A mass spectrometry method for detecting harmful residues in imported and exported food

Abstract

The present invention relates to the technical field of food safety detection, and in particular to a mass spectrometry detection method for harmful residues in imported and exported foods, the method comprising: obtaining the mass-to-charge ratio and relative abundance of heavy metal ions in the mass spectrum of the imported and exported foods to be detected; determining the matching degree between the target heavy metal ions and the standard substance; determining the correction value of the detection result of the target heavy metal ions; determining the matrix effect intensity during the mass spectrometry detection process; constructing the precision loss rate during the mass spectrometry detection process using the correction value, the matching degree and the matrix effect intensity; adjusting the mass spectrometry detection scheme according to the precision loss rate and detecting the imported and exported foods to be detected based on the adjusted mass spectrometry detection scheme. In this way, the present invention improves the detection accuracy, comprehensiveness and reliability of harmful residues in imported and exported foods.

Description

Technical Field

[0001] The present invention relates to the technical field of food safety detection, and in particular to a mass spectrometry detection method for harmful residues in imported and exported food. Background Art

[0002] With the rapid advancement of global trade, food is circulated more and more frequently in society, and food safety issues have become the focus of widespread social attention. In the field of import and export food trade, it is a vital task to ensure that there are no harmful substances in food and to protect the health and safety of consumers. Rapid and accurate screening and quantification of harmful substances in imported and exported food has become the key to food safety.

[0003] In some scenarios, mass spectrometry (MS), as an advanced analytical tool with high sensitivity and high resolution, has emerged in the detection of harmful residues in imported and exported foods and has become one of the mainstream detection technologies because it can simultaneously perform qualitative and quantitative analysis of multiple components in complex samples. However, the existing mass spectrometry technology still has many shortcomings in practical applications. First, the existing methods often target specific types of harmful substances, such as pesticides or veterinary drugs, and it is difficult to cover multiple categories and types of targets at the same time, such as heavy metals, which makes the detection work limited and cannot fully guarantee food safety. Second, when it comes to foods with complex matrices, the existing mass spectrometry technology may experience a decrease in sensitivity, and even lead to missed detection of the detected objects, seriously affecting the accuracy of the test results. Therefore, the detection accuracy, comprehensiveness and reliability of harmful residues in imported and exported foods in the existing methods are relatively low. Summary of the invention

[0004] In order to solve the technical problem of low detection accuracy, comprehensiveness and reliability of harmful residues in imported and exported foods, the purpose of the present invention is to provide a mass spectrometry detection method for harmful residues in imported and exported foods. The technical scheme adopted is as follows:

[0005] The embodiment of the present invention provides a mass spectrometry detection method for harmful residues in imported and exported food, comprising: obtaining the mass-to-charge ratio and relative abundance of heavy metal ions in the mass spectrum of the imported and exported food to be detected; determining the matching degree between the target heavy metal ion and the standard substance according to the mass-to-charge ratio corresponding to the peak point in the mass spectrum, the mass-to-charge ratio of the standard substance, the first relative abundance of the isotope ion of the target heavy metal ion, and the second relative abundance of the isotope ion of the standard substance; determining the correction value of the detection result of the target heavy metal ion according to the half-height width of the peak area of ​​the peak point of the target heavy metal ion, the first relative abundance, and the third relative abundance of the target heavy metal ion; determining the correction value of the detection result of the target heavy metal ion according to the total relative abundance of all numbers in the peak area of ​​the additional signal peak The intensity of the matrix effect in the mass spectrometry detection process is determined based on the first average value of the standard deviation of the points, the third relative abundance and the fourth relative abundance of the additional signal peak, the first concentration and the second concentration of the target heavy metal ion, the first concentration is the concentration before the standard substance is added to the imported and exported food, the second concentration is the concentration after the standard substance is added to the imported and exported food, and the additional signal peak is the peak point other than the peak point corresponding to the target heavy metal ion and the peak point corresponding to the isotope ion; the accuracy loss rate in the mass spectrometry detection process is constructed using the correction value, the matching degree and the matrix effect intensity; the mass spectrometry detection scheme is adjusted according to the accuracy loss rate and the imported and exported food to be detected is detected based on the adjusted mass spectrometry detection scheme.

[0006] Optionally, determining the degree of match between the target heavy metal ion and the standard substance based on the mass-to-charge ratio corresponding to the peak point in the mass spectrum, the mass-to-charge ratio of the standard substance, the first relative abundance of the isotope ions of the target heavy metal ion, and the second relative abundance of the isotope ions of the standard substance includes: determining the absolute value of a first difference between the mass-to-charge ratio corresponding to the peak point in the mass spectrum and the mass-to-charge ratio of the standard substance; determining the probability that the peak point corresponding to the minimum value in the absolute value of the first difference belongs to the target heavy metal ion based on the maximum allowable value of the difference between the mass-to-charge ratio of the ion and the mass-to-charge ratio of the standard substance and the minimum value in the absolute value of the first difference; and when the probability is greater than a first threshold, determining that the peak point corresponding to the minimum value in the absolute value of the first difference belongs to the target heavy metal ion. ion; subtract the mass-to-charge ratio of the peak point corresponding to the minimum value in the absolute value of the first difference from the mass-to-charge ratios corresponding to the other peak points in turn to obtain a second difference, and sort the second difference in ascending order to obtain a data sequence; subtract adjacent second differences in the data sequence to obtain a third difference, determine the first position where the maximum value is located from the third difference, use the second difference before the first position in the data sequence as the mass-to-charge ratio of the isotope ion of the target heavy metal ion, and mark the second position where the mass-to-charge ratio of the isotope ion is located; determine the first relative abundance of the isotope ion at the second position and the second relative abundance of the isotope ion of the standard substance; determine the matching degree between the target heavy metal ion and the standard substance according to the probability, the first relative abundance and the second relative abundance.

