Aromatic ester compound detection device based on mass spectrum ion source and application

Abstract

The invention discloses an aromatic ester compound detection device based on a mass spectrum ion source and application. The detection device comprises an electrospray assembly and a low-temperature plasma beam assembly, the front end of a metal capillary in the electrospray assembly extends out of a main pipe of an insulating medium pipe by 4-12 cm, and an outer electrode in the low-temperature plasma beam assembly is 5-13 mm away from an outlet of the main pipe of the insulating medium pipe; an included angle between the low-temperature plasma beam assembly and the horizontal reference plane is 120-160 degrees, and an included angle between the low-temperature plasma beam assembly and the electrospray assembly is 45-90 degrees, so that the electro-liquid drop spray generated by the electrospray assembly is formed under the synergistic effect of the low-temperature plasma beam generated by the low-temperature plasma beam assembly; therefore, the plasma beam can better hit the surface of the sample, and ions can be effectively released from liquid drops. Therefore, the detection device can improve the detection sensitivity of the aromatic ester compounds, can be applied to rapid detection of food, traditional Chinese medicinal materials and Baijiu adulteration, and has the advantages of high automation and low price.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of aromatic ester compound detection, and particularly relates to an aromatic ester compound detection device based on a mass spectrometry ion source and application. BACKGROUND

[0002] As a key flavor ingredient and quality marker, the accurate detection of aromatic ester compounds is of great significance for food authenticity identification and adulteration identification. Based on the high sensitivity and high specificity of mass spectrometry analysis technology, it has become an indispensable core tool for the detection of such compounds. Due to the π electron delocalization of the benzene ring of aromatic ester compounds, the positive charge is dispersed, which reduces the stability of [M] + or [M+H] + in the ionization source, and aromatic ester compounds are neither strongly acidic (such as -COOH functional groups) nor strongly basic (such as -NH functional groups), and are "moderate" compounds in common ionization mechanisms.

[0003] For the relatively mature ionization technology ESI, ESI requires polar solvents (such as methanol or water), but the solubility of aromatic ester compounds in polar solvents may be poor (especially long-chain esters), resulting in reduced sensitivity; for low-temperature plasma ionization source (LTP), although it is easy to integrate and low in cost, its plasma energy is low, usually 1-10 eV, and it is difficult to effectively desorb solid or high-boiling aromatic ester compounds, resulting in insufficient gas-phase molecules, so a single ionization source has great limitations for the ionization of aromatic ester compounds.

[0004] CN 109545648 A discloses a composite ionization device, which comprises an insulating medium pipe, the outer wall of the insulating medium pipe is coated with a first outer electrode and a second outer electrode, the first outer electrode and the second outer electrode are electrically connected through a first power module; a fixed seat is sleeved on the left side of the insulating medium pipe, a first working gas inlet and a second working gas inlet are sequentially arranged on the top end of the fixed seat from left to right, a gas pipe is arranged in the fixed seat, a sample injection capillary is arranged in the gas pipe, a second power module is arranged on the sample injection capillary, a mass spectrometry port is arranged on the right side of the insulating medium pipe, a sample loading platform is arranged at the bottom end of the right side of the insulating medium pipe, and a heating and temperature control module is arranged in the fixed seat at the top end of the gas pipe. The patent realizes the combination of ESI and LTP, and can realize the detection of different polar compounds, but since the ionization behavior and efficiency of actual samples under the composite ionization mode are not fully investigated, the detection sensitivity and quantitative accuracy still need to be further verified, so the quantitative and accurate detection of aromatic ester compounds cannot be realized. SUMMARY

[0005] The main purpose of the present application is to provide a mass spectrometry ion source-based aromatic ester compound detection device and application, so as to realize efficient detection of aromatic ester compounds.

[0006] The specific technical solutions are as follows: A mass spectrometry ion source-based aromatic ester compound detection device comprises: An electrospray assembly comprises a first T-shaped insulating medium pipe and a metal capillary tube, the first T-shaped insulating medium pipe comprises a first main pipe and a first branch pipe; the metal capillary tube is inserted into the first main pipe and coaxially arranged with the first main pipe, the front end of the metal capillary tube extends 4-12 cm from the pipe opening of the first main pipe, and the tail end of the metal capillary tube is connected to a sample injection unit; A low-temperature plasma beam assembly comprises a second T-shaped insulating medium pipe, an inner electrode and an outer electrode, the second T-shaped insulating medium pipe comprises a second main pipe and a second branch pipe; the inner electrode is inserted into the second main pipe and coaxially arranged with the second main pipe; the outer electrode is spirally wound and attached to the outer surface of the second main pipe, and is 5-13 mm away from the outlet of the second main pipe; A mass spectrometer comprises a mass analyzer, and the mass analyzer has a mass spectrometry inlet; Two ion source supports are respectively used to fix the electrospray assembly and the low-temperature plasma beam assembly; Two XYZ displacement slides are each provided with an ion source support fixed thereon, and are used to position the azimuth angle between the electrospray assembly, the low-temperature plasma beam assembly and the mass spectrometry inlet, wherein the low-temperature plasma beam assembly is 120°-160° to a horizontal reference plane, and the angle between the electrospray assembly and the low-temperature plasma beam assembly is 45°-90°, the horizontal reference plane refers to a vertical plane where the mass spectrometry inlet is located, and the electrospray assembly and the low-temperature plasma beam assembly are aligned in the vertical direction; the horizontal distance between the electrospray assembly and the low-temperature plasma beam assembly and the mass spectrometry inlet is respectively 2-10 mm.

