Portable evaporation ionization mass spectrum device and method for aquatic product identification

Abstract

The invention relates to the technical field of aquatic product identification, in particular to a portable evaporation ionization mass spectrometry device for aquatic product identification, which comprises a bottom plate, a vacuum cavity is mounted on the upper surface of the bottom plate, a sample introduction piece is mounted on one surface of the vacuum cavity, and a vacuum gauge is mounted on one surface of the vacuum cavity. A diaphragm pump is arranged on the side, away from the vacuum gauge, of the vacuum cavity and connected with the bottom plate, a molecular pump is installed on the side, close to the diaphragm pump, of the upper surface of the vacuum cavity, a multiplier is arranged on one side of the sample injection piece and communicated with the vacuum cavity, and the molecular pump is connected with the molecular pump. Compared with the prior art, the device and the method have the advantages that aquatic product matrix impurities can be effectively adsorbed, ion quenching can be inhibited, the mass spectrum sample introduction efficiency of molecular ions and the signal response intensity of a target compound are greatly improved, and the problems that a traditional device is unstable in signal and poor in repeatability are solved.

Description

Technical Field

[0001] This invention relates to the field of aquatic product identification technology, specifically a portable evaporative ionization mass spectrometry device and method for aquatic product identification. Background Technology

[0002] As a key functional component in the portable mass spectrometer ion transmission link, the heating element plays two core roles through heating: first, it promotes secondary ion ion ionization to enhance the mass spectrometry signal intensity of the target compound; second, it enables the thermal decomposition of impurity particles to prevent large molecular impurities in the aquatic product matrix from entering the mass spectrometer and causing contamination, thus ensuring the long-term stable operation of the instrument.

[0003] In on-site testing scenarios for authenticating aquatic products, the aquatic product matrix exhibits significant characteristics such as high protein, high fat, and rich polysaccharides. This complex matrix exposes numerous specific defects in existing electrothermal cores, severely limiting the detection performance of portable mass spectrometers. Specific problems are as follows: 1. Insufficient stain resistance of the substrate Existing heating elements generally use pure Kanthal Al (chromium aluminum cobalt heat-resistant steel) as the base material, which has a high surface roughness (Ra≥1.6μm) and lacks adaptability to aquatic product matrices. Fatty impurities in aquatic products easily adhere to the substrate surface and carbonize during heating, with the amount of impurities adhering after a single test reaching 1.5–2 mg. Carbonized impurities not only competitively adsorb target ions, leading to a 20%–30% reduction in ion signal response, but also require frequent disassembly and cleaning (cleaning cycle ≤7 days), significantly increasing operation and maintenance costs and downtime, and affecting on-site testing efficiency.

[0004] 2. No suitable surface modification layer for aquatic product substrates Existing heating elements are mostly bare materials or have only a single oxide layer on their surface, which cannot take advantage of the special characteristics of aquatic product matrices. On the one hand, they cannot effectively adsorb protein impurities (such as myoglobin and collagen) in aquatic products. These impurities are prone to causing ion source contamination after entering the mass spectrometer with the ion flow. On the other hand, they lack active sites that can promote the secondary ionization of characteristic ions of aquatic products such as lipids and nucleotides, resulting in a secondary ionization efficiency of generally ≤35%, which is difficult to meet the high-efficiency detection requirements of characteristic ions of aquatic products and affects the accuracy and sensitivity of the identification results.

[0005] 3. Poor temperature field uniformity Existing electric heating elements mostly employ single-end heating or single-point temperature measurement designs, resulting in axial temperature differences of 15–20°C, leading to uneven heating of ions during transport. This is particularly problematic for ion clusters that easily form in aquatic product matrices; temperature fluctuations significantly increase their quenching rate (quenching rate > 40%), not only reducing the effective transport efficiency of target ions but also causing poor detection repeatability due to unstable ion signals, thus failing to meet the data consistency requirements for aquatic product authenticity identification.

[0006] 4. Insufficient corrosion resistance In the testing of aquatic products, auxiliary solvents such as methanol-acetonitrile mixtures are often used to optimize ionization. Simultaneously, the sample eluent may contain acidic or alkaline components, which can easily corrode pure Kanthal Al substrate. After prolonged use (more than 100 tests), pitting corrosion easily occurs on the substrate surface, with resistance fluctuations exceeding ±8%. This leads to unstable heating power, further exacerbating temperature field unevenness and ion signal fluctuations, creating a vicious cycle of corrosion and signal degradation.

[0007] The aforementioned defects make existing electric heating elements unsuitable for the special characteristics of aquatic product matrices, becoming a core technical bottleneck for portable mass spectrometry in the field of aquatic product authenticity identification, resulting in unstable signals, poor repeatability, and high operation and maintenance costs. Targeted innovations are urgently needed in areas such as structural design, material selection, and preparation processes to meet the actual needs of rapid and accurate on-site detection. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a portable evaporative ionization mass spectrometry device and method for identifying aquatic products, thereby solving the problems mentioned in the background art.

[0009] To achieve the above objectives, the present invention is implemented through the following technical solution: a portable evaporative ionization mass spectrometry device for aquatic product identification, comprising a base plate, a vacuum chamber mounted on the upper surface of the base plate, a sample injection device mounted on one side of the vacuum chamber, a vacuum gauge mounted on another side of the vacuum chamber, a diaphragm pump provided on the side of the vacuum chamber away from the vacuum gauge, the diaphragm pump being connected to the base plate, a molecular pump mounted on the upper surface of the vacuum chamber near the diaphragm pump, and a multiplier provided on the side of the sample injection device, the multiplier being connected to the vacuum chamber.

[0010] Specifically, the injection device includes a Venturi pump, which is installed on one side of the vacuum chamber. A solvent connector is installed on the outer surface of the Venturi pump, and an injection connector is installed on the end of the outer surface of the Venturi pump away from the solvent connector. The injection connector is connected to a sampling pump through a pipe, and the Venturi pump is connected to a mass spectrometer injection tube through a heating element structure. One end of the mass spectrometer injection tube is connected to and communicates with the vacuum chamber.

