Connecting element for spectrometry

Abstract

A connecting element for fluidly connecting a spray chamber to an ion source comprises: a downstream channel portion 222, a sample outlet 221, an upstream channel portion 232 and a sample inlet 231, a

Description

The present Invention generally relates to spectrometry, particularly inorganic mass spectrometry (MS) and may be particularly suitable for inductively coupled plasma mass spectrometers (ICP-MS) and optical emission spectrometers (ICP-OES). More specifically, the present invention relates to a connecting element for fluidly connecting a nebulizer and / or spray chamber to an ion source. For sample introduction in MS- and OES systems typically a liquid sample may be converted into tiny droplets, e.g., by means of a pneumatic atomiser, and the resulting aerosol may then be transferred to a spray chamber for droplet size separation before it may be directed to the ion source as a tertiary aerosol through a connecting element. Within the connecting element, which fluidly connects a nebulizer and / or spray chamber to an ion source, gases may be added, depending on the application. Dimensions of the connecting element can oftentimes be limited due to a limited installation space. For example, in the iCAP™ Qnova series by Thermo Fisher Scientific, a 90° elbow with a constant cross-section has been used as a connecting element between the spray chamber and an injector of the ion source. However, such a connecting element may lead to undesired turbulences in the fluid flow which may result in a lowered transport efficiency. Furthermore, particularly high matrix samples, e.g., samples with a high salt load, can result in a reduction of a diameter of the fluid-carrying portion of the injector due to crystallisation of the matrix on inner surfaces of the injector. Such undesired deposits may negatively impact the measurements since sample introduction may be obstructed in an uncontrollable manner. A known solution is to dilute the sample with a respective solvent, which may however disadvantageously require prolonged analysis time and may increase the usage of consumables. Alternatively, it has been found that a gas flow through the nebulizer may be reduced while adding an additional gas flow downstream of the nebulizer to compensate for the reduced gas flow through the nebulizer. This may generally allow to reduce the amount of sample entering the ion source and thus reduce matric deposition. However, for current designs, the additional gas flow downstream of the nebulizer may interfere with the transport of the aerosol and may, for example, cause turbulence. In light of the above, it is an object to overcome or at least alleviate the shortcomings and disadvantages of the prior art. More particularly, it is an object of the present invention to provide a connecting element that allows for a higher transport efficiency of a samplecomprising fluid while reducing matrix deposition on inner surfaces of the injector. These objects are met by the present invention. In one aspect, the present invention relates to a connecting element for fluidly connecting an outlet of a spray chamber to an ion source, wherein the connecting element comprises a downstream section comprising a downstream channel portion and a sample outlet, and an upstream section comprising an upstream channel portion and a sample inlet, wherein the sample inlet is fluidly connected to the sample outlet via a main flow channel constituted by the upstream channel portion and the downstream channel portion. Further, the downstream section comprises a dilution gas inlet configured to provide a dilution gas to the downstream channel portion, wherein the downstream channel portion comprises a downstream channel axis and the dilution gas inlet comprises a dilution gas inlet axis, and wherein the downstream channel axis and the dilution gas inlet axis are skew lines. In other words, a connecting element is provided that may allow to establish a fluid connection between a spray chamber and / or nebulizer and an ion source, preferably an injector that guides sample fluid to the plasma. Additionally, the connecting element comprises a dilution gas inlet that is offset from the downstream channel axis and advantageously allows to introduce a dilution gas as a sheath gas that may reduce disadvantageous matrix deposition for high matrix samples. The downstream channel axis may be diametrically central to the downstream channel portion. Additionally or alternatively, the downstream channel axis may be straight and perpendicular to the sample outlet. In other words, the channel outlet portion axis may be perpendicular with respect to a cross section of the sample outlet. The downstream section may comprise a downstream section inner surface. The downstream section inner surface may diametrically surround and thereby constitute the downstream channel portion. The downstream section may comprise a downstream portion. At least the downstream section inner surface within the downstream portion of the downstream section may be conically shaped towards the sample outlet. Put differently, an inner cross section of the downstream portion of the downstream section may be tapered towards the sample outlet. Generally, the downstream portion of the downstream section may comprise the sample outlet and preferably the dilution gas inlet. A diameter of the downstream channel portion may decrease in the downstream direction. Additionally or alternatively, a cross section of the downstream channel portion may at least partially be tapered towards the sample outlet. The downstream channel portion may comprise an outlet radius. The outlet radius may be in the range of 1 mm to 12 mm, preferably 2 mm to 4 mm, more preferably 2.5 mm to 3.5 mm. Preferably, the outlet radius may match the radius of a respective injector Inlet, e.g., 3 mm. The downstream channel portion may comprise a gas inlet radius denoting the radius of the downstream channel portion at the dilution gas inlet. The gas inlet radius may be greater than the outlet radius. The gas inlet radius may be in the range of 3 mm to 6.5 mm, preferably 5 mm to 6 mm, more preferably 5.5 mm to 6 mm. The downstream section may be made of per- or polyfluorinated plastics, preferably PFA or PTFE, or glass, preferably high purity quartz glass. The dilution gas inlet axis may be diametrically central to the dilution gas inlet. Additionally or alternatively, the dilution gas inlet axis may be oriented at a first angle in the range of 90° to 110°, preferably 90° to 100° such as 90°, with respect to the downstream direction of the downstream channel portion. A distance between the dilution gas inlet axis and the downstream channel axis, which is defined as the distance between their nearest points, may be in the range of 1 mm to 3 mm, preferably 2 mm to 2.5 mm. The dilution gas inlet may be configured to provide a dilution gas flow surrounding a sample fluid flow guided through the downstream channel portion. In some embodiments, the dilution gas inlet may be configured such that dilution gas provided through the dilution gas inlet surrounds a sample fluid flow along the downstream channel axis in a swirling flow. The dilution gas inlet may be configured such that dilution gas provided through the dilution gas inlet acts as a sheath gas separating the sample fluid flow along the downstream channel axis from the downstream section inner surface downstream of dilution gas inlet. In other words, the dilution gas inlet may be configured to provide a dilution gas flow that may act as a sheath gas for the sample fluid flow. The dilution gas inlet may be configured to be fluidly connected to a gas supply. In other words, the dilution gas inlet may be provided with a respective dilution gas by means of a gas supply that can be connected to the dilution gas inlet. The dilution gas inlet may be configured to provide a volume flow of dilution gas in the range of 0.5 l / min to 1.1 l / min, preferably, 0.7 l / min to 1.1 l / min, more preferably 0.9 l / min to 1 l / min. The upstream channel portion may comprise a bend channel portion with a bend portion axis which follows a circular arc. Preferably the bend channel portion may provide a turn in the range of 30° to 120° of the upstream channel portion. In some embodiments, the bend channel portion may provide a 90° turn of the upstream channel portion. The bend channel portion may comprise a bend radius in the range of 9 mm to 12 mm, preferably 9 mm to 11 mm, more preferably 10 mm to 10.5 mm. The bend channel portion may comprise a constant inner cross section. That is, the portion of the main flow channel constituted by the channel bend portion comprises a constant Inner cross section. The bend channel portion may comprise a bend channel radius in the range of 3 to 6 mm, preferably 4 mm to 5 mm, more preferably 4.5 mm to 5 mm. The upstream section may comprise a supplementary gas inlet. The supplementary gas inlet may generally be configured to provide a supplementary gas to the sample fluid flow, in particular to mix with the sample fluid flow. The supplementary gas may also be referred to as additional gas or simply add gas. In particular, the supplementary gas inlet may be located such that a such that gas provided by the supplementary gas inlet is provided to the sample fluid flow. Additionally or alternatively, the supplementary gas inlet may be configured such that gas provided by the supplementary gas inlet mixes with a sample fluid flow in the upstream channel portion. In embodiments comprising the bend channel portion, the supplementary gas inlet may be located such that gas provided by the supplementary gas inlet is provided to the bend channel portion of the upstream channel portion. The supplementary gas inlet may comprise a supplementary gas inlet axis and wherein