Method for detecting content of benzene substances in nitrocellulose

Abstract

The invention relates to the technical field of nitrocellulose, and discloses a nitrocellulose benzene substance content detection method, which comprises: preparing standard benzene-free nitrocellulose, preparing a benzene-free nitrocellulose standard solution, preparing a benzene substance standard solution, and preparing a benzene-containing nitrocellulose standard solution, testing by using a headspace-gas chromatograph, drawing a standard curve, dissolving the nitrocellulose sample, detecting by using the headspace-gas chromatograph, and obtaining the content of the benzene substances in the nitrocellulose sample through the standard curve. The detection method is high in test speed, high in accuracy and wide in application range.

Description

Technical Field

[0001] The invention relates to the technical field of nitrocellulose, and in particular to a method for detecting the content of benzene substances in nitrocellulose. Background Art

[0002] Nitrocellulose is the product of the esterification reaction between nitrocellulose and nitric acid and sulfuric acid. After being stabilized, nitrocellulose is driven out of water by ethanol or isopropanol and used in the coating field. Due to the quick drying of nitro coatings, the construction period can be greatly shortened. In addition, nitrocellulose is also widely used in the field of inks. Nitrocellulose is used as a raw material to manufacture sprayable food packaging, toy packaging, cigarette packages, etc. With the improvement of environmental protection requirements, the ink field has put forward benzene control requirements for alcohol-containing nitrocellulose products, that is, the benzene content is required to be zero, the toluene content is not more than 5ppm, and the sum of o-xylene, m-xylene, and p-xylene is not more than 20ppm.

[0003] Since nitrocellulose is a hazardous chemical, it can spontaneously combust when exposed to air, and is extremely prone to burning and exploding when exposed to open flames or high temperatures. It can react violently with oxidants and most organic amines and also cause combustion or explosion. Therefore, directly heating a solid nitrocellulose sample at high temperature for testing may cause safety accidents. If nitrocellulose is made into a solution and directly tested using a gas chromatograph, although the results can be measured, after the nitrocellulose solution enters the chromatographic instrument as a liquid, it is easy to form a film and has a certain viscosity, so it is easy to deposit on the chromatographic column and the injection port, causing contamination. Frequent replacement of the liner will affect the service life of the chromatographic column, taking up too much time to troubleshoot equipment failures and causing waste of resources.

[0004] In addition, at present, standard solutions are generally prepared by adding standard reagents of the components to be tested to a fixed volume reagent. When testing the content of benzene substances in nitrocellulose, it is necessary to consider the influence of the morphology and proportion of nitrocellulose in the nitrocellulose sample to be tested. If a standard solution of benzene substances is directly prepared for testing, there may be an error between the test value and the actual value of the benzene content in the nitrocellulose sample to be tested.

[0005] Therefore, it is necessary to propose a method for detecting the content of benzene substances in nitrocellulose to solve the above problems. Summary of the invention

[0006] Based on the above, the purpose of the present invention is to provide a method for detecting the content of benzene substances in nitrocellulose, which has fast detection speed, high accuracy, wide application range and high safety.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for detecting the content of benzene substances in nitrocellulose comprises the following steps:

[0009] Preparation of standard benzene-free nitrocellulose: taking a stabilization-treated benzene-free nitrocellulose sample, replacing water with anhydrous ethanol, and centrifuging to obtain a standard benzene-free nitrocellulose that does not contain benzene substances;

[0010] Prepare a benzene-free nitrocellulose standard solution, add anhydrous ethanol and an ester solvent to the standard benzene-free nitrocellulose in sequence, and let stand after forming a uniform transparent solution to obtain a benzene-free nitrocellulose standard solution, repeat the above operation to obtain multiple identical benzene-free nitrocellulose standard solutions;

[0011] Prepare a standard solution of benzene substances. Add benzene substances into a volumetric flask, use an ester reagent to make up the volume, and dilute step by step to prepare standard solutions of benzene substances with different contents.

