Mineral oil automatic detection method and device based on secondary difference quotient filtering and medium

Abstract

The invention relates to the technical field of mineral oil detection, and provides a mineral oil automatic detection method and equipment based on quadratic difference quotient filtration and a medium, which can automatically judge the hump contour and content calculation of mineral oil detection chromatographic data, reduce the reproducibility difference caused by manual hump judgment, greatly improve the detection speed and reduce the detection cost. And the working efficiency of daily detection is improved. According to the method, the characteristic that the quadratic difference quotient of the peak is a relatively large negative value is utilized, and multiple times of quadratic difference quotient filtering are performed on the valley point sequence of the chromatographic data, so that a correct hump contour is obtained. The content of the mineral oil can be automatically calculated by integrating the area between the hump contour and the base line and combining the mass and the peak area of the quantitative internal standard, the sample weighing amount and the dilution multiple of the quantitative internal standard.

Description

Technical Field

[0001] The invention relates to the technical field of mineral oil detection, and in particular to a mineral oil automatic detection method, equipment and medium based on secondary difference quotient filtering. Background Art

[0002] Mineral oil is a hydrocarbon contaminant commonly found in food and paper food packaging materials, which can be roughly divided into two parts: saturated hydrocarbons (MOSH) and aromatic hydrocarbons (MOAH). Because mineral oil (especially the 3-7 ring MOAH part) is carcinogenic and genotoxic, the EU has gradually tightened its regulation of mineral oil in the past decade. Since the chemical composition of mineral oils from different sources varies greatly and will continue to change with the development of the petrochemical industry, it is difficult to find standard substances to match them. Therefore, commonly used selective detectors such as ultraviolet, fluorescence and mass spectrometry cannot measure mineral oil. At present, the hydrogen flame ionization detector (FID) is recognized as an ideal detector for the determination of mineral oil, because its response to all hydrocarbons is almost exactly the same, and no reference substance is required. Quantitative analysis can be achieved using internal standards. GC-FID spectrum of mineral oil Figure 1 Generally, it presents an unseparable hump of approximately normal distribution. Find an internal standard outside the hump and use its peak area to achieve quantitative analysis of mineral oil. However, FID is a general detector and cannot distinguish mineral oil from non-mineral oil. Although saponification or silica gel, activated alumina and epoxidation methods have been developed to remove mineral oil analysis interferences such as triglycerides, natural alkanes and inherent alkenes in food, there are still synthetic hydrocarbons such as POH, PAO and ROH that cannot be separated and removed, which will interfere with the accurate identification of mineral oil hump. In addition, natural sterenes that are difficult to epoxidize also interfere with the hump of MOAH. The chromatograms of these interferences often present a wide clustered peak shape, which creates a "gap" in the hump and affects the identification of the hump contour. The calculation of mineral oil content requires the use of the integrated area between the hump contour and the baseline of the chromatographic data, but there are usually many peaks on the hump of the chromatogram, and a large number of peaks merge to form a gap above the hump. Experienced experimental personnel are required to remove these gaps and judge the hump contour. The contour division and area integration of the hump are highly subjective, and require experienced experimenters to obtain more accurate results. However, the uncertainty caused by human judgment of the hump will lead to poor reproducibility of mineral oil analysis results. Summary of the invention

[0003] In view of this, the present invention provides a method, device and medium for automatic detection of mineral oil based on quadratic difference quotient filtering, which can automatically determine the hump contour and content calculation of mineral oil detection chromatographic data, reduce the reproducibility difference caused by manual hump identification, and greatly improve the detection speed and the work efficiency of daily detection.

[0004] An automatic detection method for mineral oil based on second-order difference quotient filtering performs multiple second-order difference quotient filtrations on the valley point sequence of chromatographic data to obtain the correct hump profile; by integrating the area between the hump profile and the baseline, combining the mass of the quantitative internal standard, its peak area, the sample weighing amount, and the dilution factor, the content of the mineral oil is calculated.

[0005] Among them, the steps to obtain the correct hump profile are as follows: First, find the valley points in the effective area and establish the basic profile of the mineral oil hump; then filter the invalid points in the basic profile to remove the invalid valley points and determine the accurate mineral oil spectral line.

[0006] Among them, the process of finding the valley points in the effective area is specifically as follows:

[0007] The chromatographic data for mineral oil detection is defined as a data sequence:

[0008]

[0009] where x i represents the time corresponding to the data, in minutes; y i is the data generated by the detector, which is the potential data corresponding to the detector, in microvolts (μV).

