Method for determining the content of vanillin in vanilla planifolia using gas chromatography

Abstract

The application relates to the technical field of gas chromatography detection, in particular to a method for determining the content of vanillin in vanilla by using gas chromatography, which comprises the following steps: obtaining the gas chromatogram of a sample solution to be analyzed, a standard solution and a control solution, and the environmental temperature at each moment during the process; obtaining a chromatographic peak to be analyzed in the gas chromatogram to be analyzed; calculating a first interference value of the gas chromatogram to be analyzed; calculating a temperature influence degree, obtaining an interference difference degree, a second interference value and an interference coefficient of the gas chromatogram to be analyzed, combining a heuristic threshold rule to determine a heuristic threshold value of a wavelet denoising algorithm, filtering the gas chromatogram to be analyzed by using the wavelet denoising algorithm, and determining the content of vanillin in vanilla by using the peak area of the chromatographic peak to be analyzed in the filtered gas chromatogram to be analyzed. The application effectively removes the noise interference in the gas chromatogram to be analyzed, and improves the accuracy of the determination of the content of vanillin in vanilla.

Description

Technical Field

[0001] This application relates to the field of gas chromatography detection technology, specifically to a method for determining the vanillin content in vanilla using gas chromatography. Background Technology

[0002] Vanilla, also known as vanilla grass or herb, is a precious natural spice plant. An important standard for measuring the intensity of vanilla's aroma is its vanillin content. Vanillin can give food a unique milky aroma, but long-term intake of vanillin can lead to adverse reactions such as dizziness and nausea, thus harming human health. Therefore, it is necessary to measure the vanillin content in vanilla to ensure that the quality of vanilla meets the requirements, and at the same time effectively control the safe amount of additives used in food.

[0003] Gas chromatography-mass spectrometry (GC-MS) is widely used for vanillin analysis due to its high separation capability and qualitative and quantitative accuracy. In chromatographic analysis, parameters such as peak retention time, width, and area are crucial for vanillin identification and quantification. In determining vanillin content in vanilla orchids using GC, traditional methods typically measure vanillin content by the peak area corresponding to the vanillin peak in the chromatogram. However, GC-MS instruments can be affected by various interfering factors during chromatographic analysis, including instrument performance fluctuations, ambient temperature changes, and sample matrix residues. These interfering factors can lead to peak shape distortion, peak position shift, or increased noise, thus affecting the accuracy of vanillin quantification. Summary of the Invention

[0004] To address the aforementioned technical problems, a method for determining vanillin content in vanilla using gas chromatography is provided to resolve the existing issues.

[0005] The solution to the technical problem of this application is to provide a method for determining the vanillin content in vanilla using gas chromatography, comprising the following steps:

[0006] Chromatograms of the sample solution to be analyzed, the standard solution, and the control solution were obtained and denoted as the gas chromatogram of the sample solution to be analyzed, the standard gas chromatogram, and the control gas chromatogram, respectively. The ambient temperature of the three solutions at each moment during the instrumentation process was also obtained.

[0007] Based on the size of the peaks in the gas chromatogram to be analyzed, the peaks in the gas chromatogram to be analyzed are screened to obtain significant peaks; the differences between the different significant peaks in the gas chromatogram to be analyzed and the maximum peak value in the standard gas chromatogram at corresponding times are analyzed to obtain the chromatographic peaks to be analyzed in the gas chromatogram to be analyzed.

[0008] Analyze the difference in peak width between the peak to be analyzed in the gas chromatogram and the maximum peak value in the standard gas chromatogram, as well as the shift at the corresponding time, and calculate the first interference value of the gas chromatogram to be analyzed.

[0009] Based on the fluctuations of the response values ​​at all times in the reference gas chromatogram and the fluctuations of the ambient temperature during the loading of the reference solution, the temperature influence is calculated. Combined with the differences in the fluctuations of the ambient temperature during the loading of the sample solution and the standard solution, the interference difference of the gas chromatogram to be analyzed is obtained. Combined with the first interference value, the second interference value of the gas chromatogram to be analyzed is determined.

[0010] By analyzing the discreteness of the response values ​​in the gas chromatogram except for the local area where the significant peak is located, and the second interference value, the interference coefficient of the gas chromatogram to be analyzed is determined. Combined with the heuristic threshold rule, the heuristic threshold of the wavelet denoising algorithm is determined. The wavelet denoising algorithm is used to filter the gas chromatogram to be analyzed. The peak area of ​​the chromatographic peak to be analyzed in the filtered gas chromatogram is used to determine the vanillin content in vanilla.

[0011] Preferably, the process of obtaining the significant peak is as follows: obtaining the peak of the response value at all times in the gas chromatogram to be analyzed, obtaining the segmentation threshold of the peak value of all peaks in the gas chromatogram to be analyzed; and recording the peaks in the gas chromatogram to be analyzed that have a peak value greater than or equal to the segmentation threshold as significant peaks.