[0007] Further, the electrospray assembly further comprises a direct-current high-voltage power supply unit connected to the metal capillary tube, a first carrier gas pipe connected to the first branch pipe and a first working gas, the first working gas is injected into the first main pipe from the first branch pipe through the first carrier gas pipe; in this way, charged droplet atomization spraying can be stably generated, the charged droplet spraying is ionized by the action of an electric field, and the low-temperature plasma is combined to provide efficient ionization effect.

[0008] Preferably, the metal capillary tube has a diameter of 100-150 μm, such as 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, etc. The metal capillary tube is made of an electrically conductive material, such as stainless steel, aluminum, copper, etc. To reduce the cost, the metal capillary tube is made of stainless steel. The sample injection unit comprises a syringe and a sample injection tube connecting the syringe and the metal capillary tube. Preferably, the supply voltage of the direct current high voltage power supply unit is 1-3 kV.

[0009] Further, the low-temperature plasma beam assembly further comprises a second carrier gas tube connected to the second branch pipe, an alternating current high voltage power supply unit connected to the inner electrode, a ground voltage connected to the outer electrode, and a second working gas, which is injected into the second main pipe from the second branch pipe through the second carrier gas tube; to achieve spatial superposition and high stability output of the plasma beam.

[0010] The electro-spray assembly and the low-temperature plasma beam assembly operate simultaneously, the direct current high voltage power supply unit and the alternating current high voltage power supply unit are started, the electro-spray assembly generates electro-spray droplets, the low-temperature plasma beam assembly generates a low-temperature plasma beam with high stability and high efficiency output, which cooperates with the electro-spray droplets to realize efficient ionization of the sample to be tested. Among them, the sample to be tested contains aromatic ester compounds.

[0011] The material of the inner electrode can be an electrically conductive metal material such as stainless steel, copper, aluminum, tungsten, titanium, etc. To reduce the cost while ensuring the effect, the inner electrode is preferably a stainless steel cylindrical rod with a diameter of 0.5-1 mm and a length of 100-120 mm; the outer electrode can be a copper sheet, a stainless steel sheet, an aluminum sheet, a tungsten sheet, a titanium sheet, etc. Preferably, the outer electrode is a copper sheet with a thickness of 0.1-0.5 mm and a length of 5-10 mm. Preferably, the power supply parameters of the alternating current high voltage power supply unit are: alternating current high voltage frequency is 50-100 kHz, peak voltage is 2-3 kVpp, and working power is 5-250 W.

[0012] Further, the materials and structures of the first and second T-shaped insulating medium pipes are the same, and are prepared from high dielectric strength materials, including but not limited to fused quartz, aluminum oxide ceramic, or polyether ether ketone polymer material; the inner diameters of the main pipes and branch pipes of the first and second T-shaped insulating medium pipes are 3-4 mm and 6-7 mm, respectively, the lengths of the main pipes are 60-100 mm, and the lengths of the branch pipes are 20-50 mm, respectively.

[0013] Further, the first working gas and the second working gas are the same, and are nitrogen, oxygen or argon. The flow rates of the first working gas and the second working gas are accurately controlled by mass flow controllers, and the flow rates are 0.5-1.0 L / min, such as 0.6 L / min, 0.7 L / min, 0.8 L / min, 0.9 L / min, 1.0 L / min, etc.

[0014] Further, each ion source support is rectangular or circular. One of the two ion source supports is provided with a groove with the same diameter as the outer diameter of the first main pipe, and the other is provided with a groove with the same diameter as the outer diameter of the second main pipe. Each ion source support is fixed on the corresponding XYZ displacement slide table by screws. That is, the electrospray assembly and the low-temperature plasma beam assembly are respectively fixed on one of the two ion source supports.

[0015] The two XYZ displacement slide tables are existing knob-operated, in which the X-axis stroke is used to adjust the left-right distance between the electrospray assembly, the low-temperature plasma beam assembly and the mass spectrometry inlet; the Y-axis stroke is used to adjust the front-rear distance between the electrospray assembly, the low-temperature plasma beam assembly and the mass spectrometry inlet; the Z-axis stroke is used to adjust the up-down distance between the electrospray assembly, the low-temperature plasma beam assembly and the mass spectrometry inlet; and the R-axis stroke is used to adjust the angle between the plasma beam generated by the outlet of the low-temperature plasma beam assembly and the horizontal reference plane. In this way, the angle between the electrospray assembly, the low-temperature plasma beam assembly and the mass spectrometry inlet can be positioned by adjusting the above positional relationships of the XYZ displacement slide table, so as to ensure that the sample ions can smoothly enter the mass spectrometry inlet, make the complex ionization region more concentrated, and improve the ionization efficiency.

[0016] An application of the above detection device in detecting aromatic ester compounds.

[0017] Further, the application includes: inputting the sample solution to be detected into the metal capillary at a flow rate of 5-10 μL / min; forming a uniform charged droplet spray at the front end of the metal capillary by the electrospray assembly; generating a low-temperature plasma beam by the low-temperature plasma beam assembly; and introducing the measured components in the sample solution to be detected into the mass spectrometry inlet in a lossless scattering and efficient ionization state under the high synergy of the charged droplet spray and the low-temperature plasma beam, and performing mass spectrometry detection. The sample to be detected is a mixture containing aromatic ester compounds.

[0018] The aromatic ester compounds include, but are not limited to, ethyl phenylacetate, methyl o-methylamino benzoate, ethyl 3-phenylpropionate and dimethyl phthalate.

[0019] Further, the application includes the application of the above-mentioned detection device in detecting aromatic ester compounds in food or Chinese herbal medicines. The food can include wine, fruits, fermented foods, etc. The Chinese herbal medicines can be dried tangerine or orange peel, angelica, Szechuan lovage, etc.

