Method for detecting AKD sizing agent in paper

Abstract

The invention provides a method for detecting an AKD (Alkyl Ketene Dimer) sizing agent in paper, which comprises the following steps: sequentially carrying out pretreatment including hydrolysis treatment and extraction treatment on a to-be-detected paper sample to obtain a to-be-detected liquid; determining the to-be-detected liquid by adopting a gas chromatography-mass spectrometry method, and determining whether the to-be-detected liquid contains the AKD sizing agent hydrolysate or not according to the retention time of a gas chromatography peak in a determination result and the ratio of the ion strength of daughter ions to parent ions of a mass spectrum, the hydrolysis product of the AKD sizing agent comprises 16-trihenone, 16-tridecanone and 18-pentacosanone. The invention further discloses a preparation method of the AKD sizing agent. The detection method provided by the invention fills the blank of detection of the AKD sizing agent in the paper in the identification field, and provides a more accurate physical evidence identification direction for identification through qualitative and quantitative detection of the AKD sizing agent in the paper.

Description

Technical Field

[0001] The present invention relates to a method for detecting AKD sizing agent in paper, belonging to the technical field of physical evidence identification. Background Art

[0002] As a medium for information dissemination, paper is everywhere in daily life, and paper also appears at many crime scenes. Analyzing and identifying the paper found at the crime scene can provide clues and directions, which is of great significance. Common paper analysis and identification mainly include fiber analysis, filler analysis, sizing agent analysis, etc. Among them, alkyl ketene dimer (AKD) is widely used as a neutral sizing agent in paper preparation. By qualitatively and quantitatively detecting AKD in paper, it is possible to effectively determine whether the papers are from the same source.

[0003] However, there is currently no report on using the detection of AKD in paper for identification, and there is an urgent need to study a method for detecting AKD in paper. Summary of the Invention

[0004] The present invention provides a method for detecting AKD sizing agent in paper. This detection method can effectively determine the AKD sizing agent in paper through qualitative and quantitative detection methods, providing more options for paper identification in forensic science.

[0005] The present invention provides a method for detecting AKD sizing agent in paper, comprising:

[0006] Performing pretreatment including hydrolysis treatment and extraction treatment on the paper sample to be tested in sequence to obtain a liquid to be detected;

[0007] Using gas chromatography-mass spectrometry (GC-MS) to measure the liquid to be detected, and determining whether the liquid to be detected contains hydrolysis products of AKD sizing agent according to the retention time of the gas chromatography peak and the ratio of the ion intensities of the daughter ion and the parent ion in the mass spectrometry;

[0008] The hydrolysis products of the AKD sizing agent include 16 - hentriacontanone, 16 - tritriacontanone, and 18 - pentatriacontanone.

[0009] The above-mentioned detection method further includes: recording the gas chromatography peak area of the hydrolysis products of the AKD sizing agent measured according to the liquid to be detected, and calculating and determining the content of the hydrolysis products of the AKD sizing agent contained in the liquid to be detected by the external standard method based on the peak area.

[0010] The above-mentioned detection method further includes:

[0011] Calculating the raw material composition of the paper sample to be tested according to formula 1;

[0012] Obtain the raw material composition of the comparison paper sample; determine whether the paper sample to be tested is the same as the comparison paper sample according to the raw material composition of the paper sample to be tested and the raw material composition of the comparison paper sample;

[0013] A 16酸 : 18酸 =(2C 16-三十一酮 +C 16-三十三酮 ):(2C 18-三十五酮 +C 16-三十三酮 ) Equation 1

[0014] Wherein, the A 16酸 : 18酸 is the concentration ratio of 16-acid to 18-acid, and the C 16-三十一酮 is the content of 16-hentriacontanone, mg / L; the C 16-三十三酮 is the content of 16-tritriacontanone, mg / L; the C 18-三十五酮 is the content of 18-pentatriacontanone, mg / L.

[0015] In the detection method as described above, the liquid to be detected further contains an internal standard substance system, and the internal standard substance system includes a compound with the molecular formula C n H 2n+2 , where 28 ≤ n ≤ 30.

[0016] In the detection method as described above, the internal standard substance system further includes a mixed solvent of chloroform and toluene, and the volume ratio of chloroform to toluene is 1:1.

[0017] In the detection method as described above, the hydrolysis treatment includes:

[0018] Place the weighed paper sample in a container, add a hydrolysis solvent, and stir for hydrolysis; wherein, the hydrolysis solvent includes at least one of an HCl solution and an oxalic acid solution.

