Rapid detection method for exhaled ammonia in nasal cavity

Abstract

The invention relates to a method for detecting ammonia exhaled by a nasal cavity, and belongs to the technical field of chemical analysis and detection. The method comprises the following specific steps: preparing standard gases of expiratory ammonia with different concentrations, sampling the standard gases into an ion mobility spectrometer, and sequentially detecting the standard gases to obtain quantitative standard curves with different concentrations; the method comprises the following steps: directly sampling exhaled air of the nasal cavity into an ion mobility spectrometry, obtaining an ion mobility spectrometry of a to-be-detected sample in real time, tracking a change curve of exhaled air ammonia signal intensity in real time, judging the ammonia of the nasal cavity at an exhaling end, obtaining a quantitative factor of the exhaled air ammonia of the nasal cavity, and calculating the ammonia concentration of the exhaled air ammonia of the nasal cavity according to a quantitative curve of the exhaled air ammonia of the nasal cavity. By adopting a direct photoionization single photon ion mobility spectrometry online detection technology, the method has very high sensitivity and specific signal response to low-concentration ppbv ammonia in human nasal exhaled gas, the concentration of ammonia in nasal exhaled gas can be monitored in real time, an effective detection method is provided for monitoring functions of organs such as liver and kidney, and the method is suitable for popularization and application. And life health is protected.

Description

Technical Field

[0001] The present invention belongs to the field of analytical chemistry instrument detection, and particularly relates to an analytical detection method for detecting ammonia in nasal exhaled breath by ion mobility spectrometry. Background Art

[0002] Ammonia is an important component of human metabolism, participating in multiple physiological processes of the human body. It is closely related to diseases such as renal failure, cirrhosis or hepatitis, hepatic encephalopathy, Helicobacter pylori infection, and halitosis. It is also a potential biomarker for sports physiology and drug metabolism research. At the same time, ammonia has neurotoxicity, and rapid bedside monitoring is crucial for the identification and early warning of critical illnesses. The partial pressure of ammonia in the alveoli is almost equal to that in the arteries. Therefore, changes in the exhaled ammonia concentration level can indicate corresponding pathophysiological changes. The concentration of ammonia in human exhaled breath is low, the humidity is high, and the background is complex, which requires very high requirements for the sampling and detection of exhaled ammonia. Therefore, it is necessary to develop detection methods with high specificity and sensitivity.

[0003] In recent years, there have been many studies on the on-line detection of exhaled ammonia. In 2011, Z.H. Endre et al. used SIFT-MS to continuously monitor exhaled ammonia in hemodialysis patients, indicating that exhaled ammonia can well evaluate the dialysis efficacy; in 2016, Bayrakli et al. detected exhaled ammonia in healthy people and Helicobacter pylori patients based on spectroscopy, demonstrating the potential advantages of exhaled ammonia detection in non-invasive diagnosis of Helicobacter pylori; in 2020, Chen Mingren et al. used semiconductor sensors to detect respiratory ammonia in 121 chronic kidney disease patients, and the results showed that there was a good correlation between exhaled ammonia and blood urea nitrogen level, serum creatinine level, and glomerular filtration rate; in 2021, Jinya Ishida et al. used chemical sensors to detect exhaled ammonia in chronic liver disease patients, confirming the relationship between exhaled ammonia and liver insufficiency and verifying the feasibility of applying exhaled ammonia to the diagnosis of chronic liver disease.