[0012] Prepare a nitrocellulose-containing standard solution, and add preset volumes of the standard solutions of benzene substances with different contents to the plurality of identical nitrocellulose-free standard solutions, to obtain nitrocellulose-containing standard solutions with different contents;

[0013] Drawing a standard curve, testing the standard solutions containing benzene nitrocellulose with different contents using a headspace-gas chromatograph to obtain gas chromatograms of nitrocellulose containing benzene with different contents, and drawing a standard curve Y=aX+b, wherein: Y is the peak area of ​​different benzene substances, X is the ppm value of the corresponding benzene substance in the standard solution, and a and b are constants;

[0014] Infiltration and dissolution of nitrocellulose sample: adding anhydrous ethanol to the nitrocellulose sample to fully infiltrate it, then adding an ester solvent to mix and dissolve it, forming a uniform transparent solution and then letting it stand to obtain a sample solution to be tested;

[0015] The nitrocellulose sample test is to test the sample solution to be tested and the benzene-containing nitrocellulose standard solution under the same conditions using the headspace-gas chromatograph to obtain a gas chromatogram of the nitrocellulose sample, and to calculate using the area external standard method to obtain the peak area of ​​the corresponding benzene substance in the nitrocellulose sample through the gas chromatogram of the nitrocellulose sample, and to obtain the ppm value X=(Yb) / a of the corresponding benzene substance in the nitrocellulose sample through the standard curve.

[0016] As a preferred embodiment of a method for detecting the content of benzene substances in nitrocellulose, the head space-gas chromatograph comprises a head space injector and a gas chromatograph.

[0017] As a preferred solution for the detection method of benzene content in nitrocellulose, in the headspace sampler, the heating box temperature is 70-80°C, the quantitative loop temperature is 150-180°C, the transmission line temperature is 160-200°C, the equilibration time is 30-60min, and the injection time is 45s-1min.

[0018] As a preferred embodiment of a method for detecting the content of benzene substances in nitrocellulose, in the gas chromatograph, the detector is a FID detector, the chromatographic column is a DM series 60m capillary chromatographic column, the injection port temperature is 160-180°C, the detector temperature is 230-250°C, the injection split ratio is (20-25):1, and the carrier gas flow rate is 0.8-1.2mL / min;

[0019] The temperature program was set as follows: 40-55°C for 2-4 min, then raised to 220-240°C at 6-10°C / min.

[0020] As a preferred embodiment of a method for detecting the content of benzene substances in nitrocellulose, the benzene substances are chromatographic grade reagents, including one or more of benzene, toluene, ethylbenzene, m-p-xylene and o-xylene.

[0021] As a preferred embodiment of a method for detecting the content of benzene substances in nitrocellulose, the ester reagent is a chromatographic grade ester reagent, including one of ethyl acetate, butyl acetate and triacetin.

[0022] As a preferred embodiment of a method for detecting the content of benzene substances in nitrocellulose, the anhydrous ethanol is a chromatographic grade reagent.

[0023] The beneficial effects of the present invention are:

[0024] The present invention provides a method for detecting the content of benzene substances in nitrocellulose. The method does not use a component to be tested to directly prepare a standard solution. In the preparation process, standard benzene-free nitrocellulose and a standard solution of benzene substances are prepared separately, and then different contents of benzene substances are added to the standard benzene-free nitrocellulose to obtain a standard solution of nitrocellulose containing benzene. The standard solution is prepared by adding a constant volume reagent to the standard reagent of the component to be tested and the content of benzene substances in the nitrocellulose is detected, so that the state of the sample to be tested in the headspace bottle containing nitrocellulose is simulated, and the influence of the state when the pure reagent is directly used is eliminated.

[0025] The present invention dissolves nitrocellulose by adding anhydrous ethanol as a wetting agent, thereby preventing the explosion hazard caused by direct high-temperature heating test of nitrocellulose; adopts headspace-gas chromatography to detect the content of benzene substances in nitrocellulose, because after the sample after the nitrocellulose is dissolved enters the headspace-gas chromatograph, the solvent component therein will form gas, and the gas can be directly tested by gas chromatography, thereby preventing equipment failure caused by directly adding the nitrocellulose solution in liquid form to the gas chromatograph, saving equipment maintenance time and avoiding resource waste; the testing method also has the characteristics of a wide range of applications, and can be applied to the field of low-content ppm level. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the contents of the embodiments of the present invention and these drawings without paying any creative work.