[0019] In the detection method as described above, the hydrolysis solvent is an HCl solution, and the mass molar ratio of the paper sample to HCl in the HCl solution is 1 g:0.6 mol.

[0020] In the detection method as described above, after the extraction treatment, it further includes successively performing a washing treatment, a concentration treatment, and a filtration treatment on the extraction system;

[0021] The detergent selected for the washing treatment includes a sodium bicarbonate solution;

[0022] And / or, the filtration treatment is performed using a 0.22 μm hydrophobic PTFE needle filter.

[0023] In the gas chromatography-mass spectrometry analysis as described above, the conditions of gas chromatography are:

[0024] An Agilent DB-35MS gas chromatography column with a model of 60m×0.25mm×0.25μm and a temperature limit of 50 - 340°C; the carrier gas is He, the flow rate is 1 mL / min, the split ratio is 3:1; the injection volume is 1 μL; the injection port temperature is 280°C; the temperature programming: the initial temperature is 50°C, rising to 300°C at a rate of 30°C / min and holding for 40 min.

[0025] In the detection method as described above, in the gas chromatography - mass spectrometry method, the mass spectrometry conditions are: electron impact ionization source, bombardment energy 70 eV, transfer line temperature 300°C, ion source temperature 250°C, quadrupole temperature 150°C, solvent delay 5 min; the data acquisition mode is full scan mode, and the scanning mass - to - charge ratio range is 30 - 600 amu.

[0026] In the present invention, by hydrolyzing the paper sample to obtain a liquid to be detected, and using gas chromatography - mass spectrometry to analyze the liquid to be detected, it is determined whether the liquid to be detected contains the hydrolysis product of AKD sizing agent, and further determine whether the paper sample contains AKD sizing agent. Under this method, through qualitative analysis, the blank in the identification of AKD sizing agent in paper is filled. Description of the Drawings

[0027] Figure 1 It is the mass spectrum of 16 - hentriacontanone standard sample;

[0028] Figure 2 It is the mass spectrum of 16 - tritriacontanone standard sample;

[0029] Figure 3 It is the mass spectrum of 18 - pentatriacontanone standard sample. Detailed Embodiments

[0030] To make the objectives, 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. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0031] The present invention provides a method for detecting AKD sizing agent in paper, including:

[0032] Performing pretreatment including hydrolysis treatment and extraction treatment on the paper sample to be tested in sequence to obtain a liquid to be detected;

[0033] The gas chromatography-mass spectrometry (GC-MS) method is used to determine the test solution. According to the retention time of the gas chromatography peak and the ratio of the ion intensities of the daughter ions and parent ions in the mass spectrometry in the determination results, it is determined whether the test solution contains the hydrolysis products of AKD sizing agent;

[0034] Among them, the hydrolysis products of AKD sizing agent include 16 - hentriacontanone, 16 - tritriacontanone, and 18 - pentatriacontanone.

[0035] As a commonly used neutral sizing agent, AKD sizing agent is widely used in paper preparation. Among them, the chemical structural formula of AKD is as follows:

[0036]

[0037] However, the structure of AKD is unstable and it is extremely easy to hydrolyze and decarboxylate to form corresponding ketone compounds. Therefore, directly detecting AKD in paper samples cannot achieve the qualitative and quantitative analysis of AKD sizing agent in paper samples. The ketone compounds formed after the hydrolysis and decarboxylation of AKD have relatively high stability. The qualitative analysis of AKD sizing agent in paper can be achieved by detecting the test solution after hydrolyzing the paper sample and judging whether the test solution contains ketone compounds.

[0038] The detection method provided by the present invention uses the gas chromatography-mass spectrometry (GC-MS) method to detect the hydrolysis products of paper samples, and can achieve the accurate qualitative determination of AKD sizing agent in paper samples, that is, it can determine whether the paper samples contain AKD sizing agent by determining the types of hydrolysis products of paper samples, which has important significance in the field of identification.

[0039] Specifically, the pretreatment including hydrolysis treatment and extraction treatment is sequentially performed on the paper sample to be tested to obtain the test solution.

[0040] The present invention does not limit the specific steps and reagents used for the hydrolysis treatment and extraction treatment of paper samples, as long as the hydrolysis of paper samples and the separation of hydrolysis products can be achieved. Hydrolysis reagents and extraction reagents commonly used in the art can be selected according to the actual situation.

