Hollow cathode glow discharge reagent ion source for IMR / PTR-MS

Abstract

The present invention relates to a device and a method for operating a device for ion molecule reaction-mass spectrometry (IMR-MS) and / or proton transfer reaction-mass spectrometry (PTR-MS) for analyzing a gas for at least one compound to be analyzed by chemical ionization via specific types of reagent ions, the device comprising: a source of reagent ions, the device has a hollow cathode glow discharge (HCD) region (101) and a source drift (SD) region (102); a drift tube region (103) adjacent to the source of reagent ions, comprising at least one inlet (107) for the gas to be analyzed and at least one source for an electric field; a mass analyzer region (104) adjacent to the drift tube region (103); the HCD region (101) comprises at least one port (105) connected to at least one pump, at least two electrodes serving as anodes (201, 203) and at least one electrode serving as a cathode (202), the SD region (102) comprises at least one port (106) connected to at least one source gas supply, and the control device is configured to control a discharge current in the HCD region (101), controlling the source gas flow through the reagent ion source, adjusting the pressure in the drift tube region (103) between 1 and 10 hPa, adjusting the electric field in the drift tube region (103) wherein the electric field comprises at least a DC field configured to attract ions in the direction of the mass analyzer region (104).

Description

Technical Field

[0001] This invention relates to an apparatus for ion-molecular-reaction mass spectrometry and / or proton-transfer-reaction mass spectrometry, for analyzing a gas for at least one analyte compound by chemical ionization of a specific type of reagent ions. The apparatus comprises: a reagent ion source having a hollow cathode glow discharge region and a source drift region; a drift tube region adjacent to the reagent ion source, including at least one inlet for the analyte gas and at least one source for an electric field; a mass analyzer region adjacent to the drift tube; and control equipment. The invention also relates to a method of operating the apparatus for ion-molecular-reaction mass spectrometry and / or proton-transfer-reaction mass spectrometry according to the invention. Background Technology

[0002] Ion-molecular-reaction mass spectrometry (IMR-MS) or proton-transfer-reaction mass spectrometry (PTR-MS) is a direct injection method for the online detection and quantification of trace gases. Crucially, reagent ions are generated in a spatially separated reagent ion source. Subsequently, the reagent ions and a trace amount of gas containing the analyte are injected into an IMR / PTR drift tube, where the analyte undergoes chemical ionization through interaction with the reagent ions under a well-controlled electric field. Finally, the neutral gas is removed, and the ions are introduced into the mass spectrometer / analyzer.

[0003] IMR / PTR-MS instruments known in this art consist of the following components:

[0004] HCD-SD reagent ion source

[0005] The main design of currently used hollow cathode glow discharge (HCD)-source drift (SD) reagent ion sources was introduced in the 1990s (see, for example, A. Hansel et al., Proton transfer reaction mass spectrometry: on-line tracegas analysis at the ppb level, Int. J. Mass Spectrom. Ion Proc. 149 / 150 (1995) 609-619, and W. Lindinger et al., On-line monitoring of volatile organic compounds atpptv levels by means of Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) Medical applications, food control and environmental research, Int. J. Mass Spectrom. Ion Proc. 173 (1998) 191-241).

[0006] - An HCD region with an inlet for the source gas, followed by

[0007] The -SD region, which is the region where ions generated in the HCD region react with the neutral source gas under the influence of an electric field, has an outlet to the vacuum pump.

[0008] In order to produce H3O + Reagent ions are typically introduced into the HCD region at a rate of approximately 0.1-10 sccm (mL / min under standard conditions) using pure water vapor (source gas), while the discharge current is controlled between 0.5-10 mA. Within the HCD region, some H₂O molecules are converted to O₂. + OH + H + H2 + These ions, along with neutral H2O vapor, are subsequently attracted to the SD region by the electric field and pressure difference, where they react primarily with H3O via these reactions. + The reaction will proceed as follows:

[0009] H2 + +H₂O→H₂O + +H2

[0010] H + +H₂O→H₂O + +H

[0011] O+ +H₂O→H₂O + +O

[0012] And finally

[0013] H2O + +H₂O→H₂O.H + +OH.

[0014] H3O achieved using this type of ion source + (H2O.H + The reagent ion purity level renders the quality filters used for further purification obsolete; the main parasitic ion is O2. + and NO + Furthermore, H3O emitted from this type of reagent ion source + The reagent ion current is abnormally high. Finally, the operating pressure in this type of ion source is 10... -1 It is on the order of -1 hPa and therefore fits well with the operating pressures (1-10 hPa) of conventional PTR-MS reaction chambers.

[0015] It has been discovered that, in addition to H3O, + Besides this type of reagent ion source, a range of other reagent ions can be generated with high purity and high intensity, the most common example of which is:

[0016] -O2 + When pure O2 is introduced into the HCD region (see A. Jordan et al., Int. J. Mass Spectrom. 286 (2009) 32-38),

[0017] -NO + When a mixture of N2 and O2 is introduced into the HCD region,

[0018] -Kr + When pure Kr is introduced into the HCD (and a buffer gas is added to the IMR / PTR drift tube) (EP2606505B1 and P. Sulzer et al., Int. J. Mass Spectrom. 321-322 (2012) 66-70),

[0019] -NH4 + When a mixture of N2 and H2O vapors (especially without NH3) is introduced into the HCD region (EP3503161B1).

[0020] The switching between these different reagent ions is performed by changing the source gas, adjusting the electric field and discharge current, and adjusting the pumping power in the SD region (affecting the pressure), for example via the interconnecting valve between the SD region and the vacuum pump.

[0021] Regarding the switching time, it is reported in the literature, for example, from H3O + Switch to NH4 + It takes about 10 seconds, while from NH4 + Switch back to H3O + It takes several minutes until the reagent ions are completely balanced (see M. Müller et al., Int. J. Mass Spectrom. 447 (2020) 116254).

[0022] It has been demonstrated in the literature that, after switching the electrode polarity, when H2O vapor is used as the source gas, OH- can be generated in the HCD ion source. - Reagent ions (see Y. Pan et al., J. Am Soc. Mass Spectrom. 28 / 5 (2017) 873-879).

[0023] However, regardless of the reagent ions produced, it is important to note that the corresponding source gas is always introduced into the HCD region and discharged from the SD region. That is, the source gas flow is always in the direction of the ion flight path.

[0024] Furthermore, it is noteworthy that the HCD-SD reagent ion source device has remained virtually unchanged despite decades of development and improvement of IMR / PTR-MS. This clearly demonstrates that it works exceptionally well, and even the most renowned experts see no room for conceptual improvement.

[0025] Drift tube

[0026] The IMR / PTR reaction chamber is directly adjacent to the reagent ion source, meaning there are no mass filters or similar interconnections. In the very comprehensive PTR-MS literature, this reaction chamber is primarily referred to as a PTR drift tube. Unfortunately, this terminology can lead to confusion with drift tubes in ion mobility spectrometry (IMS), where the drift tube operates in pulse mode and is used to chromatographically separate ionized analytes based on their migration rates within the matrix. Furthermore, in IMS, drift tubes operate primarily at or near atmospheric pressure, three orders of magnitude higher than in IMR / PTR-MS. Therefore, it should be noted that an IMS drift tube is a fundamentally different device.

[0027] In an IMR / PTR drift tube, the analyte undergoes chemical ionization via interaction with reagent ions. As a specific gas stream containing the analyte is continuously injected, an electric field attracts ions along the drift tube. Typically, IMR / PTR-MS analyzes air containing trace amounts of impurities (e.g., trace amounts of volatile organic compounds), but many other matrices containing compounds of interest (e.g., residual impurities in purified gases, gas standards, etc.) have been successfully studied with various reagent ions. In some embodiments, the matrix containing the analyte (e.g., air with trace amounts of volatile organic compounds) is diluted with a buffer gas before injection into the IMR / PTR drift tube (e.g., for simple dilution purposes or for the use of specific reagent ions).