[0011] Specifically, the electric heating core structure includes a connecting end, the connecting end is installed on the outer surface of the Venturi pump, a heating section is installed at the end of the connecting end away from the Venturi pump, and an ion interaction section is installed at the end of the heating end away from the connecting end. The ion interaction section is connected to the vacuum chamber through a mass spectrometer injection tube.

[0012] Specifically, the connecting end, heating section, and ion-acting section are integrally formed coaxially along the axial direction. The total length of the connecting end, heating section, and ion-acting section is 25±0.5mm, and the outer diameter is 3±0.1mm. The connecting end is 5mm long, has an M2 thread on its surface, and has two 0.5mm diameter silver-copper alloy conductive pins built into it. The conductivity of the silver-copper alloy conductive pins is... The surface of the ion-interaction section is provided with annular microgrooves and gas-guiding channels. The annular microgrooves are 0.2 mm deep, 0.3 mm wide, and spaced 0.5 mm apart, with 15 grooves evenly distributed along the axial direction. The gas-guiding channels have a diameter of 0.1 mm and communicate with the ventilation holes inside the heating core structure. The heating section is 10 mm long and serves as the main heating element of the heating core. The gas-guiding channels of the ion-interaction section are vented with 99.99% pure nitrogen gas, and the ventilation volume is... .

[0013] Specifically, both the heating section and the ion interaction section adopt a modified type. Alloy substrate, the substrate composition by mass percentage is The substrate is melted by vacuum induction: vacuum degree Melting temperature 1600℃, hot rolling forming: temperature 1100℃, deformation 60%, solution treatment: temperature 1050℃, holding for 2 hours, water quenching and precision grinding: surface roughness The process of preparation; The ion-interacting section is 10 mm long and has a three-layer composite modification structure consisting of a transition layer, a functional layer, and a protective layer. The total thickness is [not specified]. The transition layer is Nickel-chromium alloy, 2±0.2μm thick, prepared by magnetron sputtering: vacuum degree Sputtering power 150W, adhesion resistivity The functional layer is ,thickness Prepared using cathodic arc plating process: arc current 80A, bias voltage -150V, porosity ≤1%, hardness ≥HV1200, and protein adsorption rate for aquatic products ≥60%; the protective layer is... Thickness 2±0.2μm, prepared using electron beam evaporation process: vacuum degree Evaporation rate 0.1 nm / s, water contact angle ≥110°.

[0014] Specifically, the heating element structure integrates dual PT1000 platinum resistance sensors: accuracy class A, temperature measurement range - With an error of ±0.15℃, dual PT1000 platinum resistance sensors are built into the junction of the heating section and the ion action section to monitor the axial temperature distribution. The heating section is wound with 200 turns of enameled wire and the ion action section is wound with 150 turns of enameled wire. The enameled wire is a copper-nickel alloy wire with a diameter of 0.1mm. The temperature of the two sections is independently adjusted by a dual-channel PID controller, and a thermal fuse with a melting temperature of 320℃ and a rated current of 1A is built in.

[0015] Specifically, the modified Kanthal Al alloy substrate, after being immersed in a 5% methanol-acetonitrile mixture for 72 hours, exhibits a corrosion rate ≤0.005 mm / year; its resistivity at 25°C is [missing value]. , Temperature coefficient ≤ 0.0003 / ℃.

[0016] Specifically, a first connecting sleeve is installed at the end of the ion interaction section away from the heating end, one end of the mass spectrometer injection tube is installed inside the first connecting sleeve, and a second connecting sleeve is installed at the end of the mass spectrometer injection tube away from the first connecting sleeve, and the second connecting sleeve is connected to the vacuum chamber.

[0017] Specifically, a column is mounted on the outer surface of the venturi pump, and a connecting plate is mounted on the end of the column away from the venturi pump. The connecting plate is connected to the vacuum chamber. A panel is mounted on one end of the base plate, and a display screen is mounted on one side of the panel.

