CN205808992U - Gas phase ion molecule collision section gauge instrument under normal pressure - Google Patents

Abstract

The utility model relates to a gas-phase ion molecule collision cross-section measuring instrument under normal pressure. The measuring instrument includes an ultraviolet lamp ionization device, a sample feeding device, an electric field chamber, a power supply device, a microcurrent detector, a data acquisition and processing system and a gas delivery device. The sample injection device is connected to the inlet of the ultraviolet lamp ionization device, a signal gate is provided between the outlet of the ultraviolet lamp ionization device and the inlet end of the electric field chamber, and the positive and negative poles of the power supply device are respectively connected to the The inlet end and the outlet end of the electric field chamber are electrically connected by wires, the microcurrent detector is arranged at the outlet end of the electric field chamber, the microcurrent detector is electrically connected with the data acquisition and processing system, and the electric field chamber is provided with The air inlet of the electric field chamber and the gas outlet of the electric field chamber, the gas conveying device is connected with the air inlet of the electric field chamber, has a simple structure and is easy to use, and can complete online measurement of the collision cross section of ions and molecules under atmospheric pressure.

Description

Gas Phase Ion Molecule Collision Cross Section Measuring Instrument at Normal Pressure

technical field

The utility model relates to a gas phase ion molecule collision section measuring instrument under normal pressure.

Background technique

At present, there are mass spectrometry and ion mobility spectrometry to retrieve the ion collision cross section. Mass spectrometry measures the collision cross section through the information of the ion molecular reaction, but the mass spectrometer needs to work under high vacuum conditions, which increases the cost and cost of the detection device. The complexity is not suitable for the use and maintenance of non-professionals. Ion mobility spectrometry is a gas-phase ion separation technique in which ions travel through a drift cell (drift tube) of known length containing a buffer gas (drift gas) of known composition (e.g. nitrogen), pressure, and temperature. ) and become separated in time. During this travel, the ions become separated based on their different collision cross sections (CCS) which may be related to their different mobilities through the buffer gas. Ion mobility spectrometry systems typically include an ion source to ionize molecules of a sample of interest, followed by a drift cell to receive the ions, followed by an ion detector to count the separated ions. The ion detector is in communication with electronics configured to process output signals from the ion detector as necessary to produce a user interpretable drift spectrum. A drift spectrum is typically presented as a graph containing a series of peaks indicative of the relative abundance of detected ions as a function of their drift time through the drift cell. Drift spectra can be used to identify and distinguish different analyte nuclides of a sample.

If the drift time of the ion through the drift cell, the pressure in the drift cell and the voltage across the drift cell are known, we can calculate the CCS of the ion. This CCS parameter is ion-specific and device-independent, and thus can be used as the only parameter for compound identification, but the device also suffers from many disadvantages, such as being very long for the amount of measurement time and measuring Time Quantities don't play well with modern color schemes,

In view of this, there is a need for a utility model that has a simple structure, is easy to use, and can complete the measurement of ion molecule collision cross section under atmospheric pressure.

Utility model content

The purpose of the utility model is to overcome the defects of the prior art and provide a gas-phase ion-molecule collision cross-section measuring instrument under normal pressure with a simple structure and convenient use.

In order to achieve the above object, the technical scheme that the utility model takes is as follows:

On the one hand, the utility model provides a gas-phase ion molecule collision cross section measuring instrument under normal pressure, which includes an ultraviolet lamp ionization device, a sample feeding device, an electric field chamber, a power supply device, a micro-current detector, a data acquisition and processing system, and a gas delivery device. The sample injection device is connected to the inlet of the ultraviolet lamp ionization device, a signal gate is set between the outlet of the ultraviolet lamp ionization device and the inlet end of the electric field chamber, and the positive and negative poles of the power supply device are respectively connected to the The inlet end and the outlet end of the electric field chamber are electrically connected by wires, the microcurrent detector is arranged at the outlet end of the electric field chamber, the microcurrent detector is electrically connected with the data acquisition and processing system, and the electric field chamber is provided with The gas inlet of the electric field chamber and the gas outlet of the electric field chamber, the gas conveying device communicates with the gas inlet of the electric field chamber.

As a further improvement of the utility model, the gas delivery device includes a steel cylinder, a pressure reducing valve, a purification device and a flow meter, the steel cylinder communicates with the purification device through the pressure relief valve, and the purification device communicates with the air inlet of the flow meter , the gas outlet of the flowmeter communicates with the gas inlet of the electric field cavity.

As a further improvement of the utility model, the electric field cavity is electrically connected with the ionization device and the signal gate.

Compared with the prior art, the beneficial effects obtained by the utility model are as follows:

The ultraviolet lamp ionization device of the utility model is used to generate the required ion signal; the sample feeding device is used to control the concentration and flow of the sample to be tested through the sealed gas circuit and the gas flow controller; the signal gate is used to provide the ion to enter the electric field cavity The channel; the electric field chamber provides the cavity where the ion signal collides with the air molecules, and provides the electric field required for ion movement; the microcurrent detector is at the outlet of the electric field chamber to measure the current signal generated by the ion flow, and the output of the microcurrent detector The signal is connected with the data acquisition and processing system, and the output signal is analyzed by the data acquisition and processing system to obtain the measurement result of the collision cross section.

