Photoionization mass spectrometry rapid qualitative analysis method for in-vitro unknown drugs

Abstract

The invention discloses an in-vitro unknown drug photoionization mass spectrometry rapid qualitative analysis method, which comprises: S1, dissolving a captured suspected drug sample in an acetone or methanol solution, taking out the supernatant, and transferring into a sample bottle; s2, selecting a polar or non-polar SPME probe to penetrate through the sample bottle isolation pad to be inserted into the sample bottle isolation pad, and extracting; and S3, inserting the probe tube into the sample inlet, pushing the handle rod, extending out of the probe extraction head, and performing thermal desorption to desorb the sample to be detected and enter a mass spectrum ionization area. According to the method, richer ionized ion fragment information and molecular ions are provided in the rapid qualitative analysis and accurate identification process of on-site investigation of drugs and precursor chemicals by using a miniaturized mass spectrum technology, and molecular structure information can be provided for analyzing chemical components of unknown novel drugs by using a compound mass spectrum library.

Description

Technical Field

[0001] The present invention belongs to the technical field of drug qualitative analysis, and in particular relates to a method for rapid qualitative analysis of unknown drugs in vitro by photoionization mass spectrometry. Background Art

[0002] Drugs are numerous and widespread. In recent years, new drugs such as fentanyl-like substances and synthetic marijuana have emerged in large numbers, coexisting with more common traditional drugs like heroin and methamphetamine. By July 2024, my country had regulated 509 narcotics and psychotropic substances. The sheer variety of drugs and precursor chemicals makes qualitative analysis and identification challenging.

[0003] Currently, laboratory testing and identification commonly utilize gas chromatography, gas chromatography-mass spectrometry, high-performance liquid chromatography, and liquid chromatography-mass spectrometry. By 2023, my country had issued fifteen national standards for suspected drug testing, including GB / T 39882-2021 and GB / T 29636-2013, utilizing chromatography and mass spectrometry. These methods are highly sensitive and accurate, but they require complex sample pretreatment and long testing cycles, making them inadequate for rapid on-site testing.

[0004] Rapid on-site drug detection helps investigators seize opportunities to combat crime. Rapid on-site detection technologies and portable instruments are constantly being updated. Currently, methods used for in vitro suspected drug detection include colloidal gold immunochromatography, Raman spectroscopy, infrared spectroscopy, gas chromatography, ion mobility spectrometry, and mass spectrometry. Mass spectrometry, among others, can distinguish between similar molecular masses and provide information on molecular mass, molecular structure, and fragment ions. It is currently an irreplaceable qualitative analysis tool in drug detection, drug development, and other fields, and boasts high sensitivity and rapid response. In recent years, small, portable mass spectrometers have developed rapidly, primarily in ion trap, quadrupole, and time-of-flight formats. Ionization methods primarily include electron impact ionization (EI), chemical ionization (CI), electrospray ionization (ESI), and vacuum ultraviolet photoionization (VUV-PI).

[0005] Ionization methods can be categorized as hard ionization and soft ionization. EI and ESI hard ionization methods provide ion fragmentation information, including characteristic ion pair peak positions and relative abundances. Under specific ionization energy and mass analyzer settings, a rich mass spectral database is available, making it more conducive to qualitative analysis of the molecular structure of unknown compounds. However, hard ionization methods may or may not produce molecular ion peaks. Utilizing mass spectral databases for comparison and retrieval requires specific instrument conditions, which are difficult to achieve with miniaturized and lightweight on-site testing instruments. Miniaturized mass spectrometers typically utilize mass analyzers such as ion traps, quadrupoles, and time-of-flight (TOF). Due to the inherent characteristics of the mass analyzers and the limitations of instrument size and weight, mass accuracy is typically limited to 0.5-1 amu, making it difficult to achieve high resolution and distinguish between primary ions, isotopes, modifications, minor structural variations, or complexes associated with small molecules. Chemical ionization (CI) is a soft ionization technique in which reagent ions react with sample molecules to achieve ionization without breaking the ionic chemical bonds. This provides molecular ion information and can determine the sample's molecular weight. However, CI produces almost no fragment ions and requires vaporization, making it unsuitable for analyzing nonvolatile or thermally unstable samples. Commercial mass spectrometers often utilize a combination of soft and hard ionization sources to enhance ionization capabilities, leveraging their complementary analytical and identification advantages. However, these instruments are complex and unsuitable for rapid on-site testing.

