CN111239234B - Non-radioactive method for on-line monitoring of ammonia gas - Google Patents

Abstract

The invention discloses a non-radioactive device and method for fast, accurate and continuous monitoring of ammonia. The invention utilizes the non-radioactive ion mobility spectrum assisted by photoionization of reagent molecules, and selects methyl ethyl ketone as the reagent molecule in the positive ion mode to realize fast, accurate and highly sensitive online measurement of ammonia gas. The detection device includes: drift gas, carrier gas, reagent molecule generating device, ion mobility spectrometry system, pump, etc.

Description

A non-radioactive method for on-line monitoring of ammonia gas

technical field

The invention belongs to the technical field of ion mobility spectrometry. Utilize non-radioactive vacuum ultraviolet lamp ion mobility spectrometry, adopt suction sampling in positive ion mode, and optimize the screening of reagent molecules, p-xylene, trigger chemical reactions, improve the sensitivity and selectivity of ammonia detection, and realize ammonia Rapid and accurate online monitoring of gas.

technical background

Ammonia is a colorless inorganic gas with a strong pungent odor, easily soluble in water, a Lewis base, and exists in the human body and the environment.

In humans, ammonia plays an important role and is considered an important exhaled breath biomarker. The main sources of ammonia in the human body include: deamination of amino acids, most of the amino acids in the kidney will form glutamic acid through transamination with α-ketoglutarate under the action of glutaminase. In addition, ammonia can also be produced by the metabolism of purine and pyrimidine compounds; the decomposition of amino acids in food by intestinal bacteria and the decomposition of monoamine oxidase can also produce ammonia. Ammonia is absorbed at the porta hepatis and is converted to urea in the liver through the urea cycle. Part of the ammonia is also excreted in exhaled breath. In fact, ammonia is a harmful gas that is transformed into harmless substances in the liver and kidneys. When the ammonia in the blood cannot be filtered out normally, the ammonia will cause functional disorders in these organs. Ammonia can also damage the nervous system and cause hepatic encephalopathy. When ammonia levels in the blood increase, it can diffuse to the lungs and be expelled in exhaled air. Current studies have found that ammonia in exhaled breath is associated with many diseases, such as renal failure, asthma, Helicobacter pylori infection, and bad breath.

In the environment, ammonia is the only high-concentration alkaline gas in the atmosphere, which can react with sulfur dioxide, nitrogen oxides and volatile organic compounds (VOCs) to generate aerosol particles, thereby affecting the global radiation balance. It is an important reason for the formation of secondary particles and can cause eutrophication of rivers and lakes.

Therefore, the detection of ammonia is of great significance in the diagnosis of human diseases and the detection of air quality.

At present, the main instruments and methods used to detect ammonia are mass spectrometry (MS), gas chromatography-mass spectrometry (GC-MS), spectroscopic methods, such as cavity ring-down spectroscopy (CRDS), acousto-optic spectroscopy (PAS), and chemical sensors. wait. The detection limit of mass spectrometry and GC-MS can reach the level of ppb to ppt, but they are bulky and expensive, requiring professionals to operate. The detection limit of the spectroscopic method can reach the ppb level, but there is a large background interference. Chemical sensors are portable, simple, and have low detection limits, but they generally suffer from poor stability and short lifetime.

Ion mobility spectrometry is an instrument that uses the difference in ion mobility to separate ions at atmospheric pressure. It has simple structure, low cost and easy miniaturization, and the sensitivity of ion mobility spectrometer is high, and the response time is short, which is very suitable for online monitoring. However, the ionization sources currently used are all radioactive ⁶³ Ni, which limits its wide application.

Contents of the invention

The object of the present invention is to provide a non-radioactive device and method for rapid on-line monitoring of ammonia gas.

A non-radioactive device and method for on-line ammonia monitoring includes: sample gas, carrier gas, reagent molecule generator, pump, exhaust gas, radio frequency vacuum ultraviolet lamp, transfer tube system, and drift gas.