The utility model adopts the detection mode of photoionization, ion injection, ion molecule collision, and ion movement in the electric field, and utilizes the double-channel air intake mode to realize the measurement of the collision cross section between gas phase ion molecules at normal temperature through data processing and corresponding algorithms. It breaks through the difficulty of measuring the collision cross section under normal pressure and fills the gap in this technology.

Description of drawings

In order to more clearly illustrate the specific implementation of the utility model or the technical solutions in the prior art, the accompanying drawings that need to be used in the description of the specific implementation or the prior art will be briefly introduced below. Obviously, the following descriptions The accompanying drawings are some implementations of the utility model, and those skilled in the art can obtain other drawings according to these drawings without any creative work.

Accompanying drawing 1 is the structural representation of the utility model;

Accompanying drawing 2 is the spectrogram that the utility model device measures ethanol and nitrogen collision section;

In the accompanying drawings: 1 ultraviolet lamp ionization device, 2 sample injection device, 3 signal gate, 4 electric field cavity, 5 power supply, 6 microcurrent detector, 7 data acquisition and processing system, 8 steel cylinder, 9 pressure reducing valve, 10 Purification device, 11 flow meter, 12 air inlet pipe, 13 electric field chamber air inlet, 14 electric field chamber air outlet.

detailed description

In order to make the purpose, technical solution and advantages of the utility model clearer, the utility model is clearly and completely described below in conjunction with the accompanying drawings and specific embodiments.

As shown in Figure 1, a gas-phase ion molecule collision cross-section measuring instrument under normal pressure includes an ultraviolet lamp ionization device 1, a sampling device 2, an electric field chamber 4, a power supply device 5, a microcurrent detector 6, and data acquisition and processing System 7 and gas delivery device, the sampling device 2 is connected to the inlet of the ultraviolet lamp ionization device 1, and a signal gate is arranged between the outlet of the ultraviolet lamp ionization device 1 and the inlet end of the electric field chamber 4 3. The positive and negative poles of the power supply device (5) are electrically connected to the inlet end and the outlet end of the electric field chamber (4) respectively through wires, and the micro-current detector 6 is arranged at the outlet end of the electric field chamber 4, so The input end of the micro-current detector (6) is connected to the outlet end of the electric field chamber, and the output end of the micro-current detector 6 is connected to the data acquisition and processing system.

The electric field cavity 4 is provided with an electric field cavity inlet 13 and an electric field cavity gas outlet 14, and the gas conveying device includes a steel cylinder (8), a pressure reducing valve 9, a purification device 10 and a flow meter 11, and the steel cylinder 8 Communicate with the purification device (10) through the pressure reducing valve (9), and the purification device (10) communicates with the air inlet of the flow meter (11), and the gas outlet of the flow meter 11 and the air inlet 13 of the electric field cavity The intake pipe 12 is connected.

One end of the signal gate 3 of the utility model communicates with the ionization source inside the ultraviolet lamp ionization device 1 , and the other end communicates with the entrance end of the electric field cavity 4 .

The working principle of this device is as follows: small organic molecules in the gas phase are ionized by ultraviolet lamps to form ion signals, and the formed product ions are introduced into the electric field, and the product ions move in the electric field filled with nitrogen, and collide with neutral nitrogen molecules in the electric field , and obtain a certain velocity, which contains the collision cross-section information between ions and neutral nitrogen molecules. At the end of the electric field, the collision cross section between ion molecules is fed back by measuring the movement time of the product ion signal.

The ultraviolet lamp ionization device in this device is used to generate the required ion signal; the sampling device is used to control the concentration and flow of the measured sample through the sealed gas circuit and the gas flow controller; the signal gate is used to provide the ion to enter the electric field cavity The channel; the electric field chamber provides the cavity where the ion signal collides with the air molecules, and provides the electric field required for ion movement; the microcurrent detector is at the outlet of the electric field chamber to measure the current signal generated by the ion flow, and the output of the microcurrent detector The signal is connected with the data acquisition and processing system, and the output signal is analyzed by the data acquisition and processing system to obtain the measurement result of the collision section.

Utilize the method of the utility model device to measure ion molecular collision cross-section as follows: by the time and intensity of collecting signal by data acquisition and processing system, calculate collision cross-section according to following formula (6);

(6)

In the formula:

Ω _avg is the collision cross section of ion molecule, the unit is Å ² ;

m is the mass of the ion in g;

M is the mass of a neutral gas molecule in g;

N is the ion number density, the unit is m ^-3 ;

k _B is the Boltzmann constant, the unit is J·K ^-1 ;

T is the temperature of the gas in K;

e is the electric quantity of electrons, the unit is C;

z is the number of charges carried by the ion;

S is the length of the electric field cavity, in m;

U is the total voltage at both ends of the electric field cavity, and the unit is V.

t is the movement time of ions in the electric field cavity, the unit is s.

