A method for controlling the composition of buffer gas to improve the sensitivity of ion mobility spectrometry

Abstract

A method for controlling the composition of buffer gas to improve the sensitivity of ion mobility spectrometry. By controlling the composition ratio of the buffer gas, a higher reagent ion intensity can be obtained, which then reacts with sample molecules to increase the signal intensity of product ions, thereby improving the sensitivity of the target sample to be measured. To solve the problem that O2 in the buffer gas composition used in conventional ion mobility spectrometry also has a certain absorption of ultraviolet light, which thus has a certain weakening effect on the signal intensity of reagent molecules. The present invention improves the sensitivity of ion mobility spectrometry to a certain extent by reducing the concentration of oxygen in the carrier gas or drift gas components of reagent molecules. When the ion mobility spectrometry instrument device and condition settings are fixed, the sensitivity of ion mobility spectrometry can be improved by the above method. The method is simple and easy to operate, and is suitable for meeting the need of improving the sensitivity of photoionization source analysis instruments.

Description

Technical Field

[0001] The present invention belongs to the field of analytical chemistry instruments, and particularly relates to a method for controlling the composition of buffer gas to improve the sensitivity of ion mobility spectrometry. Background Art

[0002] The operation and work of ion mobility spectrometry instruments require clean buffer gas. Commonly used buffer gases include air, with a certain proportion of 21% oxygen and 78% nitrogen in the air. Since oxygen has a certain absorption effect on the energy of the photoionization source, it affects the sensitivity of analytical instruments such as ion mobility spectrometry. Therefore, the present invention designs a method for controlling the composition of buffer gas to improve the sensitivity of ion mobility spectrometry.

[0003] A method for improving the sensitivity of an ion mobility spectrometer (patent number ZL201811458994.6) invented by Li Jinghua et al. After the sample is injected into the ion mobility spectrometer, 200 consecutive analyses are performed, with each analysis cycle being 20 milliseconds. Among them, the opening time of each analysis cycle for the first 100 times is 200 microseconds, and the opening time of each analysis cycle for the last 100 times is 1000 microseconds, so as to achieve the simultaneous detection of high-concentration sample A and low-concentration sample B, improve the detection sensitivity, and improve the sensitivity of the ion mobility spectrometer from the parameter of the ion gate opening time.

[0004] A device and method for improving the sensitivity and resolution of ion mobility spectrometry (patent number ZL 202010647868.6) invented by Yu Jianna et al. On the premise of maintaining the basic structure of the ion mobility spectrometer, through the complete electrical isolation of the ion source region and the migration region, the electric field strength in the ionization region and the migration region is kept constant during the entire working process of the ion mobility spectrometer, and the working stability of the ion source is not affected. At the same time, the working electric field in the migration region always remains in a single state, and the sensitivity of the ion mobility spectrometer is improved by controlling the application method of the electric field.

[0005] Aiming at the problem that in the above-mentioned photoionization ion mobility spectrometry, the sensitivity is improved by adjusting physical parameters. During the process of detecting samples by ion mobility spectrometry, since oxygen in the buffer gas composition has a certain absorption of photoionization photon energy and has a certain weakening effect on the signal intensity of sample molecules, the present invention controls the concentration of oxygen in the carrier gas or drift gas of sample molecules, which has a certain effect on improving the sensitivity of ion mobility spectrometry to a certain extent. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to further improve the sensitivity of ion mobility spectrometry by changing the composition of buffer gas.

[0007] The ion mobility spectrometer uses a photoionization source, with a sample gas inlet provided in the reaction region and a drift gas inlet provided at one end of the migration region far from the reaction region. The sample gas has an O 2 content of O 2 and N 2 mixed gas as the dilution gas, and the drift gas is an O 2 -containing O 2 and N 2 mixed gas.

[0008] The photoionization source is a vacuum ultraviolet lamp ionization source, and the dilution gas and the drift gas are buffer gases.