[0028] Some common reactions between reagent ions and analytes that occur in IMR / PTR drift tubes are:

[0029] Proton transfer reactions, non-dissociative or dissociative, in which AH + It is a reagent ion (in most cases, H₂O·H₂O). + ), and BC is the analyte.

[0030] AH + +BC→A+BC.H +

[0031] AH + +BC→A+B+CH ++

[0032] Charge transfer reaction, non-dissociative or dissociative, wherein A + It is a reagent ion (e.g., O2). + NO + Kr + (etc.), and BC is the analyte:

[0033] A + +BC→A+BC +

[0034] A + +BC→A+B+C +

[0035] Clustering reaction, where A + It is a reagent ion (e.g., H3O) + NO + NH4 + (etc.), and BC is the analyte:

[0036] A + +BC→BC.A +

[0037] In addition, other types of reactions can occur (such as ligand switching).

[0038] In the negatively charged reagent ion OH - In this case, H can be observed + extract

[0039] OH - +MH→H2O+M -

[0040] The most common IMR / PTR drift tube consists of a series of ring electrodes electrically connected via resistors of equal resistance (other reported embodiments are, for example, tubes with a resistive coating), such that a DC voltage U can be applied to the IMR / PTR drift tube of length d, resulting in an electric field strength E = U / d (in V / cm) (1). Another important parameter of the IMR / PTR drift tube is the gas number density N, which is defined by equation (1):

[0041]

[0042] Here, N A It is Avogadro's constant (6.022 × 10⁻⁶). 23 mol -1 V M (22.414×10 3 cm 3 mol -1 (T) is the molar volume at 1013.25 hPa and 273.15 K. d Temperature is expressed in Kelvin (K), and P... d This refers to the pressure in the IMR / PTR drift tube, measured in hPa.

[0043] Dividing E by N results in a decrease in electric field strength, which is related to the collision energy of ion-molecule reactions in the IMR / PTR drift tube, and is most commonly and simply expressed as E / N, where the unit is Townsend (1Td = 10⁻⁶). -17 V cm 2 ).

[0044] Recently, new drift tubes have been introduced that offer improved sensitivity and / or selectivity. Most of these include one or more RF (radio frequency) devices, such as ion funnels or ion directors, to focus ions, thereby avoiding loss of mass analyzer on the walls and orifices.

[0045] However, a key prerequisite for any IMR / PTR drift tube is that the chemical ionization conditions can be well controlled either by directly adjusting the parameters in equation (1) or by the methods described in EP 3309817 B1. This is one of the main differences between the IMR / PTR-MS used in this paper and general IMR-MS, which incorporates chemical ionization techniques using a universal reaction chamber that provides little or no control over the ion chemistry during the ionization process.

[0046] IMR / PTR drift tubes operate between 1 and 10 hPa (most commonly 2–4 hPa). At pressures <1 hPa, analyte ionization becomes inefficient, and therefore the overall sensitivity of the instrument is insufficient for real-time trace gas analysis. At pressures >10 hPa, ion chemistry is no longer well controlled (e.g., H₃O₂). + (H2O) n The intense formation of reagent ion clusters requires extremely high voltage, which makes quantification quite complex.

[0047] Quality analyzers and detectors

[0048] Various mass spectrometers are used in IMR / PTR-MS instruments. The most prominent example of a low-resolution mass spectrometer is a quadrupole mass filter, while for high-resolution measurements, a time-of-flight (TOF) analyzer is typically used. However, the use of other types of mass spectrometers, such as ion trap analyzers, has also been reported, and even MS measurements can be achieved. n Mass spectrometers separate ions injected from the IMR / PTR drift tube based on their m / z, and quantify the ion yield of the separated m / z using a suitable detector (e.g., a secondary electron multiplier, microchannel plate, etc.). It is important to note that each mass spectrometer has mass-dependent ion transport, which is further affected by the transfer system between the IMR / PTR drift tube and the analyzer and other equipment. Therefore, to obtain comparable measurements, and even more importantly, comparable branching ratios, the obtained ion yield should be corrected for mass-dependent transport. This can be done fairly readily by analyzing gaseous standards containing well-defined amounts of compounds distributed over (preferably) a wide mass range and approximating the correction factor using an appropriate fitting function. Using this fitting function, correction factors for all relevant m / z can be calculated with high precision.

[0049] Difference from corona discharge ion source

[0050] Corona discharge ion sources are primarily used in IMS devices as a substitute for radioactive ion sources (see M. Tabrizchi et al., Rev. Sci. Instrum. 71 (2000) 2321). In IMS, operating pressures are in the atmospheric pressure range, and the requirements for ion purity are relatively low. Therefore, corona discharge ion sources are an ideal choice because they operate very well under high pressure. It has been demonstrated that reversing the flow of dry air through the corona needle at atmospheric pressure can reduce unwanted ozone and NO. x (See SK Ross et al., Int. J. Mass Spectrom. 218 (2002) L1-L6).

[0051] In 2017, Breitenlechner et al. (Anal. Chem. 89 / 11(2017) 5824-5831) introduced the “PTR3,” an instrument based on the PTR-MS principle but with considerable modifications. The pressure in the reaction zone (a tertiary structure with a rotating electric field, but without a DC field) was between 50 and 80 hPa, compared to 1 and 10 hPa (more typically, 2–4 hPa) for conventional IMR / PRT drift tubes. The pressure in the PTR3 reagent ion source was approximately 80 hPa. At this high pressure, a corona discharge reagent ion source was required instead of an HCD ion source. To improve the performance of the corona discharge ion source, they introduced a mixture of N2 and H2O (instead of pure H2O vapor) and additional N2 into the ion source at a total flow rate of 100 sccm, pumping out approximately 50 sccm upstream of the corona discharge while simultaneously introducing approximately 50 sccm of the mixture into the PTR3 reaction zone. The primary reagent ion was claimed to be clustered H3O. + H2O has a higher strength than H3O. + 3.8 times higher.

[0052] Differences from Selected Ion Flow Tube-to-Mass Spectrometry (SIFT-MS)

[0053] In SIFT-MS, microwave discharge reagent ion sources using moist air as the source gas are employed. These ion sources emit excessive amounts of ions, necessitating the use of a mass filter between the reagent ion source and the IMR reaction zone. Consequently, the reagent ion purity after the mass filter is very high, but the reagent ion yield is limited due to unavoidable transport losses within the mass filter.

[0054] One advantage of the SIFT-MS device is that, due to the mass filter, O2 - It can be used as a reagent ion in the reaction zone. This is impossible using a known IMR / PTR-MS device (i.e., without a mass filter) because it is difficult to generate O2 in an HCD-SD reagent ion source.- The reagent ion purity was low at that time.

[0055] Define IMR / PTR-MS

[0056] In this paper, the abbreviation IMR / PTR-MS is used as a more accurate term than what is commonly described in the literature as proton-transfer-reaction-mass spectrometry (PTR-MS). When PTR-MS was invented in the 1990s, H3O + It is the only available relevant reagent ion. H3O + The chemical ionization of reagent ions primarily occurs via proton transfer to the analyte, hence the name PTR. However, in the following decades, methods for generating alternative reagent ions (NO3- ... + O2 + Kr + The methods (etc.) involve only minor modifications to the PTR-MS apparatus. Some of these apparatuses are labeled as SRI-MS (Switched Reagent Ion or Selective Reagent Ionization) instruments, but many publications still use PTR-MS, despite minor inaccuracies.

