Flow Control Devices

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] The present invention relates to flow control devices, and more particularly to droplet separation devices for use in inductively coupled plasma (ICP) analytical systems for performing mass spectrometry (MS) or optical emission spectroscopy (OES). [Background technology]

[0002] In inductively coupled plasma mass spectrometry (ICP-MS) or inductively coupled plasma optical emission spectroscopy (ICP-OES), using current radio frequency generator designs, argon plasmas can typically tolerate aerosol loading rates of about 20 to 50 μL / min and droplets less than about 10 μm in size before the plasma becomes unstable or completely dissipates. The sample introduction stage of an ICP-MS or ICP-OES system often uses a spray chamber, and transfer efficiencies are typically less than 5%, meaning that less than 5% of the sample aerosol is transferred to the plasma. Thus, typical uptake rates for liquid samples are in the range of 300 μL / min to 1000 μL / min. Spray chambers can also separate larger droplets created in the nebulization process, with the efficiency of such separation depending on the specific spray chamber design. This is relevant for both water-based and organic-based samples.

[0003]

[0003] It is generally desirable to separate larger droplets from the aerosolized stream, thus providing more consistent droplet size and more uniform mixing of the nebulized sample, thereby enabling smoother introduction of the sample into the plasma. It is also noted that ICP-MS systems that use interface cones with small (between 250 and 1000 μm in diameter) machined orifices between the plasma and the mass analyzer to support a strong vacuum in the mass analyzer chamber can tend to block when samples with high (greater than 0.1% wt / wt) total dissolved solids are nebulized.

[0004]

[0004] A spray chamber can only provide certain 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 necessary, 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 Publication No. 2017 / 0338092A1. This disclosure is primarily concerned with reducing droplet deposition on the surfaces of one or more portions of a spray chamber assembly. This reduction can be achieved by injecting a tangential flow of makeup gas into the spray chamber through an inlet formed in the spray chamber. This gas flow, in combination with the structural arrangement of microchannels formed in the spray chamber, can help protect the chamber and the surfaces of internal tubes disposed within the chamber from droplet formation.

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

[0007]

[0007] The reference to any prior art in this specification is not an acknowledgment or suggestion that this prior art forms part of the common general knowledge in any jurisdiction or that a person skilled in the art could reasonably be expected to understand this prior art, consider it relevant, and / or combine it with other prior art. Summary of the Invention

[0008] In a first aspect, the present invention provides a flow control device for aerosolized sample delivery in an inductively coupled plasma (ICP) analytical system, the device comprising: a body at least partially defining a sample flow separation region, the sample flow separation region having a longitudinal flow direction and an upstream end through which an aerosolized sample enters and a downstream end through which a modified aerosolized sample exits; The body includes an injection duct having an opening proximate to the sample flow separation region, the injection duct configured to direct a stream of gas in an injection direction into the sample flow separation region, the injection direction 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, the vortex flow having a direction opposite to the direction of flow of the aerosolized sample to provide droplet size control within the modified aerosolized sample.

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

[0010]

[0010] In accordance with the present invention, the modified aerosolized sample flow toward the plasma therefore has an increased proportion of relatively smaller droplets, allowing for smoother introduction of the sample into the plasma and more uniform mixing of the aerosolized sample that reaches the plasma. The flow control device may also have a shattering effect (i.e., a secondary nebulization effect) of larger droplets contained in the aerosolized sample flow, again resulting in a modified aerosolized sample flow that has a higher proportion of smaller droplets than would otherwise be the case.

[0011]

[0011] The present invention can therefore provide greater control over the composition of the aerosolized sample and the amount of sample that progresses beyond the separation region (thus directly impacting issues of transfer efficiency and matrix effects). 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 that progress within the modified aerosolized sample and the amount of aerosolized sample that progresses within the modified aerosolized sample. Thus, the flow control device can effectively provide an aerosol filtration function.

