A method for determining mangiferin in mango extract

Abstract

The present invention discloses a method for determining mangiferin in a mango extract, and belongs to the technical field of plant detection. The determination method first ionizes sample ions from a target material, and at least part of the sample ions enter a mobility cell. After capturing the sample ions, mass spectrum data is generated, and first sampling data and second sampling data are extracted from the mass spectrum data. The present invention separates mangiferin and other xanthone derivatives in the mango extract based on the mobility cell, and then determines the content of mangiferin by flight mass spectrometry. The present invention adjusts the migration interval where the component to be measured is located according to the measured signal peak, intercepts the corresponding sampling data from the migration interval, and then adjusts the electric field parameters to avoid too small a signal peak spacing, so as to distinguish mangiferin from other xanthone derivatives and ensure the measurability of the sampling data.

Description

Technical Field

[0001] The present invention relates to the technical field of plant detection, and in particular to a method for determining mangiferin in a mango extract. Background Art

[0002] Mango extract contains mango polyphenols, and the content of its characteristic component mangiferin is usually used as a standard when studying mango polyphenols. Mangiferin, as a xanthone C-glycoside, has a mass-to-charge ratio of 421.11, and its content can be determined using mass spectrometry, as described in Chinese Patent Publication No. CN105866285A. Mango extract contains a variety of macromolecules similar to mangiferin, especially other xanthone derivatives, which have similar mass-to-charge ratios. In order to avoid signal overlap, it is necessary to first distinguish mangiferin from other xanthone derivatives in order to more accurately determine the content of mangiferin. For this reason, Chinese Patent Publication No. CN112461913A discloses a method for improving the ability to distinguish isomeric compounds. This method increases the potential difference between the inlet and outlet of the mobility cell, reduces the number of coexisting conformations of isomeric ions, and improves the separation of similar macromolecules in the ion mobility spectrum. Although the increase in potential difference improves the resolution of substances with similar mass-to-charge ratios, it significantly reduces the signal peak spacing, thereby causing signal overlap and increasing the difficulty of measurement. Therefore, the prior art needs to be further improved. Summary of the Invention

[0003] In order to address the defects of the above-mentioned technology, the present invention proposes a method for determining mangiferin in mango extract. This method calibrates the migration interval of the component to be measured and then intercepts the corresponding sampling data. The electric field parameters of the mobility cell are adjusted according to the peak width and peak spacing of the signal peak to avoid the signal peak spacing being too small, thereby ensuring the measurability of the sampling data.

[0004] The technical solution of the present invention is achieved as follows:

[0005] A method for determining mangiferin in a mango extract comprises the following steps:

[0006] Step 1: The mango extract has a first component and a second component, and a first migration interval and a second migration interval are calculated based on first properties of the first component and the second component, and a first flight interval and a second flight interval are calculated based on second properties of the first component and the second component;

[0007] Step 2: Mixing the mango extract with the matrix to prepare a target material, introducing the target material and the first medium into the ionization channel, and introducing the first medium into the mobility cell;

[0008] Step 3: Ionize sample ions from the target material, activate entrance gating at the initial time, and allow at least some of the sample ions to enter the mobility cell;

[0009] Step 4: The sample ions pass through the flight channel, and mass spectrum data is generated after the sample ions are captured. The first sampling data and the second sampling data are extracted from the mass spectrum data based on the first flight interval and the second flight interval;

[0010] Step 5: extracting the measured signal peaks of the first sampling data and the second sampling data, adjusting the first migration interval and the second migration interval according to the measured signal peaks, and adjusting the electric field parameters of the mobility cell according to the peak width and peak spacing of the measured signal peaks;

[0011] Step 6: Calculate the measured signal-to-noise ratio based on the first sampling data and the second sampling data, adjust the ionization parameter of the ionization channel, and if the ionization parameter is greater than the voltage upper limit, remove the first medium from the mobility cell and introduce the second medium, and return to step 2; otherwise, proceed to step 7;

[0012] Step 7: Repeat steps 1 to 4 to predict the contents of the first component and the second component in the mango extract based on the first sampling data and the second sampling data, respectively.