[0012] Preferably, the step of obtaining the chromatographic peaks to be analyzed in the gas chromatogram includes: obtaining the peaks of the response values ​​at all times in the standard gas chromatogram, and recording the peak corresponding to the maximum peak value as the chromatographic peak; calculating the time interval between the time corresponding to each significant peak in the gas chromatogram to be analyzed and the time corresponding to the chromatographic peak in the standard gas chromatogram; and selecting the significant peak corresponding to the minimum time interval as the chromatographic peak to be analyzed.

[0013] Preferably, the calculation of the first interference value of the gas chromatogram to be analyzed includes:

[0014] Calculate the difference between the half-peak width (WHM) of the chromatographic peak in the gas chromatogram to be analyzed and the half-peak width (WHM) of the chromatographic peak in the standard gas chromatogram, and record it as the relative difference.

[0015] The first interference value is the product of the result of positive mapping of the relative difference and the result of positive mapping of the minimum interval time.

[0016] Preferably, the calculation process for the temperature influence is as follows:

[0017] Calculate the degree of dispersion of the response at all times in the reference gas chromatogram, and denote it as the first degree of dispersion;

[0018] The dispersion of ambient temperature at all times during the loading of the control solution is calculated and denoted as the second dispersion.

[0019] The temperature influence is the ratio of the first dispersion to the second dispersion.

[0020] Preferably, obtaining the interference difference degree of the gas chromatogram to be analyzed includes:

[0021] The dispersion of ambient temperature at all times during the process of analyzing the sample solution and the standard solution is calculated and multiplied by the temperature influence, respectively, and used as the relative fluctuation of the gas chromatogram of the sample solution and the standard gas chromatogram.

[0022] The interference difference is the difference in relative fluctuation between the gas chromatogram to be analyzed and the standard gas chromatogram.

[0023] Preferably, determining the second interference value of the gas chromatogram to be analyzed includes: if the interference difference is 0, the second interference value of the gas chromatogram to be analyzed is the first interference value; otherwise, the second interference value of the gas chromatogram to be analyzed is the ratio of the first interference value to the interference difference.

[0024] Preferably, determining the interference coefficient of the gas chromatogram to be analyzed includes:

[0025] The local window is defined as all times within the neighborhood of the time corresponding to each significant peak in the gas chromatogram to be analyzed; the degree of dispersion of the response values ​​of all other times in the gas chromatogram to be analyzed, excluding the times contained in the local windows corresponding to all significant peaks, is defined as the baseline interference of the gas chromatogram to be analyzed.

[0026] The interference coefficient is the normalized result of the product of the second interference value and the baseline interference degree.

[0027] Preferably, determining the heuristic threshold for the wavelet denoising algorithm includes:

[0028] Wavelet decomposition is performed on the response at all times in the gas chromatogram to be analyzed. The wavelet coefficients after decomposition are squared and arranged in ascending order to form a wavelet coefficient vector.

[0029] For each element in the wavelet coefficient vector, calculate the corresponding risk value.

[0030] Select the element corresponding to the minimum risk value in the wavelet coefficient vector, denoted as The sum of all elements in the wavelet coefficient vector is denoted as... ;make , Then the heuristic threshold It can be represented as: ,in, The length of the wavelet coefficient vector. The interference coefficient is the coefficient mentioned above. This represents the number of times in the gas chromatogram to be analyzed at all time points. This represents the logarithmic function with base 2. Represents the logarithmic function with base 10. This represents the function that takes the minimum value. It represents the square root.

[0031] Preferably, the wavelet coefficient vector contains the first... Risk value of each element The calculation formula is: ,in, The first wavelet coefficient vector is the first wavelet coefficient vector. The element value corresponding to each element. The first wavelet coefficient vector is the first wavelet coefficient vector. The index of each element. The first wavelet coefficient vector is the first wavelet coefficient vector. The element value corresponding to each element.

[0032] This application has at least the following beneficial effects:

[0033] This application obtains significant peaks by screening peaks in the gas chromatogram to be analyzed. The advantage of this method is that it can eliminate interference from low-intensity noise peaks and retain characteristic peaks related to vanillin. It also obtains the chromatographic peaks to be analyzed in the gas chromatogram, which allows for the selection of the vanillin-corresponding peaks from the gas chromatogram by comparing the retention times of the significant peaks in the gas chromatogram to those in the standard gas chromatogram. Finally, it calculates the first interference value of the gas chromatogram, which allows for the comparison of the vanillin-corresponding peaks in the gas chromatogram to those in the standard gas chromatogram. Differences in peak width and timing are used to assess the stability of instrument performance and reflect interference encountered by the analyte solution during chromatographic detection. Calculating the temperature effect is beneficial because it considers the impact of unit temperature changes on the fluctuation of the response value in the reference gas chromatogram, reflecting the sensitivity of the response value to unit ambient temperature fluctuations. Obtaining the interference difference in the analyte gas chromatogram is beneficial because it considers the consistency of the interference effects of ambient temperature on the analyte solution and the standard solution during chromatographic detection. Determining the second interference value of the analyte gas chromatogram is beneficial because... By compensating for the interference differences between the analytical gas chromatogram and the standard gas chromatogram due to temperature changes, the effects of ambient temperature interference on the analytical gas chromatogram and the standard gas chromatogram are made more consistent. This allows for a more accurate reflection of the characteristic differences of the vanillin-corresponding chromatographic peak between the analytical gas chromatogram and the standard gas chromatogram, thus accurately assessing the impact of noise interference on the analytical gas chromatogram. Determining the interference coefficient of the analytical gas chromatogram is beneficial because it considers the influence of multiple interference sources on the analytical gas chromatogram, comprehensively evaluating the performance of the analytical sample solution during chromatographic detection. This study analyzes the impact of noise interference on gas chromatograms and, based on heuristic threshold rules, determines the heuristic threshold for wavelet denoising algorithms. The wavelet denoising algorithm is then used to filter the gas chromatograms under analysis. The peak area of ​​the analyzed chromatographic peaks in the filtered gas chromatograms is then used to determine the vanillin content in vanilla. The beneficial effect lies in dynamically adjusting the wavelet denoising threshold based on the degree of noise interference in the gas chromatograms under analysis, thereby effectively removing noise interference from the gas chromatograms under analysis, more accurately measuring the peak area of ​​the analyzed chromatographic peaks, and improving the accuracy of vanillin content determination in vanilla. Attached Figure Description