[0027] Figure 1 It is the gas chromatogram of the standard solution containing phenyl nitrocellulose;

[0028] Figure 2 It is the standard curve of benzene in the nitrocellulose standard solution containing benzene;

[0029] Figure 3 It is the standard curve of toluene in the nitrocellulose standard solution containing benzene;

[0030] Figure 4 It is the standard curve of ethylbenzene in the nitrocellulose standard solution containing benzene;

[0031] Figure 5 It is the standard curve of m-xylene in the nitrocellulose standard solution containing benzene;

[0032] Figure 6 It is the standard curve of p-xylene in the standard solution of nitrocellulose containing benzene;

[0033] Figure 7 It is the standard curve of o-xylene in the standard solution of nitrocellulose containing benzene;

[0034] Figure 8 It is the gas chromatogram of benzene in the nitrocellulose sample to be tested;

[0035] Fig. 9 It is the gas chromatogram of toluene in the nitrocellulose sample to be tested. DETAILED DESCRIPTION

[0036] For ease of understanding of the present invention, the present invention will be described more fully below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive. Unless otherwise defined, all technical and scientific terms used in the present invention belong to the technical field of the present invention.

[0037] The present invention provides a method for detecting the content of benzene substances in nitrocellulose, comprising the following steps:

[0038] (1) preparing a standard benzene-free nitrocellulose, taking a benzene-free nitrocellulose sample after stabilization, replacing water with anhydrous ethanol, and centrifuging to obtain a standard benzene-free nitrocellulose that does not contain benzene substances;

[0039] Specifically, during the production of nitrocellulose, acid participates in the esterification reaction, causing the instability of nitrocellulose, which allows nitrocellulose to undergo chemical self-decomposition. Therefore, it is necessary to remove the acid substances in it to improve the stability of nitrocellulose; the stabilization treatment methods include fine cutting, alkali washing, etc. For industrial nitrocellulose, the stabilization treatment method mainly uses a combination of pressurized water boiling and washing to drive out residual acid and unstable impurities in nitrocellulose and reduce viscosity. Then use anhydrous ethanol to replace the water and centrifuge to make the wetting agent in nitrocellulose within the specified range.

[0040] (2) preparing a benzene-free nitrocellulose standard solution, adding anhydrous ethanol and an ester solvent to a standard benzene-free nitrocellulose sample in sequence to form a uniform transparent solution and then standing to obtain a benzene-free nitrocellulose standard solution, repeating the above operation to obtain multiple identical benzene-free nitrocellulose standard solutions;

[0041] Specifically, in this embodiment, 1 g of standard benzene-free nitrocellulose (accurate to 0.0001 g) is accurately weighed into a headspace bottle, 1 mL of anhydrous ethanol is added, and then 1 mL of ethyl acetate or other ester solvents is added. After a uniform transparent solution is formed, it is allowed to stand to obtain multiple identical benzene-free nitrocellulose standard solutions. The same operation is repeated four times, and they are numbered 6 in sequence. # , 7 # , 8 # , 9 # The ester reagent and anhydrous ethanol are both chromatographic grade reagents, and the ester reagent includes one of ethyl acetate, butyl acetate, and triacetin. Since ethyl acetate has a lower molecular weight, ethyl acetate is preferred.

[0042] (3) preparing a standard solution of benzene substances, adding benzene substances to a volumetric flask, using an ester reagent to make up the volume, and diluting step by step to prepare standard solutions of benzene substances with different contents;

[0043] Specifically, in this embodiment, about 0.1-0.3 g of each chromatographic grade benzene substance was added to a 100 mL volumetric flask, accurate to 0.0001 g, and the volume was fixed with ethyl acetate (chromatographic grade) to obtain a 1000-3000 ppm solution, number 1 # Solution;

[0044] Take 1 # 1 mL of solution, diluted to 100 mL, to obtain a 10-30 ppm solution, No. 2 # Solution;

[0045] Take 2 # Solution 50mL, diluted to 100mL, to obtain 5-15ppm solution, No. 3 # Solution;

[0046] Take 2 # Solution 20mL, diluted to 100mL, to obtain 2-6ppm solution, No. 4 # Solution;

[0047] Take 2 # Solution 10mL, diluted to 100mL, to obtain 1-3ppm solution, No. 5 # Solution.

