Device and method for rapidly detecting residual pesticide based on X-ray
阅读说明：本技术 一种基于x射线快速检测残余农药的装置及方法 (Device and method for rapidly detecting residual pesticide based on X-ray ) 是由 孙培伟 王瑞杰 王凯锐 吴长浩 于 2021-08-16 设计创作，主要内容包括：本发明公开了一种基于X射线快速检测残余农药的装置及方法,在室温条件下,利用X射线对待检测的试样进行照射,激发试样表面元素；利用探测器间隔捕捉待检测试样被激发出的特征X射线,得到对应浓度下氮、磷、硫元素的特征X射线强度,然后将所有特征X射线强度拟合得到氮、磷、硫元素浓度—特征X射线强度曲线；将氮、磷、硫元素浓度—特征X射线强度曲线与已知氮、磷、硫元素在不同浓度范围时的特征X射线强度进行比较,根据待检测试样表面的元素与已知特征谱线的对比情况得到待检测试样中残余农药的含量；与设定含量进行比较,实现残余农药检测。本发明能有效处理农药残余检测的工作,符合在日常生活中具体的农药残余量检测问题的实用要求。(The invention discloses a device and a method for rapidly detecting residual pesticides based on X-rays, wherein under the condition of room temperature, a sample to be detected is irradiated by the X-rays to excite elements on the surface of the sample; capturing characteristic X-rays excited by a sample to be detected at intervals by using a detector to obtain the characteristic X-ray intensities of nitrogen, phosphorus and sulfur elements at corresponding concentrations, and then fitting all the characteristic X-ray intensities to obtain a nitrogen, phosphorus and sulfur element concentration-characteristic X-ray intensity curve; comparing the concentration-characteristic X-ray intensity curve of the nitrogen, phosphorus and sulfur elements with the characteristic X-ray intensity of known nitrogen, phosphorus and sulfur elements in different concentration ranges, and obtaining the content of the residual pesticide in the sample to be detected according to the comparison condition of the elements on the surface of the sample to be detected and the known characteristic spectral lines; and comparing the content with the set content to realize the detection of the residual pesticide. The invention can effectively process the work of pesticide residue detection and meet the practical requirements of the specific pesticide residue detection problem in daily life.)
1. A method for rapidly detecting residual pesticides based on X-rays is characterized by comprising the following steps:
s1, irradiating the sample to be detected by using X-rays at room temperature to excite elements on the surface of the sample;
s2, capturing characteristic X-rays excited by the sample to be detected in the step S1 to obtain the characteristic X-ray intensities of nitrogen, phosphorus and sulfur elements at corresponding concentrations, and fitting all the characteristic X-ray intensities to obtain a nitrogen, phosphorus and sulfur element concentration-characteristic X-ray intensity curve;
s3, comparing the concentration-characteristic X-ray intensity curve of the nitrogen, phosphorus and sulfur elements obtained in the step S2 with the characteristic X-ray intensities of known nitrogen, phosphorus and sulfur elements in different concentration ranges, and obtaining the content Q of the residual pesticide in the sample to be detected according to the comparison condition of the elements on the surface of the sample to be detected and the known characteristic spectral lines;
and S4, comparing the content Q of the residual pesticide in the sample to be detected in the step S3 with the set content, and detecting the residual pesticide.
2. The method according to claim 1, wherein in step S1, before the measurement of the sample, the characteristic X-ray intensity relation functions and curves of nitrogen, phosphorus and sulfur are determined, and a plurality of groups of solutions containing nitrogen, phosphorus and sulfur are respectively configured with a concentration gradient of 0.1ppm and 0.1 ppm.
3. The method according to claim 1, wherein in step S1, the X-ray has a wavelength of 5-50 nm.
4. The method of claim 1, wherein in step S2, the characteristic X-rays are captured in a spaced manner.
5. The method according to claim 1, wherein in step S2, the results obtained after at least 3 measurements are averaged and fitted to obtain an elemental concentration-characteristic X-ray intensity function as:
m＝kE
wherein E is the characteristic X-ray intensity, k is the proportionality coefficient, and m is the sample surface element concentration.
