Determination method of VOC content in cellulose ether

Abstract

The invention relates to the technical field of material analysis, in particular to a method for measuring the content of VOC in cellulose ether. According to the test method provided by the invention, an internal standard method is adopted, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol butyl ether, triethylene glycol dimethyl ether, 1, 2-propylene glycol and the like are taken as calibration compounds, cyclopropyl methyl ketone is taken as an internal standard compound, and solid powdery cellulose ether is subjected to specific pretreatment; by combining certain gas chromatography conditions, the efficient separation of 10 VOCs such as ethylene glycol monomethyl ether is realized, and the content of the VOCs in the cellulose ether can be accurately determined. According to the method, the defect of detection of the VOC content in the cellulose ether is overcome, the stable and efficient analysis method is established, and the method is easy and convenient to operate, high in sensitivity, good in reproducibility and high in long-term stability.

Description

Technical Field

[0001] This invention relates to the field of materials analysis technology, and in particular to a method for determining the VOC content in cellulose ethers. Background Technology

[0002] Cellulose ethers, as key functional additives in the building materials industry, mainly include types such as hydroxypropyl methylcellulose (HPMC), hydroxyethyl cellulose (HEC), and methylcellulose (MC). They are widely used in various building materials due to their unique properties. In mortar and putty, cellulose ethers delay water evaporation through water retention, promote full cement hydration to improve strength, and optimize rheological properties to enhance application smoothness and reduce sagging. When used in tile adhesives, they extend open time for easier installation and adjustment, and improve bond strength to reduce hollow areas and detachment. Self-leveling mortars rely on cellulose ethers to regulate flowability and anti-segregation capabilities to achieve a smooth surface. Thermal insulation mortars utilize cellulose ethers to improve the encapsulation and overall adhesion of insulation particles. For coatings and latex paints, cellulose ethers act as thickeners, imparting suitable thixotropy, preventing storage sedimentation, and improving application uniformity. In gypsum-based products, they optimize working time and enhance material flexibility through retarding. Furthermore, waterproofing materials enhance impermeability through their film-forming properties, while sealants extend joint durability by utilizing their anti-shrinkage characteristics. Cellulose ethers also offer advantages in environmental safety and viscosity adjustability. Their natural origin and biodegradable properties align with the trend of green building materials, and their flexible molecular structure allows for precise adaptation to different application scenarios. From low-viscosity dispersion aids to high-viscosity thickening and enhancement, they comprehensively support the modern building materials' integrated requirements for workability, mechanical properties, and environmental friendliness, becoming a significant driving force for the industry's progress towards high performance and sustainable development.

[0003] VOCs (Volatile Organic Compounds) are any organic compounds with an initial boiling point below or equal to 250°C under a pressure of 101.3 kPa. Their characteristics include low boiling point, small molecular weight, and high volatility at room temperature. Currently, VOC control is required for products in the market, including building materials, coatings, furniture, clothing, packaging materials, and toys. These products mainly originate from petrochemicals and organic chemicals. Controlling VOCs aligns with national environmental protection requirements, benefits human health, and protects the natural world. As is well known, VOCs, which are harmful to health, are diverse and complex. Therefore, choosing efficient and comprehensive analytical methods can ensure product quality while enhancing the product's competitiveness in the market.

[0004] Cellulose ethers, as additives, are added to various building materials at levels ranging from 0.5‰ to 7‰, thus contributing little to the VOC content of these products. However, with increasing public concern about indoor air health, cellulose has become one of the main sources of VOC emissions from putty, mortar, and gypsum products. The main health hazards of VOCs from cellulose ethers are shown in Table 1 below.

[0005] Table 1: Major health hazards of VOCs in cellulose ethers

[0006]

[0007] The harmful effects of these compounds in cellulose ethers on human health are internationally recognized. Therefore, international environmental certifications for building materials all have corresponding release limits for these compounds. See Table 2 below for details.

[0008] Table 2: VOC release limits from cellulose ethers

[0009]

[0010] Therefore, the environmental performance of cellulose ethers is becoming increasingly important, and accurately determining the VOC content in cellulose ethers is an important basis for evaluating their environmental performance.

[0011] Currently, the standard for cellulose ethers, JC / T 2190-2024 "Cellulose Ethers for Dry-Mixed Mortars in Buildings", covers technical indicators such as appearance, fineness, viscosity, methoxy content, hydroxypropyl content, and hydroxyethyl content, but does not cover environmental performance indicators such as VOC content and specific harmful substances like ethylene glycol methyl ether.