[0004] Currently, the detection methods for exhaled ammonia include gas chromatography, photometry, sensors, and other methods. Among them, chromatography and chromatography-mass spectrometry coupling technology are the most widely used in the detection of exhaled ammonia, but they have disadvantages such as high cost, large volume, and the need for specialized technical personnel to operate. The operation steps of photometry are simple, but its stability and reproducibility are poor. Although the sensor method has advantages such as miniaturization and short response time, the quantification is inaccurate, etc. The low concentration, high humidity, complex components of human exhaled gas, and the adsorption characteristics of ammonia pose challenges to the accurate qualitative identification and highly sensitive detection of exhaled ammonia. A kind of exhaled ammonia detection sensor device disclosed by Han Yiping et al. (CN 110780063 A), which involves the adsorption and desorption of ammonia, lacks accuracy. So far, there is no stable and accurate detection technology and real-time analysis and detection method. However, only nasal exhaled ammonia can truly reflect the ammonia concentration after blood exchange in the alveoli, and the concentration is relatively low, at 10-200 ppb. How to develop a method for highly sensitive detection of nasal exhaled ammonia?

[0005] Ion mobility spectrometry has high specificity in monitoring trace exhaled components and is very suitable for the detection of gaseous ammonia in complex matrices under a high-humidity background. Through automatic quantitative correction of humidity, it is not necessary to remove water vapor, and highly sensitive and highly selective detection of exhaled ammonia can be achieved. Aiming at the various problems existing in the above analysis and detection methods, the present invention uses direct photoionization ion mobility spectrometry to detect nasal exhaled ammonia, and further improves the accuracy of qualitative identification of nasal exhaled ammonia by regulating different gas flow modes. Applying it to the detection of ammonia content in human nasal exhaled gas, the technology and analysis method of the present invention provide the possibility for comparing the exhaled ammonia concentrations of normal people and patients with organ dysfunction and for non-invasive diagnosis and condition monitoring. Summary of the Invention

[0006] Aiming at the problems existing in the prior art, the purpose of the present invention is to provide a rapid detection method for nasal exhaled ammonia. This method can achieve highly sensitive detection of nasal exhaled ammonia, eliminate the interference of other components in nasal exhaled gas, solve the influence of high humidity (100% RH) in nasal exhaled gas and other components in exhaled gas on the detection of trace low-concentration ppbv ammonia in exhaled gas, and can be used for the correlation research of the clinical diagnosis model of exhaled ammonia concentration and organ function monitoring.

[0007] In order to achieve the above purpose, the following technical solutions are adopted by the present invention:

[0008] A rapid detection method for nasal exhaled ammonia, which specifically includes the following steps:

[0009] (1) Use an ion mobility spectrometer to detect standard ammonia gas at different concentrations, collect the ion mobility spectra of standard ammonia gas at different concentrations, and establish a standard curve for exhaled ammonia; the specific process is as follows: Select 8 groups of standard ammonia samples with 100% RH humidity in the concentration range of 10 - 200 ppb, and the concentrations are: 20 ppbv, 30 ppbv, 50 ppbv, 80 ppbv, 100 ppbv, 120 ppbv, 150 ppbv, 200 ppbv; Take five parallel samples for each group, use ion mobility spectrometry to detect the above 8 groups of standard ammonia gas at different concentrations, obtain the ion mobility spectra and quantitative factors of ammonia at different concentrations, and the quantitative factors are 0.051, 0.076, 0.131, 0.210, 0.265, 0.314, 0.406, and 0.508 respectively. The linear equation of the standard curve for quantifying nasal exhaled ammonia obtained by fitting is Y = 2.714 * 10 -3 X - 0.002, R 2 = 0.999, where Y represents the quantitative factor of exhaled ammonia, X represents the concentration of exhaled ammonia, and R 2 represents the goodness of fit of the quantitative curve.

[0010] Furthermore, the quantitative factor of ammonia is the ratio of the signal intensity of ammonia in the ion mobility spectrum to the total ion signal intensity in the ion mobility spectrum.

[0011] (2) Use ion mobility spectrometry to perform real-time sampling and detection on nasal exhaled air. Exhale and sample through the sampling nozzle of the ion mobility spectrometer facing the nose. The exhaled air sample is pumped into the ion mobility spectrometer by a suction pump for real-time detection, obtaining the ion mobility spectrum of nasal exhaled ammonia and the monitoring curve of real-time exhaled air, as well as the change curve continuously tracking the quantitative factor of nasal exhaled ammonia, and obtaining the concentration of nasal exhaled ammonia within a single respiratory cycle.