[0020] Further, the application includes the application of the above-mentioned detection device in detecting the authenticity of Chinese herbal medicines or wine screening.

[0021] The above-mentioned aromatic ester compound detection device provided by the application combines ESI and LTP together to form a composite ionization source based on cross-type electrospray coupled with low-temperature plasma, which can greatly cover the "blind area" of the ionization of aromatic ester compounds. ESI can ionize the benzene ring and ester group in the aromatic ester compound through protonation (M+H + ) or adduct ion (such as M+Na + ) ionization generated by the formation of charged droplets and solvent evaporation; LTP (such as He or Ar plasma) is rich in high-energy electrons, excited-state species and active particles (such as O2 + , N2 + ), which can directly ionize non-volatile or non-polar molecules through charge transfer or Penning ionization. For aromatic ester compounds, the π electron system in the benzene ring is easy to interact with plasma active species, which can significantly improve the ionization sensitivity. In addition, in the ESI-LTP composite source, the plasma can pretreat complex matrix to reduce the competition ionization of non-target substances, and ESI can maintain a stable ion flow, so that the ionization of aromatic ester compounds in the "purified" system is more efficient. Therefore, the above-mentioned scheme provided by the application makes up for the limitations of single ESI and LTP in detecting aromatic ester compounds, and is suitable for rapid detection of food, Chinese herbal medicines and liquor adulteration. In addition, the entire detection device is built quickly and has a low price. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A schematic diagram of the aromatic ester compound detection device based on the mass spectrometry ion source provided by the first embodiment of the application is shown in the figure; Figure 2 A relationship diagram of the key parameters in the detection device and the mass spectrometry signal intensity provided by the first embodiment of the application is shown in the figure; Figure 3 ESI-LTP composite mode mass spectrometry graph (A), ESI mode mass spectrometry graph (B) and the structure of aromatic ester compounds (C) in the second embodiment of the application are shown in the figure; Figure 4 A standard curve of o-methylamino benzoic acid methyl ester in the third embodiment of the application is shown in the figure; Figure 5Mass spectrum of five different aroma types of wine in ESI-LTP composite mode (A) and the result of different aroma types of wine being distinguished in ESI-LTP mode (B) in Example Four of the present application. DETAILED DESCRIPTION

[0023] Example One: Device for detecting aromatic ester compounds based on mass spectrometry ion source and application Please refer to Figure 1 The present embodiment provides a device for detecting aromatic ester compounds based on mass spectrometry ion source, which comprises an ion source support 1, a metal capillary 2, a direct-current high-voltage power supply unit 3, a T-shaped insulating medium pipe 4, a carrier gas pipe 5, an ion source support 6, a T-shaped insulating medium pipe 7, an outer electrode 8, an inner electrode 9, a carrier gas pipe 10, an alternating-current high-voltage power supply unit 11, a grounding voltage 12, a sample to be tested 13, a charged droplet spray 14, a low-temperature plasma beam 15, and a mass spectrometer MS. The mass spectrometer MS comprises a mass analyzer having a mass spectrometer inlet 16.

[0024] In the present embodiment, the ion source supports 1 and 6 have the same structure, which is a rectangle with a length of 15 cm and a width of 5 cm, made of rigid polylactic acid material, and has a groove on the top for clamping the electrospray device and the low-temperature plasma beam device, positioning the angle between the electrospray, the plasma beam, and the mass spectrometer inlet. The ion source supports 1 and 6 are fixed on the XYZ displacement slide table by screws. The two XYZ displacement slide tables have the same result, which is the existing knob operation. The R axis has a scale, and the angle between the plasma beam generated by the LTP outlet and the horizontal reference plane can be adjusted by directly rotating to the corresponding scale. The X axis has a travel of 100 mm, which is used to adjust the left-right distance between the charged droplet electrospray 14, the low-temperature plasma beam 15, and the mass spectrometer inlet 16. The Y axis has a travel of 100 mm, which is used to adjust the front-back distance between the charged droplet electrospray 14, the low-temperature plasma beam 15, and the mass spectrometer inlet 16. The Z axis has a travel of 100 mm, which is used to adjust the up-down distance between the charged droplet electrospray 14, the low-temperature plasma beam 15, and the mass spectrometer inlet 16. In this way, by adjusting the above positional relationship, it is ensured that the sample ions can smoothly enter the mass spectrometer inlet 16. The T-shaped insulating medium pipes 4 and 7 are made of PEEK material, with a main pipe outer diameter of 6 mm, an inner diameter of 3 mm, and a length of 60 mm, and a branch pipe outer diameter of 6 mm, an inner diameter of 3 mm, and a length of 20 mm.

[0025] The electrospray component (ESI) comprises a metal capillary 2, a direct current high voltage power supply unit 3, a T-shaped insulating medium tube 4, and a carrier gas tube 5. The metal capillary 2 has a diameter of 100-150 μm, is precisely centered along the axial direction and embedded in the main tube of the T-shaped insulating medium tube 4, and the front end extends 4-12 mm from the outlet of the main tube; the working gas is injected into the T-shaped insulating medium tube 4 through the carrier gas tube 5 from the branch inlet of the T-shaped insulating medium tube 4; the direct current high voltage supplied by the direct current high voltage power supply unit 3 is coupled with the metal capillary 2, and can stably generate a charged liquid droplet spray 14, which is ionized by the action of an electric field and combined with a low-temperature plasma beam 15 to provide high-efficiency ionization.