The technical scheme is: the device includes a migration spectrum with a radio frequency vacuum ultraviolet lamp as an ionization source, the migration tube of the migration spectrum includes a reaction zone, an ion gate, and an ion migration zone, and a drift gas inlet is provided on the side of the ion migration zone far away from the reaction zone ; There is a total gas outlet on the side of the reaction area far away from the ion migration area, and a pump is provided at the main gas outlet; there are sample gas and carrier gas inlets on the side of the reaction area near the ion gate, and sample gas and carrier gas inlets The sample gas and carrier gas inlets are connected to the gas outlet of the reagent molecule generating device through pipelines, and the gas inlet of the reagent molecule generating device is connected to the carrier gas source; the reagent molecule generating device is a closed container , an open container containing reagent molecules is placed in the airtight container, and a gas outlet and a gas inlet are arranged on the upper part of the airtight container; the reagent molecule is butanone.

The tubes used in the gas path are made of polytetrafluoroethylene to reduce ammonia gas adsorption.

The reagent molecule used in ion mobility spectrometry is 2-butanone. The reagent molecule generating device includes a constant temperature system with a temperature range of 30-60°C to keep the temperature of the reagent molecule generating device within a specific temperature range.

The carrier gas flow rate range is 50-100ml/min, the drift gas flow rate range is 500-600ml/min, and the tail gas flow rate range is 600-750ml/min;

The temperature range of the migration tube is 100-150° C., and the electric field intensity range of the migration region is 450-500 V/cm.

The advantages of the present invention are:

The instrument and method developed by the present invention are based on ion mobility spectrometry technology with simple structure, using vacuum ultraviolet lamp non-radioactive ionization source, methyl ethyl ketone as reagent molecule, can quickly and accurately monitor ammonia on-line, improve the selectivity of ammonia detection, and facilitate large-scale application.

Description of drawings

Figure 1 is a structural schematic diagram of rapid on-line ammonia monitoring. Among them: 1 is the radio frequency vacuum ultraviolet lamp, 2 is the reaction area, 3 is the ion gate, 4 is the migration area, 5 is the migration tube system, 6 is the drift gas, 7 is the carrier gas, 8 is the reagent molecule generating device, 9 is the sample Gas, 10 is the pump, and 11 is the exhaust gas.

Figure 2 is the ion mobility spectrum of ammonia gas when 2-butanone is used as a reagent molecule

Figure 3 Ammonia working curve

Figure 4 is the outdoor atmospheric spectrum of continuous monitoring for one day

Detailed ways

The following examples illustrate the use of the invention without limiting the scope of application described.

The device used includes a mobility spectrum using a radio frequency vacuum ultraviolet lamp as an ionization source. The migration tube of the mobility spectrum includes a reaction zone and an ion migration zone, and a drift gas inlet is provided on the side of the ion migration zone far away from the reaction zone; on the side far away from the ion migration zone There is a total gas outlet on one side of the reaction zone, and a vacuum pump is installed at the total gas outlet; there are sample gas and carrier gas inlets on the side of the reaction zone close to the ion migration zone, and the sample gas and carrier gas inlets are connected to the sample gas through the pipeline. The gas source is connected, the sample gas and carrier gas inlet are connected to the gas outlet of the reagent molecule generator through pipelines, the gas inlet of the reagent molecule generator is connected to the carrier gas source; the reagent molecule generator is a closed container, and the sealed container is placed An open container containing reagent molecules, and a gas outlet and a gas inlet are arranged on the upper part of the airtight container; the reagent molecule is butanone.

Example 1

Ammonia gas is detected by reagent molecule-assisted photoionization positive ion mobility spectrometry. The reagent molecule is butanone, the carrier gas flow rate range is 50-100ml/min, the drift flow rate range is 500-600ml/min, and the tail gas flow rate range is 600-750ml/min. min; the temperature range of the migration tube is 100-150°C, and the electric field intensity range of the migration region is 450-500V/cm. The ion mobility spectrum of ammonia gas is shown in Figure 2. The product ion is a complex of methyl ethyl ketone and ammonia gas with a reduced mobility of 1.87, and the reduced mobility of the reagent ion is 1.66. The two can be completely separated.