[0012] (3) Compare the detected ion mobility spectrum of nasal exhaled ammonia with the ion mobility spectrum of the ammonia standard gas for exhaled air, and calculate the actual concentration of ammonia in nasal exhaled air according to the standard curve of exhaled ammonia.

[0013] Furthermore, the ion mobility spectrometer is a photoionization ion mobility spectrometer with acetone modifier, including the sampling port of the ion mobility spectrometer, the acetone reagent molecule generating device, the vacuum ultraviolet lamp ionization source, the ion-molecule reaction zone, the ion gate, and the migration zone;

[0014] The vacuum ultraviolet lamp ionization source and the Faraday disk are respectively arranged at the relative positions at the left and right ends of the ion mobility spectrometer. An ion gate is arranged between the vacuum ultraviolet lamp ionization source and the Faraday disk. The area between the vacuum ultraviolet lamp ionization source and the ion gate is the ion-molecule reaction zone, the area between the ion gate and the Faraday disk is the migration zone, and the Faraday disk is connected to the ion mobility spectrum data acquisition device;

[0015] An air outlet is provided on the upper wall surface of the ion-molecule reaction region of the ion mobility spectrometer, on the side close to the vacuum ultraviolet lamp ionization source. One end of the air outlet pipe is connected to the air outlet, and the other end is connected to a vacuum pump and then vented (connected to the atmosphere). A sample inlet is provided on the upper wall surface of the ion-molecule reaction region of the ion mobility spectrometer, on the side close to the ion gate. The air outlet, the sample inlet, and a drift gas inlet provided below the Faraday disk on the outer wall surface of the migration region of the ion mobility spectrometer together form the external interface of the gas path circulation system of the ion mobility tube.

[0016] One end of a glass sampling tube is a sampling nozzle. Exhaled nasal air is sampled through the sampling nozzle and enters the glass sampling tube. The other end of the glass sampling tube is connected to the sample inlet of the ion-molecule reaction region of the ion mobility spectrometer through a pipeline. A purge gas inlet is provided at one end of the glass sampling tube close to the sampling nozzle. A dilution gas inlet is provided on the pipeline connecting the glass sampling tube and the sample inlet of the ion-molecule reaction region. During the sampling process, the dilution gas enters the pipeline through the dilution gas inlet to dilute the sampled exhaled nasal air.

[0017] One end of a drift gas pipeline is connected to the drift gas inlet, and the other end is connected to a drift gas source. One end of a reagent molecule pipeline is connected to the drift gas inlet, and the other end is connected to the outlet of an acetone reagent molecule generator. The inlet of the acetone reagent molecule generator is connected to a reagent molecule carrier gas.

[0018] A +5000V high-voltage power supply is provided between the electrode ring on the side of the vacuum ultraviolet lamp ionization source and the electrode ring on the side of the Faraday disk.

[0019] Furthermore, during the sampling and detection process, the set condition parameters of the ion mobility spectrometer are as follows: the electric field strength of the migration tube is 300 - 400V / cm, the temperature of the migration tube is 50 - 200°C, the flow rate of the acetone carrier gas is 50 - 200mL / min, the concentration of acetone is 10 - 50ppm, the flow rate of the drift gas is 200 - 500mL / min, the sampling flow rate is 50 - 200mL / min, the flow rate of the purge gas is 50 - 3000mL / min, the flow rate of the ion mobility spectrometer for pumping the sample is 400 - 900mL / min, and the carrier gas and the drift gas are both compressed air treated with silica gel, activated carbon, and molecular sieve, with the water vapor content being less than 1ppm.