[0009] The dilution gas and the drift gas have the same composition, which is an O 2 -containing O 2 and N 2 mixed gas. The specific content includes:

[0010] A method for controlling the buffer gas composition to improve the sensitivity of the ion mobility spectrometer, which is composed of a certain proportion of N 2 -O 2 . By controlling the proportion of O 2 , the sensitivity of photoionization of the ion mobility spectrometer is improved. The content of the O 2 component is 21%, and the sensitivity of the target component is improved by further reducing the proportion of the O 2 component.

[0011] A certain proportion of N 2 -O 2 buffer gas can enter the inside of the ion mobility tube from the tail of the ion mobility spectrometer or at the photoionization reagent molecule inlet. Description of the Drawings

[0012] Figure 1 A schematic structural diagram of an ion mobility spectrometer for controlling the buffer gas composition. 1 is a sampling pump, 2 is a mass flow meter, 3 is a 10 ppm acetone standard gas (a certain O 2 -N 2 ratio); 4 is a TPG ion gate, 5 is a conductive ring, 6 is a grid, 7 is a drift gas (a certain O 2 -N 2 ratio), 8 is an amplifier, 9 is a high voltage, 10 is grid 1, 11 is grid 2, and 12 is a radio frequency lamp;

[0013] Figure 2 The signal intensity of 10 ppm acetone changes with the change of the O 2 -N 2 buffer gas composition. Detailed Embodiments

[0014] Example 1

[0015] A method for controlling the composition of buffer gas to improve the sensitivity of ion mobility spectrometry, wherein a certain proportion of N 2 -O 2 Composition, by controlling O 2 The ratio of O 2 The component is 21%, increasing O 2 The sensitivity of the target component can be improved by adjusting the component ratio. 2 -O 2 The buffer gas can enter from the tail of the ion mobility spectrometer or from the inlet of the photoionization source reagent molecule into the interior of the ion migration tube. The electric field strength in the migration zone is 600V / cm and the gate voltage is 350V.

[0016] Prepare 10ppm acetone standard gas of different components, take 0.48ul acetone into the gas bag, fill it with a certain proportion of O 2 and N 2 In the air bag, respectively configure O 2 O at 2%, 5%, 10%, 15% and 20% volume concentrations 2 -N 2 The 10ppm acetone standard gas is sampled by the ion mobility spectrometer at a flow rate of 100ml / min, such as Figure 1 As shown, the drift gas flow rate is 400 ml / min, and the components of the drift gas correspond to O 2 O with a volume concentration of 0%, 0.2%, 2%, 5%, 10%, 15% and 20% 2 -N 2 Buffer gas. Record the total ion current, peak height and peak area of ​​acetone product ions as O 2 The concentration changes with the 2 As the concentration ratio decreases, the acetone concentration signal intensity increases, such as Figure 2 As shown, the sensitivity of ion mobility spectrometry can be further improved by controlling the gas component ratio.

Claims

1. A method for controlling the composition of buffer gas to improve the sensitivity of ion mobility spectrometry. The ion mobility spectrometry uses a photoionization source, has a sample gas inlet in the reaction region, and has a drift gas inlet at one end of the migration region far from the reaction region. Characterized in that: The sample gas is O with a volume concentration of 2% - 20% 2 of O 2 and N 2 The mixture gas is used as the dilution gas, and the purge gas is O with a volume concentration of 2% - 20% 2 of O 2 and N 2 mixture gas.

2. The method according to claim 1, Characterized in that: The photoionization source is a vacuum ultraviolet lamp ionization source, and the diluent gas and the drift gas are buffer gases.

3. The method described in claim 1, Characterized in that: The dilution gas and purge gas are a mixed gas of O with a volume concentration of 2% - 20% 2 O 2 and N 2 .

4. The method according to claim 1, Characterized in that: The diluent gas and the drift gas have the same composition.

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