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

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

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

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

[0016] Preferably, the component of the injection direction is in the upstream direction of the sample flow, thereby resulting in the creation of a vortex flow having a direction opposite to the flow of the aerosolized sample (ie, in the upstream direction).

[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 reduced diameter section adjacent the opening, thereby accelerating the stream of gas into the gas jet flow. The generated gas jet flow can be configured to further atomize larger droplets contained in the aerosolized sample flow into smaller droplets. The generated gas jet flow can be configured to slow or prevent the passage of larger droplets in the aerosolized sample flow. Preferably, the generated gas jet flow is configured to further atomize larger droplets contained in the aerosolized sample flow into smaller droplets, as well as to slow or prevent the passage of larger droplets in the aerosolized sample flow. The diameter of the reduced diameter section can be between 0.1 mm and 0.5 mm. The injection duct may be configured to generate a gas jet flow in 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 in 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] In one embodiment, the injection duct is angled between about 70° and about 88°, preferably between about 75° and about 85°, for example about 80°, relative to the longitudinal flow direction.

[0019] In one embodiment, the flow control device is a single entity adapted for installation between the nebulizer and 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 help control the aerosolized sample flow. In one embodiment, the flow control device is part of the ICP-MS or ICP-OES instrument, for example, integrated into another part of the instrument.

[0020]

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

[0021] The upstream portion may be adapted to connect to an upstream component 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 component. Alternatively, the upstream portion may be configured for press-fit engagement with the upstream component. In one embodiment, the upstream portion may be provided in the form of a ball joint adapted to connect to a socket of the upstream component. The downstream portion may be adapted to connect to a downstream component 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 component. Alternatively, the downstream portion may be configured for press-fit engagement with the downstream component. In one embodiment, the downstream portion may be provided in the form of a ball joint adapted to connect to a socket of the downstream component. Preferably, a fluid (i.e., gas and liquid) seal is established between the flow control device and each of the upstream and downstream components.

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

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

[0024] In one embodiment, the intermediate portion includes a radially outwardly projecting collar portion, with the injection duct extending through the collar. Preferably, the injection duct extends through a 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, with the injection duct extending substantially perpendicular to the planar facets.

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

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

[0027]

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

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

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

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

[0031] In one embodiment, the system includes a gas source configured to provide a stream of gas to the 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, using oxygen can be advantageous in reducing carbon buildup on 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 stream of gas from the gas source.

[0033] It will be appreciated that features disclosed in relation to the first aspect of the invention are also applicable in relation to the second aspect of the invention described above, including different combinations of the disclosed features.

[0034] In a third aspect, the present invention provides a mass spectrometry or spectroscopy system comprising a flow control device of the first aspect of the invention.

[0035] It will be appreciated that the features disclosed in relation to the first and second aspects of the invention are also applicable in relation to the third aspect of the invention described above, including different combinations of the disclosed features.

[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 comprising: providing an aerosolized sample flow to a sample flow separation region having a longitudinal flow direction; introducing a gas jet flow into the sample flow separation region to form a vortex flow having a direction opposite to the flow of the aerosolized sample to provide droplet size control as the modified aerosolized sample exits the sample flow separation region; Includes.

[0037]

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

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

[0039] Preferably, the method further comprises subjecting the aerosolized sample flow to a droplet separation process prior to providing the aerosolized sample flow to the sample flow separation region. Subjecting the aerosolized sample flow to a droplet separation process is preferably performed in a spray chamber.

[0040] In one embodiment, the method further comprises using a gas jet flow to nebulize the aerosolized sample flow in the sample flow separation region.

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

[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 optical emission spectroscopy (ICP-OES).