[0020] This method can be used to continuously monitor the change in the ammonia concentration of exhaled nasal air of humans, obtain the change curve of exhaled nasal air ammonia, be used to evaluate the basal metabolic level of the human body, serve as an auxiliary evaluation index for organ function monitoring, or be used to evaluate the effect before and after hemodialysis.

[0021] The technical innovation of the present invention lies in:

[0022] The present invention is applicable to the detection of low-concentration ammonia in human nasal exhaled air, and the exhaled air sample does not require complex pretreatment and can be directly sampled and detected online in real time.

[0023] 1. The method of the present invention can directly sample and detect exhaled air in real time, broadening the use of ion mobility spectrometry, without any impact on humans, and having the advantages of non-invasive, non-intrusive, fast detection speed, high sensitivity, strong specificity, low detection limit, low detection cost, and the operator does not need to be professionally trained to operate, facilitating on-site rapid detection by detection personnel.

[0024] 2. The method of the present invention can use the concentration of nasal exhaled air detected as an index of human ammonia basal metabolism and can be used as an auxiliary evaluation index for organ function monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic structural diagram of an ion mobility spectrometer for detecting ammonia in nasal exhaled air.

[0026] Among them, 1 is nasal exhaled air, 2 is a sampling nozzle, 3 is a glass sampling tube, 4 is a purge gas inlet, 5 is a dilution gas inlet, 6 is a sample inlet, 7 is a reagent molecule carrier gas, 8 is an acetone reagent molecule generating device, 9 is a purge gas inlet, 10 is an outlet, 11 is a suction pump, 12 is a vacuum ultraviolet lamp ionization source, 13 is an ion-molecule reaction region, 14 is an ion gate, 15 is a migration region, 16 is a +5000V high-voltage power supply, 17 is a Faraday disk, and 18 is an ion mobility spectrometry data acquisition device.

[0027] Figure 2 Standard curve of exhaled ammonia.

[0028] Figure 3 Real-time tracking change curve of nasal exhaled ammonia concentration.

[0029] Figure 4 Change in nasal exhaled ammonia concentration before and after gargling.

[0030] Figure 5 Intraday change curve of nasal exhaled ammonia concentration.

[0031] Figure 6 Concentration distribution of nasal exhaled ammonia in healthy adults. DETAILED DESCRIPTION OF THE INVENTION

[0032] Combined with the drawings and embodiments, the specific embodiments of the present invention will be described in more detail, so as to better understand the solution of the present invention and the advantages of each aspect.

[0033] As Figure 1As shown in the figure, the ion mobility spectrometry used in the detection of the present invention includes a sampling port of the ion mobility spectrometry, an acetone reagent molecule generating device, a vacuum ultraviolet lamp ionization source, an ion-molecule reaction region, an ion gate, and a migration region;

[0034] A vacuum ultraviolet lamp ionization source and a Faraday disk are respectively arranged at the relative positions at the left and right ends of the ion mobility spectrometry. An ion gate is arranged between the vacuum ultraviolet lamp ionization source and the Faraday disk. The region between the vacuum ultraviolet lamp ionization source and the ion gate is the ion-molecule reaction region. The region between the ion gate and the Faraday disk is the migration region. The Faraday disk is connected to the ion mobility spectrometry graph data acquisition device;

[0035] An air outlet is provided on the upper wall surface of the ion-molecule reaction region of the ion mobility spectrometry near the vacuum ultraviolet lamp ionization source. One end of the air outlet pipe is connected to the air outlet, and the other end is connected to an air extraction pump and then vented (connected to the atmosphere). A sample inlet is provided on the upper wall surface of the ion-molecule reaction region of the ion mobility spectrometry near the ion gate. The air outlet, the sample inlet, and a drift gas inlet provided below the Faraday disk on the outer wall surface of the migration region of the ion mobility spectrometry together form the external interface of the gas circuit circulation system of the ion mobility tube;

[0036] One end of a glass sampling tube is a sampling nozzle. The exhaled nasal air is sampled through the sampling nozzle and enters the glass sampling tube. The other end of the glass sampling tube is connected to the sample inlet of the ion-molecule reaction region of the ion mobility spectrometry through a pipeline. A purge gas inlet is arranged near the sampling nozzle end of the glass sampling tube. A dilution gas inlet is arranged on the pipeline connecting the glass sampling tube and the sample inlet of the ion-molecule reaction region. During the sampling process, the dilution gas enters the pipeline through the dilution gas inlet to dilute the sampled exhaled nasal air.

