplets that are retarded or removed by the generated vortex flow.

[0026]

[0026] Control of the composition of the aerosolized sample flow can also be achieved by varying the dimensions of the injection duct or aperture. Thus, for a given flow rate of a gas stream, an optimal aperture size can be determined, or alternatively, for a given aperture size, an optimal flow rate of the gas stream can be determined. Accordingly, the present invention can provide better control of the composition of the aerosolized sample flow. Varying the flow rate (and / or other characteristics) of the gas stream into the sample flow separation region has the effect of varying the proportion of larger droplets traveling within the modified aerosol stream.

[0027] In view of the above, in at least one embodiment, based on the sample to be analyzed by an ICP-MS or ICP-OES system, the flow rate of the gas stream and / or the dimensions of the injection duct or aperture can be selected. For example, a flow control device of the present invention having a desired injection duct dimension or aperture size can be selected from a kit of similar flow control devices having different injection duct or aperture dimensions. Alternatively, the aperture of the flow control device can be configured to have a variable size, thereby enabling selective adjustment of the aperture size. In a further alternative embodiment, the flow control device is provided with a plurality of injection ducts each having a different dimension or aperture size, and the unused apertures can be closed.

[0028]

[0028] Preferably, the modified aerosolized sample flow will comprise droplets that are substantially smaller than about 5-6 μm. For example, about 50 to 90% of the modified aerosolized sample flow will comprise droplets smaller than 5 μm.

[0029]

[0029] In a second aspect, the present invention provides an inductively coupled plasma (ICP) analysis system, the ICP system comprising the flow control device of the first aspect of the present invention.

[0030]

[0030] The ICP system can be an inductively coupled plasma mass spectrometry system (ICP-MS) or an inductively coupled plasma optical emission spectrometry system (ICP-OES).

[0031]

[0031] In one embodiment, the system includes a gas source configured to provide a gas stream to a sample flow separation region. The gas stream can be argon gas. Other suitable gases include helium, nitrogen, oxygen, and other organic and / or inert gases. In some cases, it may be advantageous to use oxygen in reducing the accumulation of carbon on the devices or other components of the ICP system.

[0032]

[0032] Preferably, the system includes a control unit configured to adjust the flow rate of the gas stream from the gas source.

[0033]

[0033] It will be understood that the features disclosed in relation to the first aspect of the present invention are also applicable to the aforementioned second aspect of the present invention, which includes different combinations of the disclosed features.

[0034]

[0034] In a third aspect, the present invention provides a mass spectrometry or spectroscopic system including a flow control device according to the first aspect of the present invention.

[0035]

[0035] It will be understood that the features disclosed in relation to the first and second aspects of the present invention are also applicable to the aforementioned third aspect of the present invention, which includes different combinations of the disclosed features.

[0036]

[0036] In a fourth aspect, the present invention provides a method for removing larger droplets from an aerosolized sample in an analytical system (such as an inductively coupled plasma (ICP) system), the method being: To provide an aerosolized sample flow in a sample flow separation region having a vertical flow direction. To provide droplet size control so that the modified aerosolized sample leaves the sample flow separation region, a gas jet flow is introduced into the sample flow separation region to form a vortex flow having a direction opposite to that of the aerosolized sample flow. Includes.

[0037]

[0037] In one embodiment, the method further includes generating an aerosolized sample flow by passing the sample through a sprayer.

[0038]

[0038] Preferably, the aerosolized sample flow provided to the sample flow separation region is received from the outlet of the spray chamber of the ICP system.

[0039]

[0039] Preferably, the method further includes subjecting the aerosolized sample flow to a droplet separation process before providing the aerosolized sample flow to the sample flow separation area. The droplet separation process is preferably carried out in a spray chamber.

[0040]

[0040] In one embodiment, the method further includes spraying an aerosolized sample flow in a sample flow separation region using a gas jet flow.