[0010] In the first 7 minutes of this data sequence, when x reaches about 10 minutes, the y value generates the first local minimum point, and its number in the data sequence is where is 1 - 2 minutes; when x reaches about 22 minutes in this data sequence, the y value generates the last local minimum point; if the y value is monotonically decreasing when x is about 22 minutes, the rightmost point of the search interval determined by the detector is regarded as the minimum point, and its number in the data sequence is J1 = {j|y j = min(y (x) , 22 - Ax < x < 22 + Δx)}, and the area corresponding to the range of the two minimum points is the effective area of the mineral oil chromatographic data;

[0011] Discriminate the valley point sequence of the y value within the area corresponding to the hump:

[0012]

[0013] The valley points formed by the mineral oil detection chromatogram reflect the basic profile.

[0014] Among them, the process of filtering the invalid points in the basic profile to remove the invalid valley points is specifically as follows:

[0015] Perform second-order difference quotient filtering on the valley point sequence to remove these invalid valley points, and the calculation method of the second-order difference quotient of the sequence is as follows:

[0016]

[0017] Among them, D0 is the discrimination threshold set by professionals based on experience, which is a negative number. When the second-order difference quotient of a point in the valley point sequence is less than D0, it is considered to be an invalid valley point and is removed from the sequence. The algorithm sets the degree of shielding of gaps by adjusting the threshold D0. The smaller the absolute value of the threshold, the greater the shielding degree; the larger the absolute value of the threshold, the smaller the shielding degree.

[0018] Among them, the valley point sequence is filtered by forward, reverse and forward three-way difference quotient filtering to remove all gaps in the chromatographic data; for some special gaps, if the removal effect is not good, the threshold D0 is adjusted to increase or decrease the degree of gap removal, thereby optimizing the mineral oil spectrum.

[0019] Among them, the baseline corresponding to the actual experimental conditions is tested, the baseline data is loaded before the integral is calculated, and a quadratic curve fitting is performed on the baseline data;

[0020] When calculating numerical integrals, calculate the corresponding y value on the broken line at the specific integral position:

[0021]

[0022] Among them, j is the number of the corresponding data point on the polyline;

[0023] For the loaded data baseline, record the three parameters of the quadratic curve fitting, and directly use the quadratic curve formula to calculate the y value corresponding to the numerical integral:

[0024] y=P0+P1x+P2x 2

[0025] The upper and lower boundaries of the numerical integration are determined by determining the mineral oil spectrum line and the baseline, and then the integral area between the mineral oil spectrum line and the baseline is calculated.

[0026] Among them, when calculating the integrated area between two carbon number spectral lines separately, the carbon number spectrum is loaded, and the peak positions corresponding to different carbon numbers are formed thereby.

[0027] When calculating the content of mineral oil by the integrated area between the mineral oil spectrum and the baseline, an internal standard substance is added, wherein cyclohexylcyclohexane (Cycy) is used as the internal standard for MOSH detection, and 2-methylnaphthalene (2MN) or 1,3,5-tri-tert-butylbenzene (TBB) is used as the internal standard for MOAH;

[0028] The software that comes with the gas chromatograph workstation directly calculates the peak area corresponding to the internal standard and stores it in the chromatographic data file; when loading the test data, the internal standard peak area is directly read into the computer memory;

[0029] In the process of processing the test data, input the internal standard mass M ISTD (ng) and sample mass M smp (g);

[0030] According to the mineral oil spectrum area A smp and the peak area A of the standard substance ISTD , calculate the content of mineral oil in the sample: A secondary integration is performed using the software that comes with the gas chromatograph workstation, which integrates the total area of ​​the mineral oil and the interfering peaks on it, then integrates the area of ​​the peak, and subtracts the two to get the area of ​​the mineral oil. Then, a fixed application formula is designed using Excel, and the mineral oil content is calculated using Excel based on the internal standard mass, sample mass, mineral oil area, and peak area of ​​the standard substance.

[0031] An electronic device of the present invention comprises a processor and a memory for storing executable instructions of the processor; the processor is used to read the executable instructions from the memory and execute the instructions to implement the automatic detection method of mineral oil based on quadratic difference quotient filtering of the present invention.