[0037] One end of a drift gas pipeline is connected to the drift gas inlet, and the other end is connected to a drift gas source; one end of a reagent molecule pipeline is connected to the drift gas inlet, and the other end is connected to the outlet of the acetone reagent molecule generating device. The inlet of the acetone reagent molecule generating device is connected to a reagent molecule carrier gas;

[0038] A +5000V high-voltage power supply is arranged between the electrode ring on the side of the vacuum ultraviolet lamp ionization source and the electrode ring on the side of the Faraday disk.

[0039] The process of sampling and detecting nasal exhaled air using the above ion mobility spectrometry is as follows: Start the air pump. The nasal exhaled air enters the glass sampling tube through the sampling nozzle. At the same time, the purge gas purges the glass sampling tube through the purge gas inlet to avoid the residue of nasal exhaled air. The ion mobility spectrometry samples the exhaled air through the sample sampling port. At the same time, the dilution gas dilutes the nasal exhaled air through the dilution gas inlet. The exhaled air enters the ion mobility spectrometry through the sampling inlet for detection. The air flow is in a unidirectional air flow purge mode. While the exhaled air sample enters the ion migration tube from the reaction zone, the reagent molecule acetone enters the migration tube from the migration zone together with the drift gas through the reagent molecule generating device. In the reaction zone, the reagent molecule is ionized to generate reagent ion M2H + , and the reagent ion undergoes an ion-molecule reaction with the exhaled air in the reaction zone to generate NH4 + ·(H2O) n , and further undergoes a cluster reaction with four acetone molecules M in the migration zone to generate NH4 + ·M4. Finally, the ion current signal is converted into an electrical signal on the Faraday disk to obtain the ion mobility spectrometry diagram of ammonia in nasal exhaled air, and it has a good resolution with the reagent ion M2H + , and the signal intensity is also relatively high. Other components in the exhaled air do not respond, which is very suitable for the qualitative and quantitative analysis of ammonia in nasal exhaled air, and can perform real-time tracking and monitoring of exhaled ammonia.

[0040] Example 1

[0041] Using the above ion mobility spectrometer to detect ammonia standard gases with different low concentrations, a standard curve for ammonia in nasal exhaled air is established. As Figure 2 shown, eight groups of 100% RH humidity standard ammonia samples are selected in the concentration range of 10 - 200 ppb, and the concentrations are: 20 ppb, 30 ppb, 50 ppb, 80 ppb, 100 ppb, 120 ppb, 150 ppb, 200 ppb. Five parallel samples are taken for each group. Using the ion mobility spectrometry to detect the above eight groups of ammonia standard gases with different concentrations, the ion mobility spectrometry diagrams and quantitative factors of ammonia with different concentrations are obtained. The quantitative factors are 0.051, 0.076, 0.131, 0.210, 0.265, 0.314, 0.406, and 0.508 respectively. The linear equation of the standard curve for quantifying ammonia in nasal exhaled air obtained by fitting is Y = 2.714*10 -3 X - 0.002, where R 2 = 0.999, which can be used for the quantitative analysis of ammonia concentration in nasal exhaled air. Among them, Y represents the response quantitative factor of exhaled ammonia, X represents the concentration of exhaled ammonia, and R 2 represents the fitting degree of the quantitative curve; as Figure 2As shown, it can be seen that the concentration range of ammonia in the exhaled breath of the nasal cavity of normal healthy people is 0 - 200 ppbv, and the concentration of ammonia in the exhaled breath has a good linear response, enabling quantitative analysis of ammonia in the exhaled breath of the nasal cavity.