[0041]

[0041] In one embodiment, the method further includes transporting the modified aerosolized sample to an ICP torch.

[0042]

[0042] In one embodiment, the method is used in inductively coupled plasma mass spectrometry (ICP-MS). In a different embodiment, the method is used in inductively coupled plasma emission spectroscopy (ICP-OES).

[0043]

[0043] It will be understood that the features disclosed in relation to the first, second, and third aspects of the present invention are also applicable to the aforementioned fourth aspect of the present invention, which includes different combinations of the disclosed features.

[0044]

[0044] In a fifth aspect, the present invention provides a method for preparing an analytical system (such as an inductively coupled plasma (ICP) system) for removing larger droplets from an aerosolized sample, the method being: The method includes installing a flow control device of the first embodiment within the analytical system between a spray chamber and an ICP torch, wherein the flow control device is configured to receive an aerosolized sample flow from the spray chamber located upstream of the flow control device, and the flow control device is configured to release the modified aerosolized sample toward the ICP torch from the downstream portion of the flow control device.

[0045]

[0045] It will be understood that the features disclosed in relation to the first, second, third, and fourth aspects of the present invention are also applicable to the aforementioned fifth aspect of the present invention, which includes different combinations of the disclosed features.

[0046]

[0046] Further aspects of the present invention and further embodiments of the aspects described in the preceding paragraphs will become apparent from the following description, which is given as an example and with reference to the accompanying drawings. [Brief explanation of the drawing]

[0047] [Figure 1]

[0047] This is a perspective view showing a droplet separation device according to one embodiment of the present invention. [Figure 2]

[0048] Figure 1 is a front view showing the droplet separation device. [Figure 3]

[0049] This is a top view of the droplet separation device shown in Figure 1, with dashed lines indicating the hidden internal geometry. [Figure 4]

[0050] This is a cross-sectional view of the droplet separation device along line BB in Figure 3. [Figure 5]

[0051] Figure 4 is a cross-sectional view showing the droplet separation device, indicating the location of the O-ring positioned around the droplet separation device. [Figure 6]

[0052] This is a cross-sectional view of the droplet separation device, taken along line AA in Figure 3. [Figure 7]

[0053] This figure shows the computational fluid dynamics model of the droplet separation device shown in Figure 1 when used in an ICP-MS system. [Figure 8]

[0054] This is a side cross-sectional view showing the droplet separation device of Figure 1 when employed in an ICP-MS system having an aerosolized stream moving through the ICP-MS system. [Figure 9]

[0055] Figure 1 shows the results of various tests performed using the droplet separation device, where the graph shows the percentage of droplets with a diameter of less than 5 μm in the modified aerosolized stream (after passing through the droplet separation device) relative to the flow rate of the gas stream through the droplet separation device, for a given opening size of the droplet separation device. [Figure 10]

[0055] The figure shows the results of various tests performed using the droplet separation device of Figure 1, where the graph shows the percentage of droplets with a diameter of less than 5 μm in the modified aerosolized stream (after passing through the droplet separation device) relative to the flow rate of the gas stream through the droplet separation device, for a given opening size of the droplet separation device. [Figure 11]

[0055] The figure shows the results of various tests performed using the droplet separation device of Figure 1, where the graph shows the percentage of droplets with a diameter of less than 5 μm in the modified aerosolized stream (after passing through the droplet separation device) relative to the flow rate of the gas stream through the droplet separation device, for a given opening size of the droplet separation device. [Figure 12]

[0055] The figure shows the results of various tests performed using the droplet separation device of Figure 1, where the graph shows the percentage of droplets with a diameter of less than 5 μm in the modified aerosolized stream (after passing through the droplet separation device) relative to the flow rate of the gas stream through the droplet separation device, for a given opening size of the droplet separation device. [Figure 13]