[0007] Optionally, based on the maximum allowed value of the difference between the mass-to-charge ratio of the ion and the mass-to-charge ratio of the standard substance and the minimum value of the absolute value of the first difference, determining the probability that the peak point corresponding to the minimum value of the absolute value of the first difference belongs to the target heavy metal ion includes: determining a first ratio between the maximum allowed value and the minimum value of the absolute value of the first difference as the probability that the peak point corresponding to the minimum value of the absolute value of the first difference belongs to the target heavy metal ion.

[0008] Optionally, determining the degree of match between the target heavy metal ion and the standard substance based on the probability, the first relative abundance and the second relative abundance includes: calculating a second average value of the absolute value of the fourth difference between the first relative abundance and the second relative abundance, and a second ratio between the probability and the second average value; normalizing the second ratio to obtain the degree of match between the target heavy metal ion and the standard substance.

[0009] Optionally, determining a correction value of the detection result of the target heavy metal ion based on the half-width of the peak area of ​​the peak point of the target heavy metal ion, the first relative abundance and the third relative abundance of the target heavy metal ion includes: determining the overlap probability of the isotope peaks of the target heavy metal ion based on the half-width of the peak area of ​​the peak point of the target heavy metal ion, the first relative abundance and the third relative abundance of the target heavy metal ion; determining the first product between the matching degree and the overlap probability as the correction value of the detection result of the target heavy metal ion.

[0010] Optionally, determining the overlap probability of the isotope peaks of the target heavy metal ions based on the half-width of the peak area of ​​the peak point of the target heavy metal ion, the first relative abundance and the third relative abundance of the target heavy metal ion includes: calculating the third average of the third ratio between the first relative abundance and the third relative abundance of the target heavy metal ion, and the second product between the third average and the half-width; normalizing the second product to obtain the overlap probability of the isotope peaks of the target heavy metal ion.

[0011] Optionally, determining the intensity of the matrix effect in the mass spectrometry detection process based on the first average value of the standard deviation of all data points in the peak region of the additional signal peak, the third relative abundance and the fourth relative abundance of the additional signal peak, and the first concentration and the second concentration of the target heavy metal ion includes: marking the peak points other than the peak points corresponding to the target heavy metal ions and the peak points corresponding to the isotope ions as additional signal peaks; determining the first average value of the standard deviation of all data points in the peak region of the additional signal peak; determining the expected value of the peak shape of the signal peak in the mass spectrum based on the first average value, the third relative abundance of the target heavy metal ions and the fourth relative abundance of the additional signal peak; measuring the first concentration and the second concentration of the target heavy metal ions by liquid chromatography; and determining the intensity of the matrix effect in the mass spectrometry detection process based on the expected peak shape value, the first concentration and the second concentration.

[0012] Optionally, determining the expected value of the peak shape of the signal peak in the mass spectrum based on the first average value, the third relative abundance of the target heavy metal ion, and the fourth relative abundance of the additional signal peak includes: calculating a fourth ratio between the third relative abundance of the target heavy metal ion and a predetermined multiple of the fourth relative abundance, and a third product between the first average value and the fourth ratio; and determining the reciprocal of the third product as the expected value of the peak shape of the signal peak in the mass spectrum.

[0013] Optionally, determining the intensity of the matrix effect in the mass spectrometry detection process according to the expected peak shape value, the first concentration, and the second concentration includes: calculating the absolute value of the fifth difference between the first concentration and the second concentration; and determining a fifth ratio between the absolute value of the fifth difference and the expected peak shape value as the intensity of the matrix effect in the mass spectrometry detection process.

[0014] Optionally, constructing the precision loss rate in the mass spectrometry detection process using the correction value, the matching degree and the matrix effect intensity includes: calculating the absolute value of the sixth difference between the correction value and the matching degree, and the fourth average value of the fourth product between the absolute value of the sixth difference and the matrix effect intensity; normalizing the fourth average value to obtain the precision loss rate in the mass spectrometry detection process.

[0015] The present invention has the following beneficial effects: firstly, the mass-to-charge ratio and relative abundance of heavy metal ions in the mass spectrum of the imported and exported food to be detected are obtained; then, the matching degree between the target heavy metal ion and the standard substance is determined according to the mass-to-charge ratio corresponding to the peak point in the mass spectrum, the mass-to-charge ratio of the standard substance, the first relative abundance of the isotope ion of the target heavy metal ion and the second relative abundance of the isotope ion of the standard substance; secondly, the correction value of the detection result of the target heavy metal ion is determined according to the half-height width of the peak area of ​​the peak point of the target heavy metal ion, the first relative abundance and the third relative abundance of the target heavy metal ion; and the correction value of the detection result of the target heavy metal ion is determined according to the first relative abundance of all data points in the peak area of ​​the additional signal peak. The intensity of the matrix effect in the mass spectrometry detection process is determined by using an average value, a third relative abundance, and a fourth relative abundance of the additional signal peak, a first concentration and a second concentration of the target heavy metal ion, the first concentration being the concentration before the standard substance is added to the imported and exported food, the second concentration being the concentration after the standard substance is added to the imported and exported food, and the additional signal peak being the peak point other than the peak point corresponding to the target heavy metal ion and the peak point corresponding to the isotope ion; the correction value, the matching degree, and the matrix effect intensity are then used to construct the precision loss rate in the mass spectrometry detection process; finally, the mass spectrometry detection scheme is adjusted according to the precision loss rate, and the imported and exported food to be detected is detected based on the adjusted mass spectrometry detection scheme.