6. The method according to claim 1, wherein in step S3, the content Q of the residual pesticide in the sample to be tested is:
wherein m is the concentration of nitrogen, phosphorus and sulfur elements on the surface of the sample, A is the molecular weight of the residual concentrated medicament, and B is the molecular weight of the nitrogen, phosphorus and sulfur elements.
7. The device for rapidly detecting the residual pesticide based on the X-ray is characterized by comprising a sample container, wherein an X-ray tube (9) and a detector (11) are arranged in the sample container, the X-ray tube (9) is used for irradiating the sample (10), the detector (11) is used for capturing characteristic X-rays excited by the sample (10), then the captured characteristic X-rays are converted into digital signals and sequentially transmitted to a computer (14) through an amplifier (12) and a multi-channel pulse analyzer (13), the computer (14) compares the obtained surface elements of the sample with a set threshold value, and the concentration size and distribution of nitrogen, sulfur and phosphorus elements are analyzed to obtain whether the pesticide residue in the sample is excessive or not.
8. The apparatus for rapid detection of pesticide residues based on X-ray according to claim 7, characterized in that a screen (15) is connected to the computer (14).
9. The device for rapidly detecting residual pesticide based on X-ray according to claim 7, wherein the X-ray tube (9) comprises a cathode (1) and a rotary anode (2), the cathode (1) is arranged on the front side of the glass wall (5) and connected with a collecting and radiating cover (6) arranged in the glass wall (5), a filament (7) is arranged on the collecting and radiating cover (6), the rotary anode (2) is arranged in the glass wall (5), one end of the rotary anode is connected with the rotor (4), the rotor (4) is sleeved with a stator (3), and a target surface (8) is arranged on the rotary anode (2).
Technical Field
The invention belongs to the technical field of radioactive element detection, and particularly relates to a device and a method for quickly detecting residual pesticide based on X-rays.
Background
The development of agricultural industrialization leads the production of agricultural products to depend on exogenous substances such as pesticides, antibiotics, hormones and the like more and more, the dosage of the pesticides in the agricultural products in China is high, and the unreasonable use of the substances can lead the pesticide residue in the agricultural products to exceed the standard, thus affecting the edible safety of consumers, and causing the pathogenic, abnormal development and even direct poisoning and death of the consumers in serious cases. It is therefore of vital importance for the consumer to detect pesticide residues in food products.
The existing pesticide detection methods mainly comprise four methods, namely a physicochemical detection method, a biochemical detection method, an immunoassay method and a spectral analysis technology.
The physical and chemical inspection method is a method for measuring the element content by using various instruments, appliances and reagents under certain laboratory environment conditions and using physical and chemical methods, but certain equipment and inspection conditions are required, meanwhile, certain requirements are also required for the knowledge and operation technology of inspectors, a certain amount of commodities are often damaged, a certain amount of reagents are consumed, the cost is high, and the time required for inspection is long. Although the method has high measurement accuracy and can measure a plurality of components at one time, the method has expensive instruments, complicated pretreatment process, time consumption and complexity, needs professional operation and is not beneficial to popularization.