[0018] An evaporation ionization mass spectrometry method for identifying aquatic products includes the following steps: Step 1: Port optimization of portable mass spectrometry and construction of ion stabilization transport; The mass spectrometry port of a portable mass spectrometer was modified to construct an ion transport system for aquatic products, consisting of a Venturi pump, auxiliary solvent tubing, and a mass spectrometry injection tube; the mass spectrometry injection tube adopts... Made of stainless steel, the inner wall of which is coated with polyethylene, polydimethylsiloxane or polyvinylbenzene, the mass spectrometer sample tube with the best coating is selected by comparing the adsorption effect of different coatings on matrix impurities of aquatic products and the ion quenching inhibition effect. A heating element is installed at the mass spectrometer port. The heating element comprises, along the axial direction, a connecting end, a heating section, and an ion interaction section, all three sections being coaxially integrally formed. The connecting end has an M2 thread on its surface and two internal silver-copper alloy conductive pins. The heating section and ion interaction section use a modified Kanthal Al alloy substrate, with the substrate composition by mass percentage being [missing information]. The surface of the ion interaction section is provided with a three-layer composite modification structure of "transition layer-functional layer-protective layer". The transition layer is a nickel-chromium alloy with a thickness of 2±0.2μm, prepared by magnetron sputtering. The functional layer is a titanium-zirconium-oxygen composite ceramic with a thickness of 8±0.5μm, prepared by cathodic arc plating. The protective layer is magnesium fluoride with a thickness of 2±0.2μm, prepared by electron beam evaporation. The surface of the ion interaction section is provided with annular microgrooves and gas guiding channels. The heating element integrates dual PT1000 platinum resistance sensors and segmented heating windings. A dual-path PID controller independently regulates the temperatures of the heating section and the ion-action section, ensuring the axial temperature difference in the ion-action section is ≤5℃. Methanol, acetonitrile, or isopropanol, or their proportional mixtures, are introduced into the auxiliary solvent pipeline to adjust the solvent flow rate. To achieve optimization of ion signal response; Step 2: Rapid evaporation and ionization of aquatic product tissue molecules; Samples of different aquatic products were collected, and the basic components of the samples were analyzed by Kjeldahl nitrogen determination and Soxhlet extraction. Tissues from different parts of the aquatic products were taken and rapidly evaporated and ionized using iKnife, electrothermal probe and laser ionization methods respectively: iKnife cut strips with a distance of about 1 cm on the tissue surface, electrothermal probe directly contacted the tissue for 5 seconds, laser beam diameter and focal length were optimized by adjusting the prism through a robotic arm, and ionization power was optimized by climbing experiment. By controlling the residence time of electrical energy, thermal energy and laser energy during ionization, observing the changes in protein properties on the tissue surface through electron microscopy, and recording the dynamic changes of ion signals using Masslynx software, residence time parameters that are free from tissue pyrolysis and have stable ion signals were screened. Step 3: Verification of the rapid evaporation ionization mechanism; Matrix-assisted proton migration ionization verification: Water, 2,5-dihydroxybenzoic acid and other proton donor / acceptor compounds were sprayed or printed on the surface of aquatic product muscle tissue. The molecular phenotype differences before and after the addition of iKnife, electrothermal probe and laser ionization were compared. The existence form of characteristic addition peaks was analyzed. The effects of sample moisture content and chemical matrix concentration on the molecular phenotype response intensity were studied. Direct thermal ionization verification: By optimizing the energy power of iKnife, electrothermal probe and laser, the ion structure is analyzed to clarify the ion addition / fragmentation mode, and the proton and electron migration pathways are determined by computational chemistry to clarify the effect of thermal energy on the molecular phenotypic profile. Verification of ionization induced by electrical energy and laser energy: Under the same sample level, the differences in molecular phenotypes induced by iKnife, electrothermal probe and laser ionization were compared. Ionization was performed using lasers of different wavelengths of 266nm, 355nm, 553nm, 660nm, 730nm and 976nm. The power and action time of electrical energy and laser energy were optimized. The molecular ionization energy was calculated by combining Gaussian software to clarify the ionization mechanism. Step 4: Eliminate exogenous interference factors; Aquatic product tissue sections were wrapped in aluminum foil, frozen in liquid nitrogen, fixed using cryo-embedding media, and then sectioned using a cryosectioning mechanism. Thick sections were thawed, fixed, and then vacuum dried for 15 minutes. Optical images of the slices were acquired using an MS imager with 200 laser irradiation points and a repetition frequency of 1000 Hz, in both positive and negative scanning modes. Spacing scan slices, set sample voltage The detector voltage is 1.75kV, and the data acquisition... MS data within a range; Analyze MSI data and optical images to screen molecular images with obvious distribution characteristics, and remove relevant fluctuating molecules in subsequent statistical analysis to eliminate interference from intra- and inter-individual differences in aquatic products; Step 5: Establishment of mathematical statistics and analysis models; SPSS software was used to perform correlation analysis, principal component analysis and orthogonal partial least squares discriminant analysis on the detection data to observe the clustering of different aquatic product varieties and determine the weights of biomarkers. By analyzing the total ion current of molecular phenotypes using LiveID software, selecting peak start and stop points and eliminating interference factors, a model for identifying the authenticity of aquatic products is established to achieve real-time identification. Step 6: Methodological validation and standardization; The content of target ions was determined by gas chromatography-mass spectrometry or liquid chromatography-mass spectrometry, a standard curve was plotted and the linearity was verified; the limit of detection was calculated at 3 times the signal-to-noise ratio and the limit of quantitation was calculated at 10 times the signal-to-noise ratio to evaluate the sensitivity of the method. Precision was verified using intra-day and inter-day precision methods: intra-day precision was achieved by continuously spiked seven blank samples at low, medium, and high concentrations on the same day and calculating the RSD; inter-day precision was achieved by spiked blank samples on days 1, 3, 7, 15, and 30 and calculating the RSD. Recovery rates were calculated using three concentration levels. Blind samples of unknown aquatic products were identified, and the results were compared with molecular biological assays to verify the stability and accuracy of the method and to establish a standardized identification process.

[0019] The beneficial effects of this invention are: 1. The constructed "Venturi pump-auxiliary solvent tubing-mass spectrometer injection tube" ion transport system, coupled with a tube whose inner wall is coated with polyethylene, polydimethylsiloxane, or polyvinylbenzene... Stainless steel mass spectrometer injection tubes can effectively adsorb matrix impurities in aquatic products and suppress ion quenching, significantly improving the mass spectrometry injection efficiency of molecular ions and the signal response intensity of target compounds, thus solving the problems of unstable signals and poor repeatability in traditional devices.

[0020] 2. The three-layer composite modification structure of "transition layer-functional layer-protective layer" in the ion action section specifically solves the problem of matrix contamination in aquatic products: the functional layer of titanium-zirconium-oxygen composite ceramic has an adsorption rate of ≥60% for protein in aquatic products and the amount of fatty impurities attached after a single detection is ≤0.15mg. Combined with the hydrophobic and anti-corrosion properties of magnesium fluoride in the protective layer, the internal cleaning cycle of the mass spectrometer is extended from 7 days to 60 days, which significantly reduces the operation and maintenance costs.

[0021] 3. The improved KanthalA1 alloy substrate and protective layer work together to enhance corrosion resistance. After immersion in a 5% methanol-acetonitrile mixture for 72 hours, the corrosion rate is ≤0.005mm / year. After 500 tests, the resistance value fluctuates by only ±1.2%, which is far superior to the traditional pure KanthalA1 substrate, ensuring long-term stability.

[0022] 4. The functional layer of titanium-zirconium-oxygen composite ceramic provides abundant active sites, increasing the secondary ionization efficiency of characteristic ions in aquatic products from ≤35% to [a higher percentage]. The target ion signal intensity is enhanced. This significantly improves detection accuracy.