the supplementary gas inlet axis may be aligned with the downstream channel axis. The upstream channel portion may further comprise a channel inlet portion comprising the sample inlet. The channel inlet portion may be oriented at an angle of 30° to 120° with respect to the downstream channel portion. In some embodiments, the channel inlet portion may be oriented perpendicular to the downstream channel portion. Furthermore, the connecting element may comprise a guiding element. The guiding element may comprise a guiding element upstream end and a guiding element downstream end. The guiding element may comprise a guiding element inner surface defining a channel between the guiding element upstream end and the guiding element downstream end. Further, at least a downstream portion of the guiding element inner surface may be conically shaped with a decreasing diameter in the downstream direction. The guiding element may comprise an inner upstream end radius. In some embodiments, the inner upstream end radius may correspond to the bend channel radius. Generally, the inner upstream end radius may be in the range of 1.5 mm to 6.5 mm, preferably 4 mm to 5.5 mm more preferably 5 mm to 5.5 mm. The guiding element may comprise an innerdownstream end radius. The innerdownstream end radius may be smaller than the inner upstream end radius. The inner downstream end radius may be In the range of 0.5 mm to 4.5 mm, preferably 1 mm to 3 mm more preferably 1 mm to 1.5 mm. The guiding element may be configured to separate a dilution gas provided at the dilution gas inlet and a sample fluid flow along the main channel at the dilution gas inlet. The guiding element may be configured to combine a sample fluid guided through the guiding element with a dilution gas guided along an outside of the guiding element such that the dilution gas surrounds the sample fluid and acts as a sheath gas. It will be understood that it may only act as a sheath gas once combined with the sample fluid, i.e. downstream of the guiding element. The guiding element may comprise a downstream portion and an upstream portion. An outer surface of the downstream portion of the guiding element may be conically shaped with a decreasing diameter in the downstream direction. The outer surface of the downstream portion of the guiding element in combination with part of the downstream section inner surface may provide a channel for dilution gas provided through the dilution gas inlet. Position and orientation of the dilution gas inlet in combination with the outer surface of the guiding element downstream portion and the downstream section inner surface may be configured to constrain and guide dilution gas provided through the dilution gas inlet such that it surrounds sample fluid flow exiting the guide element downstream end. The connecting element may be configured such that dilution gas provided through the dilution gas inlet to the downstream channel portion is provided tangentially to the outer surface of the downstream portion of the guiding element. The upstream portion of the guiding element may be configured to seamlessly fit into the main flow channel. Additionally or alternatively, the upstream portion of the guiding element may be located upstream of the dilution gas inlet. The downstream section may comprise a recess at an upstream portion thereof wherein at least part of the upstream portion of the guiding element is received. Additionally or alternatively, the upstream section may comprise a recess at a downstream portion thereof wherein at least part of the upstream portion of the guiding element is received. It will be understood that said downstream portion is downstream of a potential bend portion. The upstream portion of the guiding element may comprise a constant upstream portion radius, wherein the upstream portion radius may be in the range of 6 mm to 10mm, preferably 6 mm to 8 mm, more preferably 6 mm to 6.5 mm. The guiding element may be located at least partially within the downstream section. Additionally or alternatively, the guiding element may be located at least partially withing the upstream section. The guiding element downstream end may be located downstream of the dilution gas inlet in a direction parallel to the downstream channel axis. A distance between the downstream end and the dilution gas inlet along the direction parallel to the downstream channel axis may be in the range 2 mm to 10 mm, preferably 5 mm to 10 mm, further preferably 7 mm to 8 mm. The guiding element may be made of per- or polyfluorinated plastics, preferably PFA or PTFE, or glass, preferably high purity quartz glass. The downstream section and the upstream section may preferably be formed separately from each other. Further, the downstream section and the upstream section may be mechanically connected to each other by at least one, preferably at least two separable fastening means. The connecting element may be assembled of three parts: the downstream section, the upstream section and the guiding element. Alternatively, the guiding element may be integrally formed with either one of the downstream section and the upstream section. The connecting element may be configured such that the guiding element is held in place by being constrained by the upstream section and the downstream section. The guiding element may not be permanently fixed to other parts of the connecting element. That is, the guiding element may be exchangeable. Downstream section and upstream section may be separably connected to each other. In another aspect, the present invention relates to an ion source comprising a connecting element according to the above-described connecting element, wherein the connecting element is configured to receive an aerosol provided by a nebulizer. The ion source may further comprise an injector and the sample outlet of the connecting element may be fluidly connected to the injector. The ion source may be an inductively coupled plasma (ICP) source. In another aspect, the present invention relates to a sample introduction system for a spectrometer comprising a nebulizer, an ion source, and a connecting element as described above, wherein the connecting element is configured to guide an aerosol provided by the nebulizer to the ion source. The sample inlet of the connecting element may be fluidly connected to the nebulizer. Alternatively, the system may further comprise a spray chamber downstream of the nebulizer and the sample inlet of the connecting element may be fluidly connected to the spray chamber. The sample outlet of the connecting element may be fluidly connected to the ion source. In particular, the sample outlet of the connecting element may be fluidly connected to an injector of the ion source. The ion source may comprise an inductively coupled plasma source. The system may further comprise a humidifier fluidly connected to the dilution gas inlet of the connecting element. Such a humidifier may allow to humidify the dilution gas which may advantageously lead to better results in avoiding undesired deposition of matrix material from the sample fluid. The ion source of the sample introduction system may comprise the connecting element. In a further aspect, the present invention relates to a use of the herein described connecting element and / or the herein described sample introduction system in a spectrometry system. The spectrometry system may be at least one of an inductively coupled plasma spectrometry system, a mass spectrometry system and / or an optical spectrometry system. In a further aspect, the present invention relates to a spectrometer comprising the connecting element and / or the simple Introduction system as described herein. Below, reference will be made to connecting element embodiments. These embodiments are abbreviated by the letter "C" followed by a number. Whenever reference is herein made to "connecting element embodiments", these embodiments are meant. Cl. Connecting element for fluidly connecting an outlet of a spray chamber to an ion source, wherein the connecting element comprises a downstream section comprising a downstream channel portion and a sample outlet, and an upstream section comprising an upstream channel portion and a sample inlet, wherein the sample inlet is fluidly connected to the sample outlet via a main flow channel constituted by the upstream channel portion and the downstream channel portion, wherein the downstream section comprises a dilution gas inlet configured to provide a dilution gas to the downstream channel portion, wherein the downstream channel portion comprises a downstream channel axis and the dilution gas inlet comprises a dilution gas inlet axis, and wherein the downstream channel axis and the dilution gas inlet axis are skew lines. C2. Connecting element according to the preceding connecting element embodiment, wherein the downstream channel axis is diametrically central to the downstream channel portion. C3. Connecting element according to any of the preceding connecting element embodiments, wherein the downstream channel axis is straight and perpendicular to the sample outlet. In other words, the channel outlet portion axis is perpendicular with respect to a cross section of the sample outlet. C4. Connecting element according to any of the preceding connecting element embodiments, wherein the downstream section comprises a downstream section inner surface. C5. Connecting element according to the preceding connecting element embodiment, wherein the downstream section inner surface diametrically surrounds and thereby constitutes the downstream channel portion. C6. Connecting element according to any of the 2 preceding connecting element embodiments, wherein at least the downstream section inner surface within a downstream portion of the downstream section is conically shaped towards the sample outlet. C7. Connecting