[0043]

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

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

[0045]

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

[0046]

[0046] Further aspects of the invention and further embodiments of the aspects described in the preceding paragraphs will become apparent from the following description, given by way of example and with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0047] [Figure 1] FIG. 1 is a perspective view of a droplet separation device in accordance with one embodiment of the present invention. [Figure 2]

[0048] FIG. 2 is a front view of the droplet separation device of FIG. 1. [Figure 3]

[0049] 2 is a top view of the droplet separation device of FIG. 1 with dashed lines showing hidden internal geometry. [Figure 4]

[0050] 4 is a cross-sectional view of the droplet separation device taken along line BB in FIG. 3. [Figure 5]

[0051] 5 is a cross-sectional view of the droplet separation device of FIG. 4 showing the location of an O-ring positioned around the droplet separation device. [Figure 6]

[0052] FIG. 4 is a cross-sectional view of the droplet separation device taken along line AA in FIG. 3. [Figure 7]

[0053] FIG. 2 shows a computational fluid dynamic model of the droplet separation device of FIG. 1 when employed in an ICP-MS system. [Figure 8]

[0054] 2 is a cross-sectional side view of the droplet separation device of FIG. 1 when employed in an ICP-MS system with an aerosolized stream moving through the ICP-MS system. [Figure 9]

[0055] FIG. 2 shows the results of various tests conducted using the droplet separation device of FIG. 1, whereby the graph shows the percentage of droplets with a diameter of less than 5 μm in the modified aerosolized stream (after proceeding through the droplet separation device) versus the flow rate of the gas stream through the droplet separation device for a given aperture size of the droplet separation device. [Figure 10]

[0055] A figure showing the results of various tests conducted using the droplet separation device of Figure 1, whereby the graph shows the percentage of droplets with a diameter of less than 5 μm in the modified aerosolized stream (after proceeding through the droplet separation device) versus the flow rate of the gas stream through the droplet separation device for a given aperture size of the droplet separation device. [Figure 11]

[0055] A figure showing the results of various tests conducted using the droplet separation device of Figure 1, whereby the graph shows the percentage of droplets with a diameter of less than 5 μm in the modified aerosolized stream (after proceeding through the droplet separation device) versus the flow rate of the gas stream through the droplet separation device for a given aperture size of the droplet separation device. [Figure 12]

[0055] A figure showing the results of various tests conducted using the droplet separation device of Figure 1, whereby the graph shows the percentage of droplets with a diameter of less than 5 μm in the modified aerosolized stream (after proceeding through the droplet separation device) versus the flow rate of the gas stream through the droplet separation device for a given aperture size of the droplet separation device. [Figure 13]

[0056] FIG. 2 shows the results of various tests conducted using the droplet separation device of FIG. 1 , whereby the bar on the left side of the graph indicates the percentage of droplets with diameters between 0.5 μm and 5 μm in the modified aerosolized stream (after proceeding through the droplet separation device) versus the flow rate of the gas stream through the droplet separation device, and the bar on the right side of the graph indicates the percentage of droplets with diameters between 5 μm and 10 μm in the modified aerosolized stream (after proceeding through the droplet separation device). [Figure 14]

[0057] 2 shows the results of tests carried out using the droplet separation device of FIG. 1, whereby a graph shows the percentage of droplets detected downstream of the device versus the flow rate of the gas stream. [Figure 15]

[0058] FIG. 2 shows the results of tests conducted using the droplet separation device of FIG. 1, whereby the graph shows the oxide ratio (CeO+ / Ce+) versus the flow rate of the gas stream. [Figure 16]

[0059] 2 shows the results of tests conducted using the droplet separation device of FIG. 1, whereby the graph shows the flow rate of the gas stream versus the double charge ratio (Ce++ / Ce+). [Figure 17]

[0060] FIG. 2 shows the results of tests conducted using the droplet breakup device of FIG. 1, whereby the graph shows the expected velocity of the gas jet flow versus the flow rate of the gas stream for different aperture sizes in the droplet breakup device. DETAILED DESCRIPTION OF THE INVENTION

[0048]

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

[0049]

[0062] 1 and 2, which illustrate a droplet separation device 10 for ICP-MS applications, in accordance with one embodiment of the present invention. The droplet separation device 10 is in the form of an adapter configured to be placed between the nebulizer and the plasma in an ICP-MS system, with its primary function being to reduce the proportion of relatively large droplets (greater than about 5-10 μm) in the aerosolized sample stream that enters the plasma. Thus, the device 10 effectively provides an aerosol filtration function.