[0034] The method for determining vanillin content in vanilla using gas chromatography according to this application will be further described in detail below with reference to the accompanying drawings.

[0035] Figure 1 A flowchart illustrating the steps of a gas chromatography method for determining vanillin content in vanilla, as provided in an embodiment of this application.

[0036] Figure 2A flowchart illustrating the steps of the heuristic threshold acquisition method provided in this application embodiment. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this application clearer, the method for determining vanillin content in vanilla using gas chromatography, as proposed in this application, will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit the scope of this application.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0039] Please see Figure 1 The diagram illustrates a flowchart of a method for determining vanillin content in vanilla using gas chromatography, according to an embodiment of this application. The method includes the following steps:

[0040] Step 1: Obtain the chromatograms of the sample solution to be analyzed, the standard solution, and the control solution, respectively, and record them as the gas chromatogram of the sample solution to be analyzed, the standard gas chromatogram, and the control gas chromatogram. Also, obtain the ambient temperature of the three solutions at each time point during the instrumentation process.

[0041] Gas chromatography is a chromatographic technique that uses a gas as the mobile phase to separate and analyze volatile or gaseous substances. The process is as follows: when a sample is injected into the column, it is first heated and converted into vapor in the vaporization chamber. This vapor is then carried into the column by a carrier gas (such as nitrogen, hydrogen, or helium). Within the column, the sample components pass through at different speeds due to their different partition coefficients between the stationary and mobile phases. This process ultimately generates an electrical signal in the detector, forming a chromatogram.

[0042] Therefore, vanilla was cut into 0.5cm segments, and 1g of vanilla was weighed. Then, 20mL of 75% ethanol was added to an Erlenmeyer flask, and ultrasonic extraction was performed at 40°C and 40kHz for 20min each time. After filtration, the residue was washed with 75% ethanol, the filtrates were combined, cooled to room temperature, and diluted to 50mL with 75% ethanol. The solution was shaken well and filtered through a 0.22µm microporous membrane to obtain the sample solution to be analyzed.

[0043] Next, take 500 mg of vanillin standard dried to constant weight from the desiccator, dissolve it in 75% ethanol and dilute to 50 mL, shake well, and prepare a standard solution of 10 mg / mL.

[0044] Therefore, 50 mL of 75% ethanol solution was used as a control solution;

[0045] The sample solution, standard solution, and control solution were sequentially analyzed using gas chromatography-mass spectrometry (GC-MS) to obtain gas chromatograms of the sample solution, standard solution, and control solution. Wavelet transform algorithm was used to perform baseline correction on the gas chromatograms of the sample solution, standard solution, and control solution. The wavelet transform algorithm is a well-known technique and will not be described in detail here.

[0046] It should be noted that since the control solution is a solvent solution that does not contain any vanillin, its control gas chromatogram should show a stable baseline without obvious peaks or fluctuations when there is no interference. If the chromatographic detection is affected by changes in ambient temperature, internal instrument factors or other external factors, certain fluctuations will appear in the control gas chromatogram.

[0047] By using temperature sensors, the ambient temperature at each moment during the instrument testing of the sample solution, standard solution, and control solution is obtained. Therefore, the ambient temperature at each moment during the instrument testing of the sample solution, standard solution, and control solution is obtained.

[0048] In this embodiment, the chromatographic column is a DB-5MS flexible quartz capillary column. The column temperature is initially 60°C, held for 1 min, then increased to 260°C at 10°C / min and held for 6 min, then increased to 290°C at 6°C / min and held for 8 min. The carrier gas is helium, with a flow rate of 1.0 mL / min and an injection volume of 1 μL, using splitless injection. The mass spectrometry conditions are: EI ionization mode, ion source temperature 200°C, interface temperature 220°C, electron impact voltage 70 eV, detector voltage 1.0 kV, mass-to-nucleus ratio scan range 40-500 amu, auto-tuning, and solvent delay of 3 minutes. The chromatographic data of the sample solution, standard solution, and control solution to be analyzed are recorded by gas chromatography-mass spectrometry within 43 minutes. Therefore, the temperature sensor acquisition time interval is 1 second, and the acquisition duration is 43 minutes. As for other implementation methods, the implementer can set the values ​​according to the actual situation. The wavelet transform algorithm is a well-known technology and will not be described in detail here.