[0056] Figure 1 shows the results of various tests performed using the droplet separation device, where the bars on the left of the graph represent the percentage of droplets with a diameter between 0.5 μm and 5 μm in the modified aerosolized stream (after passing through the droplet separation device) relative to the flow rate of the gas stream through the droplet separation device, and the bars on the right of the graph represent the percentage of droplets with a diameter between 5 μm and 10 μm in the modified aerosolized stream (after passing through the droplet separation device). [Figure 14]

[0057] Figure 1 shows the results of a test conducted using the droplet separation device, where the graph shows the percentage of droplets detected downstream of the device relative to the gas stream flow rate. [Figure 15]

[0058] Figure 1 shows the results of tests conducted using the droplet separation device, where the graph shows the gas stream flow rate against the oxide ratio (CeO+ / Ce+). [Figure 16]

[0059] Figure 1 shows the results of tests conducted using the droplet separation device, where the graph shows the gas stream flow rate against the dual charge ratio (Ce++ / Ce+). [Figure 17]

[0060] Figure 1 shows the results of tests conducted using the droplet separation device, and the graph therein shows the expected gas jet flow rate as a function of the gas stream flow rate for different aperture sizes of the droplet separation device. [Modes for carrying out the invention]

[0048]

[0061] The inventors have developed flow control devices, particularly droplet separation devices, to address some of the inefficiencies of existing inductively coupled plasma (ICP) analysis systems. It will be understood that the droplet separation devices described herein can also be used in other flow control applications, especially in analytical systems. While examples of inductively coupled plasma mass spectrometry (ICP-MS) applications of droplet separation devices are described below, it will be readily apparent to those skilled in the art that such devices can be used in other applications.

[0049]

[0062] Refer to Figures 1 and 2, which show a droplet separation device 10 for an ICP-MS application example according to one embodiment of the present invention. The droplet separation device 10 is in the form of an adapter configured to be placed between the atomizer and the plasma in an ICP-MS system, and its main function is to reduce the proportion of relatively large droplets (larger than approximately 5-10 μm) in the aerosolized sample stream entering the plasma. Thus, the device 10 effectively provides an aerosol filtration function.

[0050]

[0063] In this example, the device 10 is formed from polytetrafluoroethylene (PTFE) material and includes a substantially tubular, elongated body 12 extending between a first end 16 and a second end 18. The interior 14 of the tubular body 12 is oriented along the longitudinal axis 15 of the tubular body 12 and extends between the first end 16 and the second end 18, thereby providing a passage for the aerosolized sample stream through the device 10. The tubular body 12 generally comprises an upstream portion 20 adjacent to the first end 16, a downstream portion 40 adjacent to the second end 18, and an intermediate portion 30 extending between the upstream portion 20 and the downstream portion 40. The terms “downstream” and “upstream” in this context refer to the direction of flow of the aerosolized sample stream through the device 10 when it is placed in an ICP-MS system.

[0051]

[0064] See also Figures 3 and 4, the upstream portion 20 includes a first tubular portion 22 having an inner wall 21 with a first inner diameter ID1 and an outer wall 23 with a first outer diameter OD1. The circumferential flange 24 extends radially from the first tubular portion 22 at the first end 16. The inner surface 27 of the flange 24 defines a shoulder 26, which transitions smoothly toward the side wall 23. The flange 24 further includes a chamfered surface 28 on the outer surface 29 of the flange 24. The side wall 23 is adapted to receive an O-ring 25 (Figure 5) whose axial movement along the side wall 23 between the shoulder 26 and the intermediate portion 40 is generally restricted. The flange 24 further includes an inner wall 19 that tapers inward toward the inner wall 21, such that the widest internal dimension of the upstream portion 20 is presented at the first end 16.

[0052]

[0065] The upstream portion 20 is adapted to seal the connection with the upstream components of the ICP-MS system. In one example, the upstream portion 20 may be connected to a conduit or other outlet component located immediately downstream of the spray chamber of the ICP-MS system. To help form a fluid seal between the device 10 and the upstream component, the chamfered surface 28 helps slide the upstream portion 20 to engage with the upstream component while the O-ring 25 presses against the relatively thin side wall 23.