[0042] The ion mobility spectrometer is a photoionization ion mobility spectrometer with acetone modifier. The experimental conditions used are as follows: the electric field strength of the drift tube is 350 V / cm, the temperature of the drift tube is 130 °C, the flow rate of the acetone carrier gas is 100 mL / min, the concentration of acetone is 20 ppm, the flow rate of the drift gas is 400 mL / min, the sampling flow rate is 100 mL / min, the flow rate of the purge gas is 2000 mL / min, and the flow rate of the ion mobility spectrometer for sampling by pumping is 600 mL / min. The purge gas, carrier gas, and drift gas are all compressed air treated with silica gel, activated carbon, and molecular sieve, and the water vapor content is less than 1 ppm.

[0043] Example 2

[0044] Using this method to track the change of the quantitative factor of the ammonia concentration in the exhaled breath of the nasal cavity in real time, the single - breath curve of ammonia in the exhaled breath of the nasal cavity is obtained. Figure 3 It is the continuous monitoring curve of the exhaled NH3 of a volunteer for 5 consecutive times. The signal intensity of exhaled NH3 changes with exhalation. At the beginning of exhalation, the concentration of NH3 rises rapidly, and when exhalation stops, the ammonia signal curve drops sharply to the baseline. The single - breath detection only takes 3 seconds, and 5 repeatable breath curves can be recorded in less than 30 seconds. Each breath responds quickly, and the corresponding signal intensity ratio is quite stable, proving the reliability and effectiveness of this method. The ratio of the signal intensity of ammonia in the exhaled breath in the ion mobility spectrum to the total ion signal intensity in the ion mobility spectrum is used as the quantitative factor of ammonia in the exhaled breath of the nasal cavity. The maximum quantitative factor of the single - breath curve is used as the concentration of ammonia at the end of a single exhaled breath of the nasal cavity.

[0045] Example 3

[0046] Using this method to monitor the change of the ammonia concentration in the exhaled breath of the nasal cavity before and after gargling at different times for healthy adults. Twenty healthy volunteers aged 18 - 40 were selected, and the change of the ammonia concentration in the exhaled breath of the nasal cavity before and after gargling was detected for each volunteer at 9:00, 12:00, 15:00, and 18:00 respectively. As Figure 4 shown, the change of the ammonia concentration in the nasal cavity before and after gargling at different time points is between 54 - 63 ppb. Gargling has little effect on the change of the ammonia concentration in the exhaled breath of the nasal cavity, making the ammonia concentration in the exhaled breath of the nasal cavity basically unchanged before and after gargling.

[0047] Real - time Example 4

[0048] Using this method to continuously monitor the intra - day (9:00 - 16:30) change of ammonia in the nasal cavity of 15 healthy volunteers aged 18 - 40. AsFigure 5 As shown, the concentration of exhaled NH3 varies between 60 - 80 ppb over time. It can be seen that time has little impact on the intra-day variation of the ammonia concentration in nasal exhaled air. This may be related to the levels of blood ammonia and alveolar ammonia concentration, which are maintained at a normal concentration level.

[0049] Example 5

[0050] Using this method, the nasal respiration NH3 of 20 healthy volunteers aged 18 - 60 was actually detected on-site. The concentration of ammonia in nasal exhaled air was calculated according to the quantitative curve of ammonia in nasal exhaled air, and the concentration distribution of ammonia in nasal exhaled air was obtained. As Figure 6 shown, the concentration distribution of ammonia in the exhaled air of healthy people is around 40 - 180 ppbv, with an average concentration of 90 ppbv. Moreover, the concentration distribution of ammonia exhaled from the nose is more concentrated and stable, confirming the feasibility of the detection method. By monitoring the changes in the nasal ammonia concentration of different healthy people, the exhaled air of different people was detected, and real-time monitoring curves of exhaled ammonia could be obtained, providing a relatively good analytical detection method for subsequent monitoring of the relationship between exhaled ammonia concentration and organ function.