[0057] In this document, “IMR / PTR-MS” should be understood as the technology utilizing all the major components of a PTR-MS instrument, but not limited to chemical ionization via proton transfer. “IMR / PTR-MS” in this document should not be interpreted in its broadest sense, encompassing all types of instruments where ionic-molecular reactions can occur (e.g., methods and apparatus for increasing the internal energy of ions using an electric field in electrospray ionization (ESI), so-called “iodide CIMS” or “acetate CIMS”, etc.). Summary of the Invention

[0058] The purpose of this invention is to improve IMR / PTR-MS equipment with HCD-SD reagent ion sources and to achieve well-controlled ion chemistry as known from PTR-MS.

[0059] The solution to the above problem is provided by apparatus for ion molecular reaction-mass spectrometry (IMR-MS) and / or proton transfer reaction-mass spectrometry (PTR-MS), which is used to analyze gases for at least one analyte compound by chemical ionization of specific types of reagent ions, including:

[0060] ● The reagent ion source features a hollow cathode glow discharge (HCD) region and a source drift (SD) region.

[0061] ● The drift tube region adjacent to the reagent ion source includes at least one inlet for the analyte gas and at least one source for the electric field.

[0062] ●The mass analyzer region (104) adjacent to the drift tube region,

[0063] ●and control equipment,

[0064] The HCD region includes at least one port connected to at least one pump, at least two electrodes used as the anode, and at least one electrode used as the cathode.

[0065] The SD area includes at least one port connected to at least one source gas supply.

[0066] The control equipment is configured as follows:

[0067] ● Control the discharge current in the HCD region

[0068] ●Control the source gas flow through the reagent ion source.

[0069] ● Adjust the pressure in the drift tube area to between 1-10 hPa.

[0070] ● Adjust the electric field in the drift tube region, wherein the electric field includes at least a DC field, which is configured to attract ions in the direction of the mass analyzer region.

[0071] Therefore, the apparatus of this invention allows for interchangeable connections to the HCD region port and SD region port compared to existing IMR / PTR-MS devices, thereby reversing the source gas flow. That is, the source gas enters the SD region and flows into the HCD region, and is pumped out from the HCD region. The source gas flow is "reverse," upstream of the ion flight direction.

[0072] To date, this reverse-source gas flow has not been used in the HCD-SD reagent ion source of IMR / PTR-MS instruments. In fact, it generates reagent ions NH4+. + or NO + The experiments yielded disappointing results. When N2 and H2O vapor or N2 and O2 were introduced into the SD region and the source gas was pumped out from the HCD region, NH4 could not be obtained, even after adjusting the source gas flow, the gas flow to the vacuum pump, and optimizing the voltage and discharge current via control equipment. + or NO + Sufficient strength and purity.

[0073] However, when H2O vapor or O2 is introduced into the SD region and the source gas is pumped out from the HCD region, excellent H3O is obtained after adjusting the source gas flow, the gas flow to the vacuum pump, and optimizing the voltage and discharge current via control equipment. + or O2 + Strength and purity.

[0074] The absolute values ​​of purity and intensity are difficult to determine because adjusting the reagent ion source to obtain maximum reagent ion purity comes at the cost of lower reagent ion yield, and vice versa. For example, the 99.5% H3O purity claimed in the literature for common HCD-SD ion sources... + The reagent ion purity is the maximum that can only be achieved by sacrificing reagent ion strength, which leads to the lower overall sensitivity of PTR-MS instruments. Therefore, most PTR-MS instruments are calibrated to approximately 95-97% H₃O. + Purity, and simultaneously high H3O + strength.

[0075] Furthermore, the control device can be configured to switch polarity and adjust the extraction voltage, drift tube region, and mass analyzer for reagent ion sources carrying negative or positive ions. In other words, positively or negatively charged reagent ions can be extracted from the reagent ion source, and the control device allows for polarity switching.

[0076] To date, those skilled in the art will avoid reversing the common (“forward”) source gas flow direction in HCD-SD reagent ion sources because it results in the inability to generate NO. + or NH4 + A significant drawback of reagent ions.

[0077] However, most surprisingly, when the IMR / PTR-MS instrument was operated in negative ion mode via the control device, introducing essentially pure O2 as the source gas into the SD region and pumping the source gas out of the HCD region (i.e., reverse source gas flow) produced, for the first time, pure and abundant O2. - Reagent ions are used for the subsequent chemical ionization of the analyte in the IMR / PTR drift tube. As described in the background section, this has so far been achieved only by filtering O2 from a large number of parasitic ions using a mass filter adjacent to the reagent ion source. - Time limit (which restricts O2) - Reagent ion yield; comparison of SIFT-MS segments).

[0078] Therefore, in a preferred embodiment, the device includes O2. - The source, wherein the control device is configured to control the injection of O2 into the SD region through at least one port and the pumping of O2 out of the HCD region to generate O2 in the reagent ion source. - Furthermore, the extraction voltage of the reagent ion source is adjusted so that the generated reagent ions are conducted to the drift tube region. Preferably, O2 - The reagent ion purity is higher than 90%. As described above, this is possible using the apparatus of the present invention due to the reverse source gas flow.

[0079] In another embodiment, the device also includes CO2. - The source, wherein the control device is configured to control the injection of O2 and CO2 into the SD region through at least one port and the pumping of O2 and CO2 out of the HCD region to generate CO3 in the reagent ion source. - Furthermore, the extraction voltage of the reagent ion source is adjusted so that the generated reagent ions are conducted to the drift tube region. Preferably, CO3... - The reagent ion purity is higher than 80%. As described above, this is possible using the apparatus of the present invention due to the reverse source gas flow.

[0080] When the IMR / PTR-MS instrument is operated in negative ion mode via control equipment, pure and abundant CO3 can be generated by introducing substantially pure O2 and CO2 (as a mixture or via two separate source gas inlets) as source gas into the SD region and pumping source gas out of the HCD region (i.e., reverse source gas flow). - Reagent ions are used for the subsequent chemical ionization of analytes in IMR / PTR drift tubes.

[0081] Therefore, in a preferred embodiment, the device includes O2 and CO2 sources, wherein the control device is configured to control the injection of O2 and CO2 into the SD region through at least one port and the pumping of the O2 and CO2 mixture out of the HCD region to generate CO3 in the reagent ion source. - Furthermore, the extraction voltage of the reagent ion source is adjusted so that the generated reagent ions are conducted to the drift tube region.

[0082] In summary, reversing the source gas flow through the HCD-SD reagent ion source results in at least the following capabilities:

[0083] - When O2 is used as the source gas, O2 with excellent purity and strength can be produced. - Reagent ions. (Negative ion mode)

[0084] - When gaseous H2O is used as the source gas, H3O with excellent purity and strength can be produced. + Reagent ions. (Positive ion mode)

[0085] - When using O2 and CO2 as source gases, CO3 with excellent purity and strength can be produced. - Reagent ions. (Negative ion mode)

[0086] - When O2 is used as the source gas, O2 with excellent purity and strength can be produced. + Reagent ions. (Positive ion mode)

[0087] Despite the following disadvantages observed compared to the common (“forward” gas flow direction:

[0088] - Introducing N2 and gaseous H2O into the SD region cannot produce NH4 with high purity and strength. + Reagent ions. (Positive ion mode)

[0089] - Introducing N2 and O2 into the SD region cannot produce NO with high purity and strength. + Reagent ions. (Positive ion mode)

[0090] In another embodiment, at least one port of the HCD region is connected to at least one source gas supply. In this preferred embodiment, the IMR / PTR-MS device is capable of switching the source gas flow between forward and reverse directions.