[0032] A computer-readable storage medium of the present invention stores a computer program, and the computer program is used to execute the mineral oil automatic detection method based on quadratic difference quotient filtering of the present invention.

[0033] Beneficial effects:

[0034] 1. The method of the present invention utilizes the characteristic that the quadratic difference quotient of the peak is a large negative value, and performs multiple quadratic difference quotient filtering on the valley point sequence of the chromatographic data, thereby obtaining the correct hump profile. By integrating the area between the hump profile and the baseline, combined with the mass of the quantitative internal standard and its peak area, the sample weight and the dilution multiple, the mineral oil content can be automatically calculated.

[0035] 2. In the method of the present invention, it is found through experiments that all gaps in the chromatographic data can be basically removed by filtering the valley point sequence in the forward, reverse and forward directions. At the same time, for some special gaps, if the removal effect is not good, the threshold D0 can be appropriately adjusted to increase or decrease the degree of removal of the gap, thereby optimizing the mineral oil spectrum.

[0036] 3. In the method of the present invention, in order to ensure the reliability of the detection, the corresponding baseline is specifically tested for the actual test conditions. In this case, the baseline data is loaded before the integral is calculated, and a quadratic curve is fitted to the baseline data to meet the shape requirements.

[0037] 4. The device of the present invention is used to implement the method of the present invention, and utilizes the characteristic that the quadratic difference quotient of the sharp peak is a large negative value, and performs multiple quadratic difference quotient filtering on the valley point sequence of the chromatographic data, thereby obtaining a correct hump profile. By integrating the area between the hump profile and the baseline, combined with the mass of the quantitative internal standard and its peak area, the sample weight and the dilution multiple, the mineral oil content can be automatically calculated.

[0038] 5. The present invention implements the method of the present invention through software, which can automatically complete the determination and area integration of mineral oil spectral lines, and read the peak area of ​​the standard substance in the chromatographic data file. The experimenter only needs to input the internal standard mass and sample weight on the interface, and the software can automatically complete the calculation of the mineral oil content.

[0039] 6. The medium of the present invention is used to implement the method of the present invention, and the characteristic that the quadratic difference quotient of the sharp peak is a large negative value is utilized to perform multiple quadratic difference quotient filtering on the valley point sequence of the chromatographic data, thereby obtaining a correct hump profile. By integrating the area between the hump profile and the baseline, combined with the mass of the quantitative internal standard and its peak area, the sample weight and the dilution multiple, the mineral oil content can be automatically calculated. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic diagram of the mineral oil detection chromatogram and its data valid area in an embodiment of the present invention.

[0041] Figure 2 This is a schematic diagram of valley points formed in a mineral oil detection chromatogram according to an embodiment of the present invention.

[0042] Figure 3 Schematic diagram of the envelope corresponding to the mineral oil detection hump in an embodiment of the present invention.

[0043] Figure 4 Schematic diagram of the hump envelope and automatic baseline in the mineral oil detection chromatogram according to an embodiment of the present invention.

[0044] Figure 5 This is a schematic diagram of baseline data for mineral oil detection according to an embodiment of the present invention.

[0045] Figure 6 This is a schematic diagram of the mineral oil detection baseline data curve fitting in an embodiment of the present invention.

[0046] Figure 7 Schematic diagram of carbon number position in an embodiment of the present invention.

[0047] Figure 8 This is a schematic diagram of the integral area defined by carbon number in an embodiment of the present invention.

[0048] Fig. 9 Schematic diagram of mineral oil content detection and analysis software according to an embodiment of the present invention.

[0049] Fig.10 A schematic diagram of the structure of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0050] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0051] The present invention provides an automatic detection method for mineral oil based on quadratic difference quotient filtering, which automatically determines the hump profile and calculated content of mineral oil detection chromatographic data, reduces the reproducibility difference caused by manual hump identification, and greatly improves the detection speed and the work efficiency of daily detection. The specific implementation steps of the method of the present invention are as follows:

[0052] Step 1, automatically establish the mineral oil spectrum: first find the valley points in the effective area and establish the basic outline of the mineral oil hump; then filter the invalid points in the basic outline, remove the invalid valley points, and determine the accurate mineral oil spectrum.