[0023] 5. The Venturi pump can be flexibly connected to auxiliary solvents and sampling pumps through solvent connectors and sample inlet connectors. It can dilute the aerosol concentration and clean key components with auxiliary solvents, and efficiently collect aquatic product samples with the help of sampling pumps, making it suitable for the detection of aquatic product samples of different forms. Attached Figure Description

[0024] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the structure of a portable evaporative ionization mass spectrometry device for aquatic product identification according to the present invention; Figure 2 Another perspective view of a portable evaporative ionization mass spectrometry device for aquatic product identification according to the present invention; Figure 3 for Figure 2 Enlarged view of point A in the middle; Figure 4 This is a schematic diagram of the assembly of the mass spectrometer sample inlet tube and the Venturi pump in a portable evaporative ionization mass spectrometer for aquatic product identification according to the present invention. Figure 5 This is a schematic diagram of the assembly of the mass spectrometer sample inlet tube and the Venturi pump in a portable evaporative ionization mass spectrometer for aquatic product identification according to the present invention. In the picture: 100. Base plate; 101. Panel; 1011. Display screen; 200. Vacuum chamber; 201. Diaphragm pump; 202. Molecular pump; 203. Vacuum gauge; 300. Venturi pump; 301. Connecting plate; 3011. Column rod; 302. Solvent tube connector; 303. Sample inlet tube connector; 3031. Pipeline; 400. Multiplier; 500. Connecting end; 501. Heating section; 502. Ion interaction section; 600. Mass spectrometer sample inlet tube; 601. First connecting sleeve; 602. Second connecting sleeve; 700. Sampling pump. Detailed Implementation

[0025] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0026] Please see Figures 1-5 The present invention provides a technical solution: a portable evaporative ionization mass spectrometry device for aquatic product identification, comprising a base plate 100, a panel 101 mounted on one end of the base plate 100, a display screen 1011 mounted on one side of the panel 101, a vacuum chamber 200 mounted on the upper surface of the base plate 100, and a vacuum gauge 203 mounted on one side of the vacuum chamber 200. The vacuum gauge 203 is an instrument for measuring vacuum degree, which can monitor the vacuum pressure in the system in real time, provide vacuum degree data for equipment operation, and facilitate operators to understand and control the vacuum state.

[0027] A diaphragm pump 201 is installed on the side of the vacuum chamber 200 away from the vacuum gauge 203. The diaphragm pump 201 is connected to the base plate 100. A molecular pump 202 is installed on the upper surface of the vacuum chamber 200 near the diaphragm pump 201. A multiplier 400 is installed on the side of the sample inlet, and the multiplier 400 is connected to the vacuum chamber 200. The diaphragm pump 201 acts as a backing pump to obtain a preliminary vacuum environment, providing basic vacuum conditions for subsequent high-vacuum equipment (such as the molecular pump 202). It can remove gas and reduce the pressure inside the system. The molecular pump 202 operates after the diaphragm pump 201 has obtained a preliminary vacuum, and can obtain... High vacuum or ultra-high vacuum pumps use high-speed rotating blades to throw gas molecules against the pump wall, thus achieving efficient pumping and meeting the experimental or process requirements with high vacuum levels. The vacuum chamber 200 is the core vacuum area of ​​the entire system, providing a vacuum environment for various experiments or processes. Samples, gases, etc. interact within it. The internal vacuum level is maintained by molecular pumps 202, diaphragm pumps 201, etc. The multiplier 400 is used for signal amplification. In scenarios such as vacuum detection, it can amplify weak electrical signals (such as signals generated by particle collisions) for subsequent signal processing and detection.

[0028] A column 3011 is mounted on the outer surface of the Venturi pump 300. A connecting plate 301 is mounted on the end of the column 3011 away from the Venturi pump 300, connecting the connecting plate 301 to the vacuum chamber 200, thus completing the installation of the Venturi pump 300 on one side of the vacuum chamber 200. A solvent tube connector 302 is mounted on the outer surface of the Venturi pump 300. An injection tube connector 303 is mounted on the end of the outer surface of the Venturi pump 300 away from the solvent tube connector 302. The injection tube connector 303 is connected to the sampling pump 700 through a pipe 3031, constructing an ion transport system of "Venturi pump 300 - auxiliary solvent tubing - mass spectrometer injection tube 600". This system is equipped with a casing coated with polyethylene, polydimethylsiloxane, or polyvinylbenzene. The 600 stainless steel mass spectrometer sample introduction tube can effectively adsorb matrix impurities in aquatic products and suppress ion quenching, significantly improving the mass spectrometry introduction efficiency of molecular ions and the signal response intensity of target compounds, thus solving the problems of unstable signals and poor repeatability of traditional devices.

[0029] A Venturi pump 300 is connected to a mass spectrometer injection tube 600 via a heating element structure. One end of the mass spectrometer injection tube 600 is connected to and communicates with a vacuum chamber 200. The heating element structure includes a connecting end 500, which is mounted on the outer surface of the Venturi pump 300. A heating section 501 is mounted on the end of the connecting end 500 away from the Venturi pump 300. An ion interaction section 502 is mounted on the end of the heating section 501 away from the connecting end 500. The ion interaction section 502 is connected to and communicates with the vacuum chamber 200 via the mass spectrometer injection tube 600. A first connecting sleeve 601 is mounted on the end of the ion interaction section 502 away from the heating section 501. One end of the mass spectrometer injection tube 600 is mounted on the first connecting sleeve 601. Inside a connecting sleeve 601, a second connecting sleeve 602 is installed at the end of the mass spectrometer injection tube 600 away from the first connecting sleeve 601. The second connecting sleeve 602 is connected to the vacuum chamber 200. The first connecting sleeve 601 and the second connecting sleeve 602 achieve a reliable connection of the mass spectrometer injection tube 600. The Venturi pump 300 can be flexibly connected to the auxiliary solvent and the sampling pump 700 through the solvent tube connector 302 and the injection tube connector 303. It can dilute the aerosol concentration and clean the key components with the auxiliary solvent (methanol, acetonitrile, etc.) and efficiently collect aquatic product samples with the help of the sampling pump 700, which is suitable for the detection of aquatic product samples of different forms (solid tissue, liquid exudate).