[0013] In the present invention, the matrix is composed of 50% acetonitrile, 49.9% water, and 0.1% trifluoroacetic acid in a mass ratio, the first medium is nitrogen, and the second medium is argon.

[0014] In the present invention, the ionized sample ions enter the first collimator channel, which modulates the sample ions into a first ion beam. After the exit gate is opened, at least part of the sample ions enter the second collimator channel, which modulates the sample ions into a second ion beam, and then introduces the second ion beam into the flight channel.

[0015] In the present invention, in step 1, the first component is mangiferin, the second component is a xanthone derivative, the first property is the ion collision cross section, and the second property is the mass-to-charge ratio.

[0016] In the present invention, the migration time T1 is calculated based on the ion collision cross section of the first component, and the migration time T2 is calculated based on the ion collision cross section of the second component. Then, the first migration interval [T1-ΔT1, T1+ΔT1] and the second migration interval [T2-ΔT1, T2+ΔT1] are obtained by combining the detection width ΔT1.

[0017] In the present invention, the flight time T3 is calculated based on the mass-to-charge ratio of the first component, and then the first flight interval [T3-ΔT2, T3+ΔT2] is calculated. The flight time T4 is calculated based on the mass-to-charge ratio of the second component, and then the second flight interval [T4-ΔT2, T4+ΔT2] is calculated, where ΔT2 is the half-measurement interval.

[0018] In the present invention, in step 4, the sampling interval of the first component is calculated based on the first migration interval and the first flight interval, and then the minimum sampling time and the maximum sampling time of the first component are obtained in combination with the starting time and the sampling interval, and the first sampling data is intercepted from the mass spectrum data according to the minimum sampling time and the maximum sampling time.

[0019] In the present invention, in step 5, the center line of the measured signal peak of the first sampling data is extracted, and the first migration interval is translated until the midpoint of the sampling interval corresponding to the first migration interval coincides with the center line of the measured signal peak.

[0020] In the present invention, in step 5, the electric field parameters include electric field intensity, fitting peak width constraint coefficient, obtaining electric field intensity lower limit, fitting peak spacing constraint coefficient, obtaining electric field intensity upper limit, and calculating target electric field intensity based on electric field intensity upper limit and electric field intensity lower limit.

[0021] In the present invention, in step 6, the ionization parameters include the spray voltage, the ionization efficiency constant of the mango extract, the effective spray voltage and the noise growth coefficient of the ionization channel are fitted, and then the theoretical spray voltage and the corresponding theoretical signal-to-noise ratio are calculated, and the measured signal-to-noise ratio is calculated. The adjustment step size is calculated according to the theoretical spray voltage, the current spray voltage, the theoretical signal-to-noise ratio and the measured signal-to-noise ratio, and the spray voltage of the ionization channel is adjusted based on the current spray voltage and the adjustment step size.

[0022] The method for determining mangiferin in mango extract according to the present invention has the following beneficial effects: the present invention separates mangiferin and other xanthone derivatives in mango extract according to the mobility cell, and then determines the content of mangiferin by flight mass spectrometry. The present invention adjusts the migration interval where the component to be measured is located according to the measured signal peak, intercepts the corresponding sampling data from the migration interval, and then adjusts the electric field parameters to avoid too small a signal peak spacing, thereby ensuring the measurability of the sampling data. Furthermore, the sampling data of the present invention can be corrected according to the center line of the signal peak, and then the ionization parameters are adjusted according to the measured signal-to-noise ratio to increase the degree of ion fragmentation and limit the noise level. The present invention uses a first medium as the ambient gas for the ionization channel and the mobility cell. At the same time, in order to avoid excessively high ionization parameters that damage the molecular structure, the medium of the mobility cell is replaced in time to ensure resolution. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Flow chart of the method for determining mangiferin in the mango extract of the present invention;

[0024] Figure 2 Schematic diagram of the method for determining mangiferin in the mango extract of the present invention;

[0025] Figure 3 is a mass spectrum of a preferred mango extract of the present invention;

[0026] Figure 4 Schematic diagram of the principle of calculating the sampling interval of the present invention;

[0027] Figure 5 This is the sample ion arrival time distribution diagram of the present invention;

[0028] Figure 6 Schematic diagram of the content and response ratio of mangiferin of the present invention;

[0029] Figure 7 A flow chart of a preferred method for adjusting the electric field parameters of a mobility cell according to the present invention;

[0030] Figure 8 Flowchart of a preferred method for adjusting ionization parameters of an ionization channel according to the present invention.