[0026] In this embodiment, the metal capillary 2 is made of stainless steel and has an inner diameter of 100 μm; the working gas used to generate the charged liquid droplet spray 14 is nitrogen, and the flow rate of the working gas is 0.50 L·min -1 ; the direct current high voltage supplied by the direct current high voltage power supply unit 3 applied to the metal capillary 2 is 2.35 kV.

[0027] The low-temperature plasma beam component (LTP) comprises a T-shaped insulating medium tube 7, an outer electrode 8, an inner electrode 9, a carrier gas tube 10, an alternating current high voltage power supply unit 11, and a grounding voltage 12. The inner electrode 9 is connected with the alternating current high voltage supplied by the alternating current high voltage power supply unit 11, and the outer electrode 8 is connected with the grounding voltage 12. The working gas is injected into the T-shaped insulating medium tube 7 through the carrier gas tube 10 from the branch inlet of the T-shaped insulating medium tube 7. In this embodiment, the working gas used to generate the low-temperature plasma beam 15 is helium, and the flow rate is 0.50 L·min -1 . The working gas is excited by the alternating current high voltage provided by the alternating current high voltage power supply unit 11 to generate a low-temperature plasma beam 15 with high stability and high-efficiency output, which cooperates with the charged liquid droplet spray 14 to realize high-efficiency ionization of the sample. When only the low-temperature plasma ionization source is operated, the sample to be tested is sprayed through the metal capillary 2, and the direct current high voltage power supply unit 3 and the working gas in the electrospray component are not turned on.

[0028] The angle between the plasma beam 15 generated at the LTP outlet and the horizontal reference plane 17 is 120°-160°, wherein the horizontal reference plane 17 is the vertical plane where the mass spectrometry inlet 16 is located, and is perpendicular to the direction in which the composite ion flow enters the mass spectrometry inlet 16. The angle between the plasma beam 15 generated at the LTP outlet and the charged liquid droplet spray 14 generated at the ESI outlet is 45°-90°. The ESI and the LTP are aligned in the vertical direction, and the horizontal distance between the ESI and the LTP and the mass spectrometry inlet is set to 2-10 mm.

[0029] In the embodiment, the power supply parameters of the alternating high voltage power supply unit 11 applied to the inner electrode 9 are: the alternating high voltage frequency is 2.5 kHz, and the peak voltage is 100 kVpp; the inner electrode 9 is a stainless steel cylindrical rod with a diameter of 0.50 mm and a length of 100 mm, which is axially inserted into the main pipe of the T-shaped insulating medium pipe 7; the outer electrode 8 is a copper foil with a thickness of 0.1 mm and a length of 10 mm, which is spirally wound and arranged on the outer surface of the main pipe of the T-shaped insulating medium pipe 7.

[0030] The sample 13 to be detected is driven into the metal capillary by a syringe clamped on a syringe pump at a flow rate of 5-10 μL / min, and the syringe is sealed and connected to the metal capillary 2. Under the action of the direct current high voltage provided by the direct current high voltage power supply unit 3, a high uniformity charged droplet spray 14 is formed at the front end of the metal capillary 2, and under the highly synergistic action of the charged droplet spray 14 and the low temperature plasma beam 15, the measured components are introduced into the mass spectrometer inlet 16 in a lossless dispersion and high efficiency ionization state.

[0031] The embodiment of the present application also provides an application of the above detection device in detection of aromatic ester compounds, which specifically comprises the following steps: (1) connecting and adjusting the gas circuit and the circuit of ESI and LTP through the ion source support 1 and 6 and the displacement sliding table; (2) determining the relative position and angle of the electrospray device, the low temperature plasma beam device and the mass spectrometer inlet through the ion source support 1, 6 and the displacement sliding table, so as to ensure that the ions of the sample to be detected can enter the mass spectrometer inlet efficiently; (3) conveying nitrogen to the electrospray device through the carrier gas pipe 5, conveying helium to the low temperature plasma beam device through the carrier gas pipe 10, opening the syringe to convey the sample 13 to be detected, opening the direct current high voltage power supply unit 3 to apply direct current high voltage to the metal capillary 2, opening the alternating high voltage power supply unit 11 and the grounding voltage 12, and under the action of alternating high voltage and airflow, the sample 13 to be detected forms a charged droplet spray 14 at the tip of the metal capillary 2, and the low temperature plasma beam 15 is sprayed out through the main pipe of the T-shaped insulating medium pipe 7; (4) opening the mass spectrometer detection software to obtain the detection result. Specifically, under the highly synergistic action of the charged droplet spray 14 and the low temperature plasma beam 15, the measured components are introduced into the mass spectrometer inlet 16 in a lossless dispersion and high efficiency ionization state, and the detection is started. The mass spectrometer is a triple quadrupole mass spectrometer (XevoTM TQ MS, Waters, USA). The mass spectrometer operation software is MassLynx V4.1 (Waters, USA); the ionization mode is positive ion mode; the cone hole voltage is 30 V; and the scanning mode is full scan mode. TIC mode is used to determine the molecular ion peak, and ESI+LTP is used to collect mass spectrometry data for 1 min.

[0032] In the process of detecting aromatic ester compounds using the above device, the angle between the electrospray assembly, the low-temperature plasma beam assembly and the mass spectrometry inlet 16 is closely related to the mass spectrometry detection signal strength. The following further illustrates the influence of the above factors on the detection results by taking an aromatic ester mixture solution as the detection object, and the results are shown in Figure 2 The aromatic ester mixture solution is uniformly mixed by ethyl phenylacetate solution, methyl o-methylaminobenzoate solution, ethyl 3-phenylpropionate solution and dimethyl phthalate solution with concentrations of 10 -3 mg / mL respectively according to a volume ratio of 1:1:1:1.