[0050]

[0063] The device 10 includes a substantially tubular elongate body 12, in this example formed from a polytetrafluoroethylene (PTFE) material, extending between a first end 16 and a second end 18. An interior 14 of the tubular body 12 is oriented along a longitudinal axis 15 of the tubular body 12 and extends between the first end 16 and the second end 18, thereby providing a passageway for an aerosolized sample stream through the device 10. The tubular body 12 generally comprises an upstream portion 20 proximate the first end 16, a downstream portion 40 proximate 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 disposed within an ICP-MS system.

[0051]

[0064] 3 and 4 , upstream portion 20 includes 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. A circumferential flange 24 extends radially from first tubular portion 22 at first end 16. An inner surface 27 of flange 24 defines a shoulder 26 that transitions smoothly toward sidewall 23. Flange 24 further includes a chamfered surface 28 on an outer surface 29 of flange 24. Sidewall 23 is generally adapted to receive an O-ring 25 ( FIG. 5 ), which is constrained from axial movement along sidewall 23 between shoulder 26 and intermediate portion 40. Flange 24 also includes an inner wall 19 that tapers inwardly toward inner wall 21 such that the widest interior dimension of upstream portion 20 is presented at first end 16.

[0052]

[0065] The upstream portion 20 is adapted to seal a connection with an upstream component of an ICP-MS system. In one example, the upstream portion 20 may be connected to a conduit or other outlet component immediately downstream of a spray chamber of an ICP-MS system. The chamfered surface 28 assists in sliding the upstream portion 20 into engagement with the upstream component, while the O-ring 25 presses against the relatively thin sidewall 23 to help form a fluid-tight seal between the device 10 and the upstream component.

[0053]

[0066] It will be appreciated that in the above example, device 10 is disposed downstream of a spray chamber. In such an arrangement, device 10 provides a second stage of droplet separation after the initial droplet separation conventionally performed in a spray chamber. However, it is also envisioned that device 10 could instead be disposed immediately downstream of a sprayer in an ICP-MS system. In such an arrangement, device 10 could serve as the first stage (or only stage) of droplet separation. Further, in the above example, upstream portion 20 engages the upstream component by press-fitting upstream portion 20 within the upstream component. It will be appreciated that upstream portion 20 can be configured to perform a reverse engagement with the upstream component, i.e., to allow the upstream component to slide into interior 14 of tubular body 12. To this end, tapering inner wall 19 assists in sliding the upstream component into tubular body 12.

[0054]

[0067] The downstream portion 40 is very similar in configuration to 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 that smoothly transitions toward the sidewall 43. The flange 44 further includes a chamfered surface 48 on the outer surface 13 of the flange 44. The sidewall 43 is generally adapted to receive an O-ring 45 ( FIG. 5 ), which is constrained from axial movement along the sidewall 43 between the shoulder 46 and the intermediate portion 40. The flange 44 further includes an inner wall 11 that tapers inwardly toward the inner wall 41 such that the widest interior dimension of the downstream portion 40 is presented at the second end 18 .

[0055]

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

[0056]

[0069] In the above example, the downstream portion 40 engages the downstream component by press-fitting the downstream portion 40 inside the downstream component. However, the downstream portion 40 can be configured to enable reverse engagement with the downstream component, i.e., allowing the downstream component to slide into the interior 14 of the tubular body 12. To this end, tapering the inner wall 11 assists in allowing the downstream component to slide 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 FIG. 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 its length generally extending from the first end 16 and terminating in a neck 91 located inside the intermediate portion 30, a second inner diameter ID2 along its length generally extending from the second end 18 and terminating in a neck 92 located inside the intermediate portion 30, and a third inner diameter ID3 along its length extending from the neck 91 and terminating in the neck 92.