[0041] Subsequently, gas chromatography-mass spectrometry (GC-MS) was used to detect the liquid to be tested. The above-mentioned ketone compounds all have specific chromatographic peak retention times and parent ion / daughter ion pairs in the mass spectrum (i.e., the molecular ion (parent ion) peak of the target compound and the fragment ions (daughter ion peaks) generated by the further fragmentation of the parent ion in the mass spectrum). There may be multiple daughter ions. Generally, one or two representative daughter ions with the best signal and highest stability can be selected as the above-mentioned qualitative daughter ions. The chromatographic peak retention time and the ion pair abundance ratio measured from the liquid to be tested can be compared with the chromatographic peak retention time and the ion pair abundance ratio of the ketone compound standard sample to determine whether the above-mentioned ketone compounds are contained in the liquid to be tested, and further determine whether AKD sizing agent is contained in the paper.

[0042] Among them, the chromatographic peak retention time and the ion pair abundance ratio of the ketone compound standard sample can be obtained by conventional means in the art. For example, the chromatographic peak retention time and the ion pair abundance ratio of the above-mentioned ketone compound standard sample can be measured independently, and it is best to measure the standard sample and the liquid to be tested using the same instrument and under the same operating conditions to minimize errors as much as possible.

[0043] Specifically, the above-mentioned GC-MS method can be used to measure the ketone compound standard sample to obtain the measurement results of the standard sample including the chromatographic peak retention time and the ion pair abundance ratio of each ketone compound standard sample; compare the chromatographic peak retention time and the ion pair abundance ratio in the measurement results of the liquid to be tested with the measurement results of the standard sample to determine whether the above-mentioned ketone compounds are contained in the liquid to be tested, and further determine whether AKD sizing agent is contained in the paper sample.

[0044] Among them, the chromatographic peak retention time and the ion pair abundance ratio of the above-mentioned ketone compound standard sample can be measured sequentially, or the above-mentioned ketone compound standard samples can be mixed and the obtained mixed standard sample can be measured to obtain the measurement results of the mixed standard sample including the chromatographic peak retention time and the ion pair abundance ratio of each of the above-mentioned ketone compounds.

[0045] Specifically, compare the measurement results of the liquid to be tested with the measurement results of the standard sample. If the retention time of a certain chromatographic peak in the measurement results of the liquid to be tested is basically the same as the chromatographic peak retention time of a certain ketone compound standard sample in the measurement results of the standard sample, and an ion pair abundance ratio that is basically the same as the ion pair abundance ratio obtained from the measurement of this standard sample appears, it is determined that this ketone compound exists in the liquid to be tested, and further it is determined that AKD sizing agent exists in the paper sample.

[0046] Considering factors such as errors existing in the operation process, generally, the relative error between the retention time of a gas chromatographic peak in the liquid to be detected and the retention time of the gas chromatographic peak of a standard sample of a certain ketone compound is within 1%, and the relative error between the ion pair abundance ratio of the liquid to be detected and the ion pair abundance ratio of the standard sample of this ketone compound is within 20%. Then it can be determined that the liquid to be detected contains this ketone compound, and thus it can be determined that the paper sample contains AKD sizing agent.

[0047] For example, if there is a retention time T1 of a gas chromatographic peak in the measurement result of the liquid to be detected, and the retention time T2 of the gas chromatographic peak of the 16 - hentriacontanone standard sample is measured, and the relative error between T2 and T1 is within 1%. At the same time, in the measurement result of the liquid to be detected, the parent ion / daughter ion pair (after background subtraction) measured according to the 16 - hentriacontanone standard sample appears, and its ion pair abundance ratio satisfies that the difference is less than 20%. Then it is determined that 16 - hentriacontanone exists in the liquid to be detected, and further it is determined that the paper sample contains AKD sizing agent.

[0048] The detection method provided by the present invention uses gas chromatography - mass spectrometry to detect the hydrolysis products of paper samples, and further determines whether the paper samples contain AKD sizing agent by measuring the components of the hydrolysis products. It not only eliminates the problem that the structure of AKD itself is unstable and the results obtained by directly detecting AKD are not accurate enough, but also fills the blank in the determination of AKD sizing agent in paper in the identification.

[0049] Furthermore, in a specific embodiment of the present invention, the above - mentioned detection method further includes: recording the gas chromatographic peak area of the AKD sizing agent hydrolysis products measured according to the liquid to be detected, and calculating and determining the content of the AKD sizing agent hydrolysis products contained in the liquid to be detected by the peak area according to the external standard method.