The enzyme inhibition method is most widely used in biochemical detection methods. Because the organophosphorus pesticide can inhibit the activity of acetylcholinesterase in the central nervous system and peripheral nervous system of insect, and result in accumulation of nerve conduction medium acetylcholine, the insect will die after its function is paralyzed, and this principle is used in detecting pesticide residue by enzyme inhibition method. Many researchers have conducted extensive studies on the rapid detection of pesticides using acetylcholinesterase. Joseph Wang studied the application of microchip technology of enzyme in detecting organophosphorus substances, and the research shows that the detection limit of paraoxon and methyl parathion by applying the technology is 5mg/L and 3 mg/L. Nikolaos G studied a quartz crystal microbalance biosensor, which converted acetylcholine into trimethylamine-ethyl lactone with production of hydroperoxide by a two-enzyme system (acetylcholinesterase and vitamin B oxidase), and oxidized diaminobiphenyl with peroxidase to form a precipitate, because organophosphorus pesticides can inhibit the activity of esterase, and the generation of precipitate is reduced, the minimum detection limit for carbaryl and dichlorvos by using this microbalance sensor is 1 mg/L. Three esterases are respectively used by Akkad, Qieunkun, Wangjinbin and the like, acetylcholinesterase in the brain, liver and muscle of crucian carp is used as an enzyme for detection, and an enzyme inhibition method of acetylcholinesterase and the like is adopted to detect and research organophosphorus pesticides. The result shows that although the enzyme inhibition method belongs to a rapid detection method and is easy to operate, the enzyme reagent is easy to inactivate, the reaction is unstable, the sensitivity of the detection on various organophosphorus pesticides is different, the repeatability and the recovery rate are not high, the detection result error is large, the confirmation rate in practical application is only about 60-70%, and the method is only suitable for field qualitative and semi-quantitative detection. In addition, the rapid determination method mainly adopts animal source acetylcholinesterase or butyrylcholinesterase, but the cholinesterase is expensive and is not easy to obtain.
Another rapid detection method is immunoassay, which is a method for detecting trace substances in a specimen by using antigen-antibody reaction. The range of applications of immunoassays is extremely widespread, based on the specificity and sensitivity of antigen-antibody reactions. Any substance can be detected by immunoassay as long as it can obtain a specific antibody, and extensive studies have been made in recent years. For example, Kumar et al used enzyme-linked immunoassay and flow injection to detect methyl parathion in environment and food. Liu et al found that a D12-B5 monoclonal antibody has remarkable specificity in detecting organophosphorus pesticides such as methyl parathion, chlorpyrifos, fenthion, fenitrothion and the like. However, because the immunoassay method has strong specificity, one kit can only detect single organophosphorus pesticide but not multiple residues of the pesticide, and corresponding artificial antigen is synthesized when small molecular substances are detected, so that the hapten synthesis not only has large workload and long period, but also has certain degree of cross on compounds with similar structures, and also has the problems of difficult antigen extraction, high kit cost and the like.
Chromatography is a separation analysis method which achieves the separation purpose according to the difference of the distribution coefficient of an analysis substance between a stationary phase and a mobile phase, converts the concentration of the analysis substance into an electric signal (voltage, current and the like) which is easy to measure, and records the electric signal by a recorder. Although the spectral analysis is a simple and rapid detection method, the near infrared spectrum belongs to a vibration spectrum, has weak characteristics, and can cause the problems of unstable absorption peak, difficult accuracy meeting the quantitative detection requirement and the like when being directly used for the identification, the class identification and the structural analysis of general compound groups such as organophosphorus pesticides and the like.
Disclosure of Invention
The invention aims to solve the technical problem of providing a device and a method for quickly detecting residual pesticide based on X-ray, which are convenient to carry and simple to operate, can quickly detect the pesticide content of agricultural products on the premise of not damaging the agricultural products and meet the use requirements of the public in daily life.
The invention adopts the following technical scheme:
a method for rapidly detecting residual pesticides based on X-rays comprises the following steps:
s1, irradiating the sample to be detected by using X-rays at room temperature to excite elements on the surface of the sample;
s2, capturing characteristic X-rays excited by the sample to be detected in the step S1 to obtain the characteristic X-ray intensities of nitrogen, phosphorus and sulfur elements at corresponding concentrations, and fitting all the characteristic X-ray intensities to obtain a nitrogen, phosphorus and sulfur element concentration-characteristic X-ray intensity curve;
s3, comparing the concentration-characteristic X-ray intensity curve of the nitrogen, phosphorus and sulfur elements obtained in the step S2 with the characteristic X-ray intensities of known nitrogen, phosphorus and sulfur elements in different concentration ranges, and obtaining the content Q of the residual pesticide in the sample to be detected according to the comparison condition of the elements on the surface of the sample to be detected and the known characteristic spectral lines;
and S4, comparing the content Q of the residual pesticide in the sample to be detected in the step S3 with the set content, and detecting the residual pesticide.