[0049] Thus, we obtain the gas chromatograms of the sample solution, standard solution, and control solution, as well as the ambient temperatures at various times during the instrumentation process.

[0050] Step 2: Based on the peak sizes in the gas chromatogram to be analyzed, the peaks in the gas chromatogram to be analyzed are screened to obtain significant peaks; the differences between the different significant peaks in the gas chromatogram to be analyzed and the maximum peak value in the standard gas chromatogram at corresponding times are analyzed to obtain the chromatographic peaks to be analyzed in the gas chromatogram to be analyzed; the differences in peak width between the chromatographic peaks to be analyzed and the maximum peak value in the standard gas chromatogram to be analyzed, as well as the shift at corresponding times, are analyzed to calculate the first interference value of the gas chromatogram to be analyzed.

[0051] When performing analysis using a gas chromatography-mass spectrometry (GC-MS) system, the instrument's performance may change due to various factors, such as sample matrix residue at the injection port, column aging, and state drift of the mass spectrometer detector. These changes can cause the measurement results to deviate from the true value, thereby introducing system bias, generating interference noise, and ultimately affecting the accuracy of subsequent vanillin content detection.

[0052] Secondly, if the interference between the gas chromatogram to be analyzed and the standard gas chromatogram is small, the retention time of vanillin in the sample solution to be analyzed in the gas chromatogram to be analyzed should be relatively consistent with its retention time in the standard gas chromatogram, and the duration of the chromatographic peak corresponding to vanillin should be relatively consistent.

[0053] Based on the above analysis, the chromatographic peaks to be analyzed in the gas chromatogram of the target gas chromatogram are obtained by analyzing the interval between the peaks in the gas chromatogram of the target gas chromatogram and the peaks in the standard gas chromatogram. Specifically:

[0054] Obtain the peaks of the response values ​​at all times in the standard gas chromatogram, and record the peak corresponding to the maximum peak value as the chromatographic peak;

[0055] In this embodiment, the AMPD (Automatic Multiscale-based Peak Detection) peak detection algorithm is used to obtain the peak. The AMPD peak detection algorithm is a well-known technology and will not be described in detail here.

[0056] It should be noted that since the standard gas chromatogram is obtained by detecting a standard solution prepared with vanillin, the peak corresponding to the largest peak in the standard gas chromatogram, except for the peaks caused by noise interference, is the chromatographic peak corresponding to vanillin.

[0057] Obtain the peak values ​​of the response values ​​at all times in the gas chromatogram to be analyzed, and obtain the peak value segmentation threshold of all peak values ​​in the gas chromatogram to be analyzed.

[0058] In this embodiment, the peak detection algorithm AMPD (Automatic Multiscale-based Peak Detection) is used to obtain the peak. The AMPD peak detection algorithm is a well-known technology and will not be described in detail here. Secondly, the Otsu threshold segmentation algorithm is used to obtain the segmentation threshold. The Otsu threshold segmentation algorithm is a well-known technology and will not be described in detail here. As other implementation methods, implementers can use other methods of the prior art, such as cross-validation, etc. This embodiment does not impose any special restrictions on this.

[0059] Peaks in the gas chromatogram to be analyzed that have a peak value greater than or equal to the segmentation threshold are recorded as significant peaks.

[0060] It should be noted that, due to the large number of components contained in vanilla, there will be many peaks in the gas chromatogram to be analyzed. By screening out the significant peaks, we can avoid peak interference caused by noise and eliminate the influence of minor fluctuations caused by instrument fluctuations or sample matrix residues.

[0061] Calculate the time interval between the time corresponding to each significant peak in the gas chromatogram to be analyzed and the time corresponding to the chromatographic peak in the standard gas chromatogram.

[0062] Select the significant peak corresponding to the smallest interval time and record it as the chromatographic peak to be analyzed;

[0063] It should be noted that the smaller the interval, the closer the retention time of this significant peak is to the retention time of the chromatographic peak corresponding to vanillin in the standard gas chromatogram, and the more likely this significant peak is the chromatographic peak corresponding to vanillin in the sample solution to be analyzed.

[0064] Calculate the difference between the half-peak width (WHM) of the chromatographic peak in the gas chromatogram to be analyzed and the half-peak width (WHM) of the chromatographic peak in the standard gas chromatogram, and record it as the relative difference.

[0065] In this embodiment, the absolute value of the difference between the half-peak width (WHM) of the chromatographic peak to be analyzed in the gas chromatogram to be analyzed and the half-peak width (WHM) of the chromatographic peak to be analyzed in the standard gas chromatogram is calculated and denoted as the relative difference.

