Qualitative detection method and system for types of fluorescent whitening agents in paper

Abstract

The invention provides a qualitative detection method and system for types of fluorescent whitening agents in paper. According to the qualitative detection method for the types of the fluorescent whitening agents in the paper, a fluorescent whitening agent standard substance and a paper sample are analyzed and detected through a real-time direct analysis mass spectrum, and the types of the fluorescent whitening agents contained in the paper sample are determined; the method solves the problem that a paper sample is greatly damaged in the qualitative detection process of the fluorescent whitening agent at present, can qualitatively detect the fluorescent whitening agent in the paper under the condition that the paper sample is not damaged, and is suitable for valuables such as archives, paintings and calligraphies.

Description

Technical Field

[0001] The invention relates to a qualitative detection method and system for the types of fluorescent whitening agents in paper, and relates to the technical field of forensic identification. Background Art

[0002] In the field of forensic science, it is necessary to analyze the paper of paper materials such as contracts, bills, and archives to determine the source of the paper used. Currently, one effective method to determine the source of paper is to qualitatively characterize the papermaking chemicals used in the paper to trace the source of the paper. Fluorescent brighteners are commonly used paper additives in paper. They are of various types and varied structures, and are suitable as characteristic indicators for distinguishing paper.

[0003] At present, the main methods for qualitative determination of fluorescent whitening agents in paper are liquid chromatography and liquid chromatography-mass spectrometry. However, this method requires the destruction of paper, which is highly destructive and is not suitable for indestructible specimens such as contracts and archives in the field of forensic science. Summary of the invention

[0004] The present invention provides a method for qualitatively detecting the types of fluorescent whitening agents in paper. The method uses real-time direct analysis mass spectrometry to analyze and detect fluorescent whitening agent standards and paper samples, so as to determine the types of fluorescent whitening agents contained in the paper samples, thereby solving the problem that the current fluorescent whitening agent qualitative detection process is highly destructive to paper samples.

[0005] The invention also provides a qualitative detection system for the types of fluorescent whitening agents in paper.

[0006] The first aspect of the present invention provides a method for qualitatively detecting the type of fluorescent whitening agent in paper, comprising the following steps:

[0007] preparing a fluorescent whitening agent standard solution, and detecting the fluorescent whitening agent standard solution using a real-time direct analysis mass spectrometer to obtain characteristic ion pairs of the fluorescent whitening agent standard;

[0008] The paper sample to be tested is analyzed by using real-time direct analysis mass spectrometry, and the ion flow corresponding to the characteristic ion pair is extracted according to the characteristic ion pair of the fluorescent whitening agent standard;

[0009] Determine the type of fluorescent brightener contained in the paper sample to be tested.

[0010] In one specific embodiment, preparing a fluorescent whitening agent standard solution comprises the following steps:

[0011] The fluorescent whitening agent standard product is mixed with acetonitrile and water to prepare a fluorescent whitening agent standard sample solution, wherein the mass ratio of the fluorescent whitening agent standard product, acetonitrile and water is 1:(100-800):(200-900).

[0012] In a specific embodiment, the fluorescent whitening agent standard includes six kinds, each having a structure shown in Formula 1-6:

[0013]

[0014]

[0015] In a specific embodiment, in the real-time direct analysis mass spectrometry, the parameters of the real-time direct analysis source include: a helium flow rate of 1-3 L / min, and an ion source temperature of 250° C.-500° C.

[0016] In a specific embodiment, in the real-time direct analysis mass spectrometry, the mass spectrometry parameters include: capillary voltage of 1-3 kV, declustering voltage of 90-150 v, collision voltage of 10-30 eV, and acquisition range of 50-200 m / z.

[0017] In a specific embodiment,

[0018] The characteristic ion pair of the fluorescent whitening agent having the structure shown in Formula 1 is 434.29-89.99;

[0019] The characteristic ion pair of the fluorescent whitening agent having the structure shown in Formula 2 is 269.21-251.16;

[0020] The characteristic ion pair of the fluorescent whitening agent having the structure shown in Formula 3 is 327.22-88.75;

[0021] The characteristic ion pair of the fluorescent whitening agent having the structure shown in Formula 4 is 299.19-233.15;

[0022] The characteristic ion pair of the fluorescent whitening agent having the structure shown in Formula 5 is 312.25-55.43;

[0023] The characteristic ion pair of the fluorescent whitening agent having the structure shown in Formula 6 is 313.24-269.21.

[0024] In a specific embodiment, when the paper sample to be tested is subjected to real-time mass spectrometry analysis, the same analysis method as that of the fluorescent whitening agent standard is used.

[0025] In a specific embodiment, when the real-time direct analysis mass spectrometer is used to analyze the paper sample to be tested, the inclination angle between the ion source and the paper sample to be tested is 0°-75°.