[0031] Figure marks in the accompanying drawings: ionization channel 100, first pipeline 101, second pipeline 102, first collimation channel 200, mobility cell 300, entrance gate 301, exit gate 302, third pipeline 303, second collimation channel 400, flight channel 500, repulsion zone 501, acceleration zone 502, field-free zone 503, first reflection zone 504, second reflection zone 505, exhaust pipeline 506, analysis device 600. DETAILED DESCRIPTION

[0032] In order to more clearly understand the purpose, technical solutions and advantages of the present application, the present application is described and illustrated below in conjunction with the accompanying drawings and embodiments.

[0033] In existing mobility mass spectrometry techniques, the electric field strength of the mobility cell is a fixed value, typically 100–500 V / cm. The spray voltage is also a fixed value, typically 1–3 kV. The present invention calibrates the migration interval of the analyte (e.g., mangiferin) and then captures the corresponding sampled data. The electric field strength of the mobility cell is adjusted based on the peak width and peak spacing of the signal peaks. The spray voltage is then adjusted based on the signal-to-noise ratio of the sampled data to avoid excessively small peak spacing, ensuring the measurability of the sampled data while simultaneously improving ion fragmentation and limiting noise levels. Example 1

[0034] like Figures 1 to 6 As shown, a method for determining mangiferin in a mango extract of the present invention comprises the following steps.

[0035] Step 1: The mango extract comprises a first component and a second component. The first and second migration intervals are calculated based on the first properties of the first and second components, and the first and second flight intervals are calculated based on the second properties of the first and second components. The mango extract of the present invention may be a polyphenol-enriched extract obtained by liquid phase separation and extraction of mango pulp. The first component is mangiferin, and the second component is another xanthone derivative (e.g., mangiferin). The first property is the ion collision cross section, and the second property is the mass-to-charge ratio. Mangiferin has an ion collision cross section of 210 Ų and a mass-to-charge ratio of 421.11. Xanthone derivatives (e.g., isomangiferin) have an ion collision cross section of 225 Ų and a mass-to-charge ratio of 421.11. The migration duration T1 is calculated based on the ion collision cross section of the first component, and the migration duration T2 is calculated based on the ion collision cross section of the second component. Combined with the detection width ΔT1, the first migration interval [T1-ΔT1, T1+ΔT1] and the second migration interval [T2-ΔT1, T2+ΔT1] are obtained. The flight time T3 is calculated based on the mass-to-charge ratio of the first component, and then the first flight interval [T3-ΔT2, T3+ΔT2] is calculated in combination with the first migration interval. The flight time T4 is calculated based on the mass-to-charge ratio of the second component, and then the second flight interval [T4-ΔT2, T4+ΔT2] is calculated in combination with the second migration interval. ΔT2 is a half-measurement interval. Refer to the detailed description of Examples 2 and 3.

[0036] Step 2: Mix the mango extract with a matrix to form a target. The target and first medium are introduced into the ionization channel, and the first medium is introduced into the mobility cell. The matrix consists of 50% acetonitrile, 49.9% water, and 0.1% trifluoroacetic acid in a mass ratio. The matrix concentration is typically 10–20 mg / mL (a supersaturated solution to promote microcrystalline target formation). The first medium is nitrogen, and the second medium is argon. The first medium enters the ionization channel through the first conduit 101, and the target enters the ionization channel 100 through the second conduit 102. Nitrogen is low-cost and can be used in both the mobility cell and the ionization channel. Using nitrogen simplifies gas introduction and exhaust. Argon can provide higher resolution. The first medium enters the mobility cell 300 through the third conduit 303.