Specifically, in step S1, before the sample is measured, the characteristic X-ray intensity relationship function and curve of the three elements, nitrogen, phosphorus and sulfur, are determined, and a plurality of groups of solutions containing nitrogen, phosphorus and sulfur are respectively configured with a concentration gradient of 0.1ppm and 0.1 ppm.
Specifically, in step S1, the wavelength of the X-ray is 5 to 50 nm.
Specifically, in step S2, characteristic X-rays are captured in a spaced manner.
Specifically, in step S2, after at least 3 measurements are performed, the obtained result is averaged and fitted to obtain an element concentration-characteristic X-ray intensity function as:
m＝kE
wherein E is the characteristic X-ray intensity, k is the proportionality coefficient, and m is the sample surface element concentration.
Specifically, in step S3, the content Q of the residual pesticide in the sample to be detected is:
wherein m is the concentration of nitrogen, phosphorus and sulfur elements on the surface of the sample, A is the molecular weight of the residual concentrated medicament, and B is the molecular weight of the nitrogen, phosphorus and sulfur elements.
The device comprises a sample container, wherein an X-ray tube and a detector are arranged in the sample container, the X-ray tube is used for irradiating a sample, the detector is used for capturing characteristic X-rays excited by the sample, then the captured characteristic X-rays are converted into digital signals and sequentially transmitted to a computer through an amplifier and a multi-channel pulse analyzer, and the computer compares the obtained surface elements of the sample with a set threshold value and analyzes the concentration and distribution of nitrogen, sulfur and phosphorus elements to obtain whether pesticide residues in the sample are excessive.
Specifically, the computer is connected with a screen.
Specifically, the X-ray tube includes negative pole and rotary anode, and the negative pole setting is in the front side of glass wall, and the collection that sets up in with the glass wall penetrates the cover and is connected, and collection penetrates and is provided with the filament on covering, and rotary anode sets up in the glass wall, and one end is connected with the rotor, and the cover is equipped with the stator on the rotor, is provided with the target surface on the rotary anode.
Compared with the prior art, the invention has at least the following beneficial effects:
the invention relates to a method for rapidly detecting residual pesticides based on X-ray, which aims to simplify detection operation and avoid extra time cost caused by heating or cooling when the detection environment is required to be at room temperature; the long-time irradiation of the sample aims at completely irradiating the surface of the sample, exciting surface elements, facilitating subsequent sampling analysis, fitting to obtain an element concentration characteristic X-ray intensity curve, aiming at facilitating transverse comparison with a known characteristic spectral line and facilitating analysis and judgment of pesticide residues of the sample, and the obtained concentration characteristic X-ray intensity curve under corresponding concentration is directly compared with the known characteristic X-ray intensity under the concentration, so that a judgment result can be intuitively, simply and conveniently obtained.
Furthermore, in the pesticide residue compound on the surface of the sample, the contents of elements such as nitrogen, phosphorus and sulfur are higher than those of other elements, so that the three elements are taken as the basis for detecting the pesticide residue, and the accuracy of the obtained X-ray intensity relation function and curve and the smoothness of the curve can be improved by setting the experimental group by taking 0.1ppm as a concentration gradient, and the accuracy of the subsequent judgment of the pesticide residue of the sample can be improved.
Furthermore, the X-ray is electromagnetic wave with extremely high frequency and high energy, can utilize the physical chemical biological effect generated by the interaction of ionizing radiation and substances to treat the processed substances or materials, and has weaker penetrating power but better excitation function on the required pesticide residue compounds on the surface of the sample when the wavelength is longer.
Furthermore, the energy resolution of the detector is influenced by the effective detection area and the time constant of a subsequent processing circuit, and the data collected once can be completely processed by setting the capture time interval, so that the analysis accuracy is improved.