[0053]

[0066] In the above example, it will be understood that device 10 is positioned downstream of the spray chamber. In this configuration, device 10 provides a second stage of droplet separation after the initial droplet separation conventionally performed in the spray chamber. However, it is also conceivable that device 10 could instead be positioned immediately downstream of the sprayer in the ICP-MS system. In this configuration, device 10 can act as the first (or sole) stage of droplet separation. Furthermore, in the above example, the upstream portion 20 engages the upstream component by press-fitting the upstream portion 20 into the upstream component. It will be understood that the upstream portion 20 can be configured to enable reverse engagement with the upstream component, i.e., so that the upstream component slides into the interior 14 of the tubular body 12. For this purpose, the inner wall 19 is tapered to assist the upstream component in sliding into the tubular body 12.

[0054]

[0067] The downstream portion 40 has a configuration very similar to that of the upstream portion 20. The downstream portion 40 includes a second tubular portion 42 having an inner wall 41 with a second inner diameter ID2 and an outer wall 43 with a second outer diameter OD2. In this embodiment, the second outer diameter OD2 is substantially the same dimension as the first outer diameter OD1, and the second inner diameter ID2 is substantially the same dimension as the first inner diameter ID1. A circumferential flange 44 extends radially from the second tubular portion 42 at the second end 18. The inner surface 17 of the flange 44 defines a shoulder 46, which transitions smoothly toward the side wall 43. The flange 44 further includes a chamfered surface 48 on the outer surface 13 of the flange 44. The side wall 43 is generally adapted to receive an O-ring 45 (Figure 5) whose axial movement along the side wall 43 between the shoulder 46 and the intermediate portion 40 is restricted. The flange 44 further includes an inner wall 11 that tapers inward toward the inner wall 41 such that the widest internal dimension of the downstream portion 40 is presented at the second end 18.

[0055]

[0068] The downstream portion 40 is adapted to seal the connection with the downstream components of the ICP-MS system. In one example, the downstream portion 40 may be connected to a conduit or other outlet component located immediately upstream of the torch of the ICP-MS system (e.g., the sample injector of a plasma torch). To help form a fluid seal between the device 10 and the downstream component, the chamfered surface 48 helps slide the downstream portion 40 to engage with the downstream component while the O-ring 45 presses against the relatively thin side wall 43.

[0056]

[0069] In the above example, the downstream portion 40 engages with the downstream component by press-fitting the downstream portion 40 into the downstream component. However, the downstream portion 40 can be configured to enable reverse engagement with the downstream component, that is, so that the downstream component slides into the interior 14 of the tubular body 12. To this end, the inner wall 11 is tapered to facilitate the sliding of the downstream component into the tubular body 12.

[0057]

[0070] The intermediate portion 30 includes a third tubular portion 32 having an inner wall 31 with a third inner diameter ID3 and an outer wall 33 with a third outer diameter OD3. In this embodiment, the third outer diameter OD3 is larger than the first outer diameter OD1, and the third inner diameter ID3 is smaller than the first inner diameter ID1. As shown in Figure 4, it will be understood that the interior 14 of the tubular body 12 does not have a continuous inner diameter along the entire length of the tubular body. Instead, the tubular body 12 has a first inner diameter ID1 along a length generally extending from the first end 16 and terminating at a neck 91 located inside the intermediate portion 30, a second inner diameter ID2 along a length generally extending from the second end 18 and terminating at a neck 92 located inside the intermediate portion 30, and a third inner diameter ID3 along a length extending from the neck 91 and terminating at the neck 92.