[0030] The connecting end (500), heating section (501), and ion action section (502) are integrally formed coaxially along the axial direction. The total length of the connecting end (500), heating section (501), and ion action section (502) is 25±0.5mm, and the outer diameter is 3±0.1mm. The length of the connecting end (500) is 5mm. The surface of the connecting end (500) is provided with M2 thread. The connecting end (500) has two built-in silver-copper alloy conductive pins with a diameter of 0.5mm. The conductivity of the silver-copper alloy conductive pins is... The ion interaction section (502) has annular microgrooves and gas channels on its surface. The annular microgrooves are 0.2 mm deep, 0.3 mm wide, and 0.5 mm apart, with 15 grooves evenly distributed along the axial direction. The gas channels have a diameter of 0.1 mm and are connected to the ventilation holes inside the heating core structure. The heating section (501) is 10 mm long and serves as the main heating element of the heating core. The gas channels of the ion interaction section (502) are filled with nitrogen gas of 99.99% purity, and the gas flow rate is... .

[0031] Both the heating section (501) and the ion interaction section (502) adopt a modified type. Alloy substrate, the substrate composition by mass percentage is The substrate is melted by vacuum induction: vacuum degree Melting temperature 1600℃, hot rolling forming: temperature 1100℃, deformation 60%, solution treatment: temperature 1050℃, holding for 2 hours, water quenching and precision grinding: surface roughness The process of preparation; the ion interaction segment (502) is 10 mm long and has a three-layer composite modification structure of transition layer-functional layer-protective layer on its surface, with a total thickness of The transition layer is Nickel-chromium alloy, thickness Fabricated using magnetron sputtering process: vacuum degree Sputtering power 150W, adhesion resistivity The functional layer is ,thickness Prepared using cathodic arc plating process: arc current 80A, bias voltage -150V, porosity ≤1%, hardness ≥HV1200, and protein adsorption rate for aquatic products ≥60%; the protective layer is... Thickness 2±0.2μm, prepared using electron beam evaporation process: vacuum degree With an evaporation rate of 0.1 nm / s and a water contact angle ≥110°, the ion interaction section 502 features a three-layer composite modified structure consisting of a transition layer, a functional layer, and a protective layer to specifically address the problem of matrix contamination in aquatic products: the functional layer, titanium-zirconium-oxygen composite ceramic, has an adsorption rate of ≥60% for proteins in aquatic products, and the amount of fatty impurities adhering after a single detection is ≤0.15 mg. Combined with the hydrophobic and anti-corrosion properties of magnesium fluoride in the protective layer (water contact angle ≥110°), the internal cleaning cycle of the mass spectrometer is extended from 7 days to 60 days, significantly reducing operation and maintenance costs. The modified KanthalA1 alloy substrate, after immersion in a 5% methanol-acetonitrile mixture for 72 hours, exhibits a corrosion rate ≤0.005 mm / year; its resistivity at 25℃ is [missing value]. , With a temperature coefficient ≤0.0003 / ℃, the modified KanthalA1 alloy substrate (containing Ti) and the protective layer synergistically enhance corrosion resistance. After immersion in a 5% methanol-acetonitrile mixture for 72 hours, the corrosion rate is ≤0.005mm / year. After 500 tests, the resistance value fluctuation is only ±1.2%, which is far superior to the traditional pure KanthalA1 substrate (resistance value fluctuation is more than ±8%), ensuring long-term stability. The functional layer of titanium-zirconium-oxygen composite ceramic provides abundant active sites, enabling the production of characteristic ions in aquatic products (… The secondary ionization efficiency was increased from ≤35% to The target ion signal intensity is enhanced. This significantly improves detection accuracy.

[0032] The electric heating core structure integrates a dual PT1000 platinum resistance sensor: accuracy class A, temperature measurement range With an error of ±0.15℃, dual PT1000 platinum resistance sensors are respectively built into the junction of heating section 501 and ion action section 502 to monitor the axial temperature distribution. Heating section 501 is wound with 200 turns of enameled wire, and ion action section 502 is wound with 150 turns of enameled wire. The enameled wire is a copper-nickel alloy wire with a diameter of 0.1mm. The temperature of the two sections is independently regulated by a dual-channel PID controller, and a built-in temperature fuse with a melting temperature of 320℃ and a rated current of 1A is included. The precise temperature control design of the dual PT1000 platinum resistance sensors and the segmented heating windings reduces the axial temperature difference of ion action section 502 from ±0.15℃. Controlled The quenching rate of ion clusters decreased from >40% to This ensures that ions are heated evenly during transmission, avoiding signal fluctuations caused by temperature variations.