[0048] Therefore, we get 2 # , 3 # , 4 # , 5 # Benzene content in solution N i They are 10-30ppm, 5-15ppm, 2-6ppm, and 1-3ppm respectively.

[0049] Wherein, the ester reagent is a chromatographic grade reagent, and the ester reagent includes one of ethyl acetate, butyl acetate, and triacetin. Since ethyl acetate has a lower molecular weight, ethyl acetate is preferred. Benzene substances include one or more of benzene, toluene, ethylbenzene, m-p-xylene, and o-xylene. When there is a need to detect benzene substances such as benzene, toluene, ethylbenzene, m-p-xylene, and o-xylene, the above-mentioned benzene substances can be dissolved and diluted at the same time, and the standard curve of the above-mentioned benzene substances can be obtained at the same time, which is convenient for the subsequent detection of the content of benzene substances in benzene-containing nitrocellulose; in other embodiments, if only one of the benzene substances needs to be detected, only the standard curve of the corresponding benzene substance needs to be prepared, which is determined according to the actual situation.

[0050] (4) preparing a nitrocellulose standard solution containing benzene, adding a preset volume of a standard solution of a benzene substance with different contents to a plurality of identical nitrocellulose solutions without benzene, to obtain nitrocellulose standard solutions containing benzene with different contents;

[0051] Specifically, in this embodiment, the numbers are 6 # , 7 # , 8 # , 9 # To the benzene-free nitrocellulose solution, use an electronic pipette to add the number 2 # , 3 # , 4 # , 5 # 3 mL of solution was added to each headspace bottle to keep the same amount, and a standard solution containing phenyl nitrocellulose was obtained, which was numbered 6 in sequence. # , 7 # , 8 # , 9 # The ppm value of the standard solution of nitrocellulose containing benzene is N' i =3*N i / V=N i / (1+1+3)=3*N i / 5, therefore, the ppm value of the phenyl nitrocellulose standard solution in the four headspace bottles is N' i They are N'1=3*N1 / 5, N'2=3*N2 / 5, N'3=3*N3 / 5, and N'4=3*N4 / 5. Of course, in other embodiments, the preset volumes of the standard solutions of benzene substances with different contents added can also be 1mL, 2mL, or other values, and the preset volumes can be substituted by the above method, which is determined according to actual needs.

[0052] (5) drawing a standard curve, testing different contents of nitrocellulose containing benzene using a headspace-gas chromatograph to obtain gas chromatograms of nitrocellulose containing benzene at different contents, and drawing a standard curve Y=aX+b, wherein: Y is the peak area of ​​different benzene substances, X is the ppm value of the corresponding benzene substance in the standard solution, and a and b are constants;

[0053] Specifically, in this embodiment, the gas chromatogram represents the peak time and corresponding peak area of ​​benzene substances in the standard solution of benzene-containing nitrocellulose. The gas chromatography test uses a headspace-gas chromatograph, which includes a headspace injector and a gas chromatograph, wherein the detection limit of the headspace-gas chromatograph for the content of benzene substances is below 0.1ppm. Since the general detection method cannot detect when the benzene content is lower than 0.1ppm, the specific application requires that the detection limit of the headspace-gas chromatograph meets this requirement when the benzene content is lower than 0.1ppm.