[0058]

[0071] The collar portion 34 extends radially from the downstream end of the third tubular portion 32. The collar portion 34 is substantially annular in shape and has a substantially flat outer wall 51, an opposing substantially flat inner wall 52, and an outer wall 39 that extends between the outer wall 51 and the inner wall 52 and is oriented substantially parallel to the longitudinal axis 15, except for a truncated outer wall portion 35 that tapers radially inward toward the outer wall 51, as best shown in Figure 4. In other words, the plane of the truncated outer wall portion 35 is angled with respect to the longitudinal axis 15. The truncated outer wall portion 35 is angled with respect to the longitudinal axis 15 between about 2° and about 20°, preferably about 10°. The truncated outer wall portion 35 is substantially two-dimensional trapezoidal, having an outer end 61, an opposing inner end 62 which is smaller in dimension than the outer end 61, and two side ends 63 which diverge toward the outer end 61 (as best shown in Figure 2).

[0059]

[0072] Referring to Figure 6, the injection duct 36 extends inward from the truncated outer wall portion 35, close to one of the side ends 63, toward the interior 14 of the tubular body 12, and perpendicular to the plane of the truncated outer wall portion 35, thereby angling the longitudinal axis 38 of the injection duct 36 with respect to the longitudinal axis 15. In this configuration, it will be understood that the angle of the injection duct 36 with respect to the interior 14 of the tubular body 12 is the same as the angle of the truncated outer wall portion 35 (i.e., between approximately 2° and approximately 20°). The injection duct 36 has an opening 71 in the truncated outer wall portion 35, a first channel portion 81 extending inward from the opening 71, and a narrower second channel portion 82, the second channel portion 82 being concentric with the first channel portion 81 and defining an open channel 37 that terminates at the opening 72 toward the interior 14 of the tubular body 12. The vertical axis 38 defines the injection direction tangential to the interior 14 (Figure 3) of the tubular body 12 for reasons that will become clear below.

[0060]

[0073] In one embodiment, the ICP-MS system includes an argon gas source connected to an injection duct 36 via an opening 71. The injection duct 36 is configured to guide the gas stream into the interior 14 of a tubular body 12 via an opening 72. In particular, the opening 72 is configured to deliver a jet flow of argon gas into a sample flow separation region 99 of the tubular body 12. Due to the injection direction being oriented substantially tangentially to the interior 14 of the tubular body 12 (in particular substantially tangentially to the sample flow separation region 99), the jet flow of argon gas enters the interior 14 in such a way that it facilitates vortex generation as the jet flow navigates around the inner wall 31 of the intermediate portion 30. Furthermore, due to the angle between the injection duct 36 and the interior 14 of the tubular body 12, the generated vortex is guided relative to the flow direction of the aerosolized sample stream, i.e., the vortex is guided upstream. As described below, the generated vortex is an essential part of producing the desired separation of larger droplets from the aerosolized sample stream once the aerosolized sample stream enters the separation region 99.

[0061]

[0074] The following describes how device 10 is used in an ICP-MS system. In the embodiments described herein, device 10 is a separate component that can be installed in an existing ICP-MS system. Device 10 is connected to an upstream component via engagement with an upstream portion 20. In this example, the upstream component is the outlet conduit of the spray chamber of the ICP-MS system. Device 10 is also connected to a downstream component via engagement with a downstream portion 40. In this example, the downstream component is the sample injector of the plasma torch of the ICP-MS system. Device 10 is oriented substantially vertically within the ICP-MS system (i.e., as shown in Figures 1, 2, and 4 through 6).

[0062]

[0075] In conventional methods of introducing samples into an ICP-MS system, a liquid sample is introduced into a sprayer where the liquid is divided into a fine aerosolized sample stream by the pneumatic action of a gas flow that pulverizes the liquid into fine droplets. In this stage, the droplets generally vary considerably in size, typically between approximately 3 μm and 120 μm. This aerosolized sample stream passes through a spray chamber, and depending on the type of spray chamber used, larger droplets are separated from the aerosolized sample stream, resulting in an aerosolized sample stream with a reduced proportion of larger droplets. In this stage, the smaller droplets remaining in the aerosolized stream are typically between approximately 3 μm and 15 μm. The larger droplets are conventionally removed from the spray chamber by gravity via a drain tube positioned at the lower end of the spray chamber.

