Method for improving real signal proportion of Fourier transform mass spectrum

Abstract

The invention provides a method for improving the real signal proportion of Fourier transform mass spectrometry, which comprises the following steps of: (S1) obtaining a mass spectrum signal and a corresponding first type of parameters, and obtaining a time domain signal and a corresponding second type of parameters; (S2) determining time t1 according to a first parameter in the first type of parameters and a second type of parameters, performing Fourier transform on signals in the time t1 in the time domain signals, and screening out signals higher than a first threshold value from the transformed signals to obtain pre-selected signals; (S3) determining time t2 according to a second parameter in the first type of parameters and the second type of parameters, performing Fourier transform on signals in the time t2 in the time domain signals, and screening out signals higher than a second threshold value from the transformed signals to obtain verification signals; and (S4) comparing the pre-selected signal with the verification signal, and taking the repeated signal as a real signal. The method has the advantages of low ghost peak ratio and the like.

Description

Technical Field

[0001] The present invention relates to mass spectrometry, and in particular to a method for improving the real signal ratio of Fourier transform mass spectrometry. Background Art

[0002] Currently, there are several problems in high-resolution mass spectrometer data storage, such as: 1. The real signal with low response in mass spectrometry data is submerged in ghost peaks and difficult to identify.

[0003] 2. The problem of low proportion of true signals and large number of ghost peaks in mass spectrometry data.

[0004] 3. Mass spectrometry data contains a large amount of invalid data, resulting in large data storage capacity.

[0005] In order to solve the above technical problems, Thermo Fisher Scientific Inc. believes in its patent CN101088096B that the proportion of real signals is higher in shorter detection times. Therefore, only the first 25% of the data in the time domain is transformed into the frequency domain, and the target signal is screened out by setting a threshold to increase the proportion of real signals.

[0006] In patent WO2005031791A2, the signal peak range is determined by fitting the peak, the mass spectrum peak is fitted according to Gaussian distribution, and the results within the range of 2.5 times the standard deviation are identified as signal peaks.

[0007] The above solutions still have some problems, such as: 1. Using shorter data results, it is impossible to distinguish between real signals and ghost peaks, and there are still a large number of ghost peaks that are difficult to identify.

[0008] 2. Mass spectrometry has extremely different data results at different resolutions and responses. The fixed method of extracting the first 25% and setting the threshold cannot adapt to various conditions.

[0009] 3. The Gaussian fitting method is computationally complex, requires multiple iterations, has a large amount of calculations, and has a slow processing speed. Summary of the invention

[0010] In order to solve the deficiencies in the above-mentioned prior art solutions, the present invention provides a method for improving the real signal ratio of Fourier transform mass spectrometry.

[0011] The objective of the present invention is achieved through the following technical solutions: A method for improving the real signal ratio of Fourier transform mass spectrometry comprises the following steps: (S1) obtaining a mass spectrum signal and a corresponding first type parameter, and obtaining a time domain signal and a corresponding second type parameter; Setting a first threshold corresponding to a first parameter in the first category of parameters, and a second threshold corresponding to a second category of parameters; (S2) determining time t1 according to the first parameter and the second parameter in the first parameter category, performing Fourier transform on the signal in the time domain signal before time t1, and screening out the signal higher than the first threshold in the transformed signal to obtain a pre-selected signal; (S3) determining time t2 according to the second parameter in the first type of parameters and the second type of parameters, performing Fourier transform on the signal in the time domain signal after time t2, and screening out the signal higher than the second threshold in the transformed signal to obtain a verification signal; (S4) Comparing the preselected signal with the verification signal, and taking the repeated signal as the true signal.