[0053] The process of finding the valley point in the effective area is as follows:

[0054] The chromatogram data of mineral oil detection can be defined as a data sequence:

[0055]

[0056] where x i Represents the time corresponding to the data, in minutes; y i The data generated by the detector is generally the potential data corresponding to the detector, with microvolts (μV) as the unit. In this embodiment, for the convenience of display, the microvolts are converted to millivolts (mV) on the display interface when processing data, that is, 1000 times the microvolts. When calculating the integrated area, in order to maintain consistency with the chromatographic instrument, the ordinate retains the original microvolt unit; the abscissa is converted to seconds; thus, the unit of the integrated area of ​​the spectral line is microvolts per second (s˙μV).

[0057] The first 7 minutes of data in this data sequence are generally invalid data. Its y value reaches the first local minimum point around 10 minutes after x. Its number in the data sequence is:

[0058]

[0059] in Generally it takes 1 to 2 minutes.

[0060] The y value of this data sequence reaches the last local minimum point when x reaches about 22 minutes. If the y value is monotonically decreasing when x is about 22 minutes, the rightmost point of the search interval determined by the detector can be regarded as the minimum point. Its number in the data sequence is:

[0061] J1={j|y j =min(y (x) , 22-Δx <x<22+Δx)} (3)

[0062] The area corresponding to the above two "minimum value" points is the valid area of ​​mineral oil chromatographic data. The mineral oil detection chromatogram and its valid area of ​​data are as follows: Figure 1 As shown, the green straight line corresponds to the area, and the red spectrum is the gas chromatogram of mineral oil detection.

[0063] In order to identify the hump formed in the gas chromatogram of mineral oil detection, it is necessary to first identify the valley point sequence of the y value in the corresponding area:

[0064]

[0065] The valley points formed in the mineral oil detection chromatogram are as follows Figure 2 As shown, Figure 2 The purple data points, i.e. the valley points, basically reflect the shape outline, i.e. the basic outline, of the mineral oil hump.

[0066] The process of filtering invalid points in the basic contour and removing invalid valley points is as follows:

[0067] Although the valley points basically reflect the shape of the mineral oil hump, there are some data points that clearly do not belong to the hump formed by mineral oil in the chromatogram. Figure 2 The peak data points that are much higher than most of the purple data points appear in the form of spikes individually and in the form of gaps in clusters. These do not belong to the hump of mineral oil in the chromatogram. These invalid valley points have a common feature: the second-order difference quotient is a negative number with a large absolute value. That is, these invalid valley points are both local maximum points and inflection points of the data series in the valley point sequence. Therefore, the present invention performs second-order difference quotient filtering on the valley point sequence to remove these invalid valley points. The second-order difference quotient calculation method of the sequence is as follows:

[0068]

[0069] D0 is the discrimination threshold set by professionals based on experience, which is a negative number. When the second-order difference quotient of a point in the valley point sequence is less than D0, it is considered an invalid valley point and is removed from the sequence. By adjusting the threshold D0, the degree of shielding of the algorithm for the gap can be set. The smaller the absolute value of the threshold, the greater the shielding degree; the larger the absolute value of the threshold, the smaller the shielding degree.

[0070] By filtering the points with large absolute values ​​of the second-order difference quotient from the valley point sequence, a single peak can be removed. However, for the gap, since it is formed by a cluster of peaks, it is difficult to completely remove the entire gap with a single difference quotient filtering. Through experiments, it is found that by filtering the valley point sequence three times in the forward, reverse, and forward directions, all the gaps in the chromatographic data can be basically removed. At the same time, for some special gaps, if the removal effect is not good, the threshold D0 can be adjusted appropriately to increase or decrease the degree of removal of the gap, thereby optimizing the mineral oil spectrum.

[0071] The envelope curve corresponding to the mineral oil detection hump is as follows Figure 3 As shown, the dark blue data points and the broken line they form are the hump in the mineral oil gas chromatogram, that is, the correct mineral oil spectrum corresponding to the chromatogram data.

[0072] In the detection of mineral oil content, the chromatogram of the interference in the mineral oil often presents a wide cluster peak shape, which creates a "gap" in the hump and affects the identification of the hump contour (i.e., the mineral oil spectrum line). Usually, experienced experimenters are required to manually remove the peaks on the hump, divide the contour of the hump and perform area integration to obtain a more accurate content detection result. In this step, the mineral oil spectrum line is automatically established.

[0073] When processing data, if the mineral oil spectrum obtained by adjusting the threshold is not perfect enough, a function is provided to manually delete invalid data points to make the mineral oil spectrum more realistic.