[0037] Step 3: Ionize sample ions from the target material, activate the entrance gate at the start time, and at least some of the sample ions enter the mobility cell. The start time is the initial moment of ion movement. The mobility cell 300 has an entrance gate 301 and an exit gate 302. After the entrance gate 301 and the exit gate 302 are opened, the sample ions can enter and exit freely. Figure 2The ionized sample ions enter first collimator channel 200, which modulates the sample ions into a first ion beam. After exit gate 302 is opened, at least a portion of the sample ions enter second collimator channel 400, which modulates the sample ions into a second ion beam. The second ion beam is then introduced into flight channel 500. To reduce other interference, an exhaust duct 506 can be provided on the sidewall of flight channel 500 to reduce the internal air pressure.

[0038] Step 4: Sample ions pass through the flight channel, and after being captured, mass spectrometry data is generated. First sampling data and second sampling data are extracted from the mass spectrometry data based on the first flight interval and the second flight interval. The sampling interval of the first component is calculated based on the first migration interval and the first flight interval. The minimum and maximum sampling times of the first component are then calculated by combining the start time and the sampling interval. The first sampling data is then extracted from the mass spectrometry data based on these minimum and maximum sampling times.

[0039] Similarly, the sampling interval for the second component is calculated based on the second migration interval and the second flight interval. The minimum and maximum sampling times of the second component are then calculated based on the starting time and the sampling interval. Second sampled data is then extracted from the mass spectrometry data based on the minimum and maximum sampling times. The ranges of the first and second sampled data are affected by the first and second migration intervals. The present invention adjusts the migration intervals in subsequent steps to improve the accuracy of the extracted sampled data.

[0040] Step 5: Extract the measured signal peaks of the first sampling data and the second sampling data, adjust the first migration interval and the second migration interval according to the measured signal peaks, and adjust the electric field parameters of the mobility cell according to the peak width and peak spacing of the measured signal peaks. The measured signal peak of the first sampling data refers to the maximum signal intensity within the range of the first sampling data. Figure 5 As shown, the present invention extracts the centerline of the measured signal peak of the first sampled data and translates the first migration interval until the midpoint of the sampling interval corresponding to the first migration interval coincides with the centerline of the measured signal peak. The electric field parameters of the present invention include electric field intensity, fitting the peak width constraint coefficient to obtain the lower limit of the electric field intensity, and fitting the peak spacing constraint coefficient to obtain the upper limit of the electric field intensity. Based on the upper and lower limits of the electric field intensity, a target electric field intensity is calculated, and the electric field intensity of the mobility cell is adjusted to the target electric field intensity, as described in Example 4.

[0041] Step 6: Calculate the measured signal-to-noise ratio based on the first sampling data and the second sampling data, adjust the ionization parameters of the ionization channel, and if the ionization parameters are greater than the voltage upper limit, extract the first medium of the mobility cell and introduce the second medium, and return to step 2, otherwise proceed to step 7. The ionization parameters include at least the spray voltage, and the voltage upper limit can be 5kV. The ionization efficiency constant of the mango extract, the effective spray voltage and the noise growth coefficient of the ionization channel are fitted by the present invention, and then the theoretical spray voltage and the corresponding theoretical signal-to-noise ratio are calculated. The measured signal-to-noise ratio is calculated based on the measured fragment intensity and background intensity of the first sampling data and the second sampling data. Figure 3 As shown, in this embodiment, the measured fragment intensity is the average intensity value of the first sampling data and the second sampling data, which represents the signal response of the ion fragments. The background intensity is the smaller of the minimum intensity value of the first sampling data and the minimum intensity value of the second sampling data. The background intensity represents the noise signal that exists due to equipment factors when the ion signal is weak. In a simpler embodiment, the background intensity is preset to 10 counts / s. The present invention can calculate the adjustment step size based on the theoretical spray voltage, the current spray voltage, the theoretical signal-to-noise ratio and the measured signal-to-noise ratio, and adjust the spray voltage of the ionization channel based on the current spray voltage and the adjustment step size, as described in Example 5.