Here is a detailed explanation of the process of obtaining the above formula to support the accuracy and reliability of the measurement results obtained, as follows:

As known to those skilled in the art, the ultraviolet constant ionization device generates the ion signal of the sample through photoionization of the sample to be measured. The ion signal enters the electric field chamber by ion implantation under the use of the signal gate, and the ion is injected into the electric field cavity. The cavity is subjected to electric field force, Coulomb repulsion and collisions between nitrogen molecules, and the motion equation of ions in the electric field cavity over time is:

(1)

Among them, v _d is the moving velocity of the ion, _r0 is the radius of the electric field cavity, P(t) is the distribution function of the ion after entering the electric field cavity, C is a constant, D is the diffusion constant, under the condition of low electric field, , where z is the number of charges carried by the ion, e is the charge of the electron, k _B is the Boltzmann constant, T is the temperature of the gas, and K is the mobility of the ion.

The ion mobility K contains the structural information of ions. In a low electric field, the expression of K is:

Wherein, m is the quality of ion, and M is the quality of neutral gas molecule, and Ω _avg is the collision section of ion molecule, and N is ion number density, and neutral gas molecule used in the utility model is nitrogen, therefore, in formula (2), as long as the mobility K of the ion is obtained, the collision cross section Ω _avg can be obtained by calculation. Therefore, for a specific ion signal, the moving velocity V in the electric field cavity and the electric length intensity E and the mobility of the ion The relationship between K is:

The velocity V of ions can be obtained by the length S of the electric field cavity and the movement time t of ions in the electric field cavity,

Combining Equation (3) and Equation (4), we can get,

The electric field strength E in the electric field cavity can be obtained by dividing the total voltage Ut applied at both ends of the electric field cavity by the length S of the cavity. Therefore, formula (5) can be rewritten as:

Therefore, it is only necessary to know the length S of the electric field cavity, the total voltage U at both ends of the electric field cavity, and the movement time t of the ions in the electric field cavity, and the collision cross section information of the signal can be obtained by using formula (6).

The present application is explained and verified in detail below through specific examples.

Example 1

The measurement results of ion molecular collision cross sections of several compounds and nitrogen molecules

compound molecular weight Drift time (ms) Measured value CCS (Å) ethanol 46 15.1 122 butanone 72 17.4 125 octanol 130 22.8 147

Example 2

Utilize the depressive gas phase ion molecular collision cross-section measuring instrument provided by the utility model to measure the collision cross-section measurement of ethanol and nitrogen, and the measurement conditions are as follows:

T=298K, U=3500V, S=12cm

The resulting signal diagram is shown in Figure 2, and the measurement results are as follows:

Ion movement time t=15.1ms

The collision cross section Ω _avg =122A ² .

The above-mentioned implementations are only preferred embodiments of the present utility model, rather than an exhaustive list of feasible implementations of the present utility model. For those skilled in the art, any obvious changes made without departing from the principle and spirit of the utility model should be considered to be included in the protection scope of the claims of the utility model.

Claims (3)

1. A gas-phase ion molecule collision cross section measuring instrument under normal pressure is characterized in that it comprises an ultraviolet lamp ionization device (1), a sampling device (2), an electric field cavity (4), a power supply device (5), a microcurrent Detector (6), data acquisition and processing system (7) and gas conveying device, described sampling device (2) links to each other with the inlet of described ultraviolet lamp ionization device (1), and the inlet of described ultraviolet lamp ionization device (1) A signal gate (3) is arranged between the outlet and the inlet end of the electric field chamber (4), and the positive and negative poles of the power supply device (5) are respectively connected to the inlet end and the outlet end of the electric field chamber (4) through wires. connected, the microcurrent detector (6) is arranged at the outlet end of the electric field chamber (4), the microcurrent detector (6) is electrically connected with the data acquisition and processing system (7), and the electric field chamber (4 ) is provided with an electric field cavity inlet (13) and an electric field cavity gas outlet (14), and the gas delivery device communicates with the electric field cavity inlet (13). 2. A gas-phase ion-molecule collision cross-section measuring instrument under normal pressure according to claim 1, characterized in that, said gas delivery device comprises a steel cylinder (8), a pressure reducing valve (9), a purification device (10) And flow meter (11), described steel cylinder (8) communicates with purifying device (10) by decompression valve (9), and described purifying device (10) communicates with flow meter (11) air inlet, and described flow meter The gas outlet of (11) communicates with the air inlet (13) of the electric field cavity. 3. A gas-phase ion-molecule collision cross section measuring instrument under normal pressure according to claim 1, characterized in that the electric field cavity (4) is electrically connected to the ionization device (1) and the signal gate (3).