[0006] The ionization energy of organic compounds is around 10 eV. Most molecules experience maximum ionization at 50-100 eV. At 70 eV, a rich fingerprint is obtained, approaching maximum sensitivity. Lowering the ionization energy appropriately yields a stronger molecular ion signal, which can aid in qualitative analysis in some cases. However, a drawback of electron impact (EI) ionization sources is that the molecular ion signal becomes very weak, even undetectable.

[0007] Vacuum ultraviolet single-photon ionization (VUV-SPI) is a new ionization source that has rapidly developed in recent years and is suitable for gas samples. The following describes soft ionization techniques initiated by photoionization. VUV photoionization generates molecular ions of the analyte through absorption of single-photon ionization (SPI).

[0008] Single-photon ultraviolet photoionization belongs to soft ionization, and the ionization principle is as follows:

[0009] Vacuum ultraviolet light sources have high energy and can achieve efficient ionization processes, especially for high-energy and complex structural compounds. Secondly, the wavelength range of VUV light sources is usually between 100-200nm, which is very beneficial for ionization analysis. In addition, VUV-PIMS can also provide high-resolution mass spectrometry data, making the analysis of complex mixtures more accurate and reliable. In terms of application, VUV-PIMS has a wide range of applications in environmental science, chemistry, biomedicine and other fields. Vacuum ultraviolet lamps are the most common single-photon ionization source. They have simple spectra, do not consume any solvents during the ionization process, and are compact in size, making them particularly suitable for miniaturized instruments. The lamp is filled with different inert gases, and magnesium fluoride glass is used for filtering at the front end of the lamp. The resulting luminous energy is between 8-12eV. For example, an argon lamp emits photons with an energy of 10.6 eV. This ionizes all molecules with ionization energies below 10.6 eV, but is unable to ionize gas molecules with ionization energies above 10.6 eV, such as N2, O2, H2O, CO2, and common solvent molecules such as CH3OH, H2O, and CH3CN. Therefore, selective detection of the organic compounds can be achieved. Photon energy scanning can also distinguish isomers based on the differences in their ionization energies. Single-photon ionization of vacuum ultraviolet light can also be achieved by converting laser light through an optical system. Mitschke et al., while measuring VOCs in cigarette smoke, found that laser-generated vacuum ultraviolet light is more suitable for the ionization of aliphatic and carbonyl compounds.

[0010] Currently, single-photon vacuum ultraviolet photoionization is primarily used for the detection of organic compounds in air, with sensitivity reaching ppt. Kuribayashi et al. employed ion enrichment for the online detection of trichlorobenzene in incinerator flue gas. With an analysis time of 18 s, they achieved a detection limit of 10 ppt, consistent with standard GC-MS analysis. Robb et al. first applied this ionization method to LC-MS for the detection of small biomolecules, obtaining the following: 1 pmol of carbamimidazine, 1 pmol of acridine, 100 pmol of naphthalene, and 100 pmol of acaricide. The sensitivity of this ionization method was found to be eight times that of atmospheric pressure chemical ionization (APCI), and it also allows for negative ion detection. Butcher et al. used laser-generated vacuum ultraviolet photoionization to detect aromatic compounds in automobile exhaust. Summary of the Invention

[0011] The purpose of the present invention is to provide a method for rapid qualitative analysis of unknown drugs in vitro by photoionization mass spectrometry to solve the technical problems raised in the background technology.

[0012] To achieve the above object, the specific technical solution of the present invention is as follows: A method for rapid qualitative analysis of unknown drugs by photoionization mass spectrometry in vitro, comprising the following steps: S1. Dissolve the seized suspected drug sample in acetone or methanol solution, remove the supernatant and transfer it into a sample bottle; S2. Select a polar or non-polar SPME probe and insert it through the septum of the sample bottle to extract; S3. Insert the probe needle into the injection port, push the handle rod, extend the probe extraction head, and thermal desorption is performed to desorb the sample to be tested and enter the mass spectrometer ionization area; S4. Adjust the photoionization mass spectrometer ionization voltage, first adjust the ionization energy to 10.6 eV to obtain molecular ion information of the main component compounds in the sample, then adjust the ionization energy to 30-50 eV to obtain fragment ion information, and compare the characteristic peak positions and abundance ratios of the characteristic fragment ion pairs with the mass spectrometry database; S5. Combine the low ionization energy soft ionization mode and the high ionization energy hard ionization mode to comprehensively analyze the molecular structure of the compound of the main components of the sample to identify whether it contains contraband or new addictive narcotic drugs or psychotropic drugs.