[0063]

[0076] Next, the aerosolized sample stream proceeds to the device 10 and enters the interior 14 of the tubular body 12 at the first end 16. An argon gas source operably coupled to the device 10 via an injection duct 36 delivers a continuous stream of argon gas to the injection duct 36 through an opening 71, and a continuous jet flow of argon gas is injected into the separation region 99 through an opening 72. As previously mentioned, due to the injection direction being substantially tangential to the interior 14 of the tubular body 12, and due to the angle between the inlet portion 36 and the interior 14 of the tubular body 12, the jet flow of argon gas enters the separation region 99 and generates a vortex induced opposite to the direction of flow of the aerosolized sample stream. Figure 7 shows a computational fluid dynamics model of this effect. Thus, as the aerosolized sample stream enters the device 10 and proceeds toward the separation region 99, the aerosolized sample stream encounters an upstream vortex 88 (Figure 8).

[0064]

[0077] As a result of this encounter, the progress of relatively large droplets 84 in the aerosolized sample stream is slowed, or the larger droplets 84 are removed, while the relatively smaller droplets 86 are generally able to progress. The inventors hypothesize that the reason the generated vortex can slow the progress of larger droplets is that the vortex creates a pressure zone within the separation region 99 that disproportionately hinders the propulsion of larger droplets compared to smaller droplets. Furthermore, the inventors hypothesize that the argon gas jet stream, particularly by the velocity of the jet stream, contributes to further spraying (i.e., pulverizing) the larger droplets into the smaller droplets. The larger droplets are removed with the assistance of the upstream-guided vortex and guided backward toward the spray chamber (as described above) to discharge the larger particles. This removal of larger droplets helps prevent or reduce limitation or fluctuations in the aerosolized flow through the device 10.

[0065]

[0078] As a result of the vortex action, relatively small droplets travel beyond the separation region 99 and exit the device 10 from the second end 18. This further modified aerosolized sample stream then travels through the sample injector of the plasma torch and finally passes through the plasma. This modified aerosolized sample stream has been found to have a larger proportion of smaller droplets, generally between approximately 3 μm and 5 μm in size.

[0066]

[0079] Several factors influence the proportion of smaller droplets (e.g., smaller than 5 μm) remaining in the modified aerosolized sample stream when the aerosolized sample stream leaves device 10. One of these factors is the flow rate of the gas stream introduced into device 10 via the injection duct 36 (i.e., the flow rate of the gas stream from the gas source). Another of these factors is the size of the opening 72, which will affect the velocity of the gas jet flow (i.e., reducing the size of the opening 72 relative to the opening 71 will increase the velocity of the gas jet flow).

[0067]

[0080] Refer to Figures 9 to 12, which show the results of various tests performed using device 10. The graphs show the percentage of droplets with a diameter of less than 5 μm in the modified aerosolized sample stream (after passing through device 10) relative to the flow rate of the gas stream from the gas source, for an opening 72 of a given size. The flow rate of the gas stream from the gas source varies in increments of 0.1 L / min, from 0 L / min to 0.3 or 0.4 L / min, for an opening 72 of a given size, with the opening size varying in increments of 0.1 mm between 0.2 mm and 0.5 mm. As can be seen from the graphs, as the flow rate of the gas stream from the gas source increases, generally the percentage of droplets with a diameter of less than 5 μm in the modified aerosolized sample stream increases, i.e., the percentage of larger droplets in the aerosolized sample stream decreases. However, the graphs also show that variation in the flow rate of the gas stream from the gas source resulted in a more significant decrease in the percentage of larger droplets for smaller opening sizes (i.e., faster gas jet flows).