[0042] Step 7: Repeat steps 1 to 4 to predict the contents of the first component and the second component in the mango extract based on the first sampling data and the second sampling data, respectively. The signal intensity of the first sampling data is ρ, the total signal intensity of the spectral data is ρ0, and the response ratio of the first component is h=ρ / ρ0. Collect the response ratios under multiple different calibration contents, establish a coordinate system with the response ratio h as the horizontal coordinate and the content l as the vertical coordinate, and mark the response ratio of the component and the corresponding calibration content in the coordinate system. Use the correlation fitting algorithm to fit these points into a smooth curve to obtain the relationship between the content ω and the response ratio h, that is, the response function ω=f(h). The response function is only related to the characteristics of the system itself. The present invention does not limit the correlation fitting algorithm. This embodiment uses the least squares method to fit into a straight line. The fitting result is as shown below. Figure 7 As shown. The present invention integrates the signal intensity at each moment in the first sampled data to obtain the signal intensity ρ of the first sampled data. The ratio ρ / ρ0 of the signal intensity to the total signal intensity ρ0 is calculated to obtain the response ratio h of the first component. Substituting this into the response function ω=f(h) yields the content of the first component in the mango extract. The same method can also be used to determine the content of the second component. Example 2

[0043] This embodiment further discloses a preferred method for calculating the first migration interval and the second migration interval.

[0044] First, the mobility k3 is calculated based on the ion collision cross section of the first component. The ion collision cross section of mangiferin is 210Ų. In this example, according to the principle of Ion Mobility-Mass Spectrometry (IM-MS), z is the ion charge, e is the electron charge, and n is the number density of the drift gas, which refers to the number of drift gas molecules per unit volume, usually 10 21 to 10 23 pcs / m 3 μ is the reduced mass of the drift species, μ=m1m2 / (m1+m2), where m1 is the mass of the first or second medium, typically 28 Da. m2 is the mass of the first component, typically 500 Da. T' is the gas temperature of the mobility cell. k1 is the Boltzmann constant, which is 1.38×10 −23 J / calorie, k2 is the collision cross section of the first component ion (mobility measured at standard temperature and pressure). The migration time T1 is then calculated as T1 = L / (k3E), where L is the length of the migration tube, typically 5–30 cm, and E is the electric field strength.

[0045] Combined with the detection width ΔT1, the first migration interval [T1-ΔT1, T1+ΔT1] is obtained. The detection width ΔT1 can be 100 to 200 μs. Since ion mobility is measured at a specific temperature and pressure, to prevent the actual temperature and gas pressure from affecting data acquisition integrity, in a more preferred embodiment, the detection width ΔT1 = ΔT0 + K4. ΔT0 is, for example, 10 μs. T' is the gas temperature, p' is the current pressure, and β is the fitted temperature-pressure ratio.

[0046] Similarly, the migration duration T2 is calculated based on the ion collision cross section of the second component. This second component is a xanthone derivative, such as isomandibolic acid. The ion collision cross section of isomandibolic acid is 225 Ų. Combined with the detection width ΔT1, the second migration interval [T2 - ΔT1, T2 + ΔT1] is obtained. Example 3

[0047] This embodiment further discloses a preferred method for calculating the first flight interval and the second flight interval.

[0048] First, the flight duration T3 is calculated based on the mass-to-charge ratio of the first component. t1, t2, t3, t4, and t5 are the movement times of the first component in the repulsion zone 501, the acceleration zone 502, the field-free zone 503, the first reflection zone 504, and the second reflection zone 505, respectively. When the ion enters the flight channel 500, its vertical velocity is first accelerated by the repulsion zone 501 and the acceleration zone 502. When the ion enters the field-free zone 503, it maintains a uniform speed. Then, under the action of the first reflection zone 504 and the second reflection zone 505, it first decelerates to 0 and then accelerates in the opposite direction. When it enters the field-free zone 503 again, it maintains a uniform speed until the ion falls on the analysis device 600. However, its horizontal velocity remains unchanged during the flight. Therefore, the flight duration T3=t1+t2+2(t3+t4+t5).

[0049] The mass of the first component ion is m, the charge it carries is q, and the mass-to-charge ratio is m / q. L1, L2, L3, and L4 represent the lengths of the repulsion zone 501, the acceleration zone 502, the field-free zone 503, and the first reflection zone 504, respectively. E1, E2, E4, and E5 represent the electric field strengths of the repulsion zone 501, the acceleration zone 502, the field-free zone 503, the first reflection zone 504, and the second reflection zone 505, respectively. Based on the relationship between ion motion, it can be determined that: ; ; ; ; .