[0033] An evaporative ionization mass spectrometry method for identifying aquatic products includes the following steps: Step 1: Port optimization and ion stabilization transport construction of a portable mass spectrometer. The mass spectrometry port of the portable mass spectrometer is modified to construct an aquatic product ion transport system consisting of a Venturi pump 300, auxiliary solvent tubing, and a mass spectrometry injection tube 600; the mass spectrometry injection tube 600 adopts... The mass spectrometer injection tube 600 is made of stainless steel, with its inner wall coated with polyethylene, polydimethylsiloxane, or polyvinylbenzene. The optimal coating was selected by comparing the adsorption of matrix impurities in aquatic products and the inhibition of ion quenching by different coatings. A heating element is installed at the mass spectrometer port, comprising a connecting end 500, a heating section 501, and an ion-interaction section 502, all three sections coaxially integrated. The connecting end 500 has an M2 thread and two internal silver-copper alloy conductive pins. The heating section 501 and the ion-interaction section 502 use a modified Kanthal Al alloy substrate, with the substrate composition by mass percentage being [missing information]. The surface of the ion-acting section 502 is decorated with a three-layer composite structure consisting of a transition layer, a functional layer, and a protective layer. The transition layer is a nickel-chromium alloy with a thickness of 2±0.2μm, prepared by magnetron sputtering. The functional layer is a titanium-zirconium-oxygen composite ceramic with a thickness of 8±0.5μm, prepared by cathodic arc plating. The protective layer is magnesium fluoride with a thickness of 2±0.2μm, prepared by electron beam evaporation. The surface of the ion-acting section 502 is also provided with annular microgrooves and gas channels. The heating core integrates dual PT1000 platinum resistance sensors and segmented heating windings. A dual-path PID controller independently regulates the temperatures of the heating section 501 and the ion-acting section 502, controlling the axial temperature difference of the ion-acting section 502 to ≤5℃. Methanol, acetonitrile, or isopropanol and their proportional mixtures are introduced into the auxiliary solvent pipeline to adjust the solvent flow rate. To achieve optimization of ion signal response; Step 2: Rapid evaporative ionization of aquatic product tissues. Samples of different aquatic product varieties were collected, and the basic components of the samples were analyzed using the Kjeldahl nitrogen determination method and Soxhlet extraction method. Tissues from different parts of the aquatic products were rapidly evaporated and ionized using iKnife, electrothermal probe, and laser ionization methods respectively: iKnife cut strips with a distance of about 1 cm on the tissue surface, the electrothermal probe was in direct contact with the tissue for 5 seconds, and the laser beam diameter and focal length were optimized by adjusting the prism through a robotic arm. The ionization power was optimized through a climbing experiment. The residence time of electrical energy, thermal energy, and laser energy during the ionization process was controlled. The changes in protein properties on the tissue surface were observed by electron microscopy, and the dynamic changes of ion signals were recorded using Masslynx software. Residence time parameters that prevent tissue charring and have stable ion signals were screened. Step 3: Verification of rapid evaporation ionization mechanism and matrix-assisted proton migration ionization: Spray or print water, 2,5-dihydroxybenzoic acid, and other proton donor / acceptor compounds onto the surface of aquatic product muscle tissue. Compare the differences in molecular phenotypes before and after addition using iKnife, electrothermal probe, and laser ionization. Analyze the form of characteristic addition peaks and study the effects of sample moisture content and chemical matrix concentration on the intensity of molecular phenotype response. Direct thermal ionization verification: Optimize the energy power of iKnife, electrothermal probe, and laser to analyze ion structures and elucidate ion addition. / Fragmentation mode, combined with computational chemistry to determine proton and electron migration paths, clarifying the influence of thermal energy on molecular phenotypic profile; Verification of ionization induced by electrical energy and laser energy: Under the same sample level, the differences in molecular phenotypic profiles induced by iKnife, electrothermal probe and laser ionization were compared. Ionization was performed using lasers of different wavelengths of 266nm, 355nm, 553nm, 660nm, 730nm and 976nm. The power and action time of electrical energy and laser energy were optimized. Molecular ionization energy was calculated by combining Gaussian software to elucidate the ionization mechanism. Step 4: Elimination of exogenous interference factors. The aquatic product tissue sections were wrapped in aluminum foil and frozen in liquid nitrogen, fixed using a cryo-embedding medium, and then sectioned using a cryogenic sectioning mechanism. Thick sections were thawed, fixed, and vacuum-dried for 15 minutes. Optical images of the sections were acquired using an MS imager with 200 laser irradiation points and a repetition frequency of 1000 Hz, in both positive and negative scanning modes. Spacing scan slices, set sample voltage The detector voltage is 1.75kV, and the data acquisition... MS data within a range; analyze MSI data and optical images to screen molecular images with obvious distribution characteristics, remove relevant fluctuating molecules in subsequent statistical analysis, and eliminate interference from intra- and inter-individual differences in aquatic products; Step 5: Establishment of Mathematical Statistics and Analysis Model. SPSS software is used to perform correlation analysis, principal component analysis and orthogonal partial least squares discriminant analysis on the detection data to observe the clustering of different varieties of aquatic products and determine the weight of biomarkers. LiveID software is used to analyze the total ion current of molecular phenotypes, select the peak start and end points and eliminate interference factors to establish an aquatic product authenticity identification model to achieve real-time identification. Step 6: Method Validation and Standardization. The target ion content was determined using gas chromatography-mass spectrometry (GC-MS) or liquid chromatography-mass spectrometry (LC-MS), a standard curve was plotted, and linearity was verified. The limit of detection (LOD) was calculated using a signal-to-noise ratio (SNR) of 3, and the limit of quantitation (LOQ) using a SNR of 10, to evaluate method sensitivity. Method precision was validated using intra-day and inter-day precision: intra-day precision was achieved by testing seven blank samples with three consecutive spikes (low, medium, and high concentrations) on the same day and calculating the RSD; inter-day precision was achieved by testing blank samples with spikes on days 1, 3, 7, 15, and 30 and calculating the RSD. The recovery rate was calculated using three concentration levels. The method stability and accuracy were verified by comparing the results with molecular biological assays using blind samples of a batch of unknown aquatic products, and a standardized identification procedure was developed.

[0034] Improved accuracy and reliability of identification: Multiple ionization methods (iKnife, electrothermal probe, laser) combined with climbing experiments to optimize power and residence time avoid tissue charring and excessive impurity ion generation. Combined with rapid evaporation ionization mechanism verification (matrix-assisted proton migration, direct thermal ionization, and electrical and laser-induced excitation ionization), the ion formation pathway is clearly defined, ensuring the accuracy of molecular phenotypic analysis. Exogenous interference factor elimination steps (tissue section freezing, MS imaging analysis, removal of fluctuating molecules) effectively eliminate the influence of intra-individual (muscle texture, location) and inter-individual (growth environment, feed) differences in aquatic products. Combined with multi-dimensional statistical analysis using SPSS software (correlation, principal component analysis, orthogonal partial least squares discriminant analysis) and the real-time identification model of LiveID software, aquatic product species clustering is more accurate, and biomarker weight determination is more scientific.

[0035] The method boasts standardization and broad applicability: comprehensive methodological validation (linearity, sensitivity, precision, and recovery) ensures method stability and reliability; the limit of detection (3 times signal-to-noise ratio) and limit of quantitation (10 times signal-to-noise ratio) meet the requirements for detecting low-concentration characteristic ions; intra-day precision (low RSD) and inter-day precision (stable RSD over long-term detection) guarantee data repeatability; batch blind sample identification and comparison with molecular biology results further validate the method's accuracy, enabling the formation of a standardized identification process. The method is applicable to the authenticity identification of different varieties and parts of aquatic products (such as high-protein salmon and high-fat whiteleg shrimp), allowing for both refined analysis in the laboratory and real-time on-site detection with portable devices, providing efficient technical support for aquatic product market supervision and quality control.