[0033] 1) Influence of the length of the front end of the metal capillary 2 extending out of the main pipe of the T-shaped insulating medium pipe 4 on the mass spectrometry detection signal strength Detection conditions: the length of the front end of the metal capillary extending out of the main pipe of the T-shaped insulating medium pipe is 4 mm, 6 mm, 8 mm, 10 mm and 12 mm respectively, the distance between the outer electrode and the main pipe of the T-shaped insulating medium pipe is 5 mm, the angle between ESI and LTP is 45°, the horizontal distance between ESI and LTP and the mass spectrometry inlet is 2 mm, and the plasma beam generated by the LTP outlet forms an angle of 120° with the horizontal reference plane. The detection results are shown in Figure 2 A.

[0034] The front end of the metal capillary needs to extend out of the main pipe of the T-shaped insulating medium pipe by a sufficient length to form a stable Taylor cone (charged droplet). A longer extension length prolongs the flight time of the droplet in the air, which is helpful for solvent evaporation and ion release, improves the gas phase ion yield, and an excessively long extension makes the droplet path deviate from the detection area, resulting in droplet shaking or Taylor cone swinging, which destroys the stability of the electrospray. Figure 2 A shows that the mass spectrometry signal strength first increases and then decreases with the increase of the length of the metal capillary extending out of the main pipe of the T-shaped insulating medium pipe, and the signal strength is the largest when the length is 10 mm; that is, when the length of the metal capillary extending out of the main pipe of the T-shaped insulating medium pipe is 10 mm, the peak value of the ionization efficiency corresponds to the optimal extension length, and the electric field strength, droplet atomization efficiency and ion transmission reach a balance.

[0035] 2) Influence of the distance between the outer electrode 8 and the main pipe of the T-shaped insulating medium pipe 7 on the mass spectrometry detection signal strength Detection conditions: the length of the front end of the metal capillary extending out of the main pipe of the T-shaped insulating medium pipe is 10 mm, the distance between the outer electrode and the main pipe of the T-shaped insulating medium pipe is 5 mm, 7 mm, 9 mm, 11 mm and 13 mm respectively, the angle between ESI and LTP is 45°, the horizontal distance between ESI and LTP and the mass spectrometry inlet is 2 mm, and the plasma beam generated by the LTP outlet forms an angle of 120° with the horizontal reference plane. The detection results are shown in Figure 2 B.

[0036] The excitation of plasma requires a strong enough electric field, and the position of the copper sheet determines the electric field distribution between the outer electrode and the inner electrode. When the copper sheet is close to the outlet of the T-shaped insulating medium tube, the electric field is concentrated near the outlet, which is conducive to gas breakdown and plasma generation. If the copper sheet is too far from the outlet, the T-shaped insulating medium tube itself will partially shield the electric field, making the electric field at the outlet insufficient to effectively ionize the working gas, resulting in unstable or extinguished plasma. Figure 2 B shows that the mass spectrometry signal intensity gradually decreases as the length of the outer electrode distance from the outlet of the T-shaped insulating medium tube increases, and the signal intensity is maximum at 5 mm. Therefore, when the length of the outer electrode distance from the outlet of the T-shaped insulating medium tube is 5 mm, the outer electrode is the optimal position, making the electric field strength, gas flow speed, and power coupling reach a balance.

[0037] 3) Effect of the angle between ESI and LTP on mass spectrometry signal intensity Detection conditions: the length of the front end of the metal capillary protruding from the T-shaped insulating medium tube is 10 mm, the length of the outer electrode distance from the T-shaped insulating medium tube is 5 mm, the angle between ESI and LTP is 45°, 60°, 75°, 90°, 105°, and 120°, respectively, the horizontal distance between ESI and LTP and the mass spectrometry inlet is 2 mm, and the plasma beam generated by the LTP outlet forms a 120° angle with the horizontal reference plane. The detection results are shown in Figure 2 C.

[0038] From Figure 2 C, it can be seen that when the ESI and LTP are placed at a small angle close to 45°, the overlapping area of the charged droplet spray and the plasma beam is limited, resulting in insufficient reaction and low ionization efficiency. In addition, the charged droplet spray and the plasma beam are too close, which will disperse due to Coulomb repulsion, reducing the probability of effective collision. When placed at a medium angle of 45°-90°, the high-activity particles of the charged droplet spray and the plasma beam are fully mixed in the cross-sectional area, promoting the droplet-assisted desolvation reaction, charge transfer, and proton exchange reaction. The electric field directions of the two sources are complementary, forming a composite electric field that optimizes ion focusing and transmission. When placed at a large angle close to 120°, the spatial overlap of the charged droplet spray and the plasma beam decreases, and the ion path deviates from the direction of the mass spectrometry inlet, resulting in the loss of part of the ions due to diffusion. The mass spectrometry signal intensity first increases and then decreases as the angle between ESI and LTP increases, and the signal intensity is maximum at 60°. Therefore, the angle between ESI and LTP is limited to 45°-90°, preferably 45°-75°, and the optimal ionization efficiency peak angle is 60°.

[0039] 4) Effect of the horizontal distance between ESI and LTP and the mass spectrometry inlet on mass spectrometry signal intensity Detection conditions: the front end of the metal capillary extends 10 mm out of the T-shaped insulating medium tube, the outer electrode is 5 mm away from the T-shaped insulating medium tube, the angle between ESI and LTP is 60°, the horizontal distance between ESI and LTP and the mass spectrometry inlet is 2 mm, 4 mm, 6 mm, 8 mm, 10 mm respectively, and the angle between the plasma beam generated by the LTP outlet and the horizontal reference plane is 120°. The detection results are shown in Figure 2 D.