[0050] Combined with the first migration interval, the first flight interval is calculated as [T3-ΔT2, T3+ΔT2]. ΔT2 is the half-measurement interval, ensuring that all ions of this mass-to-charge ratio can be measured. ΔT2 is typically set between 10 and 50 μs. Using the above method, the mass-to-charge ratio is calculated from the mass and charge of the first component ion. The flight time, T4, is then calculated. Combined with the second migration interval, the second flight interval is calculated as [T4-ΔT2, T4+ΔT2].

[0051] Furthermore, the sampling interval for the first component is [T1-ΔT1+T3-ΔT2, T1+ΔT1+T3+ΔT2], with a starting time of t6, a minimum sampling time of t6+T1-ΔT1+T3-ΔT2, and a maximum sampling time of t6+T1+ΔT1+T3+ΔT2. The first sampled data is intercepted from the mass spectrometry data based on the minimum and maximum sampling times. In a simpler embodiment, the system clock can be calibrated to preset the starting time to 0.

[0052] Similarly, the sampling interval for the second component is [T2 - ΔT1 + T4 - ΔT2, T4 + ΔT1 + T3 + ΔT2], with a starting time of t6, a minimum sampling time of t6 + T2 - ΔT1 + T4 - ΔT2, and a maximum sampling time of t6 + T4 + ΔT1 + T3 + ΔT2. The first sample data is intercepted from the mass spectrum data based on the minimum and maximum sampling times. Example 4

[0053] like Figure 7 This embodiment further discloses a preferred method for adjusting the electric field parameters of the mobility cell. The electric field parameters of this embodiment include electric field intensity.

[0054] First fit the peak width constraint coefficient, and then obtain the lower limit of the electric field strength. In order to ensure signal resolution, the maximum allowable peak width W0 is preset, for example 0.5ms 1 / 2 The peak width is mainly caused by ion diffusion. For the same detection environment (temperature, mobility and mobility cell length remain unchanged), the diffusion variance σ 2 It is proportional to the migration time, which is inversely proportional to the electric field strength. Therefore, the peak width W (i.e., standard deviation) is inversely proportional to the square root of the electric field strength. W=(λ1 / E) 1 / 2 , λ1 is the peak width constraint coefficient. By measuring the electric field strength and peak width multiple times, the peak width constraint coefficient λ1 of the same device can be fitted. Then the lower limit of the electric field strength E under the maximum allowable peak width W0 is calculated. min =λ1 / W0 2 .

[0055] Then fit the peak spacing constraint coefficient and obtain the upper limit of the electric field strength. In order to fully display the signal peaks of different ion components, preset the minimum measurable peak spacing T0, for example 2ms. The peak spacing is the migration time difference between adjacent signal peaks. According to, the peak spacing is inversely proportional to the electric field strength. Peak spacing T=λ2 / E, λ2 is the peak spacing constraint coefficient. By measuring the electric field strength and peak spacing multiple times, the peak spacing constraint coefficient λ2 of the same device can be fitted. Then calculate the lower limit of the electric field strength E under the minimum measurable peak spacing T0. max =λ2 / T0.

[0056] Finally, the target electric field strength is calculated based on the upper and lower limits of the electric field strength. max <E min , the target electric field strength has no real number solution, and the task is terminated. Recalibrate the equipment (for example, adjust the mobility cell length L) to meet the detection requirements. If E max ≥E min , the target electric field strength is the geometric mean of the upper limit and lower limit of the electric field strength, that is, the target electric field strength E=(E max ×E min ) 1 / 2 .

[0057] Furthermore, the electric field parameters also include the dielectric pressure of the mobility cell, which is generally 5 Torr. To ensure stable operation and avoid arcing, the electric field strength and dielectric pressure are maintained within a safe range. The mobility cell of the present invention has two gas types: a first medium and a second medium. Paschen's law plots the relationship between the electric field strength in the current environment and the dielectric pressure of each gas type, or a matching table of electric field strength and dielectric pressure is developed. A feedback control system is used to adjust the gas pressure in real time according to the target electric field strength, which is not described in detail in this embodiment. Example 5

[0058] like Figure 8 This embodiment further discloses a preferred method for adjusting the ionization parameters of the ionization channel. The ionization parameters include the spray voltage.