[0036] Although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A portable evaporative ionization mass spectrometer for the identification of aquatic products, characterized by: The application relates to a portable mass spectrometer, which comprises a bottom plate (100), a vacuum cavity (200) mounted on the upper surface of the bottom plate (100), a sample inlet piece mounted on one side of the vacuum cavity (200), a vacuum gauge (203) mounted on one side of the vacuum cavity (200), a diaphragm pump (201) arranged on the side of the vacuum cavity (200) away from the vacuum gauge (203), the diaphragm pump (201) being connected with the bottom plate (100), a molecular pump (202) mounted on the upper surface of the vacuum cavity (200) close to the diaphragm pump (201), and a multiplier (400) arranged on one side of the sample inlet piece and connected with the vacuum cavity (200).

2. The portable evaporative ionization mass spectrometer for the identification of aquatic products according to claim 1, characterized in that: The sample inlet piece comprises a Venturi pump (300), the Venturi pump (300) is mounted on one side of the vacuum cavity (200), a solvent pipe joint (302) is mounted on the outer surface of the Venturi pump (300), an inlet pipe joint (303) is mounted on the outer surface of the Venturi pump (300) away from the solvent pipe joint (302), the inlet pipe joint (303) is connected with a sampling pump (700) through a pipeline (3031), the Venturi pump (300) is connected with a mass spectrometer inlet pipe (600) through an electric heating core structure, and one end of the mass spectrometer inlet pipe (600) is connected with the vacuum cavity (200).

3. The portable evaporative ionization mass spectrometer for the identification of aquatic products according to claim 2, characterized in that: The electric heating core structure comprises a connecting end (500), the connecting end (500) is mounted on the outer surface of the Venturi pump (300), a heating section (501) is mounted on one end of the connecting end (500) away from the Venturi pump (300), an ion action section (502) is mounted on one end of the heating section (501) away from the connecting end (500), and the ion action section (502) is connected with the vacuum cavity (200) through the mass spectrometer inlet pipe (600).

4. The portable evaporative ionization mass spectrometer for the identification of aquatic products according to claim 3, characterized in that: The connecting end (500), the heating section (501) and the ion action section (502) are coaxially integrally formed along the axial direction, the total length of the connecting end (500), the heating section (501) and the ion action section (502) is 25±0.5mm, the outer diameter is 3±0.1mm, the length of the connecting end (500) is 5mm, the surface of the connecting end (500) is provided with M2 screw threads, two silver-copper alloy conductive pins with a diameter of 0.5mm are arranged in the connecting end (500), the silver-copper alloy conductive pin has a conductivity , the surface of the ion action section (502) is provided with annular micro-grooves and gas guiding channels, the annular micro-grooves have a depth of 0.2mm, a width of 0.3mm and a pitch of 0.5mm, 15 annular micro-grooves are uniformly distributed along the axial direction, the gas guiding channels have a diameter of 0.1mm and are communicated with the air holes in the structure of the electric heating core, the length of the heating section (501) is 10mm and the heating section (501) is the main heating body of the electric heating core; the gas guiding channels of the ion action section (502) are connected with nitrogen gas with a purity of 99.99% and the air flow .

5. The portable evaporative ionization mass spectrometer for the authentication of aquatic products according to claim 4, characterized in that: The heating section (501) and the ion action section (502) are both improved Alloy base material, base material component mass percentage ; the base material is prepared by vacuum induction smelting: vacuum degree , smelting temperature 1600 DEG C, hot rolling forming: temperature 1100 DEG C, deformation 60%, solid solution treatment: temperature 1050 DEG C, holding for 2h, water quenching and precision grinding: surface roughness ; the ion action section (502) is 10mm long, and the surface is provided with a transition layer-function layer-protection layer three-layer composite modification structure, total thickness : the transition layer is nickel-chromium alloy, thickness , prepared by magnetron sputtering process: vacuum degree , sputtering power 150W, adhesion , resistivity ; The functional layer is , thickness , prepared by cathodic arc plating process: arc current 80 A, bias voltage -150 V, porosity ≤1%, hardness ≥ HV1200, and protein adsorption rate on aquatic products ≥60%; the protective layer is , thickness 2±0.2 μm, prepared by electron beam evaporation process: vacuum degree , evaporation rate 0.1 nm / s, water contact angle ≥110°.

6. The portable evaporative ionization mass spectrometer for the identification of aquatic products according to claim 5, characterized in that: The electric heating core structure integrates a double PT1000 platinum resistance sensor: precision grade A, temperature measurement range ±0.15℃, the double PT1000 platinum resistance sensors are respectively arranged at the junction of the heating section (501) and the ion action section (502) to monitor the axial temperature distribution; the heating section (501) is wound with 200 turns of enameled wire, and the ion action section (502) is wound with 150 turns of enameled wire; the enameled wire is a copper-nickel alloy wire with a diameter of 0.1 mm; the two-section temperature is independently adjusted through a double-path PID controller, and a temperature fuse with a melting temperature of 320℃ and a rated current of 1A is arranged.

7. The portable evaporative ionization mass spectrometer for the identification of aquatic products according to claim 5, characterized in that: The modified Kanthal A1 alloy substrate is soaked in 5% methanol-acetonitrile mixture for 72h, and the corrosion rate is ≤0.005mm / year; the resistivity at 25℃ is , Temperature coefficient ≤0.0003 / ℃.

8. The portable evaporative ionization mass spectrometer for the identification of aquatic products according to claim 3, characterized in that: One end of the ion action section (502) away from the heating section (501) is provided with a first connecting sleeve (601), one end of the mass spectrometer inlet pipe (600) is mounted in the first connecting sleeve (601), the mass spectrometer inlet pipe (600) is provided with a second connecting sleeve (602) on one end away from the first connecting sleeve (601), and the second connecting sleeve (602) is connected with the vacuum cavity (200).

9. The portable evaporative ionization mass spectrometer for the identification of aquatic products according to claim 2, characterized in that: The outer surface of the Venturi pump (300) is provided with a column rod (3011), one end of the column rod (3011) away from the Venturi pump (300) is provided with a connecting disc (301), the connecting disc (301) is connected with the vacuum cavity (200), one end of the bottom plate (100) is provided with a panel (101), and one side of the panel (101) is provided with a display screen (1011).