[0040] When ESI and LTP are too close, the two plumes are not fully developed, and the evaporation and ionization processes are not fully completed, and the stability of the plasma is reduced. After appropriately increasing the distance, the electric field can effectively guide the ions to move towards the mass spectrometry inlet, reducing ion loss. When the distance is too far, active particles are lost due to collision with the tube wall, especially light mass ions are easily carried away by the airflow. Figure 2 D shows that the mass spectrometry signal intensity increases first and then decreases with the increase of the horizontal distance between ESI and LTP and the mass spectrometry inlet, and the signal intensity is the largest at 8 mm; that is, when the horizontal distance between ESI and LTP and the mass spectrometry inlet is 8 mm, the two plumes reach the best spatial coupling state, and the ionization efficiency is the highest.

[0041] 5) The effect of the angle between the plasma beam generated by the LTP outlet and the horizontal reference plane on the mass spectrometry detection signal intensity Detection conditions: the front end of the metal capillary extends 10 mm out of the T-shaped insulating medium tube, the outer electrode is 5 mm away from the T-shaped insulating medium tube, the angle between ESI and LTP is 60°, the horizontal distance between ESI and LTP and the mass spectrometry inlet is 8 mm, and the angle between the plasma beam generated by the LTP outlet and the horizontal reference plane is 120°, 135°, 145°, 150°, 160° respectively. The detection results are shown in Figure 2 E.

[0042] When the angle between the plasma beam generated by the LTP outlet and the horizontal reference plane is too small, the interaction between the plasma beam and the sample flow is weak due to insufficient intersection area. When the angle between the plasma beam generated by the LTP outlet and the horizontal reference plane is too large, the plasma beam may "skim" the sample flow, resulting in reduced effective collision, and even part of the sample is scattered out of the detection area, Figure 2 E shows that when the angle between the plasma beam generated by the LTP outlet and the horizontal reference plane is 150°, the signal intensity is the largest, at this time, the paths of the plasma beam and the sample molecules intersect more fully, promoting more efficient ionization or excitation, and at the same time, the contact time between the plasma and the sample is prolonged, and the energy transfer is enhanced.

[0043] Therefore, the above detection device provided by the embodiment provides the optimal key parameters for detecting the aromatic ester compounds, respectively, as follows: the length of the front end of the metal capillary tube extending out of the T-shaped insulating medium pipe main pipe is 10 mm, the length of the outer electrode from the T-shaped insulating medium pipe main pipe is 5 mm, the included angle between the ESI and the LTP is 60°, the horizontal distance between the ESI and the LTP and the mass spectrometry inlet is 8 mm, and the included angle between the plasma beam generated by the LTP outlet and the horizontal reference plane is 150°. The following embodiments are all conducted under the optimal conditions to detect the aromatic ester compounds.

[0044] Example Two Application of the above detection device in detecting aromatic ester mixture solution The embodiment provides an application of the above detection device provided by the embodiment one in detecting the aromatic ester mixture solution, which is basically the same as the application method provided by the embodiment one, and the main difference is that: the sample to be detected in the embodiment is an aromatic ester mixture solution prepared by uniformly mixing ethyl phenylacetate solution, methyl o-methylaminobenzoate solution, 3-ethyl phenylpropionate solution and dimethyl phthalate solution with a concentration of 10 mg / mL respectively according to a volume ratio of 1:1:1:1; the TIC mode is used to determine the molecular ion peak, the ESI collects mass spectrometry data for 1 min, the LTP collects mass spectrometry data for 1 min, and the ESI+LTP collects mass spectrometry data for 1 min; the remaining steps and parameters are the same as those of the embodiment one, and the results are shown in -3 FIG. 2 and Table 1. Figure 2

[0045] Table 1 Signal intensity of aromatic ester mixture in ESI-LTP composite mode and ESI mode

[0046] According to the mass spectrometry diagram shown in Figure 3 Table 1, it can be obtained that the ionization efficiency of ethyl phenylacetate in the ESI-LTP mode is 15.6 times stronger than that in the ESI mode, the ionization efficiency of methyl o-methylaminobenzoate in the ESI-LTP mode is 24.7 times stronger than that in the ESI mode, the ionization efficiency of 3-ethyl phenylpropionate in the ESI-LTP mode is 12.3 times stronger than that in the ESI mode, and the ionization efficiency of dimethyl phthalate in the ESI-LTP mode is 4.4 times stronger than that in the ESI mode.

[0047] Example Three Application of the above detection device in detecting the authenticity of traditional Chinese medicinal materials ​As a traditional Chinese medicine, pericarpium citri reticulatae can be divided into common pericarpium citri reticulatae and broad pericarpium citri reticulatae according to the producing area and quality. Broad pericarpium citri reticulatae has higher medicinal value due to its unique medicinal components (e.g. the regulation of respiratory system). Currently, there are two kinds of broad pericarpium citri reticulatae on the market: 5-year-old broad pericarpium citri reticulatae 1 and 10-year-old broad pericarpium citri reticulatae 2. It has been found that methyl o-tolylcarboxamide can be used as a characteristic marker of broad pericarpium citri reticulatae to distinguish broad pericarpium citri reticulatae from common pericarpium citri reticulatae.

[0048] The embodiment of the present application provides a method for detecting broad pericarpium citri reticulatae by using the detection device constructed in embodiment one, which can be used as a fast and accurate method for identifying the authenticity of broad pericarpium citri reticulatae.