[0016] In this way, the embodiment of the present invention obtains the difference between the mass-to-charge ratio of the peak point and the mass-to-charge ratio of the known standard substance in the mass spectrum of the food sample, and then matches the heavy metal ions in the mass spectrum. The higher the matching degree, the higher the residual possibility of the heavy metal ions. Then the interference caused by the isotope ions of the target heavy metal ions in the detection process is extracted, and then the matching of the target heavy metal ions is corrected according to the interference of the isotope ions. Then the matrix effect intensity is determined by the matrix effect in the extra signal peak in the mass spectrum and the food sample detection process. The stronger the matrix effect intensity, the greater the interference effect caused by the outside world. Finally, by constructing the precision loss rate of the detection accuracy in the detection process, the precision loss rate under the influence of factors such as isotope ion interference and matrix interference is used as a control, and then a more accurate detection is determined and imported food is detected with this. In this way, the embodiment of the present invention can detect heavy metal ions, reduce the detection limitations, and make the detection of imported food more comprehensive. And the interference caused by the matrix effect and the isotope ions is taken into consideration, the influence of the matrix effect on the detection results is reduced, and the detection accuracy, comprehensiveness and reliability of harmful residues in imported and exported food are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 A flow chart of a method for mass spectrometry detection of harmful residues in imported and exported food provided by one embodiment of the present invention;

[0019] Figure 2 A mass spectrum of a food sample provided by one embodiment of the present invention;

[0020] Figure 3 A schematic structural diagram of a mass spectrometry detection system for harmful residues in imported and exported food provided by one embodiment of the present invention. DETAILED DESCRIPTION

[0021] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description of the mass spectrometry detection method for harmful residues in imported and exported food proposed by the present invention, its specific implementation method, structure, characteristics and effects, in conjunction with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0022] Unless defined otherwise, 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 invention belongs.

[0023] The specific scheme of the mass spectrometry detection method for harmful residues in imported and exported food provided by the present invention is described in detail below in conjunction with the accompanying drawings.

[0024] Embodiment 1:

[0025] See also Figure 1 , which shows a flow chart of a method for detecting harmful residues in imported and exported food by mass spectrometry according to an embodiment of the present invention, comprising:

[0026] Step S101, obtaining the mass-to-charge ratio and relative abundance of heavy metal ions in the mass spectrum of the imported or exported food to be tested.

[0027] Specifically, imported and exported foods include but are not limited to solids (such as fruits, vegetables, and grains), liquids (such as beverages, dairy products), or viscous samples (such as honey and sauces). When detecting imported and exported foods, the embodiment of the present invention takes out samples from each imported and exported food and then stores them at low temperature, and marks the food samples, and uses a unique number to record the marking. Then the food sample is processed, specifically diluting the food sample, and then filtering the extract with a 0.22μm or 0.45μm filter membrane to remove particulate matter and prevent clogging of the chromatographic column, and diluting the extract with the removed particulate matter with a suitable mobile phase (such as methanol-water) to the injection concentration, and the processed food sample is placed in the injection bottle for testing. Then the mass-to-charge ratio (m / z) of each target in the processed food sample is detected and a mass spectrum is generated to achieve qualitative and quantitative analysis of the target. Among them, the mass spectrum is a mass-to-charge ratio (m / z) distribution diagram of ions at a certain retention time point, reflecting the various types of ions detected and their intensities. The embodiment of the present invention obtains the mass-to-charge ratio of different heavy metal ions in the mass spectrum according to the relevant regulations on heavy metal ion detection and the experimental results of standard samples (obtained according to the database or literature of standard compounds). Each compound or ion has a specific characteristic peak in the mass spectrum, such as the characteristic m / z value of Pb²⁺ is 207.98, and the characteristic m / z value of Hg²⁺ is 200.59. For example, Figure 2 As shown, Figure 2 A mass spectrum of a food sample provided by one embodiment of the present invention, Figure 2 In the figure, the horizontal axis is the mass-to-charge ratio and the vertical axis is the relative abundance. By obtaining the mass spectrum of the current food sample detection process, the mass-to-charge ratios of all detectable ions in the mass spectrum can be counted.

[0028] Step S102, determining the matching degree between the target heavy metal ion and the standard substance according to the mass-to-charge ratio corresponding to the peak point in the mass spectrum, the mass-to-charge ratio of the standard substance, the first relative abundance of the isotope ion of the target heavy metal ion and the second relative abundance of the isotope ion of the standard substance.

[0029] Specifically, in the embodiment of the present invention, a peak point detection algorithm is used to obtain all peak points in the mass spectrum, and the mass-to-charge ratio m / z value at the peak point is recorded as P. In the embodiment of the present invention, lead ions (Pb) in metal ions are used as known standard substances, and the mass-to-charge ratio of the standard substance is recorded as The difference between a single peak point in the mass spectrum and the mass-to-charge ratio m / z value of the set standard substance is recorded as .

[0030] Further, as an optional embodiment of the present invention, determining the degree of match between the target heavy metal ion and the standard substance according to the mass-to-charge ratio corresponding to the peak point in the mass spectrum, the mass-to-charge ratio of the standard substance, the first relative abundance of the isotope ions of the target heavy metal ion and the second relative abundance of the isotope ions of the standard substance includes: determining the absolute value of the first difference between the mass-to-charge ratio corresponding to the peak point in the mass spectrum and the mass-to-charge ratio of the standard substance; determining the probability that the peak point corresponding to the minimum value in the absolute value of the first difference belongs to the target heavy metal ion according to the maximum allowable value of the difference between the mass-to-charge ratio of the ion and the mass-to-charge ratio of the standard substance and the minimum value in the absolute value of the first difference; when the probability is greater than a first threshold value, determining the peak point corresponding to the minimum value in the absolute value of the first difference. Belonging to the target heavy metal ion; subtract the mass-to-charge ratio of the peak point corresponding to the minimum value in the absolute value of the first difference from the mass-to-charge ratios corresponding to the other peak points in turn to obtain a second difference, and sort the second difference in ascending order to obtain a data sequence; subtract adjacent second differences in the data sequence to obtain a third difference, determine the first position where the maximum value is located from the third difference, use the second difference before the first position in the data sequence as the mass-to-charge ratio of the isotope ion of the target heavy metal ion, and mark the second position where the mass-to-charge ratio of the isotope ion is located; determine the first relative abundance of the isotope ion at the second position and the second relative abundance of the isotope ion of the standard substance; determine the degree of match between the target heavy metal ion and the standard substance based on the probability, the first relative abundance and the second relative abundance.