[0066] It should be noted that the calculation of the half-peak width is a well-known technique and will not be elaborated here.

[0067] The product of the positive mapping result of the relative difference and the positive mapping result of the minimum interval time is used as the first interference value of the gas chromatogram to be analyzed.

[0068] In this embodiment, the specific process of positive mapping is as follows: positive mapping is performed through an exponential function, assuming the relative difference is denoted as... The minimum interval time is denoted as ,but The result is used as the result of a positive mapping of the relative differences. The result is used as the result of positive mapping with minimum interval time, where, It is an exponential function with the natural constant as the base; through the process of positive mapping, it avoids the first disturbance value being 0 when the relative difference or the minimum interval time is 0.

[0069] It should be noted that a larger relative difference indicates a greater difference in the half-peak width (WHM) of the vanillin-corresponding peak between the gas chromatogram of the sample and the standard gas chromatogram, reflecting poor consistency in the duration of vanillin in the two chromatograms. This means the gas chromatogram of the sample is more significantly affected by noise interference. Similarly, a larger minimum interval indicates a greater difference in the retention time of the vanillin-corresponding peak between the gas chromatogram of the sample and the standard gas chromatogram, reflecting greater noise interference. A higher first interference value indicates a higher degree of interference from the instrument itself, reflecting greater error interference generated by the gas chromatography-mass spectrometry (GC-MS) instrument during chromatographic detection of the sample solution. Therefore, filtering and noise reduction of the data in the gas chromatogram are necessary to improve the accuracy of subsequent vanillin content determination.

[0070] Thus, the first interference value of the gas chromatogram to be analyzed is obtained.

[0071] Step 3: Based on the fluctuation of the response values ​​at all times in the reference gas chromatogram and the fluctuation of the ambient temperature during the loading of the reference solution, calculate the temperature influence. Combined with the difference in the fluctuation of the ambient temperature during the loading of the sample solution and the standard solution, obtain the interference difference of the gas chromatogram to be analyzed. Combined with the first interference value, determine the second interference value of the gas chromatogram to be analyzed.

[0072] Furthermore, because vanillin is highly sensitive to temperature and the measurement environment, the column temperature and injection port temperature of the gas chromatography-mass spectrometry (GC-MS) instrument are usually fixed at specific values ​​when detecting vanillin. However, changes in ambient temperature can affect the stability of the instrument temperature, potentially leading to additional errors.

[0073] Therefore, the temperature effect is calculated by observing the fluctuations in the reference gas chromatogram of the reference solution and the changes in ambient temperature during the instrumentation process. Specifically:

[0074] Calculate the degree of dispersion of the response at all times in the reference gas chromatogram, and denote it as the first degree of dispersion;

[0075] The dispersion of ambient temperature at all times during the loading of the control solution is calculated and denoted as the second dispersion.

[0076] In this embodiment, the degree of dispersion is measured by calculating the variance of the response at all times in the control gas chromatogram and the variance of the ambient temperature at all times during the loading of the control solution. As other implementation methods, implementers may use other methods of the prior art, such as standard deviation, coefficient of variation, etc. This embodiment does not impose any special restrictions on this.

[0077] Calculate the ratio of the first dispersion to the second dispersion, and use it as the temperature influence degree;

[0078] It should be noted that the first dispersion reflects the fluctuation of the response value on the baseline of the reference gas chromatogram during chromatographic detection of the reference solution, while the second dispersion reflects the fluctuation of the ambient temperature during chromatographic detection of the reference solution. The larger the first dispersion, the greater the fluctuation of the response value in the reference gas chromatogram and the worse the baseline stability. The larger the second dispersion, the greater the fluctuation of the ambient temperature and the worse the temperature stability. The greater the temperature influence, the greater the influence of changes in ambient temperature on the instrument during detection and analysis, indicating that the response value in the reference gas chromatogram is more sensitive to unit ambient temperature fluctuations.

[0079] Secondly, by assessing the impact of ambient temperature fluctuations on the sample solution and standard solution during the instrumentation process, the interference differences between the gas chromatograms of the sample solution and the standard gas chromatograms are evaluated, and the degree of interference difference is calculated. Specifically:

[0080] The product of the dispersion of ambient temperature at all times during the standard solution loading process and the temperature influence is calculated as the relative volatility of the standard gas chromatogram.

[0081] The product of the dispersion of the ambient temperature at all times during the process of analyzing the sample solution and the temperature influence is calculated as the relative fluctuation of the gas chromatogram to be analyzed.

[0082] In this embodiment, the degree of dispersion is measured by calculating the variance of the ambient temperature at all times during the standard solution loading process and the variance of the ambient temperature at all times during the sample solution loading process. As other implementation methods, implementers may use other methods of the prior art, such as standard deviation, coefficient of variation, etc. This embodiment does not impose any special restrictions on this.

[0083] It should be noted that the relative fluctuation reflects the degree of interference between the standard gas chromatogram and the gas chromatogram to be analyzed and the ambient temperature. The greater the relative fluctuation, the greater the influence of ambient temperature on the instrument, and the lower the accuracy of the chromatographic detection results of the sample solution and standard solution to be analyzed.