Furthermore, errors in experiments are inevitable, and the difference between a measured value and a true value can be reduced by adopting a method of measuring for multiple times and taking an average value; the conclusion obtained through the experimental data of one or two times is often accidental and incomplete, so that an accurate and comprehensive rule can be found by measuring for multiple times; the element concentration can be calculated by detecting the element-excited characteristic X-ray intensity of the object to be detected by fitting to obtain an element concentration and characteristic X-ray intensity function and curve.
Further, comparing the characteristic X-ray intensity function and curve of the concentrations of the elements of nitrogen, phosphorus and sulfur obtained in step S2 with the characteristic X-ray intensities of known elements of nitrogen, phosphorus and sulfur in different concentration ranges, the comprehensiveness and accuracy of the function and curve of the concentrations of the elements and the characteristic X-ray intensities obtained by fitting can be demonstrated, and the feasibility of calculating the concentrations of the elements by detecting the characteristic X-ray intensities of the object to be detected is also demonstrated.
A device for rapidly detecting residual pesticide based on X-ray is characterized in that an X-ray tube can provide X-ray with higher energy under working voltage and can fully excite elements in an object to be detected; the sample container is used for containing objects to be detected, the sample container is convenient to carry in a specification of 40cm X30 cm X20 cm, and in order to isolate the damage of X-ray overflow to human bodies and shield the influence of the outside, a lead plate with the thickness of 1mm is embedded in the sample container; the detector is used for capturing characteristic X-rays and converting the characteristic X-rays into digital signals; the amplifier can increase the amplitude and power of the signal to ensure that the receiver can receive a satisfactory signal level; the multichannel pulse analyzer can automatically acquire energy spectrum data, and the whole energy spectrum can be obtained by one-time measurement, so that the data acquisition time is greatly reduced; and the computer performs final data processing and judgment and transmits a judgment result to the display screen.
And further, the computer is connected with a screen, the concentration and distribution results of the nitrogen, the sulfur and the phosphorus elements are displayed to obtain whether pesticide residues in the sample are excessive or not, and when the content of the three elements on the surface of the sample is detected to exceed a threshold value, a warning is given through the screen to indicate that the sample is a harmful sample.
Further, the X-ray tube includes an anode and a cathode for receiving the target material to be bombarded by electrons and a filament for emitting electrons. Both electrodes are sealed in a high vacuum glass or ceramic envelope. The power supply part of the X-ray tube at least comprises a low-voltage power supply for heating the filament and a high-voltage generator for applying high voltage to the two poles. When the tungsten filament passes sufficient current to generate an electron cloud, and sufficient voltage is applied between the anode and cathode to draw the electron cloud toward the anode. At this time, the electrons impact the tungsten target in a high-energy and high-speed state, the high-speed electrons reach the target surface, the motion is suddenly stopped, a small part of the kinetic energy of the electrons is converted into radiation energy, and the radiation generated in the form of X-rays is emitted, and the radiation is called bremsstrahlung radiation. Changing the magnitude of the filament current changes the temperature of the filament and the amount of electron emission, thereby changing the magnitude of the tube current and the X-ray intensity.
Furthermore, the energy of the X-ray is larger than the inner-layer electron binding energy of the atom to be detected, and the inner-layer electron binding energy of several elements is obtained by a rail electron binding energy meter: n409.9 eV P2145.5 eV S2472 eV Cl 2822.4eV, namely the required minimum X-ray energy is 3000eV, in practical work, in the process of the X-ray generated by the end window type X-ray tube entering the sample, only a small part of the consumed power of the X-ray tube during normal work is converted into X-ray radiation (the rest is changed into heat energy to heat the X-ray tube, so that the target is cooled by cooling water constantly), and in the process of exciting the sample element by the X-ray, the X-ray loss is also considered, so the working voltage of the practical X-ray tube is required to enable the generated X-ray energy to be higher than 3000 eV.