[0049] The methyl o-tolylcarboxamide mother liquor in embodiment two is diluted step by step to 10 μg / mL, 5 μg / mL, 2.5 μg / mL, 1 μg / mL and 0.5 μg / mL to draw a standard curve, and the results are shown in Table 1. Figure 3 , The following pretreatment method is used in the experiment: the pericarpium citri reticulatae is ground into powder by using a blender, 0.2 g of the powder is dissolved in 5 mL of methanol, and then mixed uniformly by vortexing for 30 s and ultrasonic treatment for 20 min. Then, the solution is centrifuged at 2500 rpm for 20 min. The supernatant is titrated to 10 mL with methanol, and then filtered through a 0.22 μm organic phase filter membrane. The solution is stored at 4 °C until use. When the sample is measured, the flow rate of the injection pump is 5 μl / min. The sample solution is detected under ESI+MIP mode, and the signal intensity of methyl o-tolylcarboxamide in broad pericarpium citri reticulatae 1 (5 years old) is 2.43×10 4 , and the signal intensity of methyl o-tolylcarboxamide in broad pericarpium citri reticulatae 2 (10 years old) is 2.10×10 4 . The signal intensity of methyl o-tolylcarboxamide in broad pericarpium citri reticulatae 1 (5 years old) and broad pericarpium citri reticulatae 2 (10 years old) is taken as y value respectively, and then the x value is calculated by using the standard curve equation y=12230.004x+8995.836, and the x value of broad pericarpium citri reticulatae 1 (5 years old) is 1.2513 μg / mL, and the x value of broad pericarpium citri reticulatae 2 (10 years old) is 0.9815 μg / mL. The results are shown in Table 2.

[0050] Table 2 Comparison results of ESI and ESI-LTP for detecting pericarpium citri reticulatae

[0051] Table 2 shows that methyl o-tolylcarboxamide is not detected in common pericarpium citri reticulatae, while the two kinds of broad pericarpium citri reticulatae contain the component, which proves that the component can be used as an effective marker for identifying broad pericarpium citri reticulatae and is suitable for the rapid detection of pericarpium citri reticulatae adulteration, and provides reliable technical support for the quality control of traditional Chinese medicinal materials.

[0052] Embodiment four Application of the above detection device in wine screening Different wine flavors, such as fruit aroma, clear aroma, light sesame aroma, soy sauce aroma and wind aroma, have unique flavor characteristics, and the differences in their chemical compositions can be used for authenticity identification. However, traditional sensory evaluation and conventional analysis methods have strong subjectivity and insufficient sensitivity, and the embodiments of the present application provide a method for detecting and distinguishing wine flavors using the detection device constructed in Example 1. The method can be used as a rapid and accurate method for identifying the authenticity of wine.

[0053] All wine samples were stored at room temperature in the dark to avoid photodegradation and volatile loss. Take 1 mL of dry red wine (fruit aroma), Fenjiu (clear aroma), Jingzhi liquor (light sesame aroma), Yubing liquor (soy sauce aroma) and Xifeng liquor (wind aroma) in a sample bottle, respectively, and dilute 10 times with methanol to reduce matrix interference and improve ionization efficiency. The diluted sample was filtered through a 0.22 μm organic phase filter to remove particulates and ensure the stability of the sample injection system.

[0054] Using the detection device provided in Example 1, cross ESI-LTP complex ionization mode was used. The length of the T-shaped insulating medium pipe extending from the front end of the metal capillary was 10 mm, the distance between the outer electrode and the T-shaped insulating medium pipe was 5 mm, the angle between ESI and LTP was 60°, the horizontal distance between ESI and LTP and the mass spectrometry inlet was 8 mm, and the angle between the plasma beam generated by the LTP outlet and the horizontal reference plane was 150°. Under the conditions, the mass spectrometry data of the five kinds of flavor wines were collected, as shown in Figure 4 A. The mass spectrometry data was imported into the principal component analysis (PCA) software, and the pattern recognition was performed based on the characteristic compounds and their intensities of the different flavor wines. The PCA results are shown in Figure 5 B. Figure 5 Figure 5 B shows that the five kinds of flavor wines are significantly separated on the score plot, indicating that their chemical fingerprints have high specificity.

[0055] The PCA model clearly distinguifies the fruit aroma, clear aroma, light sesame aroma, soy sauce aroma and wind aroma wines, proving that the detection device for aromatic ester compounds based on mass spectrometry ion source provided in Example 1 can effectively capture the wine flavor-related markers. Compared with traditional methods, the method provided in the embodiments of the present application has the characteristics of no complex pretreatment, single sample analysis time < 5 min, fast analysis speed, high sensitivity, etc., and is suitable for large-scale wine sample screening.

[0056] Therefore, the detection device for aromatic ester compounds based on the mass spectrometry ion source provided by the embodiment of the present application comprises an electrospray component and a low-temperature plasma beam component, the front end of the metal capillary in the electrospray component extends 4-12 cm from the pipe opening of the main pipe of the first T-shaped insulating medium pipe, the outer electrode in the low-temperature plasma beam component is 5-13 mm away from the outlet of the main pipe of the second T-shaped insulating medium pipe, the low-temperature plasma beam component is 120°-160° to the horizontal reference plane, the mutual angle between the electrospray component and the low-temperature plasma beam component is 45°-90°, so that the electro-hydraulic droplet spray generated by the electrospray component is under the synergistic action of the low-temperature plasma beam generated by the low-temperature plasma beam component, so that the incidence directions of the two are relatively balanced, the plasma beam can better hit the sample surface and the ions can be effectively released from the droplets. Therefore, the detection device provided by the embodiment of the present application can improve the detection sensitivity of aromatic ester compounds, can be applied to rapid detection of food, traditional Chinese medicinal materials and liquor adulteration, and has the advantages of strong automation and low price.