[0091] A forward source gas flow direction means that the source gas is introduced into the HCD region and removed from the SD region and / or drift tube region (a common gas flow direction).

[0092] A reverse source gas flow direction means that the source gas is introduced into the SD region and removed from the HCD region.

[0093] Furthermore, the device may include an N2 source and an H2O source, wherein the control device is configured to control the injection of a mixture of N2 and H2O source gases through at least one port into the HCD region and pump it out from the SD region through at least one port and / or from the drift tube region to generate NH4 in the reagent ion source. + The H2O source gas is controlled to be injected into the SD region through at least one port and pumped out from the HCD region to generate H3O in the reagent ion source. + and in the NH4 in the reagent ion source + and H3O + Electron switching occurs between the generation of ions.

[0094] Preferably, the control device is further configured to control the injection of a mixture of N2 and O2 source gases into the HCD region through at least one port and to pump it out from the SD region and / or drift tube region to generate NO in the reagent ion source. + O2 source gas is controlled to be injected into the SD region through at least one port and pumped out from the HCD region to generate O2 in the reagent ion source. + The control device is also configured to electronically switch between different reagent ions.

[0095] In summary, by switching between the forward and reverse source gas flow directions, at least H3O + (Can also be reverse / forward), NO + (positive), O2 + (can also be reverse / forward), NH4 + (positive), O2- (Reverse) and CO3 - (Reverse) reagent ions can be produced with excellent purity and strength.

[0096] When a prototype of this IMR / PTR-MS device with switchable source gas flow direction was built and tested, completely unexpected results were observed. Reagent ion H3O + (Reverse) to NH4 + The switching time between (forward) and reverse directions can be reduced from 10 seconds to several minutes (compare with the background section) to <2 seconds. Furthermore, the 2-second time is determined by the response time of the mass flow controller of the source gas used, and can be further improved by using alternative, faster-responding gas feeding devices.

[0097] The present invention also relates to a method of operating an apparatus for ion-molecule-reaction mass spectrometry and / or proton-transfer-reaction mass spectrometry, the apparatus having a reagent ion source having a hollow cathode glow discharge (HCD) region and a source drift (SD) region, wherein the SD region includes at least one port connected to at least one source gas supply, and the HCD region includes at least one port connected to at least one pump, characterized by the following steps:

[0098] ● A controlled source gas flow is introduced into the SD region via at least one port, and the source gas is pumped out of the HCD region.

[0099] ● Applying ionization methods to the source gas to generate reagent ions in the reagent ion source.

[0100] • Reagent ions and the gas to be analyzed are introduced into the drift tube region, wherein the analyte is ionized by interaction with the reagent ions in the drift tube region, and the ions are analyzed in the mass analyzer region after the drift tube region.

[0101] Therefore, this method enables the realization of a reverse source gas flow in a reagent ion source and can generate O2 with excellent intensity and purity. - Reagent ions. Furthermore, it can produce CO3 with excellent strength and purity. - Reagent ions.

[0102] Preferably, the switching between positively charged and negatively charged reagent ions generated in the reagent ion source is achieved by switching the polarity of the electrodes and adjusting the extraction voltage of the reagent ion source for negatively charged or positively charged ions, the drift tube, and the mass analyzer. The switching can preferably be achieved electronically via a control device.

[0103] Furthermore, at least one port of the HCD region is connected to at least one source gas supply, wherein, depending on the reagent ions to be generated, source gas is introduced into the SD region and pumped out from the HCD region to generate a reverse source gas flow, or source gas is introduced into the HCD region and pumped out from the SD region and / or the drift tube region to generate a forward source gas flow, wherein different reagent ions are generated by electronically switching between the forward and reverse source gas flows and / or using different source gases. Therefore, by simply switching the direction of the source gas flow and the source gas, a variety of reagent ions with excellent intensity and purity can be generated using the same apparatus.

[0104] Preferably, the switching time between different reagent ions of the same polarity is less than 2 seconds.

[0105] In a particularly preferred embodiment, an O2 source gas is introduced into the SD region and pumped out from the HCD region, thereby generating a reverse source gas flow and O2 as reagent ions. - or O2 + ,or

[0106] A mixture of N2 and H2O source gases is introduced into the HCD region and pumped out from the SD region and / or drift tube region, thereby generating a forward source gas flow and NH4 as reagent ions. + ,or

[0107] A mixture of N2 and O2 source gases is introduced into the HCD region and pumped out from the SD region and / or drift tube region, thereby generating a forward source gas flow and NO as reagent ions. + ,or

[0108] H2O source gas is introduced into the SD region and pumped out from the HCD region, thereby generating a reverse source gas flow and H3O as reagent ions. + ,

[0109] The control device allows for the electronic switching of the generation of different reagent ions.

[0110] In another embodiment, an O2 source gas is introduced into the SD region and pumped out from the HCD region, thereby generating a reverse source gas flow and O2 as reagent ions. - or O2 + ,or

[0111] A mixture of O2 and CO2 source gases is introduced into the SD region and pumped out from the HCD region, thereby generating a reverse source gas flow and CO3 as reagent ions. - ,or

[0112] A mixture of N2 and H2O source gases is introduced into the HCD region and pumped out from the SD region and / or drift tube region, thereby generating a forward source gas flow and NH4 as reagent ions.+ ,or

[0113] A mixture of N2 and O2 source gases is introduced into the HCD region and pumped out from the SD region and / or drift tube region, thereby generating a forward source gas flow and NO as reagent ions. + ,or

[0114] H2O source gas is introduced into the SD region and pumped out from the HCD region, thereby generating a reverse source gas flow and H3O as reagent ions. + ,

[0115] The switching of different reagent ions is accomplished electronically via a control device. Attached Figure Description

[0116] The foregoing and other objects, features and advantages of the present invention will become more apparent from the detailed description taken with reference to the accompanying drawings.

[0117] Figure 1 A schematic diagram of the components of an IMR / PTR-MS instrument including several ports is shown.

[0118] Figure 2 A schematic diagram of the HCD-SD reagent ion source is shown.

[0119] Figure 3 An exploded view of a specific embodiment of the HCD-SD reagent ion source is shown.

[0120] Figure 4 A schematic electrical wiring diagram of the HCD-SD reagent ion source is shown.

[0121] Figure 5 H3O was shown + and NH4 + The measured switching time between reagent ions. Detailed Implementation

[0122] exist Figure 1 The diagram provides a schematic overview of the main components of the IMR / PTR-MS instrument according to the present invention: an HCD-SD reagent ion source region including an HCD region 101 and an SD region 102; a drift tube region 103; and a mass spectrometer / analyzer (including a differential pumping region) 104. Each region may be equipped with at least one port 105-108 for introducing and / or removing gases.

[0123] At least one port 105 of the HCD region can be connected to at least one vacuum pump, and optionally to at least one source gas supply.

[0124] At least one port 106 in the SD area can be connected to at least one source gas supply and optionally to at least one vacuum pump.

[0125] At least one port 107 in the drift tube region can be connected to at least one inlet for the gas to be analyzed, and optionally to at least one vacuum pump.

[0126] At least one port 108 in the mass analyzer area can be connected to at least one vacuum pump.

[0127] Preferably, the gas flow from the gas supply to the vacuum pump is well-defined and / or can be controlled by devices known in the art, such as flow-limiting capillaries, mass flow controllers, proportional valves (valves that control the gas flow rate by changing the size of the flow channel via a limiter), shut-off valves, etc.