[0074] Step 2, obtain the integrated area between the mineral oil spectrum and the baseline, as follows:

[0075] To calculate the integral value corresponding to the mineral oil spectrum, it is necessary to determine the baseline used for integration. In most cases, the baseline used for integration is the straight line connecting the start and end points of the envelope sequence. Sometimes, the middle valley point corresponding to the hump of the mineral oil spectrum will be lower than the straight line connecting the start and end points of the envelope sequence. At this time, the baseline will become a broken line composed of the start point, end point and middle valley point corresponding to the hump of the envelope sequence. The hump envelope in the mineral oil detection chromatogram is similar to the automatic baseline. Figure 4As shown. In this way, the mineral oil spectrum and baseline are obtained, and the area between the two can be numerically integrated. In order to ensure the reliability of the detection, the corresponding baseline can also be tested specifically for the actual test conditions. In this case, the baseline data can be loaded before calculating the integral. The mineral oil detection baseline data is as follows Figure 5 As shown. Figure 5 It can be seen that the baseline formed by the test data has a certain degree of interference, which is not conducive to the subsequent integral calculation. It is necessary to perform curve fitting on the baseline data. Through observation, it can be seen that the quadratic curve fitting can basically meet the shape requirements. The mineral oil detection baseline data curve fitting diagram is shown in Figure 6 shown.

[0076] When calculating the numerical integral, since the mineral oil spectrum and the automatically generated baseline data are both in the shape of a broken line, it is necessary to calculate the corresponding y value on the broken line at the specific integral position.

[0077]

[0078] Among them, j is the number of the corresponding data point on the line.

[0079] For the loaded data baseline, you can record the three parameters of the quadratic curve fitting and directly use the quadratic curve formula to calculate the y value corresponding to the numerical integral:

[0080] y=P0+P1x+P2x 2 (7)

[0081] By determining the mineral oil spectrum line and baseline, the upper and lower boundaries required for numerical integration are also determined, and the integral area between the mineral oil spectrum line and the baseline can be calculated.

[0082] In actual data processing, it is sometimes necessary to calculate the integrated area between two carbon number spectral lines separately. In this case, it is necessary to load the carbon number spectrum and form the peak positions corresponding to different carbon numbers. The carbon segment of the MOSH channel can be divided into C 10 -C 16 , C 16 -C 20 , C 20 -C 25 , C 25 -C 35 , C 35 -C 40 , C 40 -C 50 , C 10 -C 50 The carbon segment of the MOAH channel can be divided into C 10 -C 16 , C 16 -C 25, C 25 -C 35 , C 35 -C 50 , C 10 -C 50 As the basis for carbon number division, the data file contains C 10 , C 11 , C 13 , C 16 , C 20 , C 24 , C 25 , C 35 , C 40 , C 50 There are 10 carbon number position information in total. The carbon number position diagram after loading the carbon number spectrum is as follows Figure 7 Display, you can set the integration interval, such as C 40 -C 50 , the integral area defined by carbon number is as follows Figure 8 shown.

[0083] Step 3, automatic calculation of mineral oil content, is as follows:

[0084] The content of mineral oil can be calculated by using the integrated area between the mineral oil spectrum and the baseline. In actual testing, internal standard substances can be added. MOSH testing generally uses cyclohexylcyclohexane (Cycy) as an internal standard, and MOAH uses 2-methylnaphthalene (2MN) or 1,3,5-tri-tert-butylbenzene (TBB) as internal standards. The software that comes with the gas chromatograph workstation directly calculates the peak area corresponding to the internal standard and stores it in the chromatographic data file. When loading the test data, the internal standard peak area can be directly read into the computer memory.

[0085] In the actual process of processing the test data, the internal standard mass M can be manually entered. ISTD (ng) and sample mass M smp (g). Thus, according to the mineral oil spectral line area A smp and the peak area A of the standard substance ISTD , the content of mineral oil in the sample can be calculated using Formula 8.

[0086]

[0087] A secondary integration is performed using the software that comes with the gas chromatograph workstation, which integrates the total area of ​​the mineral oil and the interfering peaks on it, then integrates the area of ​​the peak, and subtracts the two to get the area of ​​the mineral oil. Then, a fixed application formula is designed using Excel, and the mineral oil content is calculated using Excel based on the internal standard mass, sample mass, mineral oil area, and peak area of ​​the standard substance.