[0059] First, we fitted the ionization efficiency constant, effective spray voltage of the ionization channel, and noise growth coefficient of the mango extract. Ion fragmentation intensity typically increases nonlinearly with increasing voltage, eventually saturating. This can be described by a negative exponential model. The measured ion fragmentation intensity S and spray voltage U can then be expressed as: S = I max {1-exp[-k6(U-U0)]}, I max is the theoretical strength (platform value), generally 10 5 counts / s. U0 is the minimum effective spray voltage. k6 is the ionization efficiency constant, usually 0.1 to 2 kV -1 Background noise is caused by random events in the ionization process (such as discharge and solvent cluster fragmentation) and is generally weakly exponentially related to voltage. Therefore, the background noise N and the spray voltage U can be expressed as: N = N0exp-k5(U-U0). N0 is the baseline noise (the noise level when not ionized), which is generally 10 counts / s. k5 is the noise growth factor, which is usually 10 to 50V. -1 Multiple measurements of ion intensity and background noise can be used to fit the ionization efficiency constant k6, the effective spray voltage U0 of the ionization channel, and the noise growth coefficient k5.

[0060] Then, the theoretical spray voltage and theoretical signal-to-noise ratio are calculated. Specifically, the signal-to-noise ratio S / N=I max {1-exp[-k6(U-U0)]} / N0×exp(-k6(U-U0)). Calculate the extreme value of the derivative of the signal-to-noise ratio, d(S / N) / dU=0, and the theoretical spray voltage U at the extreme value can be obtained. opt =U0+1 / k6×ln(1+k6 / k5). Substitute the theoretical spray voltage into I max {1-exp[-k6(U-U0)]} / {N0×exp[-k6(U-U0)]}, the theoretical signal-to-noise ratio S / N can be obtained opt.

[0061] Then according to the theoretical spray voltage and the current spray voltage U act Specifically, the current fragment intensity and the current background signal are detected based on the spectral data, and the measured signal-to-noise ratio S / N is calculated accordingly. act The adjustment coefficient is [ln(S / N act ) / U act -ln(S / N opt ) / U opt ] / ln(S / N act ), the target adjustment amount is (U max -U act ). Adjustment step (U max -U act )×[ln(S / N act ) / U act -ln(S / N opt ) / U opt ] / ln(S / N act ).

[0062] Finally, the ionization parameters of the ionization channel are adjusted based on the current spray voltage and the adjustment step size. Specifically, the spray voltage of the next cycle finally determined in this embodiment is U act +(U max -U act )×[ln(S / N act ) / U act -ln(S / N opt ) / U opt ] / ln(S / N act ).