[0128] Forward source gas flow

[0129] Source gas is introduced into HCD region 101 via port 105. Due to the fluid connection between HCD region 101 and SD region 102, the source gas diffuses into SD region 102, where it is pumped away by a vacuum pump connected to port 106 and / or by a vacuum through IMR / PTR-MS drift tube 103. A source gas flow exists downstream of the HCD-SD reagent ion source due to the continuous supply of source gas to HCD region 101 and the continuous pumping to SD region 102.

[0130] Reverse source gas flow

[0131] Source gas is introduced into SD region 102 via port 106. Due to the fluid connection between SD region 102 and HCD region 101, the source gas diffuses into HCD region 101, where it is pumped away by a vacuum pump connected to port 105. A source gas flow exists upstream of the HCD-SD reagent ion source due to the continuous supply of source gas to SD region 102 and the continuous pumping to HCD region 101.

[0132] Switching of source gas flow

[0133] In a preferred embodiment, the source gas flow direction can be electronically switched from forward gas flow to reverse gas flow and from reverse gas flow to forward gas flow. For this embodiment, port 105 in the HCD region needs to be connected at least to the source gas supply and the vacuum pump. Port 106 in the SD region needs to be connected at least to the source gas supply. Optionally, port 106 can be additionally connected to the vacuum pump. Switching is controlled via a control device. The devices used to control the supply and pumped gas flow are commonly known electronically controllable devices, such as valves and mass flow controllers, and interconnected between the respective ports and the gas supply / vacuum pump using gas lines.

[0134] Detailed discussion of HCD-SD reagent ion sources

[0135] Figure 2 A schematic diagram of the HCD-SD reagent ion source assembly is shown. Figure 3 An exploded 3D view with an approximate size ratio of a specific embodiment having an HCD-SD reagent ion source is shown.

[0136] Elements 201, 202, 203, 204, and 205 are electrodes made of conductive material. Preferably, the material is metal. Most preferably, the material is stainless steel of the EN 1.4301, 1.4405, or 1.4407 type.

[0137] In a preferred embodiment, electrodes 201, 202, and 204 are cylindrical hollow electrodes, while electrodes 203 and 205 are annular plate electrodes with a much smaller central hole. In one embodiment, electrode 205 is also the first electrode of the IMR / PTR drift tube, i.e., having a small central hole facing electrode 204 and thus defining the downstream boundary of the SD region 102, and a port 107 on the side facing the IMR / PTR drift tube region 103 for introducing sample gas into the IMR / PTR drift tube.

[0138] Element 206 is an electrically insulating gasket that provides a hermetically sealed connection between electrodes 201-204, enabling the generation of a vacuum within the internal volume of the HCD-SD reagent ion source. The gasket 206 can be made of any non-conductive material. Preferably, the material is polytetrafluoroethylene (PTFE) or polyetheretherketone (PEEK). Typical pressures in the HCD-SD reagent ion source are between 0.1 and 10 hPa, preferably between 0.2 and 4 hPa.

[0139] Different shapes and sizes of elements 201-206 are possible and are known in the art.

[0140] Component 207 is a gas line connected to at least one port 105 of HCD area 101. Component 208 is a gas line connected to at least one port 106 of SD area 102.

[0141] Figure 4 A schematic diagram of the electrical connections of the electrodes in the HCD-SD reagent ion source is shown. Regardless of the polarity of the extracted reagent ions, electrode 201 always acts as the anode, electrode 202 as the cathode, and electrode 203 as the cathode. Preferably, anodes 201 and 203 are electrically connected. First, a voltage sufficiently high to ignite the glow discharge is applied to these electrodes. The discharge current I flowing between the anode and cathode... hc It is controlled to be an adjustable value. hc Typical values ​​are between 0.5 and 10 mA, preferably between 1 and 6 mA. Extraction voltage U s and U so This affects ion transport between HCD region 101, SD region 102, and drift tube region 103. In other words, by adjusting these voltages, ion extraction can be adjusted, thereby adjusting the IMR interaction time in SD region 102. In other words, by optimizing U... s and U so This allows for optimization of the strength and purity of reagent ions entering the drift tube region 103. Furthermore, when switching between positively and negatively charged reagent ions, only U... s and U so The polarity (and obviously the corresponding polarities of 10³ and 10⁴) is altered, allowing either positively or negatively charged ions to be extracted and transported, while I hc The direction remains unchanged. That is, regardless of the polarity of the reagent ions, anodes 201 and 203 remain anodes, and cathode 202 remains cathode.

[0142] U s and U so The typical absolute voltage range is between 0 and 500V.

[0143] In a preferred embodiment, the power supply of the HCD-SD region is electrically floated on the DC voltage of the drift tube region 103.

[0144] The necessary power supply and control unit for providing and controlling power to the IMR / PTR-MS instrument are well known in the art and are not discussed in detail herein.

[0145] Devices for measuring pressure in different regions of the apparatus are well known in the art and can be any type of vacuum gauge (e.g., capacitance meter, Pirani gauge, etc.) connected to the corresponding region. Pressure in different regions of the apparatus can also be theoretically calculated based on gas flow and apparatus size. Typically, vacuum gauges are not required in commercial HCD-SD reagent ion sources because the dependence between gas flow and resulting pressure is well known in the prototype stage.

[0146] Exemplary Example 1

[0147] Port 105 of HCD region 101 is located at electrode 201 and connected to gas line 207. Gas line 207 is connected to a turbomolecular pump (e.g., the second stage of “HiPace SplitFlow” from Pfeiffer Vacuum) via a proportional valve. The turbomolecular pump is supported by a multistage diaphragm pump.

[0148] Port 106 of SD region 102 is located at electrode 204 and connected to gas line 208. Gas line 208 is connected to an O2 supply (e.g., an oxygen cylinder with a purity of 5.0) via a mass flow controller.

[0149] All valves and mass flow controllers are electrically controllable.

[0150] The HCD-SD reagent ion source operates in the reverse gas flow direction by setting the mass flow controller to a value between 0.5 and 10 sccm and opening the proportional valve. The pressure in the HCD-SD reagent ion source is maintained between 0.1 and 10 hPa, preferably between 0.2 and 4 hPa.

[0151] Electrode 201 serves as the anode, electrode 202 serves as the cathode, and electrode 203 serves as the anode (electrically connected to 201). A discharge current I flows between the anode and cathode. hc It is set to a value between 0.5 and 10 mA.

[0152] U s It is configured to extract negatively charged ions from HCD region 101 to SD region 102. U so The system is configured to extract negatively charged ions from SD region 102 to drift tube region 103. Drift tube region 103 is of "conventional type," meaning it consists of a series of ring electrodes connected via resistor chains to which a voltage between 0 and 1000V (absolute value) can be applied to accelerate downstream ions with a well-controlled E / N ratio. Preferably, the E / N ratio can be set to a value between 50 and 250Td. Electrically insulating gaskets are placed between the ring electrodes to ensure the internal volume of the drift tube is hermetically sealed. The power supply for the HCD / SD reagent ion source is electrically connected to the IMR / PTR drift tube power supply.

[0153] Port 107 of drift tube region 103 is connected to an inlet system consisting of a capillary, a mass flow controller, and a pressure controller, allowing sample gas to be continuously delivered to drift tube region 103. Drift tube region 103 is emptied via a fluid connection to a differential pumping region within 104. The pressure in IMR / PTR drift tube region 103 can be adjusted between 1 and 10 hPa. Preferably, the pressure is set to 2-4 hPa.

[0154] Mass spectrometer / analyzer region 104 includes a differential pumping region and a subsequent TOF analyzer including an ion detector. Port 108 of mass spectrometer / analyzer region 104 is connected to three turbomolecular pumps to ultimately pump the gas entering from drift tube region 103 down to a vacuum sufficient to operate the TOF analyzer (e.g., at 10⁻⁶ ppm). -5 -10 -10 (between hPa).