[0084] The difference in relative fluctuation between the gas chromatogram to be analyzed and the standard gas chromatogram is calculated as the interference difference of the gas chromatogram to be analyzed.

[0085] In this embodiment, the absolute value of the difference in relative fluctuation between the gas chromatogram to be analyzed and the standard gas chromatogram is calculated as the interference difference degree of the gas chromatogram to be analyzed.

[0086] It should be noted that the greater the interference difference, the greater the difference in relative fluctuation between the gas chromatogram to be analyzed and the standard gas chromatogram, indicating that the sample solution to be analyzed and the standard solution are affected differently by fluctuations in ambient temperature during chromatographic detection; the smaller the interference difference, the smaller the difference in relative fluctuation between the gas chromatogram to be analyzed and the standard gas chromatogram, reflecting that the sample solution to be analyzed and the standard solution are relatively consistent in terms of interference from fluctuations in ambient temperature during chromatographic detection.

[0087] Furthermore, based on the interference difference and the first interference value, a second interference value is determined, specifically as follows:

[0088] If the interference difference is 0, the second interference value of the gas chromatogram to be analyzed is the first interference value; otherwise, the second interference value of the gas chromatogram to be analyzed is the ratio of the first interference value to the interference difference.

[0089] It should be noted that if the interference difference is 0, it means that the gas chromatogram to be analyzed and the standard gas chromatogram are affected by the same ambient temperature. If the interference difference is not 0, it means that there is a significant difference in the interference effect of ambient temperature between the gas chromatogram to be analyzed and the standard gas chromatogram. The second interference value can compensate for the interference difference between the measurement results of the gas chromatogram to be analyzed and the standard gas chromatogram caused by temperature changes, so that the gas chromatogram to be analyzed and the standard gas chromatogram are more consistent in terms of the interference effect of ambient temperature. This can truly reflect the characteristic differences of the vanillin corresponding chromatographic peak between the gas chromatogram to be analyzed and the standard gas chromatogram. Therefore, the larger the obtained second interference value, the greater the influence of noise interference on the gas chromatogram to be analyzed, and the more necessary it is to filter and denoise the data in the gas chromatogram to be analyzed.

[0090] Thus, the second interference value of the gas chromatogram to be analyzed is obtained.

[0091] Step 4: By analyzing the discreteness of the response values ​​in the gas chromatogram except for the local area where the significant peak is located, and the second interference value, the interference coefficient of the gas chromatogram to be analyzed is determined. Combined with the heuristic threshold rule, the heuristic threshold of the wavelet denoising algorithm is determined. The wavelet denoising algorithm is used to filter the gas chromatogram to be analyzed. The vanillin content in vanilla is determined by using the peak area of ​​the chromatographic peak to be analyzed in the filtered gas chromatogram.

[0092] Furthermore, in the gas chromatogram to be analyzed, apart from the key components contained in vanilla exhibiting significant responses at corresponding retention times (i.e., significant peaks appearing), the fluctuations in response values ​​at other times mainly originate from baseline noise, instrument drift, or the influence of weak signals from non-critical elements. Therefore, by analyzing the fluctuations in response values ​​at times other than those encompassed by significant peaks, the baseline interference is calculated, specifically as follows:

[0093] The local window is defined as all times within the neighborhood of the time corresponding to each significant peak in the gas chromatogram to be analyzed.

[0094] In this embodiment, the size of the local window is twice the half-peak width corresponding to each significant peak. In other implementations, the implementer can set the size according to the actual situation.

[0095] The degree of dispersion of the response values ​​at all times in the gas chromatogram to be analyzed, excluding the times contained within the local windows corresponding to all significant peaks, is taken as the baseline interference of the gas chromatogram to be analyzed.

[0096] In this embodiment, the degree of dispersion is measured by calculating the variance of the response values ​​at all times in the gas chromatogram except for the times contained in the local window corresponding to all significant peaks. As another implementation method, the implementer may use other methods of the prior art, such as standard deviation, etc. This embodiment does not impose any special restrictions on this.

[0097] It should be noted that the greater the baseline interference, the greater the degree of noise interference to the gas chromatogram being analyzed.

[0098] Furthermore, based on the second interference value and the baseline interference degree, the interference coefficient is determined, specifically as follows:

[0099] The normalized result of the product of the second interference value and the baseline interference degree is used as the interference coefficient of the gas chromatogram to be analyzed.

[0100] In this embodiment, the sigmoid function is used for normalization. The sigmoid function is a well-known technique and will not be described in detail here. As other implementation methods, implementers may use other methods of the prior art, such as the tanh function, softmax function, etc. This embodiment does not impose any special restrictions on this.

[0101] It should be noted that the larger the interference coefficient, the greater the error interference that the chromatographic detection of the sample solution to be analyzed is affected. In order to improve the accuracy of vanillin content determination, it is necessary to filter and denoise the data in the gas chromatogram to be analyzed.