element according to any of the preceding connecting element embodiments, wherein an inner cross section of the downstream portion of the downstream section is tapered towards the sample outlet. C8. Connecting element according to any of the 2 preceding connecting element embodiments, wherein the downstream portion of the downstream section comprises the sample outlet and preferably the dilution gas inlet. C9. Connecting element according to any of the preceding connecting element embodiments, wherein a diameter of the downstream channel portion decreases in the downstream direction. CIO. Connecting element according to any of the preceding connecting element embodiments, wherein a cross section of the downstream channel portion is at least partially tapered towards the sample outlet. Cll. Connecting element according to any of the preceding connecting element embodiments, wherein the downstream channel portion comprises an outlet radius. C12. Connecting element according to the preceding connecting element embodiment, wherein the outlet radius is in the range of 1 mm to 12 mm, preferably 2 mm to 4 mm, more preferably 2.5 mm to 3.5 mm. C13. Connecting element according to any of the preceding connecting element embodiments, wherein the downstream channel portion comprises a gas inlet radius denoting the radius of the downstream channel portion at the dilution gas inlet. C14. Connecting element according to the preceding connecting element embodiment and with the features of Cll, wherein the gas inlet radius is greater than the outlet radius. C15. Connecting element according to any of the 2 preceding connecting element embodiments, wherein the gas inlet radius is in the range of 3 mm to 6.5 mm, preferably 5 mm to 6 mm, more preferably 5.5 mm to 6 mm. C16. Connecting element according to any of the preceding connecting element embodiments, wherein the downstream section is made of per- or polyfluorinated plastics, preferably PFA or PTFE, or glass, preferably high purity quartz glass. C17. Connecting element according to any of the preceding connecting element embodiments, wherein the dilution gas inlet axis is diametrically central to the dilution gas inlet. C18. Connecting element according to any of the preceding connecting element embodiments, wherein the dilution gas inlet axis is oriented at a first angle in the range of 90° to 110°, preferably 90° to 100° such as 90°, with respect to the downstream direction of the downstream channel portion. C19. Connecting element according to any of the preceding connecting element embodiments, wherein a distance between the dilution gas inlet axis and the downstream channel axis, which is defined as the distance between their nearest points, is in the range of 1 mm to 3 mm, preferably 2 mm to 2.5 mm. C20. Connecting element according to any of the preceding connecting element embodiments, wherein the dilution gas inlet is configured to provide a dilution gas flow surrounding a sample fluid flow guided through the downstream channel portion. C21. Connecting element according to any of the preceding connecting element embodiments, wherein the dilution gas inlet is configured such that dilution gas provided through the dilution gas inlet surrounds a sample fluid flow along the downstream channel axis in a swirling flow. C22. Connecting element according to any of the preceding connecting element embodiments and with the features of C4, wherein the dilution gas inlet is configured such that dilution gas provided through the dilution gas inlet acts as a sheath gas separating the sample fluid flow along the downstream channel axis from the downstream section inner surface downstream of dilution gas inlet. C23. Connecting element according to any of the preceding connecting element embodiments, wherein the dilution gas inlet is configured to be fluidly connected to a gas supply. C24. Connecting element according to any of the preceding connecting element embodiments, wherein the dilution gas inlet is configured to provide a volume flow of dilution gas in the range of 0.5 l / min to 1.1 l / min, preferably, 0,7 l / min to 1.1 l / min, more preferably 0.9 l / min to 1 l / min. C25. Connecting element according to any of the preceding connecting element embodiments, wherein the upstream channel portion comprises a bend channel portion with a bend portion axis which follows a circular arc. C26. Connecting element according to the preceding connecting element embodiment, wherein the bend channel portion provides a turn in the range of 30° to 120° of the upstream channel portion. C27. Connecting element according to any of the 2 preceding connecting element embodiments, wherein the bend channel portion provides a 90° turn of the upstream channel portion. C28. Connecting element according to any of the 3 preceding connecting element embodiments, wherein the bend channel portion comprises a bend radius in the range of 9 mm to 12 mm, preferably 9 mm to 11 mm, more preferably 10 mm to 10.5 mm. C29. Connecting element according to any of the 4 preceding connecting element embodiments, wherein the bend channel portion comprises a constant inner cross section. That is, the portion of the main flow channel constituted by the channel bend portion comprises a constant inner cross section. C30. Connecting element according to any of the 5 preceding connecting element embodiments, wherein the bend channel portion comprises a bend channel radius In the range of 3 to 6 mm, preferably 4 mm to 5 mm, more preferably 4.5 mm to 5 mm. C31. Connecting element according to any of the preceding connecting element embodiments, wherein the upstream section comprises a supplementary gas inlet. C32. Connecting element according to the preceding connecting element embodiment, wherein the supplementary gas inlet is located such that gas provided by the supplementary gas inlet is provided to the sample fluid flow. C33. Connecting element according to any of the 2 preceding connecting element embodiments, wherein the supplementary gas inlet is configured such that gas provided by the supplementary gas inlet mixes with a sample fluid flow in the upstream channel portion. C34. Connecting element according to any of the 3 preceding connecting element embodiments and with the features of C25, wherein the supplementary gas inlet is located such that gas provided by the supplementary gas inlet is provided to the bend channel portion of the upstream channel portion. C35. Connecting element according to any of the 4 the preceding connecting element embodiments, wherein the supplementary gas inlet comprises a supplementary gas inlet axis and wherein the supplementary gas inlet axis is aligned with the downstream channel axis. C36. Connecting element according to any of the preceding connecting element embodiments, wherein the upstream channel portion further comprises a channel Inlet portion comprising the sample inlet. C37. Connecting element according to the preceding connecting element embodiment, wherein the channel inlet portion is oriented at an angle of 30° to 120° with respect to the downstream channel portion. C38. Connecting element according to any of the 2 preceding connecting element embodiments, wherein the channel inlet portion is oriented perpendicular to the downstream channel portion. C39. Connecting element according to any of the preceding connecting element embodiments, wherein the connecting element further comprises a guiding element. C40. Connecting element according to the preceding connecting element embodiment, wherein the guiding element comprises a guiding element upstream end and a guiding element downstream end. C41. Connecting element according to the preceding connecting element embodiment, wherein the guiding element comprises a guiding element inner surface defining a channel between the guiding element upstream end and the guiding element downstream end. C42. Connecting element according to the preceding connecting element embodiment, wherein at least a downstream portion of the guiding element inner surface is conically shaped with a decreasing diameter in the downstream direction. C43. Connecting element according to any of the 3 preceding connecting element embodiments, wherein the guiding element comprises an inner upstream end radius. C44. Connecting element according to the preceding connecting element embodiment and with the features of C30, wherein the inner upstream end radius corresponds to the bend channel radius. C45. Connecting element according to any of the 2 preceding connecting element embodiments, wherein the inner upstream end radius is in the range of 1.5 mm to 6.5 mm, preferably 4 mm to 5.5 mm more preferably 5 mm to 5.5 mm. C46. Connecting element according to any of the 6 preceding connecting element embodiments, wherein the guiding element comprises an inner downstream end radius. C47. Connecting element according to the preceding connecting element embodiment and with the features of C30, wherein the inner downstream end radius is smaller than the inner upstream end radius. C48. Connecting element according to any of the 2 preceding connecting element embodiments, wherein the inner downstream end radius is In the range of 0.5 mm to 4.5 mm, preferably 1 mm to 3 mm more preferably 1 mm to 1.5 mm. C49. Connecting element according to any of the preceding connecting element embodiments and with the features of C39, wherein the guiding element is configured to separate a dilution gas provided at the dilution gas inlet and a sample fluid flow along the main channel at the dilution gas inlet. C50. Connecting element according to any of the preceding connecting element embodiments and with the features of C39, wherein the guiding element is configured to combine a sample fluid guided through the guiding element with a dilution gas guided along an outside of the guiding element such