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CN-114730694-B - Pulsating flow atmospheric real-time ionization

CN114730694BCN 114730694 BCN114730694 BCN 114730694BCN-114730694-B

Abstract

In embodiments of the present ambient ionization experiments, the abundance of background chemicals relative to target ions is reduced by pulsing a carrier gas used to generate excited species directed toward the sample. The excited species are directed progressively toward the sample, thereby reducing the overall abundance of background chemical species introduced into the ionization region. In embodiments of the present ambient ionization experiments, the combination of stepping the sample before the excited species and pulsing the carrier gas used to generate the excited species improves the sensitivity of the detection.

Inventors

  • S. Oro
  • B. D. muselman

Assignees

  • 埃昂森斯股份有限公司

Dates

Publication Date
20260505
Application Date
20201026
Priority Date
20191028

Claims (15)

  1. 1. An ionizer for pulsed atmospheric ionization of a sample, comprising: A first atmospheric pressure chamber is provided in the first chamber, the first atmospheric pressure chamber comprises: An inlet for a carrier gas; a first electrode; counter electrode, and An outlet port; A power supply configured to energize the first electrode and the counter electrode to provide current between the first electrode and the counter electrode to generate a discharge, and A pulse generator configured to introduce carrier gas pulses into the first atmospheric pressure chamber to generate two or more carrier gas pulses forming ions of the sample.
  2. 2. The ionizer of claim 1 wherein the duration of two or more carrier gas pulses reaches a time t 1 .
  3. 3. The ionizer of claim 1 or 2, wherein the two or more carrier gas pulses are separated by a time t 2 .
  4. 4. The ionizer of claim 2 wherein the interaction of the two or more carrier gas pulses with the discharge during time t 1 generates one or more ionized species.
  5. 5. The ionizer of claim 4 wherein gas contact between the one or more ionized species and the two or more pulses of carrier gas directs the one or more ionized species formed in the atmosphere to the sample through the outlet port.
  6. 6. The ionizer of claim 2 wherein the power supply is configured to energize the first electrode and the counter electrode continuously.
  7. 7. The ionizer of claim 4 wherein the one or more ionized species comprise ions, electrons, thermal atoms, thermal molecules, radicals, and metastable neutral excited species.
  8. 8. The ionizer of claim 2 wherein the sample comprises an analyte applied to a mesh, immersed probe, SPME fiber, glass or metal slide, filament, glass or metal rod, fiber or wire loop.
  9. 9. The ionizer of claim 2 further comprising a cap at the outlet port, wherein the cap has an outlet aperture therebetween: 0.1 Lower limit of mm, and 4 Mm.
  10. 10. The ionizer of claim 4 wherein the sample comprises two or more sample points, wherein a first sample point is separated from a second sample point by a distance d, wherein the two or more sample points are processed such that the one or more ionized species are directed toward the first sample point during the time t 1 of a first pulse of the two or more carrier gas pulses and the one or more ionized species are directed toward the second sample point during the time t 1 of a second pulse of the two or more carrier gas pulses.
  11. 11. The ionizer of claim 10 wherein the two or more sample points are processed such that the two or more sample points remain stationary during the time t 1 .
  12. 12. The ionizer of claim 10 wherein the two or more sample points are processed during the time t 2 such that the one or more ionized species are directed from the first sample point to the second sample point.
  13. 13. A device for ionizing a sample, comprising: A first atmospheric pressure chamber is provided in the first chamber, the first atmospheric pressure chamber comprises: An inlet for a carrier gas; a first electrode; counter electrode, and An outlet port; A power supply configured to energize the first electrode and the counter electrode to provide current between the first electrode and the counter electrode to generate a discharge, and A pulse generator configured to introduce a carrier gas into the first atmospheric pressure chamber to generate two or more carrier gas pulses, wherein the duration of the two or more carrier gas pulses is for a time t 1 , wherein the two or more carrier gas pulses are separated by a time t 2 , wherein interaction of the two or more carrier gas pulses with the discharge during time t 1 generates one or more ionized species, wherein gas contact between the one or more ionized species and the two or more carrier gas pulses directs the one or more ionized species formed in the atmosphere to a sample through the outlet port, thereby generating one or more sample ions.
  14. 14. The apparatus of claim 13, wherein the power source is configured to energize the first electrode and the counter electrode continuously.
  15. 15. A method of ionizing an analyte with a pulsed flow atmospheric pressure ionization device comprising: (a) Energizing a first electrode relative to a second electrode spaced apart from the first electrode, wherein the first electrode and the second electrode are located in a chamber, wherein the chamber includes a gas inlet and an outlet, wherein energizing the first electrode relative to the second electrode generates a discharge; (b) Introducing two or more pulses of carrier gas into the chamber through a gas inlet, wherein the two or more pulses of carrier gas have a duration of time t 1 , wherein the two or more pulses of carrier gas are separated by time t 2 ; (c) Generating the ion, electron and excited state species of the two or more carrier gas pulses, and (D) The ions, electrons, excited state species are directed to an analyte.