[0068]

[0081] Figure 13 provides a further representation, in the form of bar graphs, of the results of various tests performed using device 10, particularly the effect of variations in gas stream flow rate on droplet size. The bars on the left of the figure show the percentage of average droplet sizes between 0.5 μm and 5 μm in the modified aerosolized sample stream for different flow rates, and the bars on the right of the figure show the corresponding percentage of average droplet sizes between 5 μm and 10 μm in the modified aerosolized sample stream for each of the different flow rates. As is clearly visible, as the gas stream flow rate increases, the percentage of smaller droplets in the modified aerosolized sample stream increases as a result, and the percentage of larger droplets in the modified aerosolized sample stream decreases accordingly.

[0069]

[0082] Therefore, it will be understood that the level of droplet separation can be controlled by adjusting the flow rate of the gas stream from the gas source and the size of the opening 72 (as well as other variables). Controlling such levels of droplet separation, as well as the overall aerosol filtration, can have many advantages. For example, the level of droplet separation and the transfer efficiency of the aerosolized sample stream per sample can be controlled using device 10. This can help reduce droplet accumulation on the injector and interface cone of the ICP system (and thus reduce the effects of drift and contaminants), and improve the lifespan of the plasma torch and interface cone.

[0070]

[0083] Figures 14 to 16 further provide a display of the results of various tests performed using device 10, including tests using cerium tuning solution. Figure 14 shows the percentage of droplets detected downstream of device 10 relative to the flow rate of the gas stream from the gas source for an opening 72 of a given size. In particular, it will be understood that device 10 is capable of substantially completely restricting the passage of droplets through the flow separation region 99 at a given flow rate by generating a sufficiently high-speed gas jet flow.

[0071]

[0084] Figure 15 shows how increasing the flow rate of the gas stream from the gas source affects the oxide ratio (CeO) for a given opening size 72. + / Ce + This demonstrates whether the matrix deposition can be reduced to well below 1%. This creates a more robust plasma, ideal for higher matrix samples. A more robust plasma allows for the achievement of higher sensitivity, reduced matrix deposition on the interface, and therefore leads to improved stability of the ICP system and a reduction in the frequency of maintenance required.

[0072]

[0085] Figure 16 shows the dual charge ratio (Ce ++ / Ce +This shows the effect of the gas stream flow rate from the gas source on the plasma. In particular, the dual charge ratio is less than 3% for the appropriate working range of device 10, and the gas stream flow rate from the gas source exceeds 3% at flow rates above 0.5 L / min. In some applications, a flow rate of 0.4 L / min has been found to produce the most robust plasma conditions.

[0073]

[0086] Figure 17 shows the expected velocity of the gas jet flow for different sized openings 72 of the droplet separation device 10, relative to the gas stream flow rate. In particular, Figure 17 shows the increased velocity of the generated jet flow. As can be understood from the above considerations, a high-speed jet flow promotes vortex generation, which helps in the generation of the desired separation of larger droplets from the aerosolized sample stream, as well as the aforementioned secondary spray effect.

[0074]

[0087] Users may be provided with kits of device 10 with different injection duct configurations and dimensions, and it is assumed that users will select the appropriate injection duct based on the sample to be analyzed. By carefully selecting different variables for different types of samples, better accuracy in the sample introduction stage can be achieved.

[0075]

[0088] Device 10 can be made from any suitable material that is both inert and chemically resistant to aerosolized flow. Suitable example materials include PEEK (polyether ether ketone) and PTFE. The O-ring can also be made from any suitable material that is both inert and chemically resistant, such as Viton®.

[0076]

[0089] It will be understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features referred to or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.

[0077]

[0090] When used herein, unless otherwise required by context, the term “comprise,” and variations such as “comprising,” “comprises,” and “comprised,” are not intended to exclude further additions, components, integers, or steps.