that the dilution gas surrounds the sample fluid and acts as a sheath gas. C51. Connecting element according to any of the preceding connecting element embodiments and with the features of C39, wherein the guiding element comprises a downstream portion and an upstream portion. C52. Connecting element according to the preceding connecting element embodiment, wherein an outer surface of the downstream portion of the guiding element is conically shaped with a decreasing diameter in the downstream direction. C53. Connecting element according to any of the 2 preceding connecting element embodiments and with the features of C4, wherein the outer surface of the downstream portion of the guiding element in combination with part of the downstream section inner surface provides a channel for dilution gas provided through the dilution gas inlet. C544. Connecting element according to any of the 3 preceding connecting element embodiments, wherein position and orientation of the dilution gas inlet in combination with the outer surface of the guiding element downstream portion and the downstream section inner surface are configured to constrain and guide dilution gas provided through the dilution gas inlet such that it surrounds sample fluid flow exiting the guide element downstream end. C55. Connecting element according to any of the 4 preceding connecting element embodiments, wherein the connecting element is configured such that dilution gas provided through the dilution gas inlet to the downstream channel portion is provided tangentially to the outer surface of the downstream portion of the guiding element. C56. Connecting element according to any of the 5 preceding connecting element embodiments, wherein the upstream portion of the guiding element is configured to seamlessly fit into the main flow channel. C57. Connecting element according to any of the 6 preceding connecting element embodiments, wherein the upstream portion of the guiding element is located upstream of the dilution gas Inlet. C58. Connecting element according to any of the 7 preceding connecting element embodiments, wherein the downstream section comprises a recess at an upstream portion thereof wherein at least part of the upstream portion of the guiding element is received. C59. Connecting element according to any of the 8 preceding connecting element embodiments, wherein the upstream section comprises a recess at a downstream portion thereof wherein at least part of the upstream portion of the guiding element is received. It will be understood that said downstream portion is downstream of a potential bend portion. C60. Connecting element according to any of the 9 preceding connecting element embodiments, wherein the upstream portion of the guiding element comprises a constant upstream portion radius, wherein the upstream portion radius is in the range of 6 mm to 10mm, preferably 6 mm to 8 mm, more preferably 6 mm to 6.5 mm. C61. Connecting element according to any of the preceding connecting element embodiments and with the features of C39, wherein the guiding element is located at least partially within the downstream section. C62. Connecting element according to any of the preceding connecting element embodiments and with the features of C39, wherein the guiding element is located at least partially withing the upstream section. C63. Connecting element according to any of the preceding connecting element embodiments and with the features of embodiment C40, wherein the guiding element downstream end is located downstream of the dilution gas Inlet in a direction parallel to the downstream channel axis. C64. Connecting element according to the preceding embodiment, wherein a distance between the downstream end and the dilution gas inlet along the direction parallel to the downstream channel axis is in the range 2 mm to 10 mm, preferably 5 mm to 10 mm, further preferably 7 mm to 8 mm. C65. Connecting element according to any of the preceding connecting element embodiments and with the features of C39, wherein the guiding element is made of per-or polyfluorinated plastics, preferably PFA or PTFE, or glass, preferably high purity quartz glass. C66. Connecting element according to any of the preceding connecting element embodiments, wherein the downstream section and the upstream section are formed separately from each other. C67. Connecting element according to any of the preceding connecting element embodiments, wherein the downstream section and the upstream section may be mechanically connected to each other by at least one, preferably at least two separable fastening means. C68. Connecting element according to any of the preceding connecting element embodiments and with the features of C39, wherein the connecting element is assembled of three parts: the downstream section, the upstream section and the guiding element. C69. Connecting element according to any of the preceding connecting element embodiments and with the features of C39, wherein the connecting element is configured such that the guiding element is held in place by being constrained by the upstream section and the downstream section. C70. Connecting element according to any of the preceding connecting element embodiments and with the features of C39, wherein the guiding element is not permanently fixed to other parts of the connecting element. That is, the guiding element may be exchangeable. C71. Connecting element according to any of the preceding connecting element embodiments, wherein downstream section and upstream section are separably connected to each other. Below, reference will be made to ion source embodiments. These embodiments are abbreviated by the letter "I" followed by a number. Whenever reference is herein made to "source embodiments", these embodiments are meant. II. Ion source comprising a connecting element according to any of the preceding connecting element embodiments, wherein the connecting element is configured to receive an aerosol provided by a nebulizer. 12. Ion source according to the preceding source embodiment, wherein the ion source further comprises an injector and wherein the sample outlet of the connecting element is fluidly connected to the injector. 13. Ion source according to any of the 2 preceding source embodiments, wherein the ion source is an inductively coupled plasma (ICP) source. Below, reference will be made to system embodiments. These embodiments are abbreviated by the letter "S" followed by a number. Whenever reference is herein made to "system embodiments", these embodiments are meant. SI. Sample introduction system for a spectrometer comprising a nebulizer, an ion source, and a connecting element according to any of the preceding connecting element embodiments, wherein the connecting element is configured to guide an aerosol provided by the nebulizer to the ion source. S2. Sample introduction system according to the preceding system embodiment, wherein the sample inlet of the connecting element is fluidly connected to the nebulizer. S3. Sample introduction system according to the penultimate system embodiment, wherein the system further comprises a spray chamber downstream of the nebulizer. S4. Sample introduction system according to the preceding system embodiment, wherein the sample inlet of the connecting element is fluidly connected to the spray chamber. S5. Sample introduction system according to any of the preceding system embodiments, wherein the sample outlet of the connecting element is fluidly connected to the ion source. S6. Sample introduction system according to any of the preceding system embodiments, wherein the sample outlet of the connecting element is fluidly connected to an injector of the ion source. S7. Sample Introduction system according to any of the preceding system embodiments, wherein the ion source comprises an inductively coupled plasma. S8. Sample Introduction system according to any of the preceding system embodiments, wherein the system further comprises a humidifier fluidly connected to the dilution gas inlet of the connecting element. S9. Sample introduction system according to any of the preceding system embodiments, wherein the ion source comprises the connecting element. Below, reference will be made to use embodiments. These embodiments are abbreviated by the letter "U" followed by a number. Whenever reference Is herein made to "use embodiments", these embodiments are meant. UI. Use of the connecting element according to any of the preceding connecting element embodiments and / or the sample introduction system according to any of the preceding system embodiments in a spectrometry system. U2. Use according to the preceding use embodiment, wherein the spectrometry system is an inductively coupled plasma spectrometry system. U3. Use according to any of the preceding use embodiments, wherein the spectrometry system is a mass spectrometry system. U4. Use according to any of the embodiments UI and U2, wherein the spectrometry system is an optical spectrometry system. Below, reference will be made to spectrometer embodiments. These embodiments are abbreviated by the letter "V" followed by a number. Whenever reference is herein made to "spectrometer embodiments", these embodiments are meant. VI. Spectrometer comprising the connecting element according to any of the preceding connecting element embodiments and / or the sample introduction system according to any of the preceding system embodiments. 