[0058]

[0071] Collar portion 34 extends radially from the downstream end of third tubular portion 32. Collar portion 34 is substantially annular-shaped, having a substantially flat outer wall 51, an opposing substantially flat inner wall 52, and an outer wall 39 extending between outer wall 51 and inner wall 52 and oriented substantially parallel to longitudinal axis 15, except for truncated outer wall portion 35, which tapers radially inward toward outer wall 51, as best shown in FIG. 4. In other words, the plane of truncated outer wall portion 35 is angled relative to longitudinal axis 15. Truncated outer wall portion 35 is angled at an angle between about 2° and about 20°, preferably about 10°, relative to longitudinal axis 15. Truncated outer wall portion 35 is substantially trapezoidal in two dimensions, having an outer end 61, an opposing inner end 62 of smaller dimension than outer end 61, and two side ends 63 diverging toward outer end 61 (as best shown in FIG. 2).

[0059]

[0072] 6 , injection duct 36 extends from truncated outer wall portion 35, proximate one of side ends 63, inward toward interior 14 of tubular body 12 and in a direction perpendicular to the plane of truncated outer wall portion 35, such that longitudinal axis 38 of injection duct 36 is angled relative to longitudinal axis 15. It will be appreciated that in this configuration, the angle of injection duct 36 relative to interior 14 of tubular body 12 will be the same as the angle of truncated outer wall portion 35 (i.e., between about 2° and about 20°). Injection duct 36 has an opening 71 in truncated outer wall portion 35, a first channel portion 81 extending inward from opening 71, and a narrower second channel portion 82, concentric with first channel portion 81, defining an opening channel 37 that terminates at opening 72 to interior 14 of tubular body 12. Longitudinal axis 38 defines an injection direction that is substantially tangential to interior 14 (FIG. 3) of tubular body 12, for reasons that will become apparent below.

[0060]

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

[0061]

[0074] The following describes how device 10 is utilized in an ICP-MS system. In the embodiment 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 upstream portion 20. In this example, the upstream component is the outlet conduit of a spray chamber of the ICP-MS system. Device 10 is also connected to a downstream component via engagement with downstream portion 40. In this example, the downstream component is the sample injector of a 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 4-6).

[0062]

[0075] In the conventional mode for sample introduction into an ICP-MS system, a liquid sample is introduced into a nebulizer, where the liquid is split into a fine aerosolized sample stream by the pneumatic action of a gas flow that breaks the liquid into fine droplets. At this stage, the droplets generally vary greatly in size, typically between about 3 μm and about 120 μm. This aerosolized sample stream passes into a spray chamber, where, 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. At this stage, the smaller droplets remaining in the aerosolized stream are typically between about 3 μm and about 15 μm. The larger droplets are conventionally removed from the spray chamber under the action of gravity via a drain tube positioned at the lower end of the spray chamber.

[0063]

[0076] The aerosolized sample stream then proceeds into 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 the inlet duct 36, delivers a continuous stream of argon gas into the inlet duct 36 through opening 71, and a continuous jet flow of argon gas is injected into the separation region 99 through opening 72. As previously mentioned, due to the injection direction being oriented substantially tangentially 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 dynamic 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 will encounter an upstream-induced vortex 88 (Figure 8).

[0064]

[0077] As a result of this encounter, the progress of relatively large droplets 84 contained in the aerosolized sample stream is retarded, or the larger droplets 84 are removed while the relatively small droplets 86 are generally allowed to proceed. The inventors hypothesize that the reason the generated vortex may retard the progress of larger droplets is because the vortex creates a pressure zone within the separation region 99 that disproportionately impedes the momentum of larger droplets relative to smaller droplets. The inventors further hypothesize that the argon gas jet stream, particularly due to the velocity of the jet stream, contributes to further atomizing (i.e., breaking up) the larger droplets into smaller droplets. The larger droplets are removed with the assistance of the upstream-induced vortex, which directs the larger particles backward toward the spray chamber (as described above) for ejection. Removal of larger droplets in this manner helps prevent or reduce restriction or fluctuation of the aerosolized flow through the device 10.