[0026] In a specific embodiment, when the real-time direct analysis mass spectrometer is used to analyze the paper sample to be tested, the distance between the ion source and the paper sample to be tested is 2 mm-10 mm.

[0027] The second aspect of the present invention provides a qualitative detection system for the type of fluorescent whitening agent in paper, comprising:

[0028] An analysis unit, including a real-time direct analysis mass spectrometer, for analyzing fluorescent whitening agent standards and paper samples to be tested;

[0029] The output unit is used to output the type of fluorescent whitening agent contained in the paper sample to be tested according to the analysis result of the analysis unit.

[0030] The present invention provides a method for qualitatively detecting the type of fluorescent whitening agent in paper, which uses real-time direct analysis mass spectrometry to analyze and detect fluorescent whitening agent standards and paper samples, and determines the type of fluorescent whitening agent contained in the paper sample, thereby solving the problem that the current fluorescent whitening agent qualitative detection process is highly destructive to the paper sample, and can qualitatively detect the fluorescent whitening agent in the paper without damaging the paper sample. The method can be used for fluorescent whitening agent detection of valuable items such as archives, calligraphy and paintings. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0032] Figure 1 A schematic flow chart of a method for qualitatively detecting the types of fluorescent whitening agents in paper provided by one embodiment of the present invention;

[0033] Figure 2 A schematic diagram of a system for qualitatively detecting types of fluorescent whitening agents in paper provided by an embodiment of the present invention.

[0034] Description of reference numerals:

[0035] 100 - analysis unit;

[0036] 200 - Output unit. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] In the field of forensic science, it is necessary to analyze the paper of paper materials such as contracts, bills, and archives to determine the source of the paper used. Currently, one effective method to determine the source of paper is to qualitatively characterize the papermaking chemicals used in the paper to trace the source of the paper. Fluorescent brighteners are commonly used paper additives in paper. They are of various types and varied structures, and are suitable as characteristic indicators for distinguishing paper.

[0039] At present, the main methods for qualitative analysis of fluorescent whitening agents in paper are liquid chromatography and liquid chromatography-mass spectrometry. The main steps of this method are to dissolve the paper in an aqueous solvent, use ultrasonic, oscillation and other extraction methods to dissolve the fluorescent whitening agent in the solvent, and use ultraviolet, fluorescence, and mass spectrometry detectors to detect the fluorescent whitening agent after passing through the membrane, and compare it with the fluorescent whitening agent standard to qualitatively analyze the fluorescent whitening agent in the paper.

[0040] For example, the Chinese invention patent application with publication number CN114113415A discloses a method for determining polysulfonic acid fluorescent whitening agents in food contact materials. Paragraph 0053 thereof discloses a sample pretreatment method, which specifically includes: cutting the sample into pieces with a specification of 5mm×5mm, weighing 1.00g, and placing it in a 30mL high-speed centrifuge tube; adding 10mL of extracting solution (10% by volume acetonitrile aqueous solution, containing 1% by volume ammonia water), vortex extraction for 3min, ultrasonic extraction at 60°C for 5min, and centrifugation at 10000r / min for 10min; taking 6mL of supernatant and purifying it through a C18 solid phase extraction column, and collecting 3mL of purified liquid in the middle; passing through a 0.22μm glass fiber filter membrane, taking about 1.0mL of the filtrate in the middle into a 1.5mL injection bottle, and waiting for analysis on the machine.

[0041] The Chinese invention patent with publication number CN113376272A discloses an efficient detection method for detecting multiple fluorescent whitening agents in paper products, which comprises: (2) crushing the paper product to be detected into strips by a paper shredder to obtain strips; taking out the strips and transferring them into a high-speed pulverizer for pulverization, wherein the speed of the high-speed pulverizer is 10000-12000r / min, pulverizing 3-5 times, each pulverization time is 30-45s, and the interval is 5-10s to obtain a pulverized sample; The crushed sample was placed in a sealed bag for later use; (3) Extraction: Under light-proof conditions, weigh 0.5 g of the crushed sample, add 15 mL of 40% acetonitrile aqueous solution, and ultrasonicate in a water bath at 50-60°C for 30-45 min. After taking out, centrifuge it in a centrifuge for 5-10 min. The speed of the centrifuge is 10000-12000 r / min, and the supernatant is taken; repeat the above extraction steps 3 times, and combine the supernatants of the 3 times, dilute to 50 mL with the above 40% acetonitrile aqueous solution, and store in a dark place.

[0042] The detection of the above-mentioned fluorescent brighteners requires the destruction of the paper samples to be tested, and is not suitable for indestructible specimens such as contracts and archives in the field of forensic science.