[0031] Specifically, there is a difference between the mass-to-charge ratios corresponding to all peak points in the mass spectrum and the target heavy metal ions, and then the positions of a group of peaks with the smallest difference are obtained, and the positions are used as the positions of the suspected target heavy metal ions in the mass spectrum. The maximum value of the maximum allowable value of the difference between the mass-to-charge ratio of the ion in the comparison process and the mass-to-charge ratio of the standard substance is then recorded as U. If the mass-to-charge ratio m / z value of the peak point and the target heavy metal ion exceeds the maximum allowable value, it is determined that the heavy metal ion at the peak point does not belong to the target heavy metal ion.

[0032] Further, as an optional embodiment of the present invention, based on the maximum allowed value of the difference between the mass-to-charge ratio of the ion and the mass-to-charge ratio of the standard substance and the minimum value of the absolute value of the first difference, determining the probability that the peak point corresponding to the minimum value of the absolute value of the first difference belongs to the target heavy metal ion includes: determining a first ratio between the maximum allowed value and the minimum value of the absolute value of the first difference as the probability that the peak point corresponding to the minimum value of the absolute value of the first difference belongs to the target heavy metal ion.

[0033] Specifically, the embodiment of the present invention specifically uses the following formula to calculate the probability that the peak point corresponding to the minimum value in the absolute value of the first difference belongs to the target heavy metal ion:

[0034]

[0035] In the above formula, It represents the probability that the heavy metal ion at the location of the e-th peak point belongs to the known target heavy metal ion. It represents the maximum allowable difference between the mass-to-charge ratio of the ions in the mass spectrum and the mass-to-charge ratio of the standard substance. It represents the minimum value among the absolute values ​​of the first difference between the mass-to-charge ratio m / z value of the standard substance and the mass-to-charge ratio m / z values ​​of all heavy metal ions in the mass spectrum. The larger the value of , the closer the mass-to-charge ratio m / z value of the suspected target heavy metal ion in the mass spectrum is to the mass-to-charge ratio m / z value of the standard substance, that is, the higher the probability that the ion at the position of the e-th peak point belongs to the known target heavy metal ion. The bigger.

[0036] Further, when the probability is greater than the first threshold, it is determined that the peak point corresponding to the minimum value in the absolute value of the first difference belongs to the target heavy metal ion. Wherein, the first threshold can be determined according to actual conditions, and the embodiment of the present invention is not limited here. Then the relative abundance of all isotope ions of the target heavy metal ion is obtained, such as the natural abundance of 204 / 206 / 207 / 208 of Pb is 1.4, 24.1, 22.1, 52.4, that is, the intensity ratio of the isotope ions of each heavy metal ion in the mass spectrum is fixed.

[0037] Further, the mass-to-charge ratio of the target heavy metal ion is subtracted from the mass-to-charge ratio of the heavy metal ions at the peak points of the remaining positions, and then the differences are sorted in order from small to large to obtain a new data sequence. Then a set of differences is calculated between two adjacent data in the data sequence, and then the maximum value among all the differences is traversed. The position of the maximum value divides the data sequence into two parts, and the left part is recorded as the isotope ion of the target heavy metal ion represented by the current mass-to-charge ratio, and the position of these isotope ions is marked. Finally, the relative abundance of the marked position of the isotope ion in the mass spectrum is obtained, that is, the ordinate value of the mass spectrum, which is denoted as Q in the embodiment of the present invention, and the relative abundance of the isotope ions of the known standard substances is subtracted in order of the size of the mass-to-charge ratio.

[0038] Further, as an optional embodiment of the present invention, determining the degree of match between the target heavy metal ion and the standard substance based on the probability, the first relative abundance and the second relative abundance includes: calculating the second average value of the absolute value of the fourth difference between the first relative abundance and the second relative abundance, and the second ratio between the probability and the second average value; normalizing the second ratio to obtain the degree of match between the target heavy metal ion and the standard substance.

[0039] Specifically, the embodiment of the present invention specifically uses the following formula to calculate the matching degree between the target heavy metal ion and the standard substance:

[0040]

[0041] In the above formula, Indicates the degree of match between the heavy metal ion at the location of the e-th peak point and the standard substance. It represents the probability that the heavy metal ion at the location of the e-th peak point belongs to the known target heavy metal ion. It represents the first relative abundance of the nth isotope ion of the heavy metal ion at the position of the eth peak point screened out in the mass spectrum. It represents the second relative abundance of the nth isotope ion of the standard substance. Indicates the number of isotope ions. Represents the normalization function, which is used to Perform normalization.

[0042] in, The smaller the value, the closer the relative abundance of the isotope ions of the target heavy metal ions in the mass spectrum is to the relative abundance of the isotope ions of the standard substance, that is, the relative abundance of the isotope ions of the target heavy metal ions conforms to the relative abundance ratio of the standard substance. The larger the value is, the higher the match between the target heavy metal ion in the mass spectrum and the standard substance is, that is, the higher the probability of further verifying that the heavy metal ion at the e-th position in the mass spectrum belongs to the target heavy metal ion, that is, the higher the possibility of the residue of such harmful substances is.

[0043] Step S103, determining a correction value of the detection result of the target heavy metal ion according to the half-height width of the peak area of ​​the peak point of the target heavy metal ion, the first relative abundance, and the third relative abundance of the target heavy metal ion.

[0044] Specifically, the above embodiment of the present invention quantitatively analyzes the target heavy metal ion by the matching degree between the heavy metal ions in the screened mass spectrogram and the standard substance, but it is necessary to exclude the interference of other substances in the process of quantifying the heavy metal content in the food sample by relative abundance, such as the interference of the signal peak of the isotope ion. Therefore, this step analyzes the influence of the signal peak of the isotope ion on the detection process.