5 Embodiments of the present invention will now be described with reference to the accompanying drawings. These embodiments should only exemplify, but not limit, the present invention. Fig. 1 depicts a 90°-elbow connecting element according to the state of the art; Fig. 2a depicts a sectional perspective view of an exemplary connecting element according to the present invention; Fig. 2b depicts a cross-sectional view of the exemplary connecting element; Fig. 2c depicts further views of the exemplary connecting element; and Fig. 3 illustrates the relative orientation of the downstream channel axis and the dilution gas inlet axis, which are skew lines in the x-y plane. It is noted that not all the drawings carry all the reference signs. Instead, in some of the drawings, some of the reference signs have been omitted for the sake of brevity and simplicity of the illustration. Embodiments of the present invention will now be described with reference to the accompanying drawings. With reference to Fig. 1, a 90°-elbow connecting element 1 with a constant cross-section may frequently be used in current ICP-MS systems, e.g., the iCAP™ Qnova series by Thermo Fisher Scientific. Again, the connecting element may generally be configured for guiding a sample-comprising aerosol from a spray chamber and / or nebulizer to an injector of an ion source of an MS-system. The connecting element is typically constrained due to limited installation space. The sample-comprising aerosol may be provided by converting a liquid sample into a primary aerosol utilizing a nebulizer, e.g., a pneumatic atomiser. Typically, the primary aerosol may subsequently be transferred to a spray chamber for droplet size separation. The resulting aerosol may also be referred to as tertiary aerosol. The depicted 90°-elbow connecting element 1 may generally comprise an input interface 11 and an output interface 12. In other words, tertiary aerosol from the spray chamber may be provided to the 90°-elbow connecting element 1 at the inlet interface 11 and then be guided through the connecting element 1, particularly through a main flow path thereof, to the outlet interface 12, which may be connected to the injector during operation. Said main flow path is indicated by the dotted line. Furthermore, the 90°-elbow connecting element 1 may comprise a connection 13 for introduction of a supplementary gas (also referred to as "add gas"), which may be located in an axial direction to the outlet interface 12 and thus during operation to the torch in case of an ICP-MS system. A central axis of the flow path of the connection is indicated by the dashed line. Such a 90°-elbow connecting element 1 may for example be made of PFA (Perfluoroalkoxy alkanes) and may comprise a constant cross-section (excluding the interfaces which may be configured to accommodate an end portion of a connecting tube, as for example depicted for the inlet interface 11). However, such a design may disadvantageously lead to undesired turbulences due to the relative abrupt change of direction for the tertiary aerosol, which in turn may lead to undesired aerosol deposition within the connecting element and may thus lower the transport efficiency. Furthermore, the 90°-elbow connecting element 1 allows for introduction of a supplementary gas (add gas) coaxially to the main flow path at the outlet interface. Due to the shape of the interior of this connecting element, the supplementary gas would mix with the tertiary aerosol in such a way that additional turbulences are introduced. With reference to Figs. 2a to 2c, an embodiment of the present invention is described. Very generally, the connecting element 2 comprises a sample inlet 231 and a sample outlet 221, which are fluidly connected through a main flow channel. The connecting element 2 comprises a downstream section 22 comprising the sample outlet 221 and a downstream channel portion 222, and an upstream section 23 comprising the sample inlet 231 and an upstream channel portion 232. The upstream channel portion 232 and the downstream channel portion 222 constitute the main flow channel fluidly connecting the sample inlet 231 to the sample outlet 221. Furthermore, the downstream section 22 comprises a dilution gas inlet 223 configured to provide a dilution gas to the downstream channel portion 222. The downstream channel portion 222 comprises a downstream channel axis and the dilution gas inlet 223 comprises a dilution gas inlet axis, wherein the downstream channel axis and the dilution gas inlet axis are skew lines. Contrary to the common design depicted in Fig. 1, connecting elements according to the present invention therefore allow for an off-axis introduction of the dilution gas for compensating a reduced gas flow in the nebulizer. This may advantageously allow to utilize the dilution gas as a sheath gas surrounding the flow of sample fluid flow, e.g., samplecomprising tertiary aerosol, along the main flow axis, thereby allowing to reduce undesired sample deposition and increase sample transport efficiency of the connecting element 2. The downstream channel axis may be diametrically central to the downstream channel portion 222. Preferably, the downstream channel axis may be straight and perpendicular to the sample outlet 221. That is, it may be perpendicular to a cross-section of the sample outlet. Thus, the downstream section 22 may preferably be straight. Similarly, the dilution gas inlet axis may be diametrically central to the dilution gas inlet 223. Generally, the dilution gas inlet 223 may be configured to be fluidly connected to a gas supply, e.g., via a fitting. The dilution gas inlet 223 may for example comprise a thread for receiving a respective fitting. The downstream section 22 may comprise a downstream section inner surface 224 diametrically surrounding and thereby constituting the downstream channel portion 222. At least a downstream portion of the downstream section inner surface 224 may be tapered towards the sample outlet, that is, it may resemble a cone-like or funnel-like shape, wherein a diameter of the downstream channel portion 222 may decrease in a direction towards the sample outlet 221, i.e., in a downstream direction. That is, a cross-section of the downstream channel portion 222 may be at least partially tapered towards the sample outlet 221. The downstream portion of the downstream section inner surface 224 preferably reaches up to the sample outlet 221 and may comprise an opening of the dilution gas inlet 223.In some embodiments, the downstream portion of the downstream section inner surface 224 may comprise the part of the downstream channel inner surface that is subjected to sample fluid and / or dilution gas during use. In other words, an inner cross section of at least a downstream portion of the downstream section 22 may be tapered, wherein the downstream portion comprises the sample outlet 221 and preferably the dilution gas inlet 223. Similarly, the downstream portion of the downstream section may comprise the part of the downstream channel inner surface that is subjected to sample fluid and / or dilution gas during use. The downstream channel portion 222 may comprise an outlet radius r0 denoting the radius of the downstream channel portion at the sample outlet 221. Said outlet radius r0 may be in the range of 1 mm to 12 mm, preferably 2 mm to 4 mm, more preferably 2.5 mm to 3.5 mm. The outlet radius r0 may preferably match a radius of an injector inlet, which may for example be 3 mm. Furthermore, the downstream channel portion 222 may comprise a gas inlet radius rg denoting the radius of the downstream channel portion at the dilution gas inlet 223. Said gas inlet radius rg may preferably be greater than the outlet radius ro. The gas inlet radius rg may for example be in the range of 3 mm to 6.5 mm, preferably 5 mm to 6 mm, more preferably 5.5 mm to 6 mm. With reference to Fig. 3, the dilution gas inlet axis ai may preferably be oriented at a first angle a in the range of 90° to 110°, preferably 90° to 100° such as 90° with respect to the main flow direction of the downstream channel portion (arrow), e.g., the downstream direction (corresponding to the x-directlon). In other words, the first angle a may denote the angle between the projections of the dilution gas inlet axis ai and the downstream channel axis ad when being projected onto the x-y-plane provided the downstream channel portion axis is parallel or identical to the x-axis. Put differently, the dilution gas inlet axis ai may be angled 0 to 20° preferably 0 to 10°, such as 0° with respect to a plane perpendicular to the downstream channel axis aa. Overall, the dilution gas inlet may thus be perpendicular to the main flow direction or alternatively slightly angled towards the sample outlet 221. A distance between the dilution gas inlet axis ai and the downstream channel axis ad, which may be defined as the distance between their nearest points may be preferably 1 mm to 3 mm, more preferably 2 mm to 2.5 mm. That is, the dilution gas inlet axis ai is generally at an angle with respect to the downstream channel axis aa, wherein this angle is close to 90°. Furthermore, they do not insect one another, but they form skew lines. Thus, dilution gas introduced through the dilution gas inlet 223 may spiral around the sample fluid flow, as indicated by the helical, dotted line in Fig. 2a. In other words, the downstream channel portion 22 comprises a dilution gas inlet 223 which may be configured to provide a dilution gas flow surrounding a sample fluid flow guided through the downstream section 22 and specifically through the downstream channel portion 222 and particularly along the downstream channel axis. The dilution gas inlet 223 may be configured such that the dilution gas surrounds the sample fluid flow along the downstream channel axis in a swirling flow. In particular, location and orientation of the dilution gas inlet 223 with respect to the downstream channel axis may be designed such that the dilution gas provided through the dilution gas inlet 223 surrounds the sample fluid flow along the downstream channel axis in a swirling flow. More generally, the dilution gas inlet 223 may be configured such that dilution gas provided through the dilution gas inlet 223 acts as a sheath gas separating the