[0050] Specifically, the peak area - concentration standard curve of the above - mentioned various ketone compounds can be drawn according to the following process: Prepare detection liquids containing standard samples of a certain ketone compound with different concentrations, and use gas chromatography - mass spectrometry to measure the above - mentioned detection liquids with different concentrations in sequence to obtain the gas chromatographic peak areas corresponding to each detection liquid, and use the concentration of this ketone compound standard sample and the measured gas chromatographic peak area to fit and generate the standard curve of the gas chromatographic peak area and concentration of this ketone compound.

[0051] After it is determined that a certain ketone compound is contained in the liquid to be detected, obtain the gas chromatographic peak area y of this ketone compound in the detection result of the liquid to be detected. In the standard curve of the gas chromatographic peak area and concentration of this ketone compound, the concentration corresponding to the gas chromatographic peak area y is the concentration of this ketone compound in the liquid to be detected, that is, the content of the AKD sizing agent hydrolysis products contained in the liquid to be detected.

[0052] The operation of using the external standard method to determine the content of the hydrolyzed product of AKD sizing agent in the liquid to be detected is simple and the calculation is convenient. It can accurately obtain the hydrolyzed product of AKD sizing agent while further improving the efficiency of gas chromatography-mass spectrometry.

[0053] However, in the paper production process, there may be papers of the same batch, using the same type of AKD sizing agent, but due to different production processes, the actual usage content of the AKD sizing agent is different. Then, simply measuring the content of each hydrolyzed product of the AKD sizing agent in the paper sample and the comparison sample may not be able to accurately judge whether the paper sample and the comparison sample are from the same source. Therefore, it is also necessary to further use the raw material ratio of the AKD sizing agent to judge whether the paper sample and the comparison sample are from the same source.

[0054] Furthermore, in a specific embodiment of the present invention, the above detection method further includes:

[0055] Calculating the raw material composition of the paper sample according to Equation 1;

[0056] Obtaining the raw material composition of the comparison paper sample; judging whether the paper sample to be detected and the comparison paper sample are the same according to the raw material composition of the paper sample and the raw material composition of the comparison paper sample;

[0057] A 16酸 : 18酸 =(2C 16-三十一酮 +C 16-三十三酮 ): (2C 18-三十五酮 +C 16-三十三酮 ) Equation 1

[0058] Wherein, A 16酸 : 18酸 is the concentration ratio of 16-acid to 18-acid. Among them, the concentration units of 16-acid and 18-acid are mg / L, C 16-三十一酮 is the measured content of 16-hentriacontanone, and the unit is mg / L; C 16-三十三酮 is the measured content of 16-tritriacontanone, and the unit is mg / L; C 18-三十五酮 is the measured content of 18-pentatriacontanone, and the unit is mg / L.

[0059] Specifically, the common AKD sizing agent is prepared from 16-acid, 18-acid and a halogenating reagent. Among them, the raw material ratio of 16-acid to 18-acid affects the R1 group and R2 group in the above AKD chemical structural formula, and further affects the type of AKD hydrolysis product.

[0060] For example, if 16-acid and 16-acid are mixed and reacted with a halogenating agent to form AKD, then the R1 group and the R2 group in the chemical formula of AKD should be an alkyl group containing 14 carbons, and the hydrolysis product of AKD is 16-triacontanone. If 16-acid and 18-acid react and combine under the action of a halogenating agent to form AKD, then the R1 group and the R2 group in the chemical formula of AKD should be an alkyl group containing 14 carbons and an alkyl group containing 16 carbons, respectively, and the hydrolysis product of AKD is 16-triacontanone. Similarly, if 18-acid and 18-acid are combined under the action of a halogenating agent to form AKD, then the R1 group and the R2 group in the chemical formula of AKD should be an alkyl group containing 16 carbons, and the hydrolysis product of AKD is 18-triacontanone.

[0061] Therefore, after the specific content of ketone compounds in the test liquid is measured by gas chromatography-mass spectrometry, the raw material ratio of AKD sizing agent in the paper sample can be calculated using the above formula 1.

[0062] The raw material ratio of the comparison paper can be obtained through known paper batch production data, or the ketone compound content of the comparison paper hydrolyzate can be detected by the above-mentioned gas chromatography-mass spectrometry method and calculated using Formula 1.

[0063] Compare the AKD raw material ratio of the paper sample with the AKD raw material ratio of the reference paper. When the AKD raw material ratio differs by more than 50%, it can be determined that the paper sources are different.