[0065]

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

[0066]

[0079] There are various factors that affect the proportion of smaller droplets (e.g., smaller than 5 μm) that remain in the modified aerosolized sample stream when it leaves device 10. One of these factors is the flow rate of the gas stream introduced into device 10 via inlet duct 36 (i.e., the flow rate of the gas stream from the gas source). Another of these factors is the size of aperture 72, which will affect the velocity of the gas jet flow (i.e., decreasing the size of aperture 72 relative to aperture 71 will increase the velocity of the gas jet flow).

[0067]

[0080] 9 through 12, which show the results of various tests conducted using device 10. The graphs show the percentage of droplets with diameters less than 5 μm in the modified aerosolized sample stream (after proceeding through device 10) versus the flow rate of the gas stream from the gas source for a given size of aperture 72. The flow rate of the gas stream from the gas source was varied in 0.1 L / min increments between 0.3 and 0.4 L / min for a given size of aperture 72, with aperture sizes varying from 0.2 mm to 0.5 mm in 0.1 mm increments. As can be seen from the graphs, an increase in the flow rate of the gas stream from the gas source generally resulted in a greater percentage of droplets less than 5 μm in the modified aerosolized sample stream, i.e., a decrease in the percentage of larger droplets in the aerosolized sample stream. However, the graphs also show that variations 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 aperture sizes (i.e., gas jet flow at a higher velocity).

[0068]

[0081] 13 provides a further display of the results of various tests conducted using device 10, particularly in the form of a bar graph showing the effect on droplet size of varying the flow rate of the gas stream. The bars on the left side 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 side of the figure show the corresponding percentage of average droplet sizes between 5 μm and 10 μm in the modified aerosolized sample stream at each of the different flow rates. As can be clearly seen, an increase in the flow rate of the gas stream results in an increase in the percentage of smaller droplets in the modified aerosolized sample stream and a corresponding decrease in the percentage of larger droplets in the modified aerosolized sample stream.

[0069]

[0082] It will be appreciated that the level of droplet separation can therefore be controlled by adjusting the flow rate of the gas stream from the gas source and the size of the aperture 72 (as well as other variables). Such control of the level of droplet separation, as well as the overall aerosol filtration, can have many advantages. For example, device 10 can be used to control the level of droplet separation and the transfer efficiency of the aerosolized sample stream on a sample-by-sample basis. This can reduce droplet buildup on the injector and interface cone of the ICP system (thus reducing the effects of drift and contamination) and help improve the life of the plasma torch and interface cone.

[0070]

[0083] 14-16 further provide representations of the results of various tests conducted using device 10, including tests using a cerium tuning solution. FIG. 14 shows the percentage of droplets detected downstream of device 10 versus the flow rate of the gas stream from the gas source for a given size aperture 72. In particular, it will be appreciated that device 10 is capable of substantially completely restricting the passage of droplets through flow separation region 99 at a particular flow rate by generating a sufficiently high velocity gas jet flow.

[0071]

[0084] FIG. 15 shows how increasing the flow rate of the gas stream from the gas source affects the oxide ratio (CeO + / Ce + ) can be reduced to well below 1%. This creates a more robust plasma that is ideal for higher matrix samples. A more robust plasma allows for higher sensitivity to be achieved, reduced matrix deposition on the interface, and therefore improved stability and reduced maintenance requirements for the ICP system.