[0155] Using this control device, voltage, current, electrically controllable valves, and mass flow controllers were optimized. The control device could be, for example, a control computer. Optimization of reagent ion generation was achieved by introducing zero gas as the sample gas into the IMR / PRT drift tube and monitoring the m / z separation ion intensity detected using a TOF analyzer. The optimization aimed to obtain O2. - The highest purity and strength of the reagent ions. >90% O2 yield can be easily achieved with extremely high reagent ion yields. - Reagent ion purity. A reagent ion purity > 98% is possible.

[0156] This device allows for the detection and quantification of analytes with extremely high sensitivity. Many of these analytes are compounds that cannot be ionized by conventional PTR-MS, such as inorganic acids. Furthermore, analyte fragmentation is extensively suppressed, which makes mass spectrometry interpretation and compound quantification particularly easy.

[0157] Analytes MH and O2 - The product ions after chemical ionization are mainly, but not limited to, M. - Examples of product ions for various tested compounds are: Br for HBr - Cl for HCl - HCO2 for H2CO2 - wait.

[0158] Exemplary Example 1a

[0159] By applying the following changes to Exemplary Example 1, CO3 can be correlated with the content of CO3 using an IMR / PTR-MS instrument. - Chemical ionization:

[0160] Gas line 208 (connected to port 106 of SD area 102) is split into two gas lines. One of these gas lines is connected to the O2 cylinder via a mass flow controller, while the other gas line is connected to the CO2 cylinder via a mass flow controller.

[0161] To introduce a mixture of O2 and CO2 into SD region 102, both mass flow controllers are activated. The preferred flow rates for each source gas are between 0.1 and 15 sccm. Preferably, the O2:CO2 ratio is between 1:1 and 10:1. Preferably, the O2 flow rate is higher than the CO2 flow rate, such that the O2 concentration is higher than the CO2 concentration in the reagent ion source. An example of a source gas flow rate is 5 sccm O2 and 1 sccm CO2.

[0162] Preferably, in addition to the DC voltage along the length of the drift tube, the drift tube region 103 also includes RF ion focusing measures. The DC voltage can vary between 0-1000V. This is particularly useful when a low E / N ratio is used via CO3. - When reagent ions chemically ionize the analyte, RF ion focusing prevents excessive ion loss in drift tube region 103, thereby preventing significant loss of sensitivity in the IMR / PTR-MS instrument. The pressure in drift tube region 103 can be adjusted between 1-10 hPa. Preferably, a specific gravity of H3O is used. + The pressure of the reagent ions is slightly higher, i.e., 4-6 hPa.

[0163] CO3 can be used - An example of an analyte that is particularly well analyzed by reagent ions is SO2. In a prototype IMR / PTR-MS instrument, SO2 is compared with CO3. - Ionization produces SO5 - Ion, nominal m / z 112.

[0164] Exemplary Example 2

[0165] Port 105 of HCD region 101 is connected to gas line 207, which itself is divided into three gas lines. One of these gas lines is connected via a mass flow controller to a reservoir filled with purified water. Another gas line is connected via a mass flow controller to an N2 bottle (purity 6.0). The third gas line is connected via a proportional valve to a turbomolecular pump (e.g., the second stage of "HiPace SplitFlow" from Pfeiffer Vacuum).

[0166] Port 106 of SD region 102 is located at electrode 204 and connected to gas line 208. Gas line 208 is connected to a reservoir filled with purified water via a mass flow controller. For economic reasons, this can be the same reservoir as the one connected to the port of HCD region 101 via a (different) mass flow controller. Optionally, gas line 208 can be additionally connected to a turbomolecular pump via a proportional valve. This turbomolecular pump can be the second stage of the same "HiPace SplitFlow" used for port 105 of HCD region 101. However, it has been found that for this exemplary embodiment 2, it may be sufficient for SD region 102 to be emptied into drift tube region 103 through the orifice of electrode 205 when operating in the forward source gas flow direction. That is, for economic reasons, the rather expensive additional proportional valve at gas line 208 can be omitted.

[0167] All valves and mass flow controllers are electrically controllable. Preferably, each source gas mass flow controller can be set to a value between 0 and 10 sccm.

[0168] The pressure in the HCD-SD reagent ion source is maintained between 0.1 and 10 hPa, preferably between 0.2 and 4 hPa.

[0169] U s It is configured to extract positively charged ions from HCD region 101 to SD region 102. U so The system is configured to extract positively charged ions from SD region 102 into drift tube region 103. The IMR / PTR drift tube is of an "advanced type," consisting of a series of annular electrodes with constant orifice sizes and hermetically sealed gaskets between them, followed by a series of annular electrodes in an ion funnel configuration without hermetically sealed gaskets between them. The entire IMR / PTR drift tube is surrounded by a vacuum chamber that defines the external space surrounding the annular electrodes, thus, for this design, a portion of the introduced sample gas has already been removed within drift tube region 103.

[0170] The RF voltage can be added to the DC voltage applied to the electrodes for ion focusing. The power supply for the HCD-SD reagent ion source is electrically floated on the DC power supply of the IMR / PTR drift tube.

[0171] Port 107 of the drift tube region 103 is connected to an inlet system consisting of a capillary, a mass flow controller, and a pressure controller, allowing the sample gas to be continuously and directly delivered into the space surrounded by the electrodes of the drift tube region 103. An additional port 107 is connected to a vacuum pump, allowing the external space surrounding the annular electrodes to be emptied. This is also achieved through the gap between the electrodes of the ion funnel, which empties the space surrounded by the electrodes of the drift tube region 103. The pressure in the drift tube region 103 can be adjusted between 1 and 10 hPa. Preferably, the pressure is set to 2-4 hPa.

[0172] The mass spectrometer / analyzer region 104 includes a differential pumping region with a hexapole ion guide for ion focusing and a subsequent TOF analyzer including an ion detector. Port 108 of region 104 is connected to three turbomolecular pumps to pump the gas entering from drift tube region 103 downwards to a vacuum sufficient to operate the TOF analyzer (e.g., at 10⁻⁶ ppm). -5 -10 - 10 (between hPa).

[0173] The voltage, current, valves, mass flow controller, and other parameters were optimized using control equipment connected to the IMR / PTR-MS device. Optimization was achieved by introducing zero air as the sample gas into the drift tube region 103 and monitoring the m / z separation ion intensity detected by a TOF analyzer.

[0174] The proportional valve at gas line 207 is open and both mass flow controllers at gas line 207 are closed, causing HCD region 101 to be emptied by the turbomolecular pump. Gaseous H2O (purified water in the reservoir is emptied due to low pressure) is introduced into SD region 102 by adjusting the mass flow controller at gas line 208. If present, the proportional valve connected to gas line 208 is closed. Therefore, in this configuration, the source gas flow is reversed. Voltage, current, valves, mass flow controllers, etc., are optimized for H3O. + The reagent ions possess high purity and strength. Once found, optimized parameters can be used as "H3O". + Settings (H3O) + "sets" are stored on a storage device, such as a control computer. They can also be stored on a control device, which may include a storage device.

[0175] Subsequently, the proportional valve at gas line 207 is closed, and the two mass flow controllers connected to gas line 207 (for N2 and H2O respectively) are opened and adjusted. If present, the proportional valve connected to gas line 208 is opened. In this configuration, the source gas flow is forward. Voltage, current, valves, mass flow controllers, etc., are optimized for NH4. +The reagent ions possess high purity and strength. Once found, optimized parameters can be used as "NH4". + Set (NH4) + The "set" is stored on a storage device, such as a control computer and / or control device.