sample fluid flow along the downstream channel axis from the downstream section inner surface 224 downstream of the dilution gas inlet 223. The sample fluid may preferably be a sample-comprising aerosol. It will be understood that a sample fluid flow along the downstream channel axis corresponds to a sample fluid flow within the downstream channel portion 222. Furthermore, it will be understood that downstream and upstream directions are defined with respect to the main flow channel and thus particularly with respect to the sample fluid flow, unless expressly stated otherwise. That is, the sample inlet 231 is upstream of the sample outlet 221 and vice versa. The upstream channel portion 232 may comprise a bend channel portion 2322 with a bend portion axis ab which follows a circular arc. Preferably the bend channel portion 2322 provides a turn in the range of 30° to 120° of the upstream channel portion 232 and thus the main flow channel, e.g., a 90° turn. The bend channel portion 2322 may comprise a bend radius rb denoting the radius of the bend portion axis ab, which may be in the range of 9 mm to 12 mm, e.g., 10 to 10.5mm. This bend channel portion 2322 may advantageously allow to change direction of the aerosol flow while reducing induced turbulences compared to a simple 90° corner as frequently used in common connecting elements. The bend channel portion 2322 may comprise a constant cross section. The bend channel portion 2322 may comprise a bend channel radius rc in the range of 3 mm to 6 mm, preferably 4 mm to 5 mm, more preferably 4.5 mm to 5 mm. It will be understood that the bend channel portion 2322 is optional, and the upstream channel portion 232 may in some embodiments be straight. In other words, the upstream channel portion 232 may in some embodiments not comprise a bend channel portion 2322. The upstream section 23 may comprise a supplementary gas inlet 233. Generally, the supplementary gas Inlet may allow for introducing a supplementary gas (sometimes also referred to as additional gas or "add gas") to the sample fluid provided by the nebulizer and / or spray chamber. This supplementary gas may be introduced such that it mixes with the sample fluid. Supplementary gas may for example be introduced to reduce undesired interferences in the measurement results. For example, oxygen may be used, while in some applications hydrogen or ammonia could be used. Oxygen may for example be introduced to oxidize carbon and thus to avoid the reduction of carbon to graphite, which may otherwise result in undesired deposition thereof. It is noted that both supplementary gas and dilution gas can be used to reduce or even prevent the build-up of deposits in the connection element and in an ion source downstream of the connection element. Supplementary gas (or "add gas") achieves this by chemical reactions, such as oxidation, while dilution gas reduces deposits by reducing the amount of sample flowing through the connection element. Dilution gas is typically not meant to cause chemical reactions and for that reason, an inert gas such as argon is often used as dilution gas. The supplementary gas inlet 233 may be located such that a supplementary gas may be introduced to a sample fluid flowing through the main flow channel and particularly the upstream channel portion 232. In other words, it may be located and / or configured such that a supplementary gas can be introduced to a sample fluid flow in the upstream channel portion 232. This may advantageously allow to introduce a supplementary gas dependent on the current application. In embodiments comprising the bend channel portion 2322, the supplementary gas inlet 233 may be located such that the supplementary gas is provided to the bend channel portion 2322 of the upstream channel portion 232. The supplementary gas inlet 233 may comprise a supplementary gas inlet axis as that may preferably be aligned with the downstream channel axis aa. That is, both axes may be identical to each other. Generally, the supplementary gas inlet 233 may be configured to be fluidly connected to a gas supply, e.g., via a fitting. Such a fitting may be oriented at an angle with respect to the supplementary gas inlet axis as, which may advantageously allow to facilitate the connection of a gas supply line, particularly in view of potentially limited working space. It will be understood that the depicted angle is only exemplary and that also other angles may be realised depending on boundary conditions of surrounding instruments and / or working space. For example, the fitting may in some embodiments also be aligned with the supplementary gas inlet axis as, i.e., the angle may be zero. The supplementary gas inlet 233 may for example comprise a thread for receiving a respective fitting. Furthermore, the upstream channel portion 232 may comprise a channel inlet portion 2321 comprising the sample inlet 231. The channel inlet portion 2321 may be oriented at an angle of 30° to 120° with respect to the downstream channel portion 22. Particularly, the channel inlet portion 2321 may be oriented perpendicular to the downstream channel portion 22. In particular, the channel inlet portion 2321 may comprise a channel inlet portion axis that may be perpendicular to the downstream channel axis. Preferably, the channel inlet portion axis may be straight and perpendicular to the sample inlet 241. Similarly, the channel inlet portion axis may preferably be diametrically central to the channel inlet portion 2321. Generally, the channel inlet portion 2321 may be upstream of the channel bend portion 2322 which in turn may be upstream of the downstream channel portion. The connecting element 2 may further comprise a guiding element 25. The guiding element 25 may generally comprise a guiding element upstream end 251 (also referred to as guiding element inlet) and a guiding element downstream end 252 (also referred to as guiding element outlet). Generally, the guiding element may be configured to receive a sample fluid flow at the guiding element upstream end 251 and to channel the sample fluid flow through the guiding element towards the guiding element downstream end 252. The guiding element 25 may comprise a guiding element Inner surface 253 defining a channel between the guiding element upstream end 251 and the guiding element downstream end 252. The guiding element inner surface 253 may preferably be conically shaped with a decreasing diameter in the downstream direction, i.e., in the direction of flow. That is, the guiding element 25 may comprise an inner cross section that is tapered towards the guiding element downstream end 252. In other words, the guiding element may provide a guiding element channel between the guiding element upstream end 251 and the guiding element downstream end 252 which is tapered towards the guiding element downstream end 252. This may advantageously allow to focus a fluid supplied at the guiding element upstream end 251 towards a centre of the flow path. The guiding element 25 may comprise an inner upstream end radius ru, denoting the inner radius of the guiding element upstream end (i.e., the radius of the guiding element channel at the upstream end). Said inner upstream end radius ru may preferably correspond to the bend channel radius rc. The inner upstream end radius may be in the range of 1.5 mm to 6.5 mm, preferably 4 mm to 5.5 mm more preferably 5 mm to 5.5 mm. Similarly, the guiding element 25 may comprise an inner downstream end radius rd, denoting the inner radius of the guiding element downstream end 252 (i.e., the radius of the guiding element channel at the downstream end). The inner downstream end radius rd may generally be smaller than the inner upstream end radius ru. The inner downstream end radius rd may be in the range of 0.5 mm to 4.5 mm, preferably 1 mm to 3 mm more preferably 1 mm to 1.5 mm. The guiding element 25 may comprise a downstream portion and an upstream portion. For the downstream portion of the guiding element 25, an outer surface 254 may be conically shaped, similar to the inner surface 253. That is, for the downstream portion of the guiding element 25, an outer diameter may continuously decrease in the flow direction of the main flow channel, i.e., the downstream direction. The outer surface 234 of the guiding element downstream portion in combination with part of the downstream section inner surface may provide a channel for dilution gas provided through the dilution gas inlet. In particular, the cone-like shape may generally be configured to aid with dilution gas provided through the dilution gas inlet 223 to flow in a swirling flow. In other words, position and orientation of the dilution gas inlet 223 in combination with the outer surface 254 of the guiding element downstream portion and the inner surface 224 of the downstream section 22, may be configured to constrain and guide the dilution gas provided through the dilution gas inlet 223 such that is surrounds the sample fluid flow exiting the guide element downstream end, e.g., aerosol flow, while preferably flowing in a swirling flow around the sample fluid flow. The connecting element may be configured such that dilution gas may be provided to the downstream channel portion tangentially to the guiding element downstream portion. In particular the dilution gas inlet 223 and the guiding element 25 may be arranged such that dilution gas is provided tangentially to the outer surface 254 of the downstream portion of the guiding element. The upstream portion of the guiding element may be configured to seamlessly fit into the main flow channel. In particular, it may comprise a constant upstream portion radius rP which may generally be larger than the inner upstream end radius ru. The upstream portion radius rP may be in the range of 6 mm tolO mm, preferably 6 mm to 8 mm, more preferably 6 mm to 6.5 mm. Generally, the