[0064] Gas chromatography-mass spectrometry was used to detect the hydrolysis products of paper samples and reference paper. The above formula 1 was used to further infer whether the AKD sizing agent in the paper sample was consistent with that in the reference paper, and then to determine whether the paper was from the same source. This not only expands the ideas for paper identification, but also more intuitively describes the AKD sizing agent in paper, which is convenient for presentation.

[0065] When using gas chromatography-mass spectrometry to detect the test liquid and standard samples, factors such as instrument accuracy and actual injection volume may affect the accuracy of the test results. In particular, when using the external standard method to detect the content of ketone compounds in the test liquid, the standard curve obtained by fitting the standard sample needs to minimize the error. Therefore, it is necessary to take certain measures to improve the accuracy of gas chromatography-mass spectrometry.

[0066] Furthermore, in a specific embodiment of the present invention, the liquid to be tested also contains an internal standard system, and the internal standard system includes a molecular formula of C n H 2n+2 Compounds, 28≤n≤30.

[0067] The present invention does not limit the specific addition method and steps of the internal standard substance system, and common methods in the art can be used to add the internal standard substance system to the standard sample and the liquid to be detected.

[0068] The internal standard substance system includes a compound with the molecular formula C n H 2n+2 , where 28 ≤ n ≤ 30. For example, it includes at least one of octacosane, nonacosane, and triacontane.

[0069] The above internal standard substance has a certain chemical stability. When the standard sample and the liquid to be detected contain the above internal standard substance, during detection by gas chromatography - mass spectrometry, the peak position of the internal standard substance is close to and can be completely separated from the peak position of the component to be detected. The addition of the above internal standard substance can effectively correct the injection volume in each gas chromatography - mass spectrometry analysis process and improve the accuracy of this method.

[0070] Furthermore, in a specific embodiment of the present invention, the internal standard substance system further includes a mixed solvent of chloroform and toluene, and the volume ratio of chloroform to toluene is 1:1.

[0071] The above internal standard substance needs to be dissolved in an organic solvent before it can be further added to the standard sample and the liquid to be detected.

[0072] Among them, the inventor found through a large number of creative experiments that a mixed solvent prepared by mixing chloroform and toluene in a volume ratio of 1:1 can efficiently dissolve the internal standard substance and will not affect the detection of the standard sample and the liquid to be detected.

[0073] At the same time, the above mixed solvent can be used as an extractant to extract the mixed liquid obtained after hydrolyzing the paper sample, further reducing the reagent cost during the detection process.

[0074] Furthermore, in a specific embodiment of the present invention, the hydrolysis treatment includes:

[0075] Placing the weighed paper sample in a container, adding a hydrolysis solvent, and stirring for hydrolysis; wherein, the hydrolysis solvent includes at least one of HCl solution and oxalic acid solution.

[0076] The present invention does not limit the hydrolysis container, and common containers in the art can be selected, such as a round - bottom flask. The present invention also does not limit parameters such as the type, frequency, and time of stirring, as long as the paper can be fully hydrolyzed.

[0077] When the hydrolysis solvent includes at least one of HCl solution and oxalic acid solution, it can ensure the full hydrolysis of the paper. If the paper contains AKD sizing agent, the full hydrolysis of the paper can further improve the accuracy of qualitative and quantitative detection of AKD sizing agent in the paper by gas chromatography - mass spectrometry.

[0078] Further, in a specific embodiment of the present invention, the hydrolysis solvent is an HCl solution, and the mass molar ratio of the paper sample to HCl in the HCl solution is 1 g: 0.6 mol.

[0079] For example, when the mass of the paper sample is 1 g, 100 mL of an HCl solution with a concentration of 6 mol / L is taken for hydrolysis treatment.

[0080] The HCl solution is in the aqueous phase, which is convenient for the extraction treatment of the organic phase in the paper sample to obtain the solution to be detected; moreover, when the mass molar ratio of the paper sample to the HCl solution is selected within the above range, it can ensure the full hydrolysis of the paper while controlling the dosage, and further improve the accuracy of gas chromatography - mass spectrometry.

[0081] Further, in a specific embodiment of the present invention, after the extraction treatment, it further includes successively performing washing treatment, concentration treatment, and filtration treatment on the extraction system; the detergent selected for the washing treatment includes a sodium bicarbonate solution; and / or, the filtration treatment is performed using a 0.22 μm hydrophobic PTFE needle filter.

[0082] When analyzing the solution to be detected by gas chromatography - mass spectrometry, to avoid damage to structures such as the chromatographic column caused by the solution to be detected, the solution to be detected should be non - corrosive. Therefore, when an HCl solution is selected as the hydrolysis reagent, to eliminate the adverse effects of the possibly remaining HCl in the extraction system on the instrument, an alkaline solution needs to be selected for washing treatment. The sodium bicarbonate solution is not only simple and easily available, but also does not react with the hydrolysis products in the sample, and can ensure the quality of the solution to be detected.