[0043] Therefore, in order to solve the problem that the current qualitative detection of fluorescent whitening agents is highly destructive to paper samples and to achieve qualitative detection of fluorescent whitening agents in paper without damaging the paper samples, the first aspect of the present invention provides a method for qualitative detection of fluorescent whitening agents in paper, comprising the following steps:

[0044] preparing a fluorescent whitening agent standard solution, and detecting the fluorescent whitening agent standard solution using a real-time direct analysis mass spectrometer to obtain characteristic ion pairs of the fluorescent whitening agent standard;

[0045] The paper sample to be tested is analyzed by using real-time direct analysis mass spectrometry, and the ion flow corresponding to the characteristic ion pair is extracted according to the characteristic ion pair of the fluorescent whitening agent standard;

[0046] Determine the type of fluorescent brightener contained in the paper sample to be tested.

[0047] The present invention uses real-time direct analysis mass spectrometry to analyze and detect fluorescent whitening agent standards and paper samples, determines the type of fluorescent whitening agent contained in the paper sample, solves the problem that the current fluorescent whitening agent qualitative detection process is highly destructive to paper samples, can perform qualitative detection of fluorescent whitening agents in paper without damaging the paper samples, and is suitable for fluorescent whitening agent detection of valuable items such as archives, calligraphy and paintings.

[0048] In a specific embodiment, Figure 1 A schematic flow chart of a method for qualitatively detecting the type of fluorescent whitening agent in paper provided by an embodiment of the present invention is shown in FIG. Figure 1 As shown, the method specifically comprises the following steps:

[0049] Step 1, preparing a fluorescent whitening agent standard solution, and detecting the fluorescent whitening agent standard solution using a real-time direct analysis mass spectrometer to obtain characteristic ion pairs of the fluorescent whitening agent standard;

[0050] At present, the fluorescent whitening agent commonly used in the papermaking industry is the bistriazine distyryl type. According to the different substituents, the fluorescent whitening agent standards used in the present invention include six common fluorescent whitening agents, which have the structures shown in Formulas 1-6 respectively:

[0051]

[0052]

[0053] Based on the above fluorescent whitening agent standard, it is dissolved in a mixed solvent of acetonitrile and water to prepare a fluorescent whitening agent standard solution, wherein the mass ratio of the fluorescent whitening agent standard, acetonitrile and water is 1: (100-800): (200-900).

[0054] Subsequently, six fluorescent whitening agent standard solutions were analyzed using direct analysis in real time mass spectrometry (DART-MS). DART-MS is an analytical technology that combines an atmospheric pressure open ion source with a mass spectrometer to achieve loss-free analysis and detection.

[0055] According to the working principle of DART-MS, the present invention further controls the parameters of the real-time direct analysis source and the mass spectrometer. Specifically, the parameters of the real-time direct analysis source include: a helium flow rate of 1-3 L / min, an ion source temperature of 250°C-500°C; the parameters of the mass spectrometer include: a capillary voltage of 1-3 kV, a declustering voltage of 90-150 V, a collision voltage of 10-30 eV, and a collection range of 50-200 m / z.

[0056] In the DART-MS detection process, the ions formed by the ionization of the target compound are called parent ions, and the series of fragment ions formed by the parent ions further colliding with the collision gas in the mass spectrometer collision chamber are called daughter ions, also known as product ions; this one-to-one correspondence between the parent ions and the daughter ions is called an ion pair, which is the basis for qualitative and quantitative mass spectrometry analysis. According to the detection method provided by the present invention, the characteristic ion pairs of the six fluorescent whitening agent standards are:

[0057] The characteristic ion pair of the fluorescent whitening agent having the structure shown in Formula 1 is 434.29-89.99;

[0058] The characteristic ion pair of the fluorescent whitening agent having the structure shown in Formula 2 is 269.21-251.16;

[0059] The characteristic ion pair of the fluorescent whitening agent having the structure shown in Formula 3 is 327.22-88.75;

[0060] The characteristic ion pair of the fluorescent whitening agent having the structure shown in Formula 4 is 299.19-233.15;

[0061] The characteristic ion pair of the fluorescent whitening agent having the structure shown in Formula 5 is 312.25-55.43;

[0062] The characteristic ion pair of the fluorescent whitening agent having the structure shown in Formula 6 is 313.24-269.21.

[0063] Step 2: Analyze the paper sample to be tested using real-time direct analysis mass spectrometry, and extract the ion flow corresponding to the characteristic ion pair according to the characteristic ion pair of the fluorescent whitening agent standard;

[0064] The same detection method as that of the fluorescent whitening agent standard is used to analyze the paper sample to be tested. During the analysis, the inclination angle between the ion source and the paper sample to be tested is 0°-75°, and the distance between the ion source and the paper sample to be tested is 2mm-10mm.