[0045] Further, the embodiment of the present invention takes the mass-to-charge ratio of the target heavy metal ion as the starting point, and the mass-to-charge ratio of the last isotope ion marked as the end point, and this range is recorded as the mass-to-charge ratio range of the target heavy metal ion. Within this mass-to-charge ratio range, the signal intensity of the isotope ions is usually proportional to their natural abundance. In some cases, the isotope ions of the target heavy metal ions may have a higher relative abundance, causing the signal intensity of the target heavy metal ions to be "masked" or "enhanced" by the signal of the isotope ions. Therefore, the embodiment of the present invention needs to correct the matching degree according to the interference of the isotope ions.

[0046] Further, as an optional embodiment of the present invention, determining a correction value of the detection result of the target heavy metal ion based on the half-width of the peak area of ​​the peak point of the target heavy metal ion, the first relative abundance and the third relative abundance of the target heavy metal ion includes: determining the overlapping probability of the isotope peaks of the target heavy metal ion based on the half-width of the peak area of ​​the peak point of the target heavy metal ion, the first relative abundance and the third relative abundance of the target heavy metal ion; determining the first product between the matching degree and the overlapping probability as the correction value of the detection result of the target heavy metal ion.

[0047] Specifically, in the embodiment of the present invention, the half-height width of the peak area where the peak point of the target heavy metal ion is located is recorded as the peak width of the target heavy metal ion, that is, half of the height of the peak point is taken as a horizontal line, and there are two intersections between the horizontal line and the peak area, and the width of these two intersections is recorded as the peak width. When calculating the overlap probability, first calculate the third average value of the third ratio between the first relative abundance and the third relative abundance of the target heavy metal ion, and the second product between the third average value and the half-height width; then normalize the second product to obtain the overlap probability of the isotope peak of the target heavy metal ion.

[0048] The embodiment of the present invention specifically uses the following formula to calculate the overlap probability of the isotope peaks of the target heavy metal ions:

[0049]

[0050] In the above formula, Represents the overlap probability of the isotope peaks of the target heavy metal ions. The half-height width of the peak area at the position of the e-th peak point of the target heavy metal ion in the mass spectrum is represented. The peak width is narrow, and different isotope peaks can be separated without overlapping each other. It represents the first relative abundance of the nth isotope ion of the heavy metal ion at the position of the eth peak point screened out in the mass spectrum. represents the third relative abundance of the target heavy metal ion at the location of the e-th peak point. If the peak of the isotope ion is greater than the peak of the target heavy metal ion, it may mask the target heavy metal ion, thereby causing errors in the measurement process. The larger the product of , the greater the probability of overlap between the isotopes of the target heavy metal ions during mass spectrometry detection, that is, the larger z is, which means that the isotope ions will cause greater interference to the mass spectrometry detection of the target heavy metal ions, which may cause the final measurement result of the target heavy metal ions to be too large and not meet expectations. represents the hyperbolic tangent function, which is used to Perform normalization.

[0051] Furthermore, the embodiment of the present invention uses the following formula to calculate the correction value of the detection result of the target heavy metal ion:

[0052]

[0053] In the above formula, Indicates the correction value of the detection result of the target heavy metal ion at the location of the e-th peak point. Indicates the degree of match between the heavy metal ion at the location of the e-th peak point and the standard substance. It represents the overlap probability of the isotope peaks of the target heavy metal ion, which represents the interference of the isotope ion of the e-th target heavy metal ion on the target heavy metal ion during the mass spectrometry detection process, mainly to correct the matching degree of the target heavy metal ion, that is, The larger the product, the higher the possibility of the heavy metal ion residue in the mass spectrometry detection process and the higher the credibility. If there are some irregular or abnormal signal peaks within the expected mass-to-charge ratio range of the target heavy metal ion and isotope ion, and these signal peaks do not conform to the normal distribution of isotope ions, it is possible that there is more external interference in the mass spectrometry detection process.

[0054] Step S104, determining the intensity of the matrix effect in the mass spectrometry detection process according to the first average value of the standard deviation of all data points in the peak region of the additional signal peak, the third relative abundance, the fourth relative abundance of the additional signal peak, the first concentration and the second concentration of the target heavy metal ion.

[0055] Among them, the first concentration is the concentration before the standard substance is added to the imported and exported food, the second concentration is the concentration after the standard substance is added to the imported and exported food, and the additional signal peak is the peak point other than the peak point corresponding to the target heavy metal ion and the peak point corresponding to the isotope ion.

[0056] Specifically, the purpose of this step is to evaluate the signal peaks within the mass-to-charge ratio range of the target heavy metal ions and isotope ions during mass spectrometry detection, as well as the matrix effect during mass spectrometry detection, and then evaluate the amount of interference generated during the mass spectrometry process, providing support data for subsequent improvement of mass spectrometry detection accuracy. Among them, the matrix contains a large number of substances that may compete with the target heavy metal ions for ionization, such as fats, proteins, and salts. These substances will reduce the ionization efficiency of the target heavy metal ions, thereby affecting the intensity of the mass spectrometry signal. The complexity of the food matrix may significantly interfere with the mass spectrometry signal, resulting in deviations in the detection results or reduced sensitivity, especially when detecting low-concentration targets. The matrix effect may lead to false positive or false negative results.

[0057] Further, as an optional embodiment of the present invention, determining the intensity of the matrix effect in the mass spectrometry detection process according to the first average value of the standard deviation of all data points in the peak region of the additional signal peak, the third relative abundance and the fourth relative abundance of the additional signal peak, the first concentration and the second concentration of the target heavy metal ion includes: marking the peak points other than the peak points corresponding to the target heavy metal ions and the peak points corresponding to the isotope ions as additional signal peaks; determining the first average value of the standard deviation of all data points in the peak region of the additional signal peak; determining the expected value of the peak shape of the signal peak in the mass spectrum according to the first average value, the third relative abundance of the target heavy metal ions and the fourth relative abundance of the additional signal peak; measuring the first concentration and the second concentration of the target heavy metal ions by liquid chromatography; determining the intensity of the matrix effect in the mass spectrometry detection process according to the expected value of the peak shape, the first concentration and the second concentration.