[0102] Secondly, based on the interference coefficients and combined with heuristic threshold rules, the heuristic threshold for the wavelet denoising algorithm is determined. The specific process is as follows:

[0103] Wavelet decomposition is performed on the response at all times in the gas chromatogram to be analyzed. The wavelet coefficients after decomposition are squared and arranged in ascending order to form a wavelet coefficient vector.

[0104] It should be noted that wavelet decomposition is a well-known technique, and will not be elaborated upon here.

[0105] For each element in the wavelet coefficient vector, the risk value corresponding to each element is calculated using the following formula:

[0106]

[0107] in, The first wavelet coefficient vector is the first wavelet coefficient vector. The risk value of each element The length of the wavelet coefficient vector. The first wavelet coefficient vector is the first wavelet coefficient vector. The element value corresponding to each element. The first wavelet coefficient vector is the first wavelet coefficient vector. The index of each element. The first wavelet coefficient vector is the first wavelet coefficient vector. The element values ​​corresponding to each element, where... Indicates the preceding The sum of squares of the elements.

[0108] Select the element corresponding to the minimum risk value in the wavelet coefficient vector, denoted as Let S be the sum of all elements in the wavelet coefficient vector; , Then the heuristic threshold can be expressed as:

[0109]

[0110] in, For heuristic thresholds, The interference coefficient is the coefficient mentioned above. This represents the number of times in the gas chromatogram to be analyzed at all time points. This represents the logarithmic function with base 2. Represents the logarithmic function with base 10. This represents the function that takes the minimum value. It represents the square root.

[0111] It should be noted that heuristic threshold rules are a well-known technique and will not be elaborated upon here.

[0112] The flowchart of the heuristic threshold acquisition method provided in this application embodiment is as follows: Figure 2 As shown.

[0113] Based on heuristic thresholding, a wavelet denoising algorithm is used to filter the response values ​​in the gas chromatogram to be analyzed. The vanillin content in vanilla is determined by the peak area corresponding to the chromatographic peak in the filtered gas chromatogram.

[0114] It should be noted that wavelet denoising algorithms and peak area calculations are well-known techniques and will not be elaborated upon here.

[0115] The process for determining the vanillin content in vanilla is as follows:

[0116] Standard solutions of different concentrations were prepared by taking 0.04 mL, 0.05 mL, 0.10 mL, 0.60 mL, and 1.10 mL of the standard solution and placing them in 10.0 mL volumetric flasks, diluting with 75% ethanol to the mark, and shaking well.

[0117] Each standard solution of each concentration was analyzed by gas chromatography-mass spectrometry (GC-MS), with an injection volume of 1 μL, and the corresponding standard gas chromatograms were obtained for each concentration.

[0118] Based on the peak area of ​​the chromatographic peak in the standard gas chromatogram, a two-dimensional array is formed by combining the peak area of ​​each concentration with the peak area of ​​its corresponding standard gas chromatogram. Linear fitting is performed on all two-dimensional arrays to obtain the fitting equation.

[0119] It should be noted that the least squares method is used for linear fitting. The least squares method is a well-known technique and will not be elaborated here.

[0120] In this embodiment, the fitting equation is: ,in, This indicates the concentration of vanillin. Peak area;

[0121] The peak area corresponding to the chromatographic peak to be analyzed in the filtered gas chromatogram is substituted into the fitting equation to obtain the concentration of vanillin in the sample solution to be analyzed. Based on the dilution factor and injection volume of the sample solution to be analyzed, the vanillin content in vanilla is determined.

[0122] It should be understood that, although Figure 1The steps in the flowchart are shown sequentially as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order in which these steps are executed, and they can be performed in other orders. Figure 1 At least some of the steps in the process may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least some of the sub-steps or stages of other steps.

[0123] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0124] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application, without departing from the content of the technical solution of this application, shall fall within the protection scope of the technical solution of this application.

Claims

1. A method for determining vanillin content in vanilla using gas chromatography, characterized in that, The method includes the following steps: Chromatograms of the sample solution to be analyzed, the standard solution, and the control solution were obtained and denoted as the gas chromatogram of the sample solution to be analyzed, the standard gas chromatogram, and the control gas chromatogram, respectively. The ambient temperature of the three solutions at each moment during the instrumentation process was also obtained. Based on the size of the peaks in the gas chromatogram to be analyzed, the peaks in the gas chromatogram to be analyzed are screened to obtain significant peaks; the differences between the different significant peaks in the gas chromatogram to be analyzed and the maximum peak value in the standard gas chromatogram at corresponding times are analyzed to obtain the chromatographic peaks to be analyzed in the gas chromatogram to be analyzed. Analyze the difference in peak width between the peak to be analyzed in the gas chromatogram and the maximum peak value in the standard gas chromatogram, as well as the shift at the corresponding time, and calculate the first interference value of the gas chromatogram to be analyzed. Based on the fluctuations of the response values ​​at all times in the reference gas chromatogram and the fluctuations of the ambient temperature during the loading of the reference solution, the temperature influence is calculated. Combined with the differences in the fluctuations of the ambient temperature during the loading of the sample solution and the standard solution, the interference difference of the gas chromatogram to be analyzed is obtained. Combined with the first interference value, the second interference value of the gas chromatogram to be analyzed is determined. The interference coefficient of the gas chromatogram to be analyzed is determined by the discreteness of the response values ​​other than the local range where the significant peak is located and the second interference value in the gas chromatogram to be analyzed. The response of the gas chromatogram to be analyzed is decomposed by wavelet decomposition at all times. The decomposed wavelet coefficients are squared and arranged in ascending order to form a wavelet coefficient vector. For each element in the wavelet coefficient vector, calculate the corresponding risk value. Select the element corresponding to the minimum risk value in the wavelet coefficient vector, denoted as The sum of all elements in the wavelet coefficient vector is denoted as... ;make , The heuristic threshold of the wavelet denoising algorithm It can be represented as: ,in, The length of the wavelet coefficient vector. The interference coefficient is the coefficient mentioned above. This represents the number of times in the gas chromatogram to be analyzed at all time points. Represents the logarithmic function with base 10. This represents the logarithmic function with base 2. This represents the function that takes the minimum value. Represents the square root; The wavelet denoising algorithm was used to filter the gas chromatogram to be analyzed, and the vanillin content in vanilla was determined by using the peak area of ​​the chromatographic peak in the filtered gas chromatogram.