[0054] In the headspace sampler, the temperature of the heating box is 70-80°C, the temperature of the quantitative loop is 150-180°C, the temperature of the transfer line is 160-200°C, the equilibration time is 30-60min, and the injection time is 45s-1min; in the gas chromatograph, the detector is a FID detector, the chromatographic column is a DM series 60m capillary chromatographic column, the injection port temperature is 160-180°C, the detector temperature is 230-250°C, the injection split ratio is (20-25):1, and the carrier gas flow rate is 0.8-1.2mL / min; the program temperature is set as: 40-55°C for 2-4min, and then increased to 220-240°C at 6-10°C / min. The headspace sampler uses the sample to be tested (gas-liquid and gas-solid) for heating equilibrium, and its volatile gas part enters the gas chromatograph, which can be used to analyze volatile trace components; after heating in the heating box of the headspace sampler, the organic solvent entering the chromatographic system is in a gaseous state, which overcomes the influence of the residual nitrocellulose film formation in the chromatographic column and the injection port when the nitrocellulose liquid sample is directly injected into the chromatographic column. If the gas chromatograph is used for direct testing, the sample containing nitrocellulose enters the chromatographic column through the injection device of the gas chromatograph, but the nitrocellulose solution is easy to form a film and will form residues in the chromatographic column. If this method is used for long-term testing, the residue increases, the performance of the chromatographic column decreases, and the detection results cannot be accurate, especially for ppm-level detection.

[0055] (6) Wetting and dissolving the nitrocellulose sample: adding anhydrous ethanol to the nitrocellulose sample to fully wet it, then adding an ester solvent to mix and dissolve it, forming a uniform transparent solution and then letting it stand to obtain a sample solution to be tested;

[0056] Specifically, in this embodiment, 0.9995-1.0005g of nitrocellulose sample is accurately weighed in a headspace bottle, and the weighing is accurate to 0.0001g; 1mL of anhydrous ethanol (chromatographic grade) is added to fully infiltrate the nitrocellulose, and after about 5 minutes, 4mL of ethyl acetate (chromatographic grade) or other esters (chromatographic grade) are added, and after a uniform transparent solution is formed, it is allowed to stand to obtain a sample solution to be tested; wherein, in order to maintain the consistency of the volume of the sample solution to be tested with the volume of the standard solution of nitrocellulose containing benzene, 4mL of ethyl acetate is added to dissolve, and the total volume of the sample solution to be tested is 5mL, which is the same as the total volume of the standard solution of nitrocellulose containing benzene, and the difference from adding 1mL of ethyl acetate to the standard solution of nitrocellulose without benzene is that the standard solution of benzene substances is fixed to volume by adding ethyl acetate, and the final prepared standard solution of nitrocellulose containing benzene has the same volume of ethyl acetate as the sample solution to be tested. Specifically:

[0057] In step (2), the benzene-free nitrocellulose standard solution includes 1 g of standard benzene-free nitrocellulose, 1 mL of anhydrous ethanol and 1 mL of ethyl acetate;

[0058] In step (4), the standard solution of nitrocellulose containing benzene includes 1 g of standard nitrocellulose without benzene, 1 mL of anhydrous ethanol, 1 mL of ethyl acetate and 3 mL of the corresponding standard solution of benzene substances in step (3) (converted to volume with ethyl acetate), and the total volume is 5 mL (including 1 mL of anhydrous ethanol and 4 mL of ethyl acetate);

[0059] In step (6), the sample solution to be tested includes 1 mL of anhydrous ethanol and 4 mL of ethyl acetate;

[0060] Therefore, the volume of the sample solution to be tested can be kept consistent with the volume of the standard solution of nitrocellulose containing benzene. Of course, in other embodiments, the amount of ethyl acetate added can be set to other values, which are specifically determined according to the preset volume value of the standard solution of benzene substances added during the preparation of the standard solution of nitrocellulose containing benzene.

[0061] More specifically, when samples are continuously delivered on the production line, 1 mL of anhydrous ethanol (chromatographic grade) is used to fully soak the nitrocellulose. After about 5 minutes, 4 mL of ethyl acetate (chromatographic grade) is added. By adding anhydrous ethanol first, the dissolution of ethyl acetate is facilitated, thereby shortening the dissolution time of adding ethyl acetate alone. In the prior art, nitrocellulose can be completely dissolved after 30 minutes of dissolution. However, in the present application, after being fully soaked in anhydrous ethanol, it only needs to be shaken for 5-10 minutes to achieve complete dissolution, thereby shortening the dissolution time.