[0058] Specifically, in the embodiment of the present invention, within the mass-to-charge ratio range of the target heavy metal ions screened out above, in addition to the signal peaks of the target heavy metal ions and isotope ions, additional signal peaks appearing within the marking range. Then the waveform characteristics of the single additional signal peak are extracted, such as: extracting the standard deviation of all data points in the peak area of ​​the single additional signal peak and the relative abundance at the peak point of the single additional signal peak. Then evaluate the peak shape of the additional signal peak that appears within the mass-to-charge ratio range. Under normal circumstances, the signal of the target heavy metal ion is usually regular and matches the mass-to-charge ratio m / z value of the known standard substance. If the morphology of the additional signal peak does not match the expected, it means that it is subject to external interference.

[0059] Further, as an optional embodiment of the present invention, determining the expected value of the peak shape of the signal peak in the mass spectrum based on the first average value, the third relative abundance of the target heavy metal ion and the fourth relative abundance of the additional signal peak includes: calculating a fourth ratio between the third relative abundance of the target heavy metal ion and a predetermined multiple of the fourth relative abundance, and a third product between the first average value and the fourth ratio; determining the reciprocal of the third product as the expected value of the peak shape of the signal peak in the mass spectrum.

[0060] Specifically, the predetermined multiple in the embodiment of the present invention can be set to 2. The embodiment of the present invention specifically uses the following formula to calculate the expected value of the peak shape of the signal peak in the mass spectrum:

[0061]

[0062] In the above formula, Represents the expected value of the peak shape of the signal peak in the mass spectrum. It represents the first average value of the standard deviation of the additional signal peaks appearing in the mass-to-charge ratio range of the target heavy metal ion. represents the third relative abundance of the target heavy metal ion at the location of the e-th peak point. W represents the fourth relative abundance at a single additional signal peak. The larger the product is, the lower the expected value of the peak shape of the signal peak in the mass spectrum is. That is to say, in addition to the signal peak of the target heavy metal ion, there are unexpected signal peaks in the mass spectrum, which means that there may be more external interference in the mass spectrometry detection process.

[0063] Furthermore, in the embodiment of the present invention, the concentration of the target heavy metal ion before and after the addition of the standard substance to the food sample is measured by liquid chromatography. In the embodiment of the present invention, the concentration of the target heavy metal ion after the addition of the standard substance is recorded as , the concentration of the target heavy metal ion before adding the standard substance is recorded as .

[0064] Further, as an optional embodiment of the present invention, determining the intensity of the matrix effect in the mass spectrometry detection process according to the expected peak shape value, the first concentration, and the second concentration includes: calculating the absolute value of the fifth difference between the first concentration and the second concentration; and determining the fifth ratio between the absolute value of the fifth difference and the expected peak shape value as the intensity of the matrix effect in the mass spectrometry detection process.

[0065] Specifically, the embodiment of the present invention specifically uses the following formula to calculate the matrix effect intensity during mass spectrometry detection:

[0066]

[0067] In the above formula, It indicates the matrix effect intensity of the target heavy metal ion at the location of the e-th peak point during mass spectrometry detection. Represents the expected value of the peak shape of the signal peak in the mass spectrum. Indicates the second concentration of the target heavy metal ion after adding the standard substance. Indicates the first concentration of the target heavy metal ion before adding the standard substance.

[0068] in, The larger the difference, the more complex the matrix of the food sample is, resulting in a larger difference in the results before and after mass spectrometry detection. The larger the product of , the stronger the matrix effect introduced in the mass spectrometry detection process, that is, the greater the impact of external interference.

[0069] Step S105, constructing the precision loss rate in the mass spectrometry detection process using the correction value, the matching degree and the matrix effect strength.

[0070] Specifically, the purpose of this step is to observe the impact of external interference on the mass spectrometry detection process. The presence of influencing factors will affect the quality of the mass spectrometry signal, resulting in inaccurate quantitative analysis and difficulty in signal resolution, thereby reducing the sensitivity, accuracy and reliability of monitoring. Removing interference can improve the accuracy of harmful residue detection in food.

[0071] Further, as an optional embodiment of the present invention, constructing the precision loss rate in the mass spectrometry detection process using the correction value, matching degree and matrix effect intensity includes: calculating the absolute value of the sixth difference between the correction value and the matching degree, and the fourth average value of the fourth product between the absolute value of the sixth difference and the matrix effect intensity; normalizing the fourth average value to obtain the precision loss rate in the mass spectrometry detection process.

[0072] Specifically, the embodiment of the present invention specifically uses the following formula to calculate the precision loss rate during mass spectrometry detection:

[0073]

[0074] In the above formula, Indicates the accuracy loss rate during mass spectrometry detection. Indicates the correction value of the detection result of the target heavy metal ion at the location of the e-th peak point. Indicates the degree of match between the heavy metal ion at the location of the e-th peak point and the standard substance. It indicates the matrix effect intensity of the target heavy metal ion at the location of the e-th peak point during mass spectrometry detection. represents the hyperbolic tangent function, which is used to Perform normalization.

[0075] in, It represents the accuracy loss rate during the mass spectrometry detection of the current food sample. The higher the average value, the higher the accuracy loss rate during the detection process, that is, there is greater external interference.

[0076] Step S106, adjusting the mass spectrometry detection scheme according to the accuracy loss rate and detecting the imported and exported food to be detected based on the adjusted mass spectrometry detection scheme.

[0077] Specifically, the embodiment of the present invention obtains the precision loss rate of the current food sample according to the detection process of the current food sample, and then conducts experiments through different food samples and different equipment parameters, and uses the detected precision loss rate as a control for the experimental results. By changing the solvent gradient, sample concentration, mass spectrometer resolution and other parameters, the precision loss rate in the mass spectrometer detection process is compared to obtain the best detection equipment parameter setting scheme to ensure the accuracy of the detection process of harmful residues in imported and exported food. For example, by adjusting the ion source parameters (such as spray voltage, atomizing gas flow rate, temperature) or optimizing the liquid chromatography conditions to improve the separation of heavy metal ions, by increasing the organic phase ratio, the retention time can be shortened, but it is necessary to pay attention to whether co-elution interference will be introduced. By setting a gradient elution program, the organic phase ratio is gradually increased to separate complex components. The precision loss rate of the detection is compared during the process of changing the conditions, that is, a group of mass spectrometer detection schemes with the smallest precision loss rate are used as reference schemes for the harmful residue-free mass spectrometer detection method.