2. The method for determining vanillin content in vanilla using gas chromatography as described in claim 1, characterized in that, The process of obtaining the significant peaks is as follows: obtain the peaks of the response values ​​at all times in the gas chromatogram to be analyzed, obtain the segmentation threshold of the peak values ​​of all peaks in the gas chromatogram to be analyzed, and record the peaks in the gas chromatogram to be analyzed that are greater than or equal to the segmentation threshold as significant peaks.

3. The method for determining vanillin content in vanilla using gas chromatography as described in claim 1, characterized in that, The process of obtaining the chromatographic peaks to be analyzed in the gas chromatogram includes: obtaining the peaks of the response values ​​at all times in the standard gas chromatogram, and recording the peak corresponding to the maximum peak value as the chromatographic peak; calculating the time interval between the time corresponding to each significant peak in the gas chromatogram to be analyzed and the time corresponding to the chromatographic peak in the standard gas chromatogram; and selecting the significant peak corresponding to the minimum time interval as the chromatographic peak to be analyzed.

4. The method for determining vanillin content in vanilla using gas chromatography as described in claim 3, characterized in that, The calculation of the first interference value of the gas chromatogram to be analyzed includes: Calculate the difference between the half-peak width (WHM) of the chromatographic peak in the gas chromatogram to be analyzed and the half-peak width (WHM) of the chromatographic peak in the standard gas chromatogram, and record it as the relative difference. The first interference value is the product of the result of positive mapping of the relative difference and the result of positive mapping of the minimum interval time.

5. The method for determining vanillin content in vanilla using gas chromatography as described in claim 1, characterized in that, The calculation process for the temperature influence is as follows: Calculate the degree of dispersion of the response at all times in the reference gas chromatogram, and denote it as the first degree of dispersion; The dispersion of ambient temperature at all times during the loading of the control solution is calculated and denoted as the second dispersion. The temperature influence is the ratio of the first dispersion to the second dispersion.

6. The method for determining vanillin content in vanilla using gas chromatography as described in claim 1, characterized in that, The degree of interference difference obtained from the gas chromatogram to be analyzed includes: The dispersion of ambient temperature at all times during the process of analyzing the sample solution and the standard solution is calculated and multiplied by the temperature influence, respectively, and used as the relative fluctuation of the gas chromatogram of the sample solution and the standard gas chromatogram. The interference difference is the difference in relative fluctuation between the gas chromatogram to be analyzed and the standard gas chromatogram.

7. The method for determining vanillin content in vanilla using gas chromatography as described in claim 1, characterized in that, Determining the second interference value of the gas chromatogram to be analyzed includes: if the interference difference is 0, the second interference value of the gas chromatogram to be analyzed is the first interference value; otherwise, the second interference value of the gas chromatogram to be analyzed is the ratio of the first interference value to the interference difference.

8. The method for determining vanillin content in vanilla using gas chromatography as described in claim 1, characterized in that, The determination of the interference coefficient of the gas chromatogram to be analyzed includes: The local window is defined as all times within the neighborhood of the time corresponding to each significant peak in the gas chromatogram to be analyzed; the degree of dispersion of the response values ​​of all other times in the gas chromatogram to be analyzed, excluding the times contained in the local windows corresponding to all significant peaks, is defined as the baseline interference of the gas chromatogram to be analyzed. The interference coefficient is the normalized result of the product of the second interference value and the baseline interference degree.

9. The method for determining vanillin content in vanilla using gas chromatography as described in claim 1, characterized in that, The wavelet coefficient vector within the first... Risk value of each element The calculation formula is: ,in, The first wavelet coefficient vector is the first wavelet coefficient vector. The element value corresponding to each element. The first wavelet coefficient vector is the first wavelet coefficient vector. The index of each element. The first wavelet coefficient vector is the first wavelet coefficient vector. The element value corresponding to each element.

Images