[0176] Discovered through "NH4" + "Settings" and "H3O" + Switching between "sets" essentially involves switching the source gas flow direction and the source gas itself, achieving complete equilibrium of all reactant ions within <2 seconds (compared to minutes reported in the literature for only the forward source gas flow direction). Furthermore, it was found that the equilibrium time was primarily limited by the response of the mass flow controller. By installing additional valves and gas lines, allowing the precisely defined gas flow rate through the mass flow controller to be kept constant, and by opening or closing the source gas supply to HCD region 101 and SD region 102 via fast-acting valves, the equilibrium time can be further improved, and thus the reagent ion switching time can be further improved.

[0177] NH4 can be easily achieved + and H3O + The reagent ions all have a purity >95%, and a purity >98% is possible. Because data for two reagent ions can be acquired almost simultaneously—meaning only 1 second of data is “lost” during switching—the rapid reagent ion switching capability significantly increases the selectivity of the IMR / PTR-MS instrument.

[0178] Figure 5 The measurement results according to Exemplary Example 2 show that trace amounts of D5-siloxane (M) were added to the sample air entering the IMR / PTR drift tube. Using "H3O" + Set the applied M·H + Detected as a product ion. Switch to "NH4" + The setup is completed in approximately 1 second, and the product ions detected in this mode are primarily clusters of M·NH4. + The product ion intensities of the two reagent ions are comparable, indicating that the reagent ions have comparable (high) strength. Furthermore, aside from the expected statistical noise, the product ion intensities are constant immediately after the switching, suggesting that equilibrium has actually been reached.

[0179] Exemplary Example 3

[0180] This embodiment is capable of generating at least H3O. + NO + O2 + NH4 + and O2 -Reagent ions. Additional reactant ions are possible by adding appropriate feedstock for the source gas.

[0181] At least one port 105 of HCD region 101 shall have at least:

[0182] - Connected to the vacuum pump via a flow regulating device

[0183] - Connected to the H2O source via a flow regulation device

[0184] - Connected to the N2 source via a flow control device

[0185] - Connect to the O2 source via a flow regulation device.

[0186] At least one port 106 of SD area 102 shall have at least:

[0187] - Connected to the H2O source via a flow regulation device

[0188] -O2 source connected via flow regulation device

[0189] - Optionally, it can be connected to a vacuum pump via a flow regulating device.

[0190] All flow control devices are electrically controllable via a control device. Preferably, each source gas flow control device can be set to a value between 0 and 10 sccm.

[0191] The pressure in the HCD-SD reagent ion source is maintained between 0.1 and 10 hPa, preferably between 0.2 and 4 hPa.

[0192] Preparation of at least the above reagent ions:

[0193] -H3O + A controlled flow of gaseous H2O source gas is introduced into SD region 102. The source gas is pumped out from HCD region 101 at port 105 using a vacuum pump. That is, the source gas flow direction is reversed. The HCD-SD reagent ion source is optimized for generating H3O with high purity and intensity. + The HCD-SD reagent ion source extraction voltage, IMR / PTR drift tube, and mass spectrometer / detector configuration are used for positive ions.

[0194] -NO + A controlled flow of N2 and O2 source gases is introduced into HCD region 101. The source gas is pumped from SD region 102 through the orifice of electrode 205 to drift tube region 103 and / or to an optional vacuum pump at port 106 of SD region 102. That is, in the direction of source gas flow. The HCD-SD reagent ion source is optimized for generating NO with high purity and intensity. +The HCD-SD reagent ion source extraction voltage, IMR / PTR drift tube, and mass spectrometer / detector configuration are used for positive ions.

[0195] -O2 + A controlled flow of O2 source gas is introduced into SD region 102. The source gas is pumped out from HCD region 101 at port 105 using a vacuum pump. That is, the source gas flow direction is reversed. The HCD-SD reagent ion source is optimized for generating O2 with high purity and intensity. + The HCD-SD reagent ion source extraction voltage, IMR / PTR drift tube, and mass spectrometer / detector configuration are used for positive ions.

[0196] -NH4 + A controlled flow of N2 and gaseous H2O source gases is introduced into HCD region 101. The source gas is pumped from SD region 102 through the orifice of electrode 205 to drift tube region 103 and / or to port 106 of SD region 102 via an optional vacuum pump. That is, in the direction of source gas flow. The HCD-SD reagent ion source is optimized for generating NH4 with high purity and intensity. + The HCD-SD reagent ion source extraction voltage, IMR / PTR drift tube, and mass spectrometer / detector configuration are used for positive ions.

[0197] -O2 - A controlled flow of O2 source gas is introduced into SD region 102. The source gas is pumped out from HCD region 101 at port 105 using a vacuum pump. That is, the source gas flow direction is reversed. The HCD-SD reagent ion source is optimized for generating O2 with high purity and intensity. - The HCD-SD reagent ion source extraction voltage, IMR / PTR drift tube, and mass spectrometer / detector configuration are used for negative ions.

[0198] Additional reagent ions can be generated by introducing the corresponding source gas into HCD region 101 or SD region 102 and optimizing the HCD-SD reagent ion source to generate the corresponding reagent ions.

[0199] Optimized settings for each reagent ion can be stored on control and / or storage devices, such as the control computer of an IMR / PTR-MS device, allowing convenient activation of the corresponding reagent ions by selecting a set of settings. It should be noted that due to the high voltage of the IMR / PTR drift tube, and especially the high voltage of the mass spectrometer, switching electrode polarities (i.e., from a positive ion configuration to a negative ion configuration, and vice versa) typically takes longer than switching between reagent ions of the same polarity. The observation time required for electrode switching at the prototype ranged from 5 to 30 seconds.

[0200] IMR / PTR-MS drift tubes can be either "conventional" or "advanced." They can also be a hybrid type, somewhere between conventional and advanced. That is, around the IMR / PTR-MS drift tube, which consists of a ring electrode and an ion funnel, each element has a hermetically sealed gasket, and a vacuum chamber may be present, which is evacuated to a pressure slightly lower than the pressure inside the IMR / PTR-MS drift tube. The advantage of this option is that the IMR / PTR-MS drift tube can be conventional, but small vacuum leaks do not allow contaminants to enter the reaction zone. The electric field in the IMR / PTR-MS drift tube can be a DC field only or an additional RF field. Preferably, the IMR / PTR-MS drift tube operates at a pressure between 1 and 10 hPa.

[0201] Preferably, the E / N ratio in the IMR / PTR-MS drift tube can be adjusted to a value or range between 50-250Td.

[0202] Exemplary Example 3a

[0203] By additionally connecting a CO2 source to at least one port 106 of SD region 102 via a flow regulation device, exemplary embodiment 3 is able to generate CO3. - Reagent ions: Controlled flows of O2 and CO3 are introduced into SD region 102. The source gas is pumped out from HCD region 101 using a vacuum pump at port 105, i.e., in the reverse flow direction. The HCD-SD reagent ion source is optimized for producing CO3 with high purity and intensity. - The HCD-SD reagent ion source extraction voltage, IMR / PTR drift tube, and mass spectrometer / detector configuration are used for negative ions.

Claims

1. An apparatus for ion molecular reaction-mass spectrometry (IMR-MS) and / or proton transfer reaction-mass spectrometry (PTR-MS), for analyzing a gas for at least one analyte compound by chemical ionization via a specific type of reagent ion, said apparatus comprising: • The reagent ion source has a hollow cathode glow discharge (HCD) region (101) and a source drift (SD) region (102). The drift tube region (103) adjacent to the reagent ion source includes at least one port (107) for introducing the gas to be analyzed and at least one source for an electric field. • The mass analyzer region (104) adjacent to the drift tube region (103), ●and control equipment, The HCD region (101) includes at least one port (105) connected to at least one pump, at least two electrodes serving as anodes (201, 203), and at least one electrode serving as cathode (202). The SD region (102) includes at least one port (106) connected to at least one source gas supply. The control device is configured as follows: ● Control the discharge current in the HCD region (101), • Control the source gas flow through the reagent ion source. ● Adjust the pressure in the drift tube region (103) to between 1 and 10 hPa. ● Adjust the electric field in the drift tube region (103), wherein the electric field includes at least a DC field configured to attract ions in the direction of the mass analyzer region (104).