[0065] After the analysis is completed, the ion flow corresponding to the characteristic ion pair is extracted according to the characteristic ion pair of the fluorescent whitening agent standard, so as to determine whether the paper sample to be tested contains a certain fluorescent whitening agent standard.

[0066] Step 3: Determine the type of fluorescent whitening agent contained in the paper sample to be tested.

[0067] According to the analysis result of the paper sample to be tested in step 2, the type of fluorescent whitening agent contained in the paper sample to be tested is determined.

[0068] In summary, the present invention uses real-time direct analysis mass spectrometry to analyze and detect fluorescent whitening agent standards and paper samples, determines the type of fluorescent whitening agent contained in the paper sample, solves the problem that the current fluorescent whitening agent qualitative detection process is highly destructive to paper samples, and can perform qualitative detection of fluorescent whitening agents in paper without damaging the paper sample. It is suitable for fluorescent whitening agent detection of valuable items such as archives, calligraphy and paintings.

[0069] The second aspect of the present invention provides a qualitative detection system for the type of fluorescent whitening agent in paper, comprising:

[0070] An analysis unit, including a real-time direct analysis mass spectrometer, for analyzing fluorescent whitening agent standards and paper samples to be tested;

[0071] The output unit is used to output the type of fluorescent whitening agent contained in the paper sample to be tested according to the analysis result of the analysis unit.

[0072] In a specific embodiment, Figure 2 A schematic diagram of a qualitative detection system for the type of fluorescent whitening agent in paper provided by an embodiment of the present invention, such as Figure 2 As shown, it includes an analysis unit 100 and an output unit 200, and its role and function are as described in the first aspect of the present invention, and the present invention will not be elaborated in detail here.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A qualitative detection method for the type of fluorescent whitening agent in paper, characterized in that: The steps include: preparing a fluorescent whitening agent standard solution, and detecting the fluorescent whitening agent standard solution using a real-time direct analysis mass spectrometer to obtain characteristic ion pairs of the fluorescent whitening agent standard; The paper sample to be tested is analyzed by using real-time direct analysis mass spectrometry, and the ion flow corresponding to the characteristic ion pair is extracted according to the characteristic ion pair of the fluorescent whitening agent standard; Determine the type of fluorescent brightener contained in the paper sample to be tested.

2. The method according to claim 1, characterized in that The preparation of the fluorescent whitening agent standard solution specifically comprises the following steps: The fluorescent whitening agent standard product is mixed with acetonitrile and water to prepare a fluorescent whitening agent standard sample solution, wherein the mass ratio of the fluorescent whitening agent standard product, acetonitrile and water is 1:(100-800):(200-900).

3. The method according to claim 1 or 2, characterized in that: The fluorescent whitening agent standard products include six kinds, each having the structure shown in Formula 1-6:

4. The method according to claim 1, characterized in that In the real-time direct analysis mass spectrometry, the parameters of the real-time direct analysis source include: a helium flow rate of 1-3 L / min, and an ion source temperature of 250° C.-500° C.

5. The method according to claim 1, characterized in that In the real-time direct analysis mass spectrometry, the parameters of the mass spectrometry include: capillary voltage of 1-3 kV, declustering voltage of 90-150 v, collision voltage of 10-30 eV, and acquisition range of 50-200 m / z.

6. The method according to claim 1, characterized in that The characteristic ion pair of the fluorescent whitening agent having the structure shown in Formula 1 is 434.29-89.99; The characteristic ion pair of the fluorescent whitening agent having the structure shown in Formula 2 is 269.21-251.16; The characteristic ion pair of the fluorescent whitening agent having the structure shown in Formula 3 is 327.22-88.75; The characteristic ion pair of the fluorescent whitening agent having the structure shown in Formula 4 is 299.19-233.15; The characteristic ion pair of the fluorescent whitening agent having the structure shown in Formula 5 is 312.25-55.43; The characteristic ion pair of the fluorescent whitening agent having the structure shown in Formula 6 is 313.24-269.

21.

7. The method according to claim 1, characterized in that When the paper sample to be tested is subjected to real-time mass spectrometry analysis, the same analysis method as that of the fluorescent whitening agent standard is used.

8. The method according to claim 1, characterized in that When the real-time direct analysis mass spectrometer is used to analyze the paper sample to be tested, the inclination angle between the ion source and the paper sample to be tested is 0°-75°.

9. The method according to claim 1, characterized in that: When the real-time direct analysis mass spectrometer is used to analyze the paper sample to be tested, the distance between the ion source and the paper sample to be tested is 2 mm-10 mm.

10. A qualitative detection system for the type of fluorescent whitening agent in paper, characterized in that: include: An analysis unit, including a real-time direct analysis mass spectrometer, for analyzing fluorescent whitening agent standards and paper samples to be tested; The output unit is used to output the type of fluorescent whitening agent contained in the paper sample to be tested according to the analysis result of the analysis unit.

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