In conclusion, the reasonable X-ray wavelength and the working voltage are selected, the capture time interval of the detector is set, the reasonable X-ray pesticide residue detection device is designed, the judgment result of whether the pesticide residue exceeds the standard can be intuitively and simply obtained, and the accuracy of the judgment result can be guaranteed. Meanwhile, the X-ray pesticide residue detection device is clear, reasonable and simple in structure and portable, can effectively process the work of pesticide residue detection, and meets the practical requirement of the specific pesticide residue detection problem in daily life.
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Drawings
FIG. 1 is a schematic view of an X-ray tube;
FIG. 2 is a flow chart of the method of the present invention;
FIG. 3 is a schematic diagram of the technical solution of the present invention;
FIG. 4 is a schematic view of a time series data acquisition window;
FIG. 5 is a graph of elemental characteristic X-ray parameters.
Wherein: 1. a cathode; 2. rotating the anode; 3. a stator; 4. a rotor; 5. a glass wall; 6. a collecting and projecting cover; 7. a filament; 8. a target surface; an X-ray tube; 10. a sample; 11. a detector; 12. an amplifier; 13. a multichannel pulse analyzer; 14. a calculator; 15. and (6) a screen.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "one side", "one end", "one side", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, are not to be construed as limiting the present invention. In addition, in the description of the present invention, "a plurality" means two or more unless otherwise specified.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
It will be understood that the terms "comprises" and/or "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It is also to be understood that the terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the specification of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
It should be further understood that the term "and/or" as used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.
Various structural schematics according to the disclosed embodiments of the invention are shown in the drawings. The figures are not drawn to scale, wherein certain details are exaggerated and possibly omitted for clarity of presentation. The shapes of various regions, layers and their relative sizes and positional relationships shown in the drawings are merely exemplary, and deviations may occur in practice due to manufacturing tolerances or technical limitations, and a person skilled in the art may additionally design regions/layers having different shapes, sizes, relative positions, according to actual needs.
The invention provides a device for rapidly detecting residual pesticides based on X-rays, which combines an X-ray fluorescence analysis method with a principal component analysis method, and simulates a functional relation between element content and corresponding released characteristic X-ray energy by performing data fitting on a large amount of effective data of the characteristic X-ray energy released in the process of irradiating certain elements by the X-rays.
Basic principles of X-ray fluorescence analysis:
the intensity of the characteristic X-ray of each element is related to the content of such element in the sample in addition to the energy and intensity of the excitation source, so that information on the content of each element can be obtained from the intensity of the characteristic X-ray of each element.
Referring to fig. 1, the apparatus for rapidly detecting pesticide residues based on X-rays according to the present invention includes an X-ray tube 9, a detector 11, an amplifier 12, a multichannel analyzer 13, a computer 14, and a screen 15.
After a sample 10 is irradiated by X-rays emitted by an X-ray tube 9, characteristic X-rays excited in a certain wavelength range by the sample 10 are captured by a detector 11, the X-ray tube 9, the sample 10 and the detector 11 are arranged in a sample container, the captured characteristic X-rays are converted into digital signals by the detector 11 and then sequentially transmitted to a computer 14 through an amplifier 12 and a multi-channel pulse analyzer 13, the obtained surface elements of the sample are compared with a set threshold value by the computer 14, the concentration size and distribution of nitrogen, sulfur and phosphorus elements are analyzed, the result is displayed on a screen 15, whether pesticide residues in the sample are excessive or not is obtained, and when the content of three elements on the surface of the sample 10 is detected to exceed the threshold value, the screen 15 gives an alarm to indicate that the sample is a harmful sample.
Referring to fig. 2, the X-ray tube 9 includes a cathode 1, a rotating anode 2, a stator 3, a rotor 4, a glass wall 5, a collector-reflector 6, a filament 7, and a target surface 8.