2. The apparatus according to claim 1, wherein the control device is configured to switch polarity and adjust the extraction voltage of the reagent ion source for negatively charged or positively charged ions, the drift tube region (103), and the mass analyzer (104).

3. The apparatus according to claim 1 or claim 2, wherein the apparatus includes an O2 source, wherein the control device is configured to control the injection of O2 into the SD region (102) through the at least one port (106) and the pumping of O2 out of the HCD region (101) to generate O2 in the reagent ion source. - Furthermore, the extraction voltage of the reagent ion source is adjusted so that the generated reagent ions are conducted to the drift tube region (103).

4. The apparatus according to claim 3, wherein O2 - The reagent ion purity is greater than 90%.

5. The apparatus according to claim 1 or claim 2, wherein the apparatus comprises O2. - The source and CO2 source, wherein the control device is configured to control the injection of a mixture of O2 and CO2 into the SD region (102) through the at least one port (106) and the pumping of O2 and CO2 out of the HCD region (101) to generate CO3 in the reagent ion source. - Furthermore, the extraction voltage of the reagent ion source is adjusted so that the generated reagent ions are conducted to the drift tube region (103).

6. The apparatus according to claim 5, wherein CO3 - The reagent ion purity is greater than 80%.

7. The apparatus according to any one of the preceding claims, wherein at least one port (105) of the HCD region (101) is connected to at least one source gas supply.

8. The apparatus of claim 7, wherein the apparatus comprises an N2 source and an H2O source, wherein the control device is configured to: ● A mixture of N2 and H2O source gases is controlled to be injected into the HCD region (101) through at least one port (105) and pumped out from the SD region (102) and / or the drift tube region (103) to generate NH4 in the reagent ion source. + , ● Control the H2O source gas to be injected into the SD region (102) through at least one port (106) and pumped out from the HCD region (101) to generate H3O in the reagent ion source. + , • And NH4 in the reagent ion source + and H3O + Electron switching occurs between the generation of ions.

9. The apparatus according to claim 7 and any of the preceding claims, wherein the control device is further configured to: ● A mixture of N2 and O2 source gases is controlled to be injected into the HCD region (101) through at least one port (105) and pumped out from the SD region (102) and / or the drift tube region (103) to generate NO in the reagent ion source. + , • Controlling O2 source gas to be injected into the SD region (102) through at least one port (106) and pumped out from the HCD region (101) to generate O2 in the reagent ion source. + , The control device is also configured to electronically switch between different reagent ions.

10. The apparatus according to any one of the preceding claims, wherein the control device is configured to adjust the pressure in the reagent ion source between 0.1 and 10 hPa, preferably between 0.2 and 4 hPa.

11. A method of operating an apparatus for ion-molecular-reaction mass spectrometry and / or proton-transfer-reaction mass spectrometry, the apparatus having a reagent ion source having a hollow cathode glow discharge (HCD) region (101) and a source drift (SD) region (102), wherein the SD region (102) includes at least one port (106) connected to at least one source gas supply, and the HCD region (101) includes at least one port (105) connected to at least one pump, characterized in that... The following steps: ● A controlled source gas flow is introduced into the SD region (102) via the at least one port (106) and the source gas is pumped out of the HCD region (101). • An ionization method is applied to the source gas to generate reagent ions in the reagent ion source. ● The reagent ions and the gas to be analyzed are introduced into the drift tube region (103), wherein the analyte is ionized via interaction with the reagent ions in the drift tube region (103). ●The ions are analyzed in the mass analyzer region (104) after the drift tube region (103).

12. The method of claim 11, wherein an O2 source gas is introduced into the SD region (102) and pumped out from the HCD region (101), thereby generating a reverse source gas flow and O2 as reagent ions. - .

13. The method of claim 11, wherein a mixture of O2 and CO2 source gases is introduced into the SD region (102) and pumped out from the HCD region (101), thereby generating a reverse source gas flow and CO3 as reagent ions. - .

14. The method according to any one of claims 11 to 13, wherein positively charged and negatively charged reagent ions are generated in the reagent ion source, wherein the switching between positively charged and negatively charged reagent ions is achieved by switching polarity and adjusting the extraction voltage of the reagent ion source for negatively charged or positively charged ions, the drift tube, and the mass analyzer.

15. The method according to any one of claims 11 to 14, wherein, The at least one port (105) of the HCD region (101) is connected to at least one source gas supply, wherein, depending on the reagent ion to be generated, the source gas is introduced into the SD region (102) and pumped out from the HCD region (101) to generate a reverse source gas flow, or the source gas is introduced into the HCD region (101) and pumped out from the SD region (102) and / or the drift tube region (103) to generate a forward source gas flow, wherein different reagent ions are generated by electronically switching between the forward and reverse source gas flows and / or using different source gases.

16. The method of claim 15, wherein the switching time between different reagent ions of the same polarity is less than 2 seconds.

17. The method according to claim 15 or 16, wherein a mixture of N2 and H2O source gases is introduced into the HCD region (101) and pumped out from the SD region (102) and / or the drift tube region (103), thereby generating a forward source gas flow and NH4 as reagent ions. + ,or H2O source gas is introduced into the SD region (102) and pumped out from the HCD region (101), thereby generating a reverse source gas flow and H3O as reagent ions. + , The switching of H3O is accomplished electronically via control equipment. + and NH4 + The generation of reagent ions.

18. The method according to claim 15 or 16, wherein an O2 source gas is introduced into the SD region (102) and pumped out from the HCD region (101), thereby generating a reverse source gas flow and O2 as reagent ions. - or O2 + ,or A mixture of N2 and H2O source gases is introduced into the HCD region (101) and pumped out from the SD region (102) and / or the drift tube region (103), thereby generating a forward source gas flow and NH4 as reagent ions. + ,or A mixture of N2 and O2 source gases is introduced into the HCD region (101) and pumped out from the SD region (102) and / or the drift tube region (103), thereby generating a positive source gas flow and NO as a reagent ion. + ,or H2O source gas is introduced into the SD region (102) and pumped out from the HCD region (101), thereby generating a reverse source gas flow and H3O as reagent ions. + , The generation of different reagent ions is switched electronically via control equipment.

19. The method according to claim 15 or 16, wherein an O2 source gas is introduced into the SD region (102) and pumped out from the HCD region (101), thereby generating a reverse source gas flow and O2 as reagent ions. - or O2 + ,or A mixture of O2 and CO2 source gases is introduced into the SD region (102) and pumped out from the HCD region (101), thereby generating a reverse source gas flow and CO3 as reagent ions. - ,or A mixture of N2 and H2O source gases is introduced into the HCD region (101) and pumped out from the SD region (102) and / or the drift tube region (103), thereby generating a forward source gas flow and NH4 as reagent ions. + ,or A mixture of N2 and O2 source gases is introduced into the HCD region (101) and pumped out from the SD region (102) and / or the drift tube region (103), thereby generating a positive source gas flow and NO as a reagent ion. + ,or H2O source gas is introduced into the SD region (102) and pumped out from the HCD region (101), thereby generating a reverse source gas flow and H3O as reagent ions. + , The generation of different reagent ions is switched electronically via control equipment.

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