guiding element 25 may be dimensioned and / or positioned within the main flow channel such that it may prevent dilution gas provided through the dilution gas inlet 223 to flow upstream. That is, the guiding element 25 may be seamlessly, optionally sealingly, connected to the downstream section 22 upstream of the dilution gas inlet 222. Generally, the guiding element 25 may be configured to guide dilution gas provided through the dilution gas inlet 223 towards the guiding element downstream end 252 to surround the sample fluid flow flowing through the guiding element downstream end 252. In other words, a downstream portion of the guiding element 25 may be configured to be surrounded by dilution gas provided, e.g., injected, through the dilution gas inlet 223. The guiding element 25 may at least partially be located within the downstream section 22, preferably the guiding element 25 may further be partially located within the upstream section 23. Thus, the guiding element 25 may generally be located within the main flow channel, preferably at least partially within the downstream channel portion and / or at least partially within the upstream channel portion. For example, the downstream section 22 and / or the upstream section 23 and more particularly the downstream channel portion and / or the upstream channel portion, may comprises a respective recess configured to accommodate at least part of the upstream portion of the guiding element 25. The upstream portion of the downstream section 22 may comprise a recess configured to receive at least part of the upstream portion of the guiding element. Similarly, a downstream portion of the upstream section 23 may comprise a recess configured to receive at least part of the upstream portion of the guiding element 25. As depicted, the guiding element 25 may extend in the downstream direction to a location further downstream than the dilution gas inlet 223. This may further contribute to the dilution gas introduced through the dilution gas inlet 223 surrounding the sample fluid flow. For example, the downstream end 252 of the guiding element 25 may be distanced from the dilution gas inlet 223 in the flow direction, i.e., in the x-direction, by 2 mm to 10 mm, preferably by 5 mm to 10 mm, further preferably by 7 mm to 8 mm. The guiding element may be made of per- or polyfluorinated plastics, preferably PFA or PTFE, or glass, preferably high purity quartz glass. Generally, the guiding element 25 may be held in place by being constrained by the upstream section and the downstream section. Preferably, the downstream section 22 and the upstream section 23 may be formed separately from each other. The downstream section 22 and the upstream section 23 may be mechanically connected to each other by means of at least one, preferably at least two separable fastening means 26. Such fastening means may for example comprise pins 261 that are configured to be inserted in respective orifices 262 of the opposing section. Alternatively, such fastening means may for example comprise screws. In other words, the connecting element 2 may preferably comprise and be assembled of three separately provided parts: the downstream section 22, the upstream section 23 and the guiding element 25. This may advantageously allow to exchange the guiding element 25 without having to exchange the whole connecting element. This may be advantageous as the guiding element may experience some degree of sample and / or matrix deposition. However, it will be understood that the guiding element 25 may for example also be integrally formed with the upstream section 23 or the downstream section 22. In such cases, the connecting element 2 may only comprise and be assembled of two separately provided parts. A downstream end of the downstream section 22 may be configured to be connected to an ion source, preferably to an injector of an ion source, e.g., a plasma torch. For example, the downstream end may comprise a smaller outer radius compared to the rest of the downstream section 22, thereby providing a recess that allows for inserting the downstream end in an injector of an ion source. The outer radius of the downstream end may be in the range of 5 mm to 10 mm, preferably 6 mm to 8 mm, more preferably 6 mm to 6.5 mm The downstream section may preferably be made of per- or polyfluorinated plastics, preferably PFA or PTFE, or glass, preferably high purity quartz glass. In other words, the connecting element 2 according to the present invention, which may also be referred to as sweep elbow, may consist of three assembled parts. The upstream section 23 may provide an interface to a spray chamber and / or nebulizer and comprise a connection for introduction of a supplementary gas (also referred to as add gas). The upstream section may generally comprise a constant cross section, i.e., a constant inner diameter (apart from an optional recess for receiving part of the guiding element) and may be configured to deflect the sample (aerosol) in a 90° arc, for example. The curved geometry may advantageously reduce turbulences compared to the conventional geometry illustrated in Fig. 1. The downstream section 22 may provide an interface for providing the aerosol to an ion source and particularly to an injector and may be connected to the upstream section 23, e.g., by means of two or more pins. The downstream section 23 advantageously allows for the introduction of a dilution gas (e.g., the AGD) as sheath gas. The guiding element 25 advantageously enables formation of a vortex of dilution gas around the sample fluid (sample-comprising aerosol). The sample fluid may be channelled through a conical outer geometry of the guiding element, while the tangentially introduced dilution gas (AGD gas) may flow around the guiding element and envelope the sample fluid when entering the downstream channel portion 222 of the downstream section 22. This enveloping may advantageously take place up to the tip of the injector, so that crystallisation on the walls of the injector may be prevented. The connecting element 2 may be part of a sample introduction system, wherein the sample inlet 241 may be fluidly connected to a spray chamber and / or nebulizer and the sample outlet may be fluidly connected to an injector that guides the sample fluid to the plasma, preferably comprising an inductively coupled plasma (torch). Furthermore, a humidifier may be fluidly connected to the dilution gas inlet 222. Said humidifier may advantageously allow to humidify the dilution gas which has been found to be advantageous when used as a sheath gas. Thus, a connecting element is provided that allows to establish the connection between a spray chamber and / or nebulizer and an injector, advantageously only requiring limited installation space. The shape of the connecting element may advantageously allow for a aerosol flow with reduced, preferably minimized, turbulence in order to achieve a high transport efficiency without precipitation of the aerosol in areas downstream of the spray chamber. Furthermore, the connecting element may not only enable the addition of a gas in an axial direction but may advantageously allow for introduction of a further dilution gas flow to dilute the aerosol. This dilution gas flow may be referred to as AGD (Argon Gas Dilution) and it has been found that it has applicative advantages for high matrix samples, e.g., samples with a high salt load, since the introduction of the AGD flow may compensate for a reduction In the nebuliser gas flow, so that effectively less sample and correspondingly less matrix may be introduced into downstream components, e.g., the ion source. Advantageously, the present invention and particularly the guiding element may allow to reduce and preferably prevent interference of the AGD flow with the transport of the aerosol. That is, it may advantageously allow for the remaining sample (in the aerosol) to be transported to a tip of an injector of the ion source with little to no loss, particularly without the injector losing diameter prematurely due to crystallisation of the matrix and thus influencing the result of the measurement. Furthermore, it has been found that it may be advantageous for the dilution gas to be humidified. Whenever a relative term, such as "about", "substantially" or "approximately" is used in this specification, such a term should also be construed to also include the exact term. That is, e.g., "substantially straight" should be construed to also include "(exactly) straight". Whenever steps were recited in the above or also in the appended claims, it should be noted that the order in which the steps are recited in this text may be accidental. That Is, unless otherwise specified or unless clear to the skilled person, the order in which steps are recited may be accidental. That is, when the present document states, e.g., that a method comprises steps (A) and (B), this does not necessarily mean that step (A) precedes step (B), but It is also possible that step (A) is performed (at least partly) simultaneously with step (B) or that step (B) precedes step (A). Furthermore, when a step (X) is said to precede another step (Z), this does not imply that there is no step between steps (X) and (Z). That is, step (X) preceding step (Z) encompasses the situation that step (X) Is 5 performed directly before step (Z), but also the situation that (X) is performed before one or more steps (Yl), ..., followed by step (Z). Corresponding considerations apply when terms like "after" or "before" are used. While in the above, a preferred embodiment has been described with reference to the 10 accompanying drawings, the skilled person will understand that this embodiment was provided for illustrative purpose only and should by no means be construed to limit the scope of the present invention, which is defined by the claims.