[0088] In summary, the method of the present invention can remove various peaks in the hump, automatically determine the mineral oil hump profile (i.e., mineral oil spectrum), and calculate the mineral oil content. The method of the present invention utilizes the characteristic that the quadratic difference quotient of the peak is a relatively large negative value, and performs multiple quadratic difference quotient filtering on the valley point sequence of the chromatographic data, thereby obtaining the correct hump profile. By integrating the area between the hump profile and the baseline, combined with the mass of the quantitative internal standard and its peak area, the sample weighing amount, and the dilution multiple, the mineral oil content can be automatically calculated. Through experiments on actual samples, there is no significant difference between the mineral oil content result calculated by the method of the present invention and the manual calculation result, indicating that this method can replace manual automatic detection of mineral oil content.

[0089] The embodiment of the present application also provides an electronic device, Fig.10 The structure of the electronic device provided by the embodiment of the present invention is shown. For example, the electronic device 100 may include a processor 101, a memory 102 and a transmission device 103. The processor 101 is used to execute the automatic detection method of mineral oil based on secondary difference quotient filtering mentioned in the above embodiment, wherein the processor and the memory may be connected by a bus or other means, taking the bus connection as an example. The transmission device may be connected to the processor and the memory by wire or wirelessly. The memory, as a non-transient computer-readable storage medium, may be used to store non-transient software programs, non-transient computer executable programs and modules, such as the program instructions / modules corresponding to the automatic detection method of mineral oil based on secondary difference quotient filtering in the embodiment of the present application. The processor executes various functional applications and data processing of the processor by running the non-transient software programs, instructions and modules stored in the memory, that is, the automatic detection method of mineral oil based on secondary difference quotient filtering in the above method embodiment is realized. The memory may include a storage program area and a storage data area, wherein the storage program area may store an operating system and an application required by at least one function; the storage data area may store data created by the processor, etc. In addition, the memory may include a high-speed random access memory, and may also include a non-transient memory, such as at least one disk storage device, a flash memory device or other non-transient solid-state storage devices. In certain embodiments, the memory may optionally include a memory remotely arranged relative to the processor, and these remote memories may be connected to the processor via a network. Examples of the above-mentioned network include but are not limited to the Internet, an intranet, a local area network, a mobile communication network and a combination thereof. The one or more modules are stored in the memory, and when executed by the processor, the mineral oil automatic detection method based on secondary difference quotient filtering in the execution embodiment is executed.

[0090] An electronic device developed based on the method of the present invention - mineral oil content detection and analysis software can automatically complete the determination and area integration of mineral oil spectral lines, as well as read the peak area of ​​the standard substance in the chromatographic data file. The experimenter only needs to input the internal standard mass and sample weight on the interface, and the software can automatically complete the calculation of the mineral oil content. The mineral oil content detection and analysis software is as follows: Fig. 9 shown.

[0091] As another aspect, the present application also provides a computer-readable storage medium, which may be the computer-readable storage medium included in the device described in the above embodiment; or it may be a computer-readable storage medium that exists independently and is not assembled into the device. The computer-readable storage medium may be a tangible storage medium, such as a random access memory (RAM), a memory, a read-only memory (ROM), an electrically programmable ROM, an electrically erasable programmable ROM, a register, a floppy disk, a hard disk, a removable storage disk, a CD-ROM, or any other form of storage medium known in the technical field. The computer-readable storage medium stores one or more programs, and the programs are used by one or more processors to execute the mineral oil automatic detection method based on quadratic difference quotient filtering described in the present application.

[0092] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A mineral oil automatic detection method based on quadratic difference quotient filtering, characterized in that: The valley point sequence of the chromatographic data was filtered multiple times by quadratic difference quotient to obtain the correct hump profile; the mineral oil content was calculated by integrating the area between the hump profile and the baseline, combining the mass of the quantitative internal standard and its peak area, the sample weight and the dilution multiple.

2. The method according to claim 1, characterized in that The steps to obtain the correct hump profile are: first, find the valley points in the effective area to establish the basic profile of the mineral oil hump; then filter the invalid points in the basic profile, remove the invalid valley points, and determine the accurate mineral oil spectrum.