Claims

1. A rapid detection method for ammonia in nasal exhaled air, characterized in that, The specific steps include: (1) Using an ion mobility spectrometer to detect ammonia standard gases with different concentrations, collecting ion mobility spectra of ammonia standard gases with different concentrations, and establishing a standard curve for exhaled ammonia; (2) Using an ion mobility spectrometer to perform real-time sampling and detection on nasal exhaled gas, obtaining the ion mobility spectrum of nasal exhaled ammonia and the monitoring curve of real-time nasal exhaled gas, as well as continuously tracking the change curve of the quantitative factor of nasal exhaled ammonia; (3) Comparing the detected ion mobility spectrum of nasal exhaled ammonia with the ion mobility spectrum of ammonia standard gas in exhaled gas, and calculating the actual concentration of ammonia in nasal exhaled gas according to the standard curve of exhaled ammonia.

2. The method according to claim 1, characterized in that: The process of establishing the standard curve in step (1) is as follows: Eight groups of standard ammonia samples with 100% RH humidity were selected within the concentration range of 10 - 200 ppb, and the concentrations were 20 ppbv, 30 ppbv, 50 ppbv, 80 ppbv, 100 ppbv, 120 ppbv, 150 ppbv, and 200 ppbv respectively. Five parallel samples were taken from each group, and the above eight groups of ammonia standard gases with different concentrations were detected by ion mobility spectrometry to obtain the ion mobility spectra and quantitative factors of ammonia with different concentrations, which were 0.051, 0.076, 0.131, 0.210, 0.265, 0.314, 0.406, and 0.508 respectively. The linear equation of the standard curve for quantifying nasal exhaled ammonia was fitted as Y = 2.714*10 -3 X - 0.002, R 2 = 0.999, where Y represents the quantitative factor of exhaled ammonia, X represents the concentration of exhaled ammonia, and R 2 represents the goodness of fit of the quantitative curve.

3. The method according to claim 2, characterized in that: The quantitative factor of exhaled ammonia is the ratio of the signal intensity of exhaled ammonia in the ion mobility spectrum to the total ion signal intensity in the ion mobility spectrum.

4. The method according to claim 1, characterized in that: The process of performing real-time sampling on nasal exhaled gas in step (2) is that when exhaling, the nose is facing the sampling nozzle of the ion mobility spectrometer for sampling, and the exhaled gas sample is pumped into the ion mobility spectrometer by a pumping pump for real-time detection.

5. The method according to claim 1, characterized in that: The ion mobility spectrometer is a photoionization ion mobility spectrometer with acetone modifier, and the experimental conditions used are: the electric field strength of the migration tube is 300 - 400 V / cm, the temperature of the migration tube is 50 - 200 °C, the flow rate of acetone carrier gas is 50 - 200 mL / min, the concentration of acetone is 10 - 50 ppm, the drift gas flow rate is 200 - 500 mL / min, the sampling flow rate is 50 - 200 mL / min, the flow rate of the purge gas is 50 - 3000 mL / min, the flow rate of the ion mobility spectrometer for sampling by pumping is 400 - 900 mL / min, and the carrier gas and drift gas are both compressed air treated with silica gel, activated carbon and molecular sieve, with the water vapor content being less than 1 ppm.

6. The method according to any one of claims 1-5, characterized in that: This method can be used to continuously monitor the change in the concentration of ammonia in human nasal exhaled gas, obtain the change curve of nasal exhaled ammonia, be used to evaluate the basal metabolic level of the human body, serve as an auxiliary evaluation index for organ function monitoring, or be used to evaluate the effect before and after hemodialysis.

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