[0013] Preferably, the amount of the supernatant in step S1 is 1-10 ml.

[0014] Preferably, the extraction time in step S2 is 5-15 minutes.

[0015] Preferably, the desorption time in step S3 is 1-5 minutes.

[0016] Preferably, the molecular ion information of the main component compound in step S4 includes mass-to-charge ratio, mass spectrum characteristic peak position, half-peak width, and peak height.

[0017] Preferably, the fragment ion information in step S4 includes mass-to-charge ratio, mass spectrum characteristic peak position, half-peak width, peak height, and abundance ratio.

[0018] Preferably, the mass spectrum database in step S4 is a NIST standard database.

[0019] The rapid qualitative analysis method of unknown drugs by photoionization mass spectrometry in vitro of the present invention has the following advantages: 1. The present invention provides more abundant ionized ion fragment information and molecular ion information in the process of rapid qualitative analysis and accurate identification of drugs and precursor chemicals in the on-site investigation using miniaturized mass spectrometry technology, and can provide molecular structure information for analyzing the chemical composition of unknown new drugs using the compound mass spectrometry library.

[0020] 2. The present invention has low requirements on the vacuum degree of the instrument, and the vacuum degree is not greater than 10 -2Pa can be detected normally, with low failure rate and stable detection. The same ionization source can realize switching between soft and hard ionization working modes, which not only solves the vacuum limitation of small instruments, but also covers the detection of non-volatile and thermally unstable samples. It can provide rich and accurate molecular ion information of compounds, enrich the information that low-resolution mass spectrometry can provide, make qualitative analysis more accurate, and the adjustment setting of different ionization energies of the ionization source is simple and fast. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 It is a schematic diagram of the overall process of the present invention. DETAILED DESCRIPTION

[0023] Hereinafter, only certain exemplary embodiments are briefly described. As will be appreciated by those skilled in the art, the described embodiments may be modified in various ways without departing from the spirit or scope of the embodiments of the present invention. Therefore, the drawings and description are to be regarded as illustrative in nature and not restrictive.

[0024] In the description of the embodiments of the present invention, it should be understood that the terms "length", "vertical", "horizontal", "top", "bottom", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the embodiments of the present invention.

[0025] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0026] In the embodiments of the present invention, unless otherwise expressly specified or limited, the terms "installed," "connected," "connected," "fixed," etc. should be understood in a broad sense. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the embodiments of the present invention based on specific circumstances.

[0027] The disclosure below provides many different embodiments or examples for implementing different structures of the embodiments of the present invention. In order to simplify the disclosure of the embodiments of the present invention, the components and configurations of specific examples are described below. Of course, these are merely examples and are not intended to limit the embodiments of the present invention. In addition, the embodiments of the present invention may repeat reference numerals and / or reference letters in different examples. Such repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or configurations discussed.

[0028] In order to better understand the purpose, structure and function of the present invention, the following is a further detailed description of the photoionization mass spectrometry rapid qualitative analysis method for unknown drugs in vitro in conjunction with the accompanying drawings.

[0029] like Figure 1 As shown, the present invention provides a method for rapid qualitative analysis of unknown drugs in vitro by photoionization mass spectrometry, comprising the following steps: S1. Dissolve the seized suspected drug sample in acetone or methanol solution, take out 1-10 ml of the supernatant and transfer it into a sample bottle. The amount of supernatant is preferably 2-5 ml. S2. Select a probe based on the polarity of the suspected drug sample: If the analyte in the sample is a polar compound (such as drugs containing hydroxyl or amino groups), use a polar SPME probe; if it is a non-polar compound (such as cannabinoids), use a non-polar SPME probe. Insert the selected SPME probe through the septum of the sample bottle and extract for 5-15 minutes. S3. Insert the probe needle into the injection port, push the handle to extend the probe extraction head, and set the thermal desorption temperature to 80-250°C according to the boiling point of the suspected drug sample. The thermal desorption allows the sample to be desorbed and enter the mass spectrometer ionization area. The desorption time is 1-5 minutes. S4. Adjust the photoionization mass spectrometer ionization voltage. First, adjust the ionization energy to 10.6 eV to obtain molecular ion information (including mass-to-charge ratio, mass spectrum characteristic peak position, half-peak width, and peak height) of the main component compounds in the sample. Then adjust the ionization energy to 30-50 eV to obtain fragment ion information (including mass-to-charge ratio, mass spectrum characteristic peak position, half-peak width, peak height, and abundance ratio). Compare the characteristic peak position and abundance ratio of the characteristic fragment ion pairs with the mass spectrum database (NIST standard database); S5. Combine the low ionization energy soft ionization mode and the high ionization energy hard ionization mode to comprehensively analyze the molecular structure of the compound of the main components of the sample to identify whether it contains contraband or new addictive narcotic drugs or psychotropic drugs.