Example 2

Air and/or nitrogen containing a series of known gradient concentrations of ammonia gas is used as the standard gas. The standard gas enters the migration spectrum through the sample gas and carrier gas inlet of the migration spectrum for detection, and obtains the migration spectrum of a series of gradient concentrations of the standard gas. Concentration plotting with the signal intensity of the standard gas of a series of gradient concentrations, obtains the working curve of ammonia, as Figure 3; Its linear range is 25-455ppb, and detection limit is 6ppb.

Example 3

The sample gas to be tested is passed into the migration spectrum for detection, and the signal intensity of the migration spectrum of the sample gas to be tested is brought into the working curve equation to obtain the concentration of ammonia in the sample gas. Figure 3 shows the changes in the concentration of ammonia in the outdoor atmosphere in one day.

Claims (7)

1. A non-radioactive method capable of continuous on-line monitoring of ammonia, characterized in that: The device used includes ion mobility spectrometry using a radio frequency vacuum ultraviolet lamp as an ionization source. The migration tube of the mobility spectrum includes a reaction area, an ion gate, and an ion migration area. A drift gas inlet is provided on the side of the ion migration area away from the reaction area; There is a total gas outlet on one side of the reaction area of the ion gate, and a pump is provided at the main gas outlet; there are sample gas and carrier gas inlets on the side of the reaction area near the ion gate, and the sample gas and carrier gas inlets are connected to each other through pipelines. The sample gas source is connected, the sample gas and carrier gas inlet are connected to the gas outlet of the reagent molecule generating device through pipelines, and the gas inlet of the reagent molecule generating device is connected to the carrier gas source; the reagent molecule generating device is a closed container. An open container containing reagent molecules is placed, and a gas outlet and a gas inlet are arranged on the upper part of the airtight container; The reagent molecule is butanone, Air and/or nitrogen containing a series of known gradient concentrations of ammonia gas is used as the standard gas. The standard gas enters the migration spectrum through the sample gas and carrier gas inlet of the migration spectrum for detection, and obtains the migration spectrum of a series of gradient concentrations of the standard gas. ; The signal intensity of the standard gas with a series of gradient concentrations is plotted against the concentration to obtain the working curve of ammonia; Pass the sample gas to be tested into the migration spectrum for detection, and bring the signal intensity of the migration spectrum of the sample gas to be tested into the working curve equation to obtain the concentration of ammonia in the sample gas; Among them, the carrier gas flow rate range is 50-100ml/min, the drift gas flow rate range is 500-600ml/min, and the tail gas flow rate range is 600-750ml/min; The temperature range of the migration tube is 100-150°C, and the electric field strength range of the migration zone is 450-500V/cm; The temperature range of the reagent molecule generating device is 30-60°C. 2. The method according to claim 1, characterized in that: The drift gas inlet is connected with the drift gas source; the drift gas source is clean compressed air. 3. The method according to claim 1, characterized in that: The tail gas in the mobility spectrum is discharged through the gas outlet through the pump. 4. The method according to claim 1, characterized in that: the gas inlet of the reagent molecule generating device is connected to the carrier gas source. 5. The method according to claim 1, characterized in that: the conduits used in the gas pipeline are made of polytetrafluoroethylene. 6. The method according to claim 1, characterized in that: an electric heating device is provided on the inner wall of the airtight container of the reagent molecule generating device, that is, an electric heating belt and/or An electric heating wire, and a thermocouple temperature measuring element is arranged on the inner wall of the reagent molecule generating device. The thermocouple is connected to the temperature controller signal through a wire, and the electric heating device is connected to the external circuit through the temperature controller. 7. The method of claim 1, wherein: The ion mobility spectrometer includes 4 working gas paths, namely drift gas, carrier gas, sample gas, and tail gas. The sample gas enters the sample gas inlet of the transfer tube, and the carrier gas enters the reagent molecule generating device at a certain flow rate to generate reagent molecule gas. , and then connected to the sample gas and carrier gas inlets; The drift gas is clean air, which enters the migration spectrometer at a certain flow rate after passing through the mass flow meter; the tail gas is discharged from the pump through the tail gas port; the difference between the tail gas flow rate, the drift flow rate and the carrier gas flow rate is the sample injection volume.

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