[0083] The present invention does not limit the specific steps of the washing treatment, and common treatment methods in the art can be selected.

[0084] Since the content of AKD sizing agent in the paper is relatively low, to improve the accuracy of the test, it is also necessary to concentrate the organic phase after the washing treatment. The present invention does not limit the specific operation steps of the concentration treatment, and common equipment and methods in the art can be selected to concentrate the organic phase.

[0085] The paper contains a certain amount of fibers, and these fibers may still remain in the solution to be detected after hydrolysis treatment, extraction treatment, washing treatment, and concentration treatment.

[0086] Therefore, to avoid blockage and damage of the instrument by solid impurities such as fibers in the solution to be detected, it is necessary to perform filtration treatment on the solution to be detected.

[0087] The instrument selected for the filtration treatment in the present invention is a 0.22 μm hydrophobic PTFE needle filter, which has excellent acid - alkali resistance, high - temperature resistance, corrosion resistance, and low friction coefficient, etc., and can effectively filter solid impurities such as fibers in the sample solution.

[0088] The specific steps of the filtration treatment of the present invention are not limited, and the filtration treatment steps commonly used in the art can be selected.

[0089] Further, in a specific embodiment of the present invention, in the gas chromatography-mass spectrometry analysis, the conditions of gas chromatography are as follows:

[0090] Agilent DB-35MS gas chromatography column with a model of 60m×0.25mm×0.25μm and a temperature limit of 50 - 340°C; carrier gas: He, flow rate: 1mL / min, split ratio: 3:1; injection volume: 1μL; injection port temperature: 280°C; programmed temperature rise: initial temperature 50°C, rising to 300°C at a rate of 30°C / min, and holding for 40min.

[0091] The above gas chromatography conditions can effectively separate different substances in the liquid to be detected and the standard sample, have excellent selectivity, and can shorten the analysis time and obtain a stable chromatographic peak curve.

[0092] Further, in a specific embodiment of the present invention, in the gas chromatography-mass spectrometry method, the mass spectrometry conditions are an electron impact ion source, bombardment energy 70eV, transfer line temperature 300°C, ion source temperature 250°C, quadrupole temperature 150°C, solvent delay 5min; the data acquisition mode is a full scan mode, and the scanning mass-to-charge ratio range is 30 - 600amu.

[0093] The above mass spectrometry conditions have high sensitivity, good repeatability, convenient operation, and the fragment ions provide rich structural information, and can quickly and accurately perform qualitative and quantitative analysis on the liquid to be detected and the standard sample.

[0094] The following is the specific operation method of the present invention:

[0095] Unless otherwise specified, in the following experiments, the conditions for determination by gas chromatography-mass spectrometry are as follows:

[0096] Chromatography conditions

[0097] Agilent DB-35MS gas chromatography column with a model of 60m×0.25mm×0.25μm and a temperature limit of 50 - 340°C; carrier gas: He, flow rate: 1mL / min, split ratio: 3:1; injection volume 1μL; injection port temperature 280°C; programmed temperature rise: initial temperature 50°C, rising to 300°C at a rate of 30°C / min, and holding for 40min.

[0098] Mass spectrometry conditions

[0099] Ion source: Electron impact ion source, bombardment energy 70 eV, transfer line temperature 300 °C, ion source temperature 250 °C, quadrupole temperature 150 °C, solvent delay 5 min; The data acquisition mode is full scan mode, and the scanning mass-to-charge ratio range is 30 - 600 amu.

[0100] Example 1

[0101] 1. Preparation of the test solution and standard samples

[0102] 1) Preparation of the internal standard substance system

[0103] Weigh 0.01 g of triacontane into a 100 mL volumetric flask, and make up the volume with a mixed solvent obtained by mixing chloroform and toluene in a volume ratio of 1:1 to prepare an internal standard substance system with a concentration of 100 mg / L. Store it refrigerated at 4 °C in a refrigerator. Other concentration internal standard solutions are diluted from this.

[0104] 2) Preparation of standard samples

[0105] Weigh 0.01 g each of 16 - hentriacontanone, 16 - tritriacontanone, and 18 - pentatriacontanone with a purity ≥ 95% (GC) produced by Shanghai Macklin Biochemical Co., Ltd. into 100 mL volumetric flasks, add an internal standard solution with a concentration of 5 mg / L, and prepare a mixed standard sample stock solution with a concentration of 100 mg / L. Store it refrigerated at 4 °C in a refrigerator.