Claims

1. A flow control device for aerosolized sample delivery in an inductively coupled plasma (ICP) analysis system, comprising a body that at least partially defines a sample flow separation region having a longitudinal flow direction, wherein the sample flow separation region has an upstream end through which the aerosolized sample enters and a downstream end through which the modified aerosolized sample exits, the body includes an injection duct having an opening proximate to the sample flow separation region, the injection duct is configured to direct a stream of gas in an injection direction into the sample flow separation region, the injection direction is angled with respect to the longitudinal flow direction such that a swirling flow is generated within the sample flow separation region upon introduction of the stream of gas through the opening, the swirling flow has a direction opposite to the direction of the flow of the aerosolized sample to provide control of droplet size within the modified aerosolized sample, a flow control device.

2. The flow control device according to claim 1, configured to be disposed between a spray chamber and a plasma in the ICP analysis system.

3. The flow control device according to claim 1 or 2, configured to receive a primary aerosolized sample flow from the spray chamber and to generate a secondary aerosolized sample flow.

4. The flow control device according to claim 1 or 2, wherein the injection direction is substantially offset from a radial direction of the sample flow separation region, and the degree of the offset determines characteristics of the swirling flow.

5. The flow control device according to claim 1 or 2, wherein the injection direction is substantially tangential to the sample flow separation region.

6. The flow control device according to claim 1 or 2, wherein a component of the injection direction is in the upstream direction of the sample flow, whereby a swirling flow having a direction opposite to the flow of the aerosolized sample is generated as a result.

7. The flow control device according to claim 1 or 2, wherein the injection duct generates a gas jet flow into the sample flow separation region.

8. The injection duct has a reduced diameter portion proximate to the opening, whereby the stream of gas is accelerated into the gas jet flow. The generated gas jet flow is configured to further spray larger droplets included in the aerosolized sample flow into smaller droplets and to slow down or prevent the progression of the larger droplets in the aerosolized sample flow. The flow control device according to claim 7.

9. The injection duct is angled between about 70° and about 88° with respect to the longitudinal flow direction. The flow control device according to claim 1 or 2.

10. The flow control device is a single unit adapted for attachment between the spray chamber and the plasma in the ICP analysis system. The flow control device according to claim 1 or 2.

11. The flow control device includes a downstream portion, an upstream portion, and an intermediate portion therebetween. The intermediate portion provides at least partially the sample flow separation region. The flow control device according to claim 1 or 2.

12. The upstream portion is adapted to be connected to the spray chamber of the ICP analysis system. The downstream portion is adapted to be connected to the inlet of the torch of the ICP analysis system. The flow control device according to claim 11.

13. The intermediate portion includes a radially outwardly projecting collar portion, and the injection duct extends through the collar portion. The flow control device according to claim 11.

14. The injection duct extends through the side wall of the collar portion. The flow control device according to claim 13.

15. The collar portion is generally annular with a truncated side portion, and the truncated side portion forms the side wall through which the injection duct extends. The flow control device according to claim 14.

16. The truncated side portion has angled planar facets, and the injection duct extends substantially perpendicular to the planar facets. The flow control device according to claim 15.

17. The flow control device is configured to be oriented substantially vertically with an upward sample flow direction during use in an ICP analysis system, whereby larger droplets retarded or removed by the generated vortex flow are induced upstream by the assistance of gravity towards the drain. The flow control device according to claim 1 or 2.

18. The flow control device according to claim 1 or 2, wherein the flow rate of the gas stream and / or the dimension of the injection duct or the opening can be selected based on the sample analyzed by the ICP analysis system.

19. The flow control device according to claim 1 or 2, wherein the modified aerosolized sample flow contains droplets that are substantially smaller than about 5-6 µm.

20. An inductively coupled plasma (ICP) analysis system, wherein the ICP system includes the flow control device according to claim 1 or 2.

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