3. The method according to claim 2, characterized in that ,The process of finding the valley point in the effective area is as follows: The chromatogram data of mineral oil detection is defined as a data sequence: where x i Represents the time corresponding to the data, in minutes; y i The data generated by the detector is the potential data corresponding to the detector, in microvolts (μV); In the first 7 minutes of the data in this data sequence, the y value reaches about 10 minutes after x, and the first local minimum point is generated. The number in the data sequence is in 1 to 2 minutes; the y value of this data sequence reaches about 22 minutes, and the last local minimum point is generated; if the y value is monotonically decreasing when x is about 22 minutes, the rightmost point of the search interval determined by the detector is regarded as the minimum point, and the number in the data sequence is J1 = {j|y j =min(y (x) , 22-Δx<x<22+Δx)}, the area corresponding to the two minimum value points is the effective area of ​​mineral oil chromatography data; Determine the sequence of valley points of y values ​​in the hump corresponding area: The valley points formed in the mineral oil test chromatogram reflect the basic outline.

4. The method according to claim 3, characterized in that ,The process of filtering invalid points in the basic contour and removing invalid valley points is as follows: The second-order difference quotient of the valley point sequence is filtered to remove these invalid valley points. The second-order difference quotient of the sequence is calculated as follows: Among them, D0 is the discrimination threshold set by professionals based on experience, which is a negative number. When the second-order difference quotient of a point in the valley point sequence is less than D0, it is considered to be an invalid valley point and is removed from the sequence. The algorithm sets the degree of shielding of gaps by adjusting the threshold D0. The smaller the absolute value of the threshold, the greater the shielding degree; the larger the absolute value of the threshold, the smaller the shielding degree.

5. The method according to claim 4, characterized in that The valley point sequence is filtered by forward, reverse and forward cubic difference quotient to remove all gaps in the chromatographic data; for some special gaps, if the removal effect is not good, the threshold D0 is adjusted to increase or decrease the degree of gap removal, thereby optimizing the mineral oil spectrum.

6. The method according to any one of claims 1 to 5, characterized in that: Test the corresponding baseline for the actual experimental conditions, load the baseline data before calculating the integral, and perform quadratic curve fitting on the baseline data; When calculating numerical integrals, calculate the corresponding y value on the broken line at the specific integral position: Among them, j is the number of the corresponding data point on the polyline; For the loaded data baseline, record the three parameters of the quadratic curve fitting, and directly use the quadratic curve formula to calculate the y value corresponding to the numerical integral: y=P0+P1x+P2x 2 The upper and lower boundaries of the numerical integration are determined by determining the mineral oil spectrum line and the baseline, and then the integral area between the mineral oil spectrum line and the baseline is calculated.

7. The method according to claim 6, characterized in that When calculating the integrated area between two carbon number spectral lines separately, the carbon number spectrum is loaded, and the peak positions corresponding to different carbon numbers are formed thereby.

8. The method according to any one of claims 1 to 5, characterized in that: When calculating the content of mineral oil by the integrated area between the mineral oil spectrum and the baseline, an internal standard substance is added, wherein cyclohexylcyclohexane (Cycy) is used as the internal standard for MOSH detection, and 2-methylnaphthalene (2MN) or 1,3,5-tri-tert-butylbenzene (TBB) is used as the internal standard for MOAH; The software that comes with the gas chromatograph workstation directly calculates the peak area corresponding to the internal standard and stores it in the chromatographic data file; when loading the test data, the internal standard peak area is directly read into the computer memory; In the process of processing the test data, input the internal standard mass M ISTD (ng) and sample mass M smp (g); According to the mineral oil spectrum area A smp and the peak area A of the standard substance ISTD , calculate the content of mineral oil in the sample: A secondary integration is performed using the software that comes with the gas chromatograph workstation, which integrates the total area of ​​the mineral oil and the interfering peaks on it, then integrates the area of ​​the peak, and subtracts the two to get the area of ​​the mineral oil. Then, a fixed application formula is designed using Excel, and the mineral oil content is calculated using Excel based on the internal standard mass, sample mass, mineral oil area, and peak area of ​​the standard substance.

9. An electronic device, characterized in that: The electronic device includes a processor and a memory for storing executable instructions of the processor; the processor is used to read the executable instructions from the memory and execute the instructions to implement the automatic detection method of mineral oil based on quadratic difference quotient filtering as described in any one of claims 1-8.

10. A computer-readable storage medium, characterized in that: The storage medium stores a computer program, and the computer program is used to execute the automatic detection method of mineral oil based on quadratic difference quotient filtering as described in any one of claims 1 to 8.

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