Description

Pulsating flow atmospheric real-time ionization Technical Field The present invention relates to a method and apparatus for chemical analysis of molecules ionized in the ambient atmosphere by pulse introduction of a carrier gas. Background Analysis of target molecules at ambient atmosphere in a laboratory or field setting can be accomplished by converting the target molecules into ions using ionized species and directing or ejecting the ions into a spectrometer. However, the ambient atmosphere in a laboratory or field setting may contain many "background chemicals" that may also be detected. These background chemicals may vary depending on the local environment. For example, trace chemicals present in laboratory atmospheres may contain solvents, dust particles, aerosols, counterions, and chemicals used in synthesis or extraction. Furthermore, the background may include chemicals from human, animal, bacterial, viral or fungal activities (including from the presence of spectrometer operators/scientists), including chemicals from respiration, perfumes, fragrances, mouthwashes, cosmetics, sweat, flatulence, bacterial gases and bacterial odors. The presence of any one or more of these may result in the generation of a persistent background. When the background becomes too rich, the process of ambient ionization and ion detection of the target molecules may become inefficient because the target molecules are not detected or the abundance of the target molecules is so low that they are masked from detection by the background chemical. Trace chemicals present in the target sample may also be considered background chemicals because they are present in the ionization region but are not targets. These include chemicals originating from the sample container, solvent residues, chemicals that are typically present but not important to the characterization of the sample, and chemicals that may be introduced into the air surrounding the ionized material, including those from human activity, such as solvents, or from other nearby analytical work. For example, in urine samples, the metabolite creatinine, a chemical waste produced by muscle metabolism, is easily ionized and detected using a spectrometer. Kidneys filter creatinine and other waste products (including urea) from the circulating blood, allowing them to be expelled from the body by urination. Thus, both compounds (creatinine and urea) are present as background chemicals when analyzing human fluids. Furthermore, urea itself is difficult to extract from urine, which is why analysis of drugs of abuse in workplace drug testing is typically performed by separating urea from target molecules using chromatographic materials. The chromatographic material delays the passage of larger drug molecules while allowing urea to be directed to waste. In the absence of urea, larger drug molecules are ionized in the ambient atmosphere and are easily detected after entering the spectrometer. The solvent effect may also contribute to background chemicals, such as solvents used to dissolve the sample, e.g., dimethylsulfoxide (DMSO), and chemicals added to the sample to promote pH change or ionization buffering may also contribute to the background chemicals. In theory and practice, the elimination of background chemicals prior to ambient ionization reduces background chemical ions, i.e., chemical noise, allowing for increased sensitivity to target molecules. Disclosure of Invention In embodiments of the present invention, pulsing a carrier gas for generating an ionized species may be used to increase ionization of target molecules and thereby allow for a reduction in detection limit in ambient ionization experiments. In embodiments of the invention with ambient ionization experiments, jumping from one location and pulsing the carrier gas used to generate the ionized species can be used to increase ionization of the target molecules and thereby allow the detection limit to be lowered. Drawings All real-time Direct Analysis (DART) Atmospheric Pressure Ionization (API) measurements were performed at 300 ℃, unless specified otherwise. All samples were spotted using Mosquito (a positive displacement pipette) from TTP Labtech. All mass spectrometry was performed on a Q-Exactive TM mass spectrometer from the company Semer Fielder technology (Thermo Scientific) TM. Various embodiments of the present invention will be described in detail based on the following drawings, in which: FIG. 1 is a paper consumable holding a wire mesh in a blank inserted into an X-Y drive designed to enable presentation of a series of samples deposited at regular intervals (1-12) on a mesh surface into an ionized substance emitted from the distal end of a DART API source, according to various embodiments of the present invention; FIG. 2A is a schematic illustration of ionized species from a DART API source passing through a narrow cap and directed to a sample applied to a mesh inserted into the ionization volume of a