[0062] (7) Nitrocellulose sample testing: the sample solution to be tested and the standard solution of benzene-containing nitrocellulose are tested under the same conditions using a headspace-gas chromatograph to obtain a gas chromatogram of the nitrocellulose sample. The area external standard method is used for calculation. The peak area of ​​the corresponding benzene substance in the nitrocellulose sample is obtained through the gas chromatogram of the nitrocellulose sample. The ppm value of the corresponding benzene substance in the nitrocellulose sample is obtained through the standard curve X=(Yb) / a.

[0063] The present invention will be further described below by means of specific examples.

[0064] Example 1

[0065] (1) Preparation of standard benzene-free nitrocellulose: Take a benzene-free nitrocellulose sample that has been stabilized during production, use anhydrous ethanol (chromatographic grade) to displace water, and use a high-speed centrifuge to centrifuge. The centrifugation effect keeps the wetting agent content in the nitrocellulose at about 30±2% (the wetting agent content requirement for the product before leaving the factory), thereby obtaining a standard benzene-free nitrocellulose that does not contain benzene substances;

[0066] (2) Preparation of Benzene-free Nitrocellulose Standard Solution: Weigh 0.9997 g, 0.9998 g, 0.9997 g, and 0.9996 g of standard Benzene-free Nitrocellulose samples into four identical headspace bottles, numbered 6 in sequence. # , 7 # , 8 # , 9 # , add 1 mL of anhydrous ethanol (chromatographic grade), then add 1 mL of ethyl acetate (chromatographic grade), and let it stand until a uniform transparent solution is formed to obtain a benzene-free nitrocellulose standard solution.

[0067] (3) Prepare a standard solution of benzene: add 0.1466 g of chromatographic grade benzene, 0.2673 g of toluene, 0.2671 g of ethylbenzene, 0.1900 g of m-xylene, 0.1126 g of p-xylene and 0.2779 g of o-xylene to a 100 mL volumetric flask and make up to volume with ethyl acetate (chromatographic grade). The contents of benzene in the resulting solution are 1466 ppm for benzene, 2673 ppm for toluene, 2671 ppm for ethylbenzene, 1900 ppm for m-xylene, 1126 ppm for p-xylene and 2779 ppm for o-xylene. # Solution;

[0068] Take 1 mL of solution 1 and dilute to 100 mL. # Solution;

[0069] Take 2 # Solution 50mL, diluted to 100mL, No. 3 # Solution;

[0070] Take 2 # Solution 20mL, diluted to 100mL, No. 4 # Solution;

[0071] Take 10mL of solution 2# and dilute to 100mL, No. 5 # Solution.

[0072] Based on this, the numbers are 2 # , 3 # , 4 # , 5 # The specific content of each benzene substance standard solution is shown in Table 1:

[0073] Table 1 Content of Benzene Substances Standard Solution

[0074]

[0075] (4) Prepare a standard solution containing phenyl nitrocellulose: # , 7 # , 8# , 9 # 2 % nitrocellulose solution was added using an electronic pipette. # , 3 # , 4 # , 5 # 3 ml each, the amount added to each headspace bottle is kept consistent, and a standard solution of nitrocellulose containing benzene is obtained. The ppm value of the standard solution of nitrocellulose containing benzene is N' i =N i / V=3*N i / (1+1+3)=N i / 5, therefore, the ppm value of the phenyl nitrocellulose standard solution in the four headspace bottles is N' i They are N'1=3*N1 / 5, N'2=3*N2 / 5, N'3=3*N3 / 5, and N'4=3*N4 / 5 respectively.

[0076] For example, number 6 # In the headspace bottle: benzene content: N'1 = 3*N1 / 5 = 3*14.66 / 5 = 8.796ppm;

[0077] The calculation method for the content of other components is the same, that is, the content of benzene substances in the standard solution of nitrocellulose containing benzene is shown in Table 2:

[0078] Table 2 Content of benzene in standard solution of nitrocellulose containing benzene

[0079]

[0080] (5) Draw a standard curve and convert the above 6 # , 7 # , 8 # , 9 # The standard solution of nitrocellulose containing benzene is subjected to gas chromatography test by headspace-gas chromatograph, wherein the working parameters of the headspace-gas chromatograph are: in the headspace injector, the temperature of the heating box is 70-80°C, the temperature of the quantitative loop is 160°C, the temperature of the transfer line is 180°C, the equilibrium time is 45min, and the injection time is 1min; in the gas chromatograph, the detector is an FID detector, the chromatographic column is a DM series 60m capillary column, the injection port temperature is 160-180°C, the detector temperature is 230-250°C, the injection split ratio is 20:1 or 25:1, and the carrier gas flow rate is 0.8-1.2mL / min; the program temperature is set as: retain at 45°C for 2min, and then increase to 230°C at 6-10°C / min.