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for determining mangiferin in a mango extract, characterized in that: The following steps are involved: Step 1: The mango extract has a first component and a second component, and a first migration interval and a second migration interval are calculated based on first properties of the first component and the second component, and a first flight interval and a second flight interval are calculated based on second properties of the first component and the second component; Step 2: Mixing the mango extract with the matrix to prepare a target material, introducing the target material and the first medium into the ionization channel, and introducing the first medium into the mobility cell; Step 3: Ionize sample ions from the target material, activate entrance gating at the initial time, and allow at least some of the sample ions to enter the mobility cell; Step 4: The sample ions pass through the flight channel, and mass spectrum data is generated after the sample ions are captured. The first sampling data and the second sampling data are extracted from the mass spectrum data based on the first flight interval and the second flight interval; Step 5: extracting the measured signal peaks of the first sampling data and the second sampling data, adjusting the first migration interval and the second migration interval according to the measured signal peaks, and adjusting the electric field parameters of the mobility cell according to the peak width and peak spacing of the measured signal peaks; Step 6: Calculate the measured signal-to-noise ratio based on the first sampling data and the second sampling data, adjust the ionization parameter of the ionization channel, and if the ionization parameter is greater than the voltage upper limit, remove the first medium from the mobility cell and introduce the second medium, and return to step 2; otherwise, proceed to step 7; Step 7: Repeat steps 1 to 4 to predict the contents of the first component and the second component in the mango extract based on the first sampling data and the second sampling data, respectively. In step 1, the first component is mangiferin, the second component is a xanthone derivative, the first attribute is an ion collision cross section, and the second attribute is a mass-to-charge ratio. In step 5, the center line of the measured signal peak of the first sampling data is extracted, and the first migration interval is translated until the midpoint of the sampling interval corresponding to the first migration interval coincides with the center line of the measured signal peak. In step 5, the electric field parameters include electric field intensity, fitting peak width constraint coefficient, obtaining electric field intensity lower limit, fitting peak spacing constraint coefficient, obtaining electric field intensity upper limit, and calculating target electric field intensity based on electric field intensity upper limit and electric field intensity lower limit, wherein, Peak width W=(λ1 / E) 1 / 2 , λ1 is the peak width constraint coefficient, the electric field intensity E and peak width W are measured multiple times, the peak width constraint coefficient λ1 of the same device is fitted, and then the lower limit of the electric field intensity E under the maximum allowable peak width W0 is calculated. min =λ1 / W0 2 ; Peak spacing T=λ2 / E, λ2 is the peak spacing constraint coefficient. Measure the electric field strength E and peak spacing T multiple times, fit the peak spacing constraint coefficient λ2 of the same device, and then calculate the lower limit of the electric field strength E under the minimum measurable peak spacing T0. max =λ2 / T0; If E max <E min , the target electric field strength has no real number solution, recalibrate the equipment, if E max ≥E min , the target electric field strength is the geometric mean of the upper limit and lower limit of the electric field strength, and the target electric field strength E=(E max ×E min ) 1 / 2 .

2. The method for determining mangiferin in the mango extract according to claim 1, wherein The matrix consists of 50% acetonitrile, 49.9% water, and 0.1% trifluoroacetic acid in a mass ratio; the first medium is nitrogen; and the second medium is argon.

3. The method for determining mangiferin in the mango extract according to claim 1, wherein The ionized sample ions enter the first collimator channel, which modulates the sample ions into a first ion beam. After the exit gate is opened, at least part of the sample ions enter the second collimator channel, which modulates the sample ions into a second ion beam and introduces the second ion beam into the flight channel.

4. The method for determining mangiferin in the mango extract according to claim 1, wherein The migration time T1 is calculated based on the ion collision cross section of the first component, and the migration time T2 is calculated based on the ion collision cross section of the second component. Combined with the detection width ΔT1, the first migration interval [T1-ΔT1, T1+ΔT1] and the second migration interval [T2-ΔT1, T2+ΔT1] are obtained.

5. The method for determining mangiferin in the mango extract according to claim 4, wherein The flight time T3 is calculated based on the mass-to-charge ratio of the first component, and then the first flight interval [T3-ΔT2, T3+ΔT2] is calculated. The flight time T4 is calculated based on the mass-to-charge ratio of the second component, and then the second flight interval [T4-ΔT2, T4+ΔT2] is calculated, where ΔT2 is the half-measurement interval.

6. The method for determining mangiferin in the mango extract according to claim 5, wherein In step 4, the sampling interval of the first component is calculated based on the first migration interval and the first flight interval, and then the minimum sampling time and the maximum sampling time of the first component are obtained in combination with the starting time and the sampling interval. The first sampling data is intercepted from the mass spectrum data according to the minimum sampling time and the maximum sampling time.

7. The method for determining mangiferin in mango extract according to claim 1, wherein In step 6, the ionization parameters include spray voltage, the ionization efficiency constant of the mango extract, the effective spray voltage and noise growth coefficient of the ionization channel are fitted, the theoretical spray voltage and the corresponding theoretical signal-to-noise ratio are calculated, the measured signal-to-noise ratio is calculated, the adjustment step size is calculated according to the theoretical spray voltage, the current spray voltage, the theoretical signal-to-noise ratio and the measured signal-to-noise ratio, and the spray voltage of the ionization channel is adjusted based on the current spray voltage and the adjustment step size.

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