[0072]

[0085] Figure 16 shows the double charge ratio (Ce ++ / Ce +1 shows the effect of the flow rate of the gas stream from the gas source on the plasma density (Dp) of the plasma. Notably, the double charge ratio is less than 3% for the appropriate working range of the device 10, and exceeds 3% for flow rates above 0.5 L / min of the gas stream from the gas source. 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 predicted velocity of the gas jet flow versus the gas stream flow rate for different size openings 72 of the droplet separation device 10. In particular, Figure 17 shows the enhanced velocity of the generated jet flow. As can be seen from the above discussion, a high velocity jet flow promotes the generation of vortices, which aids in producing the desired separation of larger droplets from the aerosolized sample stream, as well as the secondary atomization effect described above.

[0074]

[0087] It is envisioned that a user may be provided with a kit of devices 10 with different injection duct configurations and dimensions, and that the user will select the appropriate injection duct based on the sample to be analyzed. By carefully selecting different variables for different types of samples, greater precision in the sample introduction stage can be achieved.

[0075]

[0088] The device 10 can be made from any suitable material that is both inert and chemically resistant to the aerosolized flow. Suitable exemplary materials include PEEK (polyetheretherketone) and PTFE. The O-rings 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 mentioned or apparent from the text or drawings, all of these different combinations constituting various alternative aspects of the invention.

[0077]

[0090] As used herein, unless the context requires otherwise, the term "comprise" and variations of the term such as "comprising," "comprises," and "comprised" are not intended to exclude further additives, components, integers, or steps.

Claims

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

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

3. A flow control device as described in claim 1, configured to receive a primary aerosolized sample flow from a spray chamber and to generate a secondary aerosolized sample flow.

4. 3. The flow control device of claim 1, wherein the injection direction is substantially offset from a radial direction of the sample flow separation region, the degree of the offset determining the characteristics of the vortex flow.

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

6. 3. The flow control device of claim 1, wherein the component of the injection direction is in an upstream direction of the sample flow, thereby resulting in the generation of the vortex flow having a direction opposite to the flow of the aerosolized sample.

7. 3. The flow control device of claim 1, wherein the injection duct generates a gas jet flow into the sample flow separation region.

8. the injection duct having a reduced diameter portion adjacent the opening, thereby accelerating the stream of gas into the gas jet flow; 8. The flow control device of claim 7, wherein the generated gas jet flow is configured to further atomize larger droplets contained in the aerosolized sample flow into smaller droplets and to slow or prevent the passage of larger droplets within the aerosolized sample flow.

9. 3. The flow control device of claim 1 or 2, wherein the injection duct is angled between about 70° and about 88° relative to the longitudinal flow direction.

10. 3. The flow control device of claim 1, wherein the flow control device is a unitary body adapted for attachment between a spray chamber and a plasma in the ICP analysis system.

11. the flow control device includes a downstream portion, an upstream portion, and an intermediate portion therebetween; 3. The flow control device of claim 1, wherein the intermediate portion at least partially provides the sample flow separation region.

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

13. 12. The flow control device of claim 11, wherein the intermediate portion includes a radially outwardly projecting collar portion, the injection duct extending through the collar portion.

14. The flow control device of claim 13 , wherein the injection duct extends through a side wall of the collar portion.

15. 15. The flow control device of claim 14, wherein the collar portion is generally annular in shape with truncated sides, the truncated sides forming the sidewalls through which the injection duct extends.

16. 16. The flow control device of claim 15, wherein the truncated side has an angled planar facet, and the injection duct extends substantially perpendicular to the planar facet.

17. 3. The flow control device of claim 1, wherein the flow control device is configured to be oriented substantially vertically with an upward sample flow direction during use in an ICP analytical system, whereby larger droplets that are delayed or removed by the generated vortex flow are directed back upstream with the assistance of gravity toward a drain.

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

19. 3. The flow control device of claim 1, wherein the modified aerosolized sample flow comprises droplets substantially smaller than about 5-6 μm.

20. 3. An inductively coupled plasma (ICP) analysis system, the ICP analysis system comprising the flow control device of claim 1 or 2.

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