[0081] A gas chromatogram containing phenyl nitrocellulose is obtained, such as Figure 1 As shown, from Figure 1The peak time of the corresponding benzene substances can be obtained, and the peak time table is shown in Table 3.

[0082] Table 3 Benzene peak timetable

[0083]

[0084] (6) Regarding the above 6 # , 7 # , 8 # , 9 # The phenyl nitrocellulose standard solution in the mixture is subjected to gas chromatography testing by a headspace-gas chromatograph, and the peak areas of the phenyl nitrocellulose standard solution at different contents can also be obtained. The specific peak areas are shown in Table 4.

[0085] Table 4 Peak area of ​​benzene substances

[0086] serial number benzene Toluene Ethylbenzene Meta-Xylene p-Xylene o-Xylene <![CDATA[6 # ]]> 1.0894 2.0715 0.9860 0.8679 1.2960 0.4935 <![CDATA[7 # ]]> 0.5379 1.0074 0.5036 0.4295 0.7079 0.2625 <![CDATA[8 # ]]> 0.2070 0.3689 0.2142 0.1665 0.3550 0.1240 <![CDATA[9 # ]]> 0.0967 0.1561 0.1177 0.0789 0.2374 0.0778

[0087] According to the values ​​in Table 4, a standard curve Y=aX+b can be drawn, where: Y is the peak area of ​​different benzene substances, X is the ppm value of the corresponding benzene substance in the standard solution, and a and b are constants, and we can get:

[0088] The standard curve for benzene is Y = 0.1254X-0.0136;

[0089] The standard curve of toluene is Y = 0.1327X-0.0567;

[0090] The standard curve of ethylbenzene is Y = 0.0602X + 0.0212;

[0091] The standard curve of m-xylene is Y = 0.0769X-0.0088;

[0092] The standard curve of p-xylene is Y=0.1741X+0.1198;

[0093] The standard curve of o-xylene is Y = 0.0277X + 0.0316;

[0094] The standard curves of benzene, toluene, ethylbenzene, m-xylene, p-xylene and o-xylene are as follows: Figure 2-6 shown.

[0095] (7) Test the sample to be tested

[0096] Test 1: Weigh 0.9998 g of the first test batch of nitrocellulose sample into a 20 mL headspace bottle, add 1 mL of anhydrous ethanol (chromatographic grade) to fully soak the nitrocellulose, and after about 5 minutes, add 4 mL of ethyl acetate (chromatographic grade) to form a uniform transparent solution and let it stand to obtain the sample solution to be tested.

[0097] This batch of sample solutions to be tested is tested under the same conditions as the nitrocellulose standard solution containing benzene to obtain a gas chromatogram of this batch of nitrocellulose samples, and calculations are performed based on the peak area values ​​of the gas chromatogram.

[0098] like Figure 7 As shown, benzene peaks at 8.044 with a peak area of ​​0.800278. Figure 2 The standard curve of benzene, formula Y=0.1254X-0.0136, calculates the benzene content to be 6.49ppm.

[0099] Test 2: 0.9997 g of the second test batch of nitrocellulose sample was weighed into a 20 mL headspace bottle, 1 mL of anhydrous ethanol (chromatographic grade) was added to fully soak the nitrocellulose, and after about 5 minutes, 4 mL of ethyl acetate (chromatographic grade) was added to form a uniform transparent solution and then allowed to stand to obtain the sample solution to be tested.

[0100] This batch of sample solutions to be tested is tested under the same conditions as the nitrocellulose standard solution containing benzene to obtain a gas chromatogram of this batch of nitrocellulose samples, and calculations are performed based on the peak area values ​​of the gas chromatogram.