The rotary anode 2 is arranged in the glass wall 5, one end of the rotary anode is connected with the rotor 4, and the stator 3 is sleeved on the rotor 4; the target surface 8 is arranged on the rotary anode 2, the cathode 1 is arranged at the front side of the glass wall 5 and is connected with a collecting and projecting cover 6 arranged in the glass wall 5, and a filament 7 is arranged on the collecting and projecting cover 6.
The X-ray energy is larger than the inner-layer electron binding energy of atoms to be detected, and through previous research on common pesticides in the market, N, P, S and Cl are elements commonly contained in pesticides, and the inner-layer electron binding energy of the elements is obtained from a track electron binding energy meter: n409.9 eV P2145.5 eV S2472 eV Cl 2822.4eV, namely the required minimum X-ray energy is 3000eV, X-rays generated by the X-ray tube 9 are transmitted through the beryllium window to be incident on the sample 10, and the characteristic X-rays of the element of the sample 10 are excited.
The size of the sample container is 40cm 30cm 20cm, most vegetables and fruits on the market can be conveniently placed in the sample container, meanwhile, for the convenience of carrying the device, stainless steel is preferably selected as the material, a lead plate with the thickness of 1mm is embedded in the sample container, the damage to a human body caused by X-ray overflow is isolated, meanwhile, the external influence is shielded, and an X-ray tube and an X-ray detector can be placed in the sample container through an interlayer.
Referring to fig. 3, a method for rapidly detecting residual pesticide based on X-ray includes the following steps:
s1, irradiating the sample by using X rays at the room temperature of 20 ℃ to excite the elements on the surface of the sample;
before a sample is measured, determining a characteristic X-ray intensity relation function and a characteristic X-ray intensity relation curve of three elements of nitrogen, phosphorus and sulfur, and respectively configuring 10 groups of solutions containing the elements of nitrogen, phosphorus and sulfur with the concentration gradient of 0.1 ppm;
s2, capturing characteristic X-rays excited by a sample in a certain wavelength range at intervals by using a detector, converting the characteristic X-rays into digital signals, carrying out digital processing through an amplifier and a pulse analyzer, sending the digital signals to a computer to obtain the characteristic X-ray intensity of corresponding elements under corresponding concentration, carrying out measurement at least 3 times each time, averaging the obtained result, obtaining a data point which is approximately in a direct proportion relationship after the test is finished, and fitting through Origin software to obtain an 'element concentration-characteristic X-ray intensity' function and a curve; and writing the fitted functional relation of the element concentration-characteristic X-ray intensity corresponding to different elements into a computer, as shown in FIG. 4.
When the wavelength range of the X-ray received by the detector is set, the set range contains the characteristic X-ray of the corresponding element and does not contain characteristic waves or interference waves of other elements.
The characteristic X-ray wavelength value of each element is obtained by theoretical calculation, and specifically comprises the following steps:
from the energy vs. wavelength equation:
derived by
Wherein E (energy) is obtainable by looking at FIG. 5; h (planck constant) 6.626 × 10-34；1KeV＝1.602177*10-16J。
Calculating to obtain: the characteristic X-ray wavelength of the N element is 3165.05 nm; the characteristic X-ray wavelength of the P element is 614.21 nm; the characteristic X-ray wavelength of the S element is 537.10 nm; the characteristic X-ray wavelength of Cl element is 473.55 nm.
When the wavelength range of the X-ray selected and received by the detector is set in step S2, different reception ranges are set for detecting different elements in the sample.
Reception range of N element: 3000-3300 nm;
reception range of P element: 570-660 nm;
reception range of S element: 500-570 nm;
reception range of Cl element: 450 to 500 nm.
S3, comparing the element concentration-characteristic X-ray intensity curve with the known characteristic X-ray intensities of elements such as nitrogen, sulfur, phosphorus and the like in different concentration ranges by the computer to obtain the comparison condition of the elements on the surface of the sample and the known characteristic spectral lines;
the known characteristic X-ray intensities of the nitrogen, sulfur and phosphorus elements in different concentration ranges substantially conform to the corresponding "element concentration-characteristic X-ray intensity" functional relationship in step S2, which illustrates the feasibility of calculating the element concentration according to the "element concentration-characteristic X-ray intensity" functional relationship.