[0012] Compared with the prior art, the present invention has the following beneficial effects: 1. Good adaptability; By setting parameters and linking with mass spectrometry data, the preselection time t1 and verification time t2 can be well adapted to mass spectrometry data with different resolutions and responses, and can quickly switch between different demand ranges. 2. The real signal is reliable; By setting simpler parameters to calculate the pre-selection time and verification time, the requirements for operators are reduced and the repeatability of data results is improved, that is, the real signal screened is reliable; 3. The proportion of ghost peaks is low; By comparing, the proportion of real signals with low response and low signal-to-noise ratio is increased, the number of ghost peaks is reduced, and the proportion of ghost peaks is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The disclosure of the present invention will become easier to understand with reference to the accompanying drawings. It is easy for those skilled in the art to understand that these drawings are only used to illustrate the technical solution of the present invention and are not intended to limit the scope of protection of the present invention. In the drawings: Figure 1 is a flow chart of a method for improving the real signal ratio of Fourier transform mass spectrometry according to the present invention; Figure 2 Schematic diagram of a preselection signal and a verification signal according to an embodiment of the present invention. DETAILED DESCRIPTION

[0014] Figure 1-Figure 2The following description describes optional specific embodiments of the present invention to teach those skilled in the art how to implement and reproduce the present invention. In order to teach the technical solution of the present invention, some conventional aspects have been simplified or omitted. Those skilled in the art will understand that variations or replacements derived from these specific embodiments will be within the scope of the present invention. Those skilled in the art will understand that the following features can be combined in various ways to form multiple variations of the present invention. Thus, the present invention is not limited to the following optional specific embodiments, but is only limited by the claims and their equivalents. Example

[0015] like Figure 1 As shown, a method for improving the real signal ratio of Fourier transform mass spectrometry according to an embodiment of the present invention comprises the following steps: (S1) obtaining a mass spectrometry signal and corresponding first-category parameters (including maximum peak height and maximum signal-to-noise ratio), and obtaining a time domain signal and corresponding second-category parameters (including detection time); Maximum peak height H = 4.7e 6 , the maximum signal-to-noise ratio N=577, and the detection time T=1.6 seconds.

[0016] The first threshold corresponding to the first parameter in the first type of parameters - the peak height threshold is set to h=0.01H, and the second threshold corresponding to the second type of parameters - the signal-to-noise ratio threshold is set to n=3.

[0017] (S2) Determine the time t1 according to the maximum peak height (i.e., the first parameter) in the first type of parameters and the second type of parameters (i.e., the detection duration): When the maximum peak height H is less than the third threshold 10 4 When t1= 0.5·log(H / h).

[0018] When the maximum peak height H is not less than the third threshold, t1=T(0.5-0.1·log(H / h)).

[0019] In this embodiment, H>10 4 , t1=T(0.5-0.1·log(H / h))=0.48 seconds, Perform Fourier transform on the signal in the time domain signal before t1, and filter out the signal above the first threshold value in the transformed signal to obtain the pre-selected signal, such as Figure 2 shown.

[0020] (S3) Determine the time t2 according to the second parameter (i.e., the maximum signal-to-noise ratio) in the first type of parameters and the second type of parameters (detection duration): t2=T(0.5-0.1·log(N / n))=0.43 seconds.

[0021] Perform Fourier transform on the signal in the time domain signal after time t2, and filter out the signal higher than the second threshold (i.e., signal-to-noise ratio threshold 3) in the transformed signal to obtain a verification signal, such as Figure 2 As shown; (S4) comparing the pre-selected signal and the verification signal, taking the repeated signal as the real signal, and deleting the non-repeated signal, such as Figure 2 shown.

[0022] like Figure 2 As shown in the figure, 237.4 is the target signal. This peak is not the maximum signal in the range of 236.9 ~ 237.8, but in the pre-selected signal and the verification signal, only this signal is a coincident value, and the other signals cannot be coincident. Therefore, only this signal is retained, and the other signals are deleted to increase the proportion of the real signal. Example

[0023] A method for improving the real signal ratio of Fourier transform mass spectrometry according to an embodiment of the present invention comprises the following steps: (S1) obtaining a mass spectrometry signal and corresponding first-category parameters (including maximum peak height and maximum signal-to-noise ratio), and obtaining a time domain signal and corresponding second-category parameters (including detection time); Maximum peak height H = 4.7e 6 , the maximum signal-to-noise ratio N=577, the detection time T=1.6 seconds. Set the first threshold (peak height threshold) h1=0.01H, the fourth threshold (peak height threshold) h2=9.8e 4 The second threshold (signal-to-noise ratio threshold) n1 is set to 1.9, and the fifth threshold (signal-to-noise ratio threshold) n2 is set to 3.4.