[0106] 3) Preparation of the test solution

[0107] Select the paper sample numbered 35 produced by Qingtu Company. It is known that this paper contains AKD sizing agent, and the raw material ratio of this AKD sizing agent is approximately 16 - acid:18 - acid = 1:1.

[0108] Weigh 0.20 g of the paper sample into a 20 mL round - bottom flask, add 10 mL of 6 mol / L HCl solution, and stir at room temperature for 2 h using a DF101S magnetic stirrer with a heating and constant temperature function (produced by Shanghai Lichen Instrument Technology Co., Ltd.) to hydrolyze the paper sample; Transfer the hydrolyzed liquid mixture to a 50 mL centrifuge tube, add 10 mL of an internal standard solution with a concentration of 5 mg / L, shake well, let it stand for extraction for 1 h to separate layers; Absorb the organic phase, wash it with 0.1 mol / L sodium bicarbonate solution until the pH value of the aqueous phase is in the range of 7 - 8; Take the organic phase, place it in a graduated container and blow it with nitrogen until the liquid level drops to one - tenth of the original concentration scale, and then filter it through a 0.22 μm hydrophobic polytetrafluoroethylene (PTFE) needle - type filter (produced by Shanghai Anpu Experimental Technology Co., Ltd.) to obtain the test solution. Use gas chromatography - mass spectrometry to detect the test solution.

[0109] 2. Qualitative analysis

[0110] Detection was carried out using a mixed standard sample of 100 mg / L, and its retention time and mass spectrometry peak information were recorded. The retention times of the standard samples are as follows: 16 - hentriacontanone is 24.85 min; 16 - tritriacontanone is 32.72 min; 18 - pentatriacontanone is 44.81 min; the mass spectrometry peak information contains the molecular ion peak and no less than two main fragment ion peaks. For details, see Figures 1-3 .

[0111] Subsequently, according to the retention time and mass spectrometry peak information of the test solution obtained by the above experimental steps, the retention times of the test solution are 24.85 min, 32.73 min, and 44.80 min respectively. The mass spectrometry peak information is basically the same as the main peaks of the standard product, and the target compound structure can be obtained through NIST retrieval. It can be seen that the retention time error of 16 - hentriacontanone in the test solution and the standard sample is less than 1%, and the mass spectrometry peak information is basically the same as that of the 16 - hentriacontanone standard sample; the difference in retention time between the test solution and the standard sample of 16 - tritriacontanone is less than 1%, and the mass spectrometry peak information is basically the same as that of the 16 - tritriacontanone standard sample; the retention time error of 18 - pentatriacontanone in the test solution and the standard sample is less than 1%, and the mass spectrometry peak information is basically the same as that of the 18 - pentatriacontanone standard sample.

[0112] Therefore, it is considered that the test solution contains 16 - hentriacontanone, 16 - tritriacontanone, and 18 - pentatriacontanone, and the paper sample contains AKD sizing agent.

[0113] 3. Quantitative analysis

[0114] Take the above - mentioned mixed standard sample mother liquor respectively and prepare 3 groups of standard samples. In each group of standard samples, the gradient of each ketone compound is 0.1 mg / L, 0.2 mg / L, 0.5 mg / L, 1 mg / L, 5 mg / L, 10 mg / L, 20 mg / L, 50 mg / L in turn. Each sample is injected into a gas chromatography - mass spectrometry instrument three times, and the average value of the peak areas is taken to make a curve. With the concentration as the abscissa and the gas chromatography peak area as the ordinate, a linear regression is carried out to draw the peak area - concentration standard curve corresponding to each ketone compound standard sample, and parameters such as the detection limit and quantification limit of each ketone compound are determined. Its linear equation, quantification limit, detection limit and other parameters are shown in Table 1. In the range of 5 - 50 mg / L, the gas chromatography peak area corresponding to each ketone compound standard sample has a linear relationship with the concentration, and the linear correlation coefficient r values are all greater than 0.97.

[0115] Inject the liquid to be detected into a gas chromatography-mass spectrometry (GC-MS) instrument to obtain a gas chromatogram curve. Determine the specific type of ketone compound based on the retention time, and read the peak area corresponding to the retention time. The peak area of 16-hentriacontanone is 10.27, the peak area of 16-tritriacontanone is 4.98, and the peak area of 18-pentatriacontanone is 3.96. Substitute the peak areas into the corresponding linear equations in turn, and calculate that the concentration of 16-hentriacontanone is 15 mg / L, the concentration of 16-tritriacontanone is 10 mg / L, and the concentration of 18-pentatriacontanone is 12 mg / L.