[0057] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application and not to limit them; although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the specific embodiments of the present application can be modified or some technical features can be replaced by equivalent ones; without departing from the spirit of the technical solutions of the present application, they should be covered in the technical solution range of the present application.

Claims

1. A device for detecting aromatic ester compounds based on a mass spectrometry ion source, characterized by, The application relates to a mass spectrometer, which comprises an electric spray component, a low-temperature plasma beam component and a mass spectrometer. The electric spray component comprises a first T-shaped insulating medium pipe and a metal capillary tube, the first T-shaped insulating medium pipe comprises a first main pipe and a first branch pipe; the metal capillary tube is inserted into the first main pipe and arranged coaxially with the first main pipe, the front end of the metal capillary tube extends 4-12 cm from the pipe opening of the first main pipe, and the tail end of the metal capillary tube is connected to a sample injection unit. The low-temperature plasma beam component comprises a second T-shaped insulating medium pipe, an inner electrode and an outer electrode, the second T-shaped insulating medium pipe comprises a second main pipe and a second branch pipe; the inner electrode is inserted into the second main pipe and arranged coaxially with the second main pipe; the outer electrode is spirally wound and arranged on the outer surface of the second main pipe, and the distance between the outer electrode and the outlet of the second main pipe is 5-13 mm. The mass spectrometer comprises a mass analyzer with a mass spectrometer inlet. Two ion source supports are respectively used for fixing the electric spray component and the low-temperature plasma beam component. Two XYZ displacement sliding tables are respectively used for fixing the ion source supports, and the ion source supports are used for positioning the azimuth angle between the electric spray component, the low-temperature plasma beam component and the mass spectrometer inlet, wherein the low-temperature plasma beam component is at an angle of 120-160 degrees with a horizontal reference plane, the electric spray component is at an angle of 45-90 degrees with the low-temperature plasma beam component, the horizontal reference plane is a vertical plane where the mass spectrometer inlet is located, the electric spray component and the low-temperature plasma beam component are aligned in the vertical direction, and the horizontal distance between the electric spray component and the mass spectrometer inlet is 2-10 mm.

2. The detection device of claim 1, wherein, The electric spray component further comprises a direct-current high-voltage power supply unit connected to the metal capillary tube, a first carrier gas pipe connected to the first branch pipe and a first working gas, wherein the first working gas is injected into the first main pipe through the first carrier gas pipe from the first branch pipe.

3. The detection device of claim 2, wherein, The diameter of the metal capillary tube is 100-150 microns, the supply voltage of the direct-current high-voltage power supply unit is 1-3 kV, the first working gas is nitrogen, oxygen or argon, and the flow rate of the first working gas is 0.5-1.0 L / min.

4. The detection device according to claim 1 or 2 or 3, characterized in that, The low-temperature plasma beam component further comprises a second carrier gas pipe connected to the second branch pipe, an alternating-current high-voltage power supply unit connected to the inner electrode, a grounding voltage connected to the outer electrode and a second working gas, wherein the second working gas is injected into the second main pipe through the second carrier gas pipe from the second branch pipe.

5. The detection device of claim 4, wherein, The diameter of the inner electrode is 0.5-1 mm, and the length of the inner electrode is 100-120 mm; the thickness of the outer electrode is 0.1-0.5 mm, and the length of the outer electrode is 5-10 mm; the supply parameters of the alternating-current high-voltage power supply unit are as follows: the alternating-current high-voltage frequency is 50-100 kHz, the peak voltage is 2-3 kVpp, and the working power is 5-250 W; the second working gas is nitrogen, oxygen or argon, and the flow rate of the second working gas is 0.5-1.0 L / min.

6. The detection device of claim 1, wherein, The inner diameter of each main pipe and branch pipe is 3-4 mm, the outer diameter of each main pipe is 6-7 mm, the length of each main pipe is 60-100 mm, and the length of each branch pipe is 20-50 mm.

7. The detection device of claim 1, wherein, The ion source supports are fixed to the XYZ displacement slides by screws, one of the two ion source supports is provided with a groove with the same diameter as the outer diameter of the first main pipe, and the other is provided with a groove with the same diameter as the outer diameter of the second main pipe; The two XYZ displacement slides can be operated by knobs, the X-axis stroke is used to adjust the left-right distance between the electrospray assembly, the low-temperature plasma beam assembly and the mass spectrometry inlet; the Y-axis stroke is used to adjust the front-back distance between the electrospray assembly, the low-temperature plasma beam assembly and the mass spectrometry inlet; the Z-axis stroke is used to adjust the up-down distance between the electrospray assembly, the low-temperature plasma beam assembly and the mass spectrometry inlet; and the R-axis stroke is used to adjust the angle between the plasma beam generated by the outlet of the low-temperature plasma beam assembly and the horizontal reference plane.

8. Use of the detection device of any one of claims 1-7 in detecting aromatic ester compounds.

9. Use according to claim 8, characterized in that, The sample solution to be detected is input into the metal capillary at a flow rate of 5-10 μL / min, the electrospray assembly forms a charged droplet spray at the front end of the metal capillary, the low-temperature plasma beam assembly generates a low-temperature plasma beam, and the charged droplet spray is synergistically acted on by the low-temperature plasma beam, so that the component to be detected in the sample is introduced into the mass spectrometry inlet for mass spectrometry detection; wherein the sample to be detected is a mixture containing aromatic ester compounds.

10. Use according to claim 8 or 9, characterized in that, The detection device is used in at least one of the following aspects: 1) detecting aromatic ester compounds in food; 2) detecting aromatic ester compounds in traditional Chinese medicinal materials; 3) detecting the authenticity of traditional Chinese medicinal materials; 4) screening wine samples.

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