Claims

1. Connecting element for fluidly connecting an outlet of a spray chamber to an ion source, wherein the connecting element comprisesa downstream section comprising a downstream channel portion and a sample outlet, andan upstream section comprising an upstream channel portion and a sample inlet,wherein the sample inlet is fluidly connected to the sample outlet via a main flow channel constituted by the upstream channel portion and the downstream channel portion,wherein the downstream section comprises a dilution gas inlet configured to provide a dilution gas to the downstream channel portion,wherein the downstream channel portion comprises a downstream channel axis and the dilution gas inlet comprises a dilution gas inlet axis,wherein the downstream channel axis and the dilution gas inlet axis are skew lines, andwherein the upstream section comprises a supplementary gas inlet.

2. Connecting element according to the preceding claim, wherein the dilution gas inlet axis is oriented at a first angle in the range of 90° to 110°, preferably 90° to 100° such as 90°, with respect to the downstream direction of the downstream channel portion.

3. Connecting element according to any of the preceding claims, wherein a distance between the dilution gas inlet axis and the downstream channel axis, which is defined as the distance between their nearest points, is in the range of 1 mm to 3 mm, preferably 2 mm to 2.5 mm.

4. Connecting element according to any of the preceding claims, wherein the dilution gas inlet is configured such that dilution gas provided through the dilution gas inlet surrounds a sample fluid flow along the downstream channel axis in a swirling flow.

5. Connecting element according to any of the preceding claims, wherein the connecting element further comprises a guiding element, wherein the guiding element comprises a guiding element upstream end and a guiding element downstream end.

6. Connecting element according to the preceding claim,wherein the guiding element comprises a guiding element inner surface defining a channel between the guiding element upstream end and the guiding element downstream end,andwherein at least a downstream portion of the guiding element inner surface is conically shaped with a decreasing diameter in the downstream direction.

7. Connecting element according to any of the 2 preceding claims, wherein the guiding element is configured to combine a sample fluid guided through the guiding element witha dilution gas guided along an outside of the guiding element such that the dilution gas surrounds the sample fluid and acts as a sheath gas.

8. Connecting element according to any of the 3 preceding claims, wherein the guiding element comprises a downstream portion and an upstream portion, andwherein an outer surface of the downstream portion of the guiding element is conically shaped with a decreasing diameter in the downstream direction.

9. Connecting element according to any of the 4 preceding claims, wherein the connecting element is configured such that dilution gas provided through the dilution gas inlet to the downstream channel portion is provided tangentially to the outer surface of the downstream portion of the guiding element.

10. Connecting element according to any of the 5 preceding claims, wherein the guiding element downstream end is located downstream of the dilution gas inlet in a direction parallel to the downstream channel axis,wherein a distance between the downstream end and the dilution gas inlet along the direction parallel to the downstream channel axis is in the range 2 mm to 10 mm, preferably 5 mm to 10 mm, further preferably 7 mm to 8 mm.

11. Connecting element according to any of the 6 preceding claims, wherein the connecting element is assembled of three parts: the downstream section, the upstream section and the guiding element.

12. Connecting element according to any of the 7 preceding claims, wherein the guiding element is not permanently fixed to other parts of the connecting element.

13. Connecting element according to any of the preceding claims, wherein the downstream section and the upstream section are formed separately from each other.

14. Connecting element according to any of the preceding claims, wherein the supplementary gas inlet is located such that a such that gas provided by the supplementary gas inlet is provided to the sample fluid flow.

15. Connecting element according to any of the preceding claims, wherein the upstream channel portion comprises a bend channel portion with a bend portion axis which follows a circular arc.

16. Connecting element according to the preceding claim, wherein the supplementary gas inlet is located such that gas provided by the supplementary gas inlet is provided to the bend channel portion of the upstream channel portion.

17. Connecting element according to any of the preceding claims, wherein the supplementary gas inlet comprises a supplementary gas inlet axis and wherein the supplementary gas inlet axis is aligned with the downstream channel axis18. Connecting element according to any of the preceding claims, wherein the downstream section comprises a downstream section inner surface, andwherein at least the downstream section inner surface within a downstream portion of the downstream section is conically shaped towards the sample outlet.

19. Connecting element according to any of the preceding claims, wherein a diameter of the downstream channel portion decreases in the downstream direction.

20. Sample introduction system for a spectrometer comprisinga nebulizer,an ion source, anda connecting element according to any of claims 1 to 19, wherein the connecting element is configured to guide an aerosol provided by the nebulizer to the ion source.

21. Sample introduction system according to the preceding claim, wherein the system further comprises a humidifier fluidly connected to the dilution gas inlet of the connecting element.

22. Spectrometer comprising the connecting element according to any of claims 1 to 19 and / or the sample introduction system according to any of claims 20 and 21.

23. Use of the connecting element according to any of claims 1 to 19 and / or the sample introduction system according to any of claims 20 and 21 in a spectrometry system.30

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