S4, irradiating the object to be detected by using X rays, obtaining the characteristic X ray intensity of the element in the object to be detected by adopting the method in the step S2, and substituting the characteristic X ray intensity of the element in the object to be detected into the corresponding function of 'element concentration-characteristic X ray intensity' obtained by fitting in the step S2 to obtain the content of the element in the object to be detected.
And displaying the result on a screen to obtain whether pesticide residue in the sample is excessive, and when the content of the three elements on the surface of the sample is detected to exceed a threshold value, warning is provided by the screen to indicate that the sample is a harmful sample.
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Assuming that the excited element on the surface of the sample is phosphorus, taking the widely used dichlorvos pesticide in the market as an example, the molecular formula C of the dichlorvos4H7Cl2O4The molecular weight of P is 220.98, the molecular weight of P element is 30.97, and the content of dichlorvos is calculated according to the following formula:
wherein Q is the content of the dichlorvos in the object to be detected, and mg/kg, and m is the concentration of the P element on the surface of the sample obtained according to the comparison condition obtained in the step S3, and mg/kg.
Two decimal places are reserved in the calculation result; and comparing the calculated content of the dichlorvos in the object to be detected with the content of the dichlorvos specified in the national NY448-2001 standard, and determining that the content exceeds the specified content, namely the content is excessive.
From the viewpoint of X-ray detectors, three types of apparatuses have been formed in the international market, which use a scintillation counter as an X-ray detector, commercial apparatuses which use a proportional counter as an X-ray detector, and apparatuses which use a room-temperature high-energy-resolution semiconductor detector as an X-ray detector. For the pesticide residue detection device with the design aim of no damage and portability, the detector is an energy dispersion X-ray spectrometer, and the room-temperature semiconductor detector is an X-ray detector (such as a CdZnTe material detector), so that the device has the advantages of high quantum efficiency, capability of working at room temperature, high energy resolution, high sensitivity, low leakage current, high resistivity, compactness, portability and the like. The electronic circuit unit adopts a full digital electronic circuit design, after the output signal of the X-ray detector is primarily processed, a high-speed ADC is used for digitizing the full waveform of the analog pulse signal, and digital filtering, digital shaping, digital baseline estimation and digital pulse amplitude extraction are carried out on the digital pulse signal by virtue of an embedded microprocessor with strong data arithmetic capability, so as to achieve high accuracy of data receiving and processing.
The invention has the following characteristics:
1. the method comprises the steps of carrying out X-ray irradiation on elements with different known contents for multiple times, collecting a large amount of effective data, and utilizing a data fitting method to effectively simulate the functional relation between the element contents and the correspondingly released characteristic X-ray energy so as to improve the measurement accuracy.
2. The step of preparing the sample is omitted, the detection speed is high, the operation is simple, the device is simple in structure and exquisite, the portable requirement and the low economic cost are met, and the market economic benefit of the pesticide residue detection product is improved.
3. The sample is irradiated and sampled by the characteristic X-ray, the characteristic is strong, the deviation generated in the detection process is small, and the quality and the edible safety of the detected sample are not influenced.
4. The detection device does not need to use special solution solvent and the like for auxiliary detection, so the method does not relate to the limitations of the device and sample storage, and can be repeatedly used for a long time.
5. The functional relation between the element content and the characteristic X-ray energy fitted by the data is input into a computer data processing system, the amplified characteristic X-ray signal excited by the sample is transmitted to a computer, and the element content of the sample can be obtained through the set functional relation, so that the using steps of operators are simplified, and the popularity of the method is greatly improved.
In conclusion, the device and the method for rapidly detecting the residual pesticide based on the X-ray solve the problems in the prior art, and the device which is personal-oriented, convenient to carry and simple to operate and can rapidly detect the pesticide content of agricultural products on the premise of not damaging the agricultural products is obtained, so that the use of the public in daily life is met.
The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.