[0030] The vacuum ultraviolet photoionization mass spectrometer adjusts the ionization voltage and uses different ionization modes of the same instrument and the same ionization source to obtain ionization information of different compounds. Experimental verification shows that the vacuum ultraviolet photoionization mass spectrometer ionization energy ranges from 30-50eV, and characteristic fragment ions similar to the EI electron bombardment ionization source ionization energy of 70eV can be obtained. The peak positions and abundance ratios of the most important fragment ions in the mass spectrum have similarities that can be recognized by the software. For example, for methamphetamine, the characteristic fragment ions (m / z 58, 91, 135) measured at 30eV ionization energy are consistent with the fragment ion peak positions at EI 70eV, and the abundance ratio similarity is more than 90%, which verifies the effectiveness of this ionization energy range. The electron bombardment EI ionization source technology needs to maintain no more than 10 -5 Pa requires a high vacuum environment for instrumentation to function properly for detection. Vacuum ultraviolet photoionization mass spectrometry requires a lower vacuum than electron impact (EI) ionization source technology, reducing instrument failure rates due to insufficient vacuum and facilitating rapid on-site detection of new drugs. The present invention has low vacuum requirements, a low failure rate, and stable detection. It implements a dual-mode detection method using a single ionization source, providing rich and accurate molecular ion information for compounds, enriching the information available from low-resolution mass spectrometry and enabling more accurate qualitative analysis. Furthermore, the ionization source allows for simple and rapid adjustment of different ionization energies.

[0031] It will be understood that the present invention is described by way of some embodiments, and it will be appreciated by those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are intended to be protected by the present invention.

Claims

1. A method for rapid qualitative analysis of unknown drugs in vitro by photoionization mass spectrometry, characterized by: The following steps are involved: S1. Dissolve the seized suspected drug sample in acetone or methanol solution, remove the supernatant and transfer it into a sample bottle; S2. Select a polar or non-polar SPME probe and insert it through the septum of the sample bottle to extract; S3. Insert the probe needle into the injection port, push the handle rod, extend the probe extraction head, and thermal desorption is performed to desorb the sample to be tested and enter the mass spectrometer ionization area; S4. Adjust the photoionization mass spectrometer ionization voltage, first adjust the ionization energy to 10.6 eV to obtain molecular ion information of the main component compounds in the sample, then adjust the ionization energy to 30-50 eV to obtain fragment ion information, and compare the characteristic peak positions and abundance ratios of the characteristic fragment ion pairs with the mass spectrometry database; S5. Combine the low ionization energy soft ionization mode and the high ionization energy hard ionization mode to comprehensively analyze the molecular structure of the compound of the main components of the sample to identify whether it contains contraband or new addictive narcotic drugs or psychotropic drugs.

2. The method for rapid qualitative analysis of unknown drugs by photoionization mass spectrometry in vitro according to claim 1, characterized in that: The amount of the supernatant in step S1 is 1-10 ml.

3. The method for rapid qualitative analysis of unknown drugs by photoionization mass spectrometry in vitro according to claim 1, characterized in that: The extraction time in step S2 is 5-15 minutes.

4. The method for rapid qualitative analysis of unknown drugs by photoionization mass spectrometry in vitro according to claim 1, characterized in that: The desorption time in step S3 is 1-5 min.

5. The method for rapid qualitative analysis of unknown drugs in vitro by photoionization mass spectrometry according to claim 1, characterized in that: The molecular ion information of the main component compound in step S4 includes mass-to-charge ratio, mass spectrum characteristic peak position, half-peak width, and peak height.

6. The method for rapid qualitative analysis of unknown drugs in vitro by photoionization mass spectrometry according to claim 1, characterized in that: The fragment ion information in step S4 includes mass-to-charge ratio, mass spectrum characteristic peak position, half-peak width, peak height, and abundance ratio.

7. The method for rapid qualitative analysis of unknown drugs in vitro by photoionization mass spectrometry according to claim 1, characterized in that: The mass spectrum database in step S4 is the NIST standard database.

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