[0116] Table 1

[0117]

[0118] Calculate the concentration of the ketone compound obtained above using Equation 1, and obtain the raw material ratio of the paper sample as 16 acid:18 acid = 1.18:1, which is less than 15.3% different from the actual raw material ratio of the paper sample. Therefore, it can be considered that the present invention can accurately detect the AKD sizing agent in the paper.

[0119] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A detection method for AKD sizing agent in paper, characterized in that, Comprising: Performing pre-treatments including hydrolysis treatment and extraction treatment on the paper sample to be tested in sequence to obtain a liquid to be detected; Using gas chromatography-mass spectrometry (GC-MS) to measure the liquid to be detected, and determining whether the liquid to be detected contains AKD sizing agent hydrolysis products according to the retention time of the gas chromatography peak and the ratio of the ion intensities of the daughter ions and parent ions in the mass spectrometry in the measurement result; The AKD sizing agent hydrolysis products include 16-hentriacontanone, 16-tritriacontanone, and 18-pentatriacontanone.

2. The detection method according to claim 1, wherein Also comprising: Recording the gas chromatography peak area of the AKD sizing agent hydrolysis products measured according to the liquid to be detected, and calculating and determining the content of the AKD sizing agent hydrolysis products contained in the liquid to be detected by external standard method based on the peak area.

3. The detection method according to claim 2, wherein The method also comprises: Calculating the raw material composition of the paper sample to be tested according to formula 1; Obtaining the raw material composition of a comparison paper sample; judging whether the paper sample to be tested and the comparison paper sample are the same according to the raw material composition of the paper sample to be tested and the raw material composition of the comparison paper sample; A 16酸 : 18酸 =(2C 16-三十一酮 +C 16-三十三酮 ):(2C 18-三十五酮 +C 16-三十三酮 ) Equation 1 Among them, the A 16酸 : 18酸 is the concentration ratio of 16-acid to 18-acid, and the C 16-三十一酮 is the content of 16-hentriacontanone, mg / L; the C 16-三十三酮 is the content of 16-tritriacontanone, mg / L; the C 18-三十五酮 is the content of 18-pentatriacontanone, mg / L.

4. The detection method according to claim 3, characterized in that The liquid to be detected further contains an internal standard substance system, and the internal standard substance system includes a compound with the molecular formula C n H 2n+2 , where 28 ≤ n ≤ 30.

5. The detection method according to claim 4, characterized in that The internal standard substance system further includes a mixed solvent of chloroform and toluene, and the volume ratio of the chloroform to the toluene is 1:

1.

6. The detection method according to any one of claims 1-5, characterized in that, The hydrolysis treatment includes: Placing the weighed paper sample in a container, adding a hydrolysis solvent, and stirring for hydrolysis; wherein, the hydrolysis solvent includes at least one of HCl solution and oxalic acid solution.

7. The detection method according to claim 6, wherein The hydrolysis solvent is HCl solution, and the mass molar ratio of the paper sample to HCl in the HCl solution is 1g:0.6mol.

8. The detection method according to claim 7, characterized in that After the extraction treatment, it further includes sequentially performing washing treatment, concentration treatment, and filtration treatment on the extraction system; The detergent selected for the washing treatment includes sodium bicarbonate solution; And / or, the filtration treatment is performed using a 0.22μm hydrophobic PTFE needle filter.

9. The detection method according to any one of claims 1-7, characterized in that, In the gas chromatography-mass spectrometry analysis, the conditions of the gas chromatography are: Agilent DB-35MS gas chromatography column with a model of 60m×0.25mm×0.25μm and a temperature limit of 50-340°C; carrier gas He, flow rate 1mL / min, split ratio 3:1; injection volume 1μL; injection port temperature 280°C; programmed temperature rise: initial temperature 50°C, rising to 300°C at 30°C / min, and holding for 40min.

10. The detection method according to any one of claims 1-8, characterized in that, In the gas chromatography-mass spectrometry method, the mass spectrometry conditions are: Electron impact ion source, bombardment energy 70eV, transfer line temperature 300°C, ion source temperature 250°C, quadrupole temperature 150°C, solvent delay 5min; The data acquisition mode is full scan mode, and the scanning mass-to-charge ratio range is 30-600amu.

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