[0078] It is worth noting that, according to actual conditions, the mass spectrometry detection scheme may also have other adjustment methods, which are not limited in the embodiments of the present invention.

[0079] The embodiment of the present invention obtains the difference between the mass-to-charge ratio of the peak point and the mass-to-charge ratio of the known standard substance in the mass spectrum of the food sample, and then matches the heavy metal ions in the mass spectrum. The higher the matching degree, the higher the residual possibility of the heavy metal ions. Then the interference caused by the isotope ions of the target heavy metal ions in the detection process is extracted, and then the matching of the target heavy metal ions is corrected according to the interference of the isotope ions. Then the matrix effect intensity is determined by the matrix effect in the extra signal peak in the mass spectrum and the food sample detection process. The stronger the matrix effect intensity, the greater the interference effect caused by the outside world. Finally, by constructing the precision loss rate of the detection accuracy in the detection process, the precision loss rate under the influence of factors such as isotope ion interference and matrix interference is used as a control, and then a more accurate detection is determined and imported food is detected with this. In this way, the embodiment of the present invention can detect heavy metal ions, reduce the detection limitations, and make the detection of imported food more comprehensive. And the interference caused by the matrix effect and the isotope ions is taken into consideration, the influence of the matrix effect on the detection results is reduced, and the detection accuracy, comprehensiveness and reliability of harmful residues in imported and exported food are improved.

[0080] Embodiment 2:

[0081] Corresponding to the mass spectrometry detection method for harmful residues in imported and exported foods provided in the above embodiment, based on the same technical concept, an embodiment of the present invention further provides a mass spectrometry detection system for harmful residues in imported and exported foods, which is used to execute the mass spectrometry detection method for harmful residues in imported and exported foods. Figure 3 A schematic diagram of a mass spectrometry detection system for harmful residues in imported and exported food provided by an embodiment of the present invention is shown in FIG. Figure 3 As shown in the hardware level, the mass spectrometry detection system for harmful residues in imported and exported food includes a processor, and optionally, an internal bus, a network interface, and a memory. Among them, the memory may include a memory, such as a high-speed random access memory (RAM), and may also include a non-volatile memory (non-volatile memory), such as at least one disk storage, etc. Of course, the mass spectrometry detection system for harmful residues in imported and exported food may also include hardware required for other businesses.

[0082] The processor, network interface and memory can be interconnected through an internal bus, which can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus. The bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, only one bidirectional arrow is used in the figure, but it does not mean that there is only one bus or one type of bus.

[0083] The memory is used to store programs. Specifically, the program may include program code, and the program code includes computer operation commands. The memory may include internal memory and non-volatile memory, and provide instructions and data to the processor.

[0084] The processor reads the corresponding computer program from the non-volatile memory into the memory and then runs it, forming a device for locating the specified user at the logical level. The processor executes the program stored in the memory and is specifically used to execute: Figure 1 The method disclosed in the illustrated embodiment implements the functions and beneficial effects of each method in the previous method embodiments, which will not be described in detail here.

[0085] It should be noted that the mass spectrometry detection system for harmful residues in imported and exported foods provided by an embodiment of the present invention and the mass spectrometry detection method for harmful residues in imported and exported foods provided by an embodiment of the present invention are based on the same application concept. Therefore, the specific implementation of this embodiment can refer to the implementation of the aforementioned mass spectrometry detection method for harmful residues in imported and exported foods, and has the same or similar beneficial effects, and the repeated parts will not be repeated.

[0086] It should be noted that the sequence of the above embodiments of the present invention is only for description and does not represent the advantages and disadvantages of the embodiments. The processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0087] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

Claims

1. A mass spectrometry method for detecting harmful residues in imported and exported food, characterized in that: The mass spectrometry detection method for harmful residues in imported and exported food comprises: Obtain the mass-to-charge ratio and relative abundance of heavy metal ions in the mass spectrum of the imported and exported food to be tested; Determining the degree of match between the target heavy metal ion and the standard substance according to the mass-to-charge ratio corresponding to the peak point in the mass spectrum, the mass-to-charge ratio of the standard substance, the first relative abundance of the isotope ion of the target heavy metal ion, and the second relative abundance of the isotope ion of the standard substance; Determining a correction value of the detection result of the target heavy metal ion according to the half-height width of the peak area of ​​the peak point of the target heavy metal ion, the first relative abundance, and the third relative abundance of the target heavy metal ion; Determine the intensity of the matrix effect in the mass spectrometry detection process according to the first average value of the standard deviation of all data points in the peak region of the additional signal peak, the third relative abundance, and the fourth relative abundance of the additional signal peak, the first concentration and the second concentration of the target heavy metal ion, wherein the first concentration is the concentration before the standard substance is added to the imported or exported food, the second concentration is the concentration after the standard substance is added to the imported or exported food, and the additional signal peak is the peak point other than the peak point corresponding to the target heavy metal ion and the peak point corresponding to the isotope ion; The accuracy loss rate in the mass spectrometry detection process is constructed using the correction value, the matching degree and the matrix effect strength; The mass spectrometry detection scheme is adjusted according to the precision loss rate, and the imported and exported food to be detected is detected based on the adjusted mass spectrometry detection scheme.