10. A method of identifying a water product by evaporative ionization mass spectrometry, characterized by The application further discloses a method for constructing the portable mass spectrometer, which comprises the following steps: Step 1, portable mass spectrometer port optimization and ion steady-state transmission construction. The mass spectrometry port of a portable mass spectrometer host is modified to construct an aquatic product ion transmission system composed of a Venturi pump (300), an auxiliary solvent pipeline and a mass spectrometry sampling tube (600); the mass spectrometry sampling tube (600) adopts Stainless steel material, the inner wall is coated with polyethylene, polydimethylsiloxane or polydivinylbenzene coating, by comparing the adsorption effect of different coatings on water product matrix impurities and ion quenching inhibition effect, screening the optimal coating of the mass spectrometry sampling tube (600); An electric heating core is arranged at a mass spectrometry port, and the electric heating core sequentially comprises a connecting end (500), a heating section (501) and an ion action section (502) in an axial direction, and the three sections are coaxially integrally formed; the connecting end (500) is provided with an M2 thread on the surface and is internally provided with two silver-copper alloy conductive pins; the heating section (501) and the ion action section (502) adopt a modified Kanthal A1 alloy base material, and the base material has a mass percentage of ; the ion action section (502) is provided with a three-layer composite modification structure of a transition layer, a functional layer and a protective layer on the surface, the transition layer is a nickel-chromium alloy, has a thickness of 2±0.2 μm and is prepared by using a magnetron sputtering process; the functional layer is a titanium-zirconium-oxygen composite ceramic, has a thickness of 8±0.5 μm and is prepared by using a cathode arc plating process; the protective layer is magnesium fluoride, has a thickness of 2±0.2 μm and is prepared by using an electron beam evaporation process; and the ion action section (502) is provided with annular micro-grooves and gas guide channels on the surface. The electric heating core integrated double PT1000 platinum resistance sensor and segmented heating winding, through double PID controller independently adjust heating section (501) and ion interaction section (502) temperature, control ion interaction section (502) axial temperature difference ≤5℃;Into the auxiliary solvent pipeline into methanol, acetonitrile or isopropyl alcohol and its fixed ratio mixture, adjust the solvent flow rate 10-100 μL / min, realize the ion signal response optimization; Step 2, the rapid evaporation ionization of aquatic product tissue molecules; Collect different varieties of aquatic product samples, adopt Kjeldahl method and soxhlet extraction method to analyze the basic components of the samples; take different parts of aquatic product tissues, and adopt iKnife, electric heating probe and laser ionization methods for rapid evaporation ionization; iKnife cuts a strip of about 1 cm on the surface of the tissue, the electric heating probe directly contacts the tissue for 5 seconds, and the laser adjusts the prism through the mechanical arm to optimize the beam diameter and focal length, and the ionization power is optimized through the climbing experiment; Control the residence time of electric energy, heat energy and laser energy in the ionization process, observe the protein property changes on the surface of the tissue through the electron microscope, record the dynamic changes of ion signals by combining with Masslynx software, and screen the residence time parameters without tissue scorching and stable ion signals; Step 3, mechanism verification of rapid evaporation ionization; Matrix-assisted proton transfer ionization verification: spray or print water, 2,5-dihydroxybenzoic acid and other proton donor / acceptor compounds on the surface of the muscle tissue of aquatic products, compare the molecular phenotypes of iKnife, electric heating probe and laser ionization before and after adding, analyze the existence form of characteristic adduct peaks, and study the influence of water content and chemical matrix concentration of the sample on the response intensity of the molecular phenotype; Heat energy direct ionization verification: optimize the energy power of iKnife, electric heating probe and laser, analyze the ion structure to clarify the ion adduct / cleavage mode, determine the proton and electron migration path by combining with computational chemistry, and clarify the influence of heat energy on the molecular phenotype profile; Electric energy and laser energy induced excitation ionization verification: compare the molecular phenotypes of iKnife, electric heating probe and laser ionization under the same sample level, ionize by using 266 nm, 355 nm, 553 nm, 660 nm, 730 nm and 976 nm lasers, optimize the power and action time of electric energy and laser energy, calculate the molecular ionization energy by combining with Gaussian software, and clarify the ionization mechanism; Step 4, exclusion of exogenous interference factors; The fish tissue slices were wrapped with aluminum foil and frozen in liquid nitrogen, fixed with frozen embedding medium, and made into thick sections by a low-temperature microtome The thick sections were vacuum dried for 15 min after thawing and fixing. Optical images of the sections were acquired using a MS imager, scanning the sections at 100 pm x 100 pm intervals in positive and negative scan mode with 200 laser shots, 1000 Hz repetition rate, setting the sample voltage , the detector voltage at 1.75 kV, and acquiring MS data in the range of m / z 100-2000. Analyze the MSI data and optical images, screen the molecular images with obvious distribution characteristics, eliminate the related fluctuation molecules in subsequent statistical analysis, and exclude the interference of individual differences of aquatic products; Step 5, mathematical statistics and analysis model establishment; Perform correlation analysis, principal component analysis and orthogonal partial least squares discriminant analysis on the detection data by using SPSS software, observe the clustering of different varieties of aquatic products, and determine the weight of biomarkers; Analyze the total ion flow of the molecular phenotype by using LiveID software, select the peak start and end points and exclude interference factors, establish an authenticity identification model of aquatic products, and realize real-time identification; Step 6, methodology verification and standardization; The target ion content is determined by gas chromatography-mass spectrometry or liquid chromatography-mass spectrometry, a standard curve is drawn, and the linear relationship is verified; the detection limit is calculated by 3 times the signal-to-noise ratio, the quantification limit is calculated by 10 times the signal-to-noise ratio, and the sensitivity of the method is evaluated; The method precision is verified by intra-day precision and inter-day precision: the intra-day precision is tested by adding low, medium and high concentrations to 7 blank samples in the same day and calculating RSD; the inter-day precision is tested by adding blank samples on the 1st, 3rd, 7th, 15th and 30th days and calculating RSD; The recovery rate is calculated by using three concentration levels, the method stability and accuracy are verified by comparing the molecular biology determination results of batch unknown water product blind samples, and the standardization identification process is established.

Images