[0101] Depend on Figure 8 As shown, toluene peaks at 12.709 with a peak area of ​​0.248706. Figure 3 The standard curve of toluene, formula Y=0.1327X-0.0567, calculates the toluene content to be 2.30ppm.

[0102] The above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention is described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A method for detecting the content of benzene substances in nitrocellulose, characterized in that: The steps include: Preparation of standard benzene-free nitrocellulose: taking a stabilization-treated benzene-free nitrocellulose sample, replacing water with anhydrous ethanol, and centrifuging to obtain a standard benzene-free nitrocellulose that does not contain benzene substances; Prepare a benzene-free nitrocellulose standard solution, add anhydrous ethanol and an ester solvent to the standard benzene-free nitrocellulose in sequence, and let stand after forming a uniform transparent solution to obtain a benzene-free nitrocellulose standard solution, repeat the above operation to obtain multiple identical benzene-free nitrocellulose standard solutions; Prepare a standard solution of benzene substances: add benzene substances to a volumetric flask, use an ester reagent to make up the volume, and dilute step by step to prepare standard solutions of benzene substances with different contents; Prepare a nitrocellulose-containing standard solution, and add preset volumes of the standard solutions of benzene substances with different contents to the plurality of identical nitrocellulose-free standard solutions, to obtain nitrocellulose-containing standard solutions with different contents; Drawing a standard curve, testing the standard solutions containing benzene nitrocellulose with different contents using a headspace-gas chromatograph to obtain gas chromatograms of nitrocellulose containing benzene with different contents, and drawing a standard curve Y=aX+b, wherein: Y is the peak area of ​​different benzene substances, X is the ppm value of the corresponding benzene substance in the standard solution, and a and b are constants; Infiltration and dissolution of nitrocellulose sample: adding anhydrous ethanol to the nitrocellulose sample to fully infiltrate it, then adding an ester solvent to mix and dissolve it, forming a uniform transparent solution and then letting it stand to obtain a sample solution to be tested; The nitrocellulose sample test is to test the sample solution to be tested and the benzene-containing nitrocellulose standard solution under the same conditions using the headspace-gas chromatograph to obtain a gas chromatogram of the nitrocellulose sample, and to calculate using the area external standard method to obtain the peak area of ​​the corresponding benzene substance in the nitrocellulose sample through the gas chromatogram of the nitrocellulose sample, and to obtain the ppm value X=(Yb) / a of the corresponding benzene substance in the nitrocellulose sample through the standard curve.

2. The method for detecting the content of benzene substances in nitrocellulose according to claim 1, characterized in that: The head space-gas chromatograph comprises a head space injector and a gas chromatograph.

3. The method for detecting the content of benzene substances in nitrocellulose according to claim 2, characterized in that: In the headspace sampler, the heating box temperature is 70-80°C, the quantitative loop temperature is 150-180°C, the transmission line temperature is 160-200°C, the equilibration time is 30-60min, and the injection time is 45s-1min.

4. The method for detecting the content of benzene substances in nitrocellulose according to claim 2, characterized in that: In the gas chromatograph, the detector is a FID detector, the chromatographic column is a DM series 60m capillary chromatographic column, the injection port temperature is 160-180°C, the detector temperature is 230-250°C, the injection split ratio is (20-25):1, and the carrier gas flow rate is 0.8-1.2mL / min; The temperature program was set as follows: 40-55°C for 2-4 min, then raised to 220-240°C at 6-10°C / min.

5. The method for detecting the content of benzene substances in nitrocellulose according to claim 1, characterized in that: The benzene substances are chromatographic grade reagents, including one or more of benzene, toluene, ethylbenzene, m-p-xylene and o-xylene.

6. The method for detecting the content of benzene substances in nitrocellulose according to claim 1, characterized in that: The ester reagent is a chromatography grade ester reagent, including one of ethyl acetate, butyl acetate and triacetin.

7. The method for detecting the content of benzene substances in nitrocellulose according to claim 1, characterized in that: The anhydrous ethanol is a chromatography grade reagent.

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