[0024] (S2) Determine the time t1 according to the maximum peak height (i.e., the first parameter) in the first type of parameters and the second type of parameters (i.e., the detection duration): When the maximum peak height H is less than the third threshold 10 4 When t1= 0.5·log(H / h).

[0025] When the maximum peak height H is not less than the third threshold, t1=T(0.5-0.1·log(H / h)).

[0026] In this embodiment, H>10 4 , t1=T(0.5-0.1·log(H / h1))=0.48 seconds.

[0027] Performing Fourier transformation on the signal in the time before t1 in the time domain signal, and screening out the signal above the fourth threshold value as the target peak in the transformed signal without comparison; The signals higher than the first threshold and lower than the fourth threshold are screened out to obtain a preselected signal.

[0028] (S3) Determine the time t2 according to the second parameter (i.e., the maximum signal-to-noise ratio) in the first type of parameters and the second type of parameters (detection duration): t2=T(0.5-0.1·log(N / n1))=0.40 seconds.

[0029] Performing Fourier transform on the signal in the time after t2 in the time domain signal, and screening out the signal higher than the fifth threshold (i.e., the signal-to-noise ratio threshold n2=3.4) as the target peak in the transformed signal without comparison; Screening out signals that are higher than the second threshold and lower than the fifth threshold to obtain a verification signal; (S4) Comparing the pre-selected signal with the verification signal, taking the repeated signal as the real signal, and deleting the non-repeated signal.

Claims

1. A method for improving the real signal ratio of Fourier transform mass spectrometry, comprising the following steps: (S1) obtaining a mass spectrum signal and a corresponding first type parameter, and obtaining a time domain signal and a corresponding second type parameter; Setting a first threshold corresponding to a first parameter in the first category of parameters, and a second threshold corresponding to a second category of parameters; (S2) determining time t1 according to the first parameter and the second parameter in the first parameter category, performing Fourier transform on the signal in the time domain signal before time t1, and screening out the signal higher than the first threshold in the transformed signal to obtain a pre-selected signal; (S3) determining time t2 according to the second parameter in the first type of parameters and the second type of parameters, performing Fourier transform on the signal in the time domain signal after time t2, and screening out the signal higher than the second threshold in the transformed signal to obtain a verification signal; (S4) Comparing the preselected signal with the verification signal, and taking the repeated signal as the true signal.

2. The method for improving the real signal ratio of Fourier transform mass spectrometry according to claim 1, characterized in that: The first parameter is the maximum peak height H, the second type of parameter is the detection time T, and the first threshold is the peak height threshold h.

3. The method for improving the real signal ratio of Fourier transform mass spectrometry according to claim 2, characterized in that: When the maximum peak height H is less than the third threshold, t1= 0.5·log(H / h); when the maximum peak height H is not less than the third threshold, t1=T(0.5-0.1·log(H / h)).

4. The method for improving the real signal ratio of Fourier transform mass spectrometry according to claim 1, characterized in that: The second parameter is the maximum signal-to-noise ratio N, the second type of parameter is the detection time T, and the first threshold is the signal-to-noise ratio threshold n.

5. The method for improving the real signal ratio of Fourier transform mass spectrometry according to claim 4, characterized in that: t2=T(0.5-0.1·log(N / n)).

6. The method for improving the real signal ratio of Fourier transform mass spectrometry according to claim 1, characterized in that: In step (S4), non-repetitive signals are deleted.

7. The method for increasing the real signal ratio of Fourier transform mass spectrometry according to claim 1, characterized in that: In step (S1), a fourth threshold corresponding to the first parameter in the first category of parameters and a fifth threshold corresponding to the second category of parameters are set; In steps (S2) and (S3), the peak whose peak height is not less than the fourth threshold or the peak whose signal-to-noise ratio is not less than the fifth threshold is taken as the target peak without comparison; Peaks with peak heights between the first threshold and the fourth threshold, or peaks with signal-to-noise ratios between the second threshold and the fifth threshold need to be compared.

Images