2. The mass spectrometry method for detecting harmful residues in imported and exported food according to claim 1, characterized in that: Determining the degree of match between the target heavy metal ion and the standard substance according to the mass-to-charge ratio corresponding to the peak point in the mass spectrum, the mass-to-charge ratio of the standard substance, the first relative abundance of the isotope ion of the target heavy metal ion, and the second relative abundance of the isotope ion of the standard substance comprises: Determine an absolute value of a first difference between the mass-to-charge ratio corresponding to the peak point in the mass spectrum and the mass-to-charge ratio of the standard substance; Determine the probability that the peak point corresponding to the minimum value in the absolute value of the first difference belongs to the target heavy metal ion according to the maximum allowable value of the difference between the mass-to-charge ratio of the ion and the mass-to-charge ratio of the standard substance and the minimum value in the absolute value of the first difference; When the probability is greater than a first threshold, determining that the peak point corresponding to the minimum value in the absolute value of the first difference belongs to the target heavy metal ion; Subtract the mass-to-charge ratio of the peak point corresponding to the minimum value in the absolute value of the first difference from the mass-to-charge ratios corresponding to the other peak points in sequence to obtain a second difference, and sort the second differences in ascending order to obtain a data sequence; Subtracting adjacent second difference values ​​in the data sequence to obtain a third difference value, determining a first position where a maximum value is located from the third difference value, taking the second difference value before the first position in the data sequence as the mass-to-charge ratio of the isotope ion of the target heavy metal ion, and marking the second position where the mass-to-charge ratio of the isotope ion is located; determining a first relative abundance of the isotope ions at the second position and a second relative abundance of the isotope ions of the standard substance; A matching degree between the target heavy metal ion and the standard substance is determined according to the probability, the first relative abundance, and the second relative abundance.

3. The method for detecting harmful residues in imported and exported food by mass spectrometry according to claim 2, characterized in that: Determining the probability that the peak point corresponding to the minimum value in the absolute value of the first difference belongs to the target heavy metal ion according to the maximum allowable value of the difference between the mass-to-charge ratio of the ion and the mass-to-charge ratio of the standard substance and the minimum value in the absolute value of the first difference comprises: A first ratio between the maximum allowable value and the minimum value among the absolute values ​​of the first differences is determined as a probability that the peak point corresponding to the minimum value among the absolute values ​​of the first differences belongs to the target heavy metal ion.

4. The mass spectrometry method for detecting harmful residues in imported and exported food according to claim 2, characterized in that: Determining the matching degree between the target heavy metal ion and the standard substance according to the probability, the first relative abundance, and the second relative abundance includes: calculating a second average of absolute values ​​of fourth differences between the first relative abundance and the second relative abundance, and a second ratio between the probability and the second average; The second ratio is normalized to obtain a matching degree between the target heavy metal ion and the standard substance.

5. The method for detecting harmful residues in imported and exported food by mass spectrometry according to claim 1, characterized in that: The step of determining the correction value of the detection result of the target heavy metal ion according to the half-height width of the peak area of ​​the peak point of the target heavy metal ion, the first relative abundance, and the third relative abundance of the target heavy metal ion includes: Determining the overlap probability of the isotope peaks of the target heavy metal ion according to the half-height width of the peak area of ​​the peak point of the target heavy metal ion, the first relative abundance, and the third relative abundance of the target heavy metal ion; A first product between the matching degree and the overlap probability is determined as a correction value of the detection result of the target heavy metal ion.

6. The method for detecting harmful residues in imported and exported food by mass spectrometry according to claim 5, characterized in that: Determining the overlap probability of the isotope peaks of the target heavy metal ion according to the half-height width of the peak area of ​​the peak point of the target heavy metal ion, the first relative abundance, and the third relative abundance of the target heavy metal ion includes: Calculating a third average of a third ratio between the first relative abundance and a third relative abundance of the target heavy metal ion, and a second product between the third average and the half-height width; The second product is normalized to obtain the overlap probability of the isotope peaks of the target heavy metal ion.

7. The method for detecting harmful residues in imported and exported food by mass spectrometry according to any one of claims 1 to 6, characterized in that: Determining the intensity of the matrix effect in the mass spectrometry detection process according to the first average value of the standard deviation of all data points in the peak region of the additional signal peak, the third relative abundance, the fourth relative abundance of the additional signal peak, the first concentration and the second concentration of the target heavy metal ion comprises: Marking peak points other than the peak point corresponding to the target heavy metal ion and the peak point corresponding to the isotope ion as additional signal peaks; determining a first average of standard deviations of all data points within a peak region of the additional signal peak; Determining an expected value of a peak shape of a signal peak in the mass spectrum according to the first average value, the third relative abundance of the target heavy metal ion, and the fourth relative abundance of the additional signal peak; measuring a first concentration and a second concentration of the target heavy metal ion by liquid chromatography; The intensity of the matrix effect during mass spectrometry detection is determined according to the expected peak shape value, the first concentration, and the second concentration.

8. The method for detecting harmful residues in imported and exported food by mass spectrometry according to claim 7, characterized in that: Determining the expected value of the peak shape of the signal peak in the mass spectrum according to the first average value, the third relative abundance of the target heavy metal ion, and the fourth relative abundance of the additional signal peak includes: Calculating a fourth ratio between a third relative abundance of the target heavy metal ion and a fourth relative abundance of a predetermined multiple, and a third product between the first average value and the fourth ratio; The reciprocal of the third product is determined as the expected value of the peak shape of the signal peak in the mass spectrum.

9. The method for detecting harmful residues in imported and exported food by mass spectrometry according to claim 7, characterized in that: Determining the intensity of the matrix effect in the mass spectrometry detection process according to the expected peak shape value, the first concentration, and the second concentration includes: calculating an absolute value of a fifth difference between the first concentration and the second concentration; A fifth ratio between the absolute value of the fifth difference and the expected value of the peak shape is determined as the intensity of the matrix effect in the mass spectrometry detection process.

10. The method for detecting harmful residues in imported and exported food by mass spectrometry according to any one of claims 1 to 6, characterized in that: The accuracy loss rate in the mass spectrometry detection process constructed by using the correction value, the matching degree and the matrix effect strength includes: calculating an absolute value of a sixth difference between the correction value and the degree of matching, and a fourth average value of a fourth product between the absolute value of the sixth difference and the matrix effect intensity; The fourth average value is normalized to obtain the precision loss rate in the mass spectrometry detection process.

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