[0012] Currently, there are many methods for VOC detection, typically including: differential method (DM), high performance liquid chromatography (HPLC), gas chromatography (GC), gas chromatography-mass spectrometry (GC-MS), sensor detection method (SM), fluorescence spectrophotometry (FL), etc., with gas chromatography being the best method for eliciting peaks from all components. However, no literature reports or relevant standards have been found regarding the testing methods for VOC content in cellulose ethers. Specifically, for example, the national standard GB / T23986.2-2023 "Determination of Volatile Organic Compounds (VOC) and / or Semi-volatile Organic Compounds (SVOC) Content in Paints and Varnishes - Part 2: Gas Chromatography" in the building materials industry provides methods for determining the content of VOCs in paints and varnishes, which are all liquids and do not cover the determination of VOC content in powders such as cellulose ethers. Furthermore, there are no reports on the separation and content determination of VOCs in these materials. Patent application 202210060666.0 discloses a method for determining VOC content in EPS foam, using thermal desorption-GCMS to determine the VOC content released from heated EPS foam; patent application 202010860923.X discloses a method for detecting VOCs in air, using thermal desorption-GC-FID / MS to determine VOCs in air; patent application CN106018657A discloses a method for detecting the release of olefin compounds in mattresses, using thermal desorption-GC-FID. These methods have poor stability and are not suitable for determining VOCs and their content in solid powders. Wang Yupeng et al.'s study on the testing method and influencing factors of VOC content in coatings used coatings as the testing object, with isobutanol and isopropanol as internal standards, but did not specify the chromatographic conditions or the method of adding the internal standards. Other similar literature mostly uses gas chromatography for liquid or gas samples, and does not involve the determination of solid powder samples.

[0013] Therefore, establishing a method that can accurately separate and determine the VOC content in cellulose ethers is very important for the product quality control of cellulose ether manufacturers, the screening of raw materials for building material manufacturers, the development of low-emission environmentally friendly building materials, and the effective control of indoor air quality. Summary of the Invention

[0014] In view of this, the present invention provides a method for determining the VOC content in cellulose ethers. This invention fills the gap in the detection of VOC content in cellulose ethers, establishing a stable and efficient analytical method that is simple to operate, highly sensitive, reproducible, and exhibits strong long-term stability.

[0015] This invention provides a method for determining the VOC content in cellulose ethers. This method is an internal standard method, with cyclopropyl methyl ketone as the internal standard compound. The VOC content includes the content of individual volatile organic compounds (IVOCs) and the total volatile organic compounds (TVOCs). VOCs include, but are not limited to, ethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol butyl ether, triethylene glycol dimethyl ether, 1,2-propanediol, propylene glycol methyl ether, (2S)-2-methoxy-1-propanol, 1-(2-methoxy-1-methylethoxy)isopropanol, and ethylene glycol. TVOCs include all compounds. The basic principle of this method is to utilize the difference in the partition coefficients of VOCs in the sample between the gas phase and the stationary phase to achieve the separation of multiple VOC components. Qualitative analysis of VOCs is performed by GC-MS, and quantitative analysis is performed by GC-FID. Details are as follows:

[0016] This invention provides a method for determining the VOC content in cellulose ethers, comprising the following steps:

[0017] S1. Plot the standard curve for the calibration compound:

[0018] Standard curves were plotted using either the single calibration compound method (SA) or the mixed calibration compound method (SB).

[0019] in,

[0020] The single calibration compound method SA includes:

[0021] (S1-A1): Preparation of calibration compound stock solution:

[0022] Weigh a single calibration compound into a volumetric flask, dilute to volume with solvent, and prepare a stock solution of the single calibration compound.

[0023] (S1-A2): Preparation of internal standard diluent:

[0024] Weigh the internal standard compound and place it in a volumetric flask. Dilute to the mark with solvent to obtain the internal standard stock solution.

[0025] Transfer the obtained internal standard stock solution to a volumetric flask and dilute to the mark with solvent to obtain the internal standard diluted solution;

[0026] The internal standard compound is cyclopropyl methyl ketone;

[0027] (S1-A3): Plot the standard curve:

[0028] ① Weigh the stock solution of the single calibration compound, and dilute it into a series of different concentrations using the internal standard diluent and diluent to obtain a series of standard solutions of the corresponding calibration compound;

[0029] ② The series of concentration standard solutions were injected into the analyzer for GC-FID analysis. The standard curve of the calibration compound was plotted with the ratio of the content of the calibration compound to the internal standard compound in the series of concentration standard solutions as the ordinate and the corresponding peak area ratio of the calibration compound to the internal standard compound as the abscissa.

[0030] Each calibration compound was subjected to the above steps (S1-A1)~(S1-A3) to obtain a standard curve for each calibration compound; the calibration compounds were: ethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol butyl ether, triethylene glycol dimethyl ether, and 1,2-propanediol.

[0031] The hybrid calibration compound method SB includes:

[0032] (S1-B1): Preparation of calibration compound stock solution:

[0033] Weigh each calibration compound into the same volumetric flask, dilute to volume with solvent, and prepare a mixed calibration compound stock solution;

[0034] The calibration compounds are: ethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol butyl ether, triethylene glycol dimethyl ether, and 1,2-propanediol.

[0035] (S1-B2): Preparation of internal standard diluent:

[0036] Weigh the internal standard compound and place it in a volumetric flask. Dilute to the mark with solvent to obtain the internal standard stock solution.

[0037] Transfer the obtained internal standard stock solution to a volumetric flask and dilute to the mark with solvent to obtain the internal standard diluted solution;

[0038] The internal standard compound is cyclopropyl methyl ketone;

[0039] (S1-B3): Plot the standard curve:

[0040] ① Weigh the mixed calibration compound stock solution, and use the internal standard diluent and diluent to dilute the mixed calibration compound stock solution into a series of different concentrations to obtain a series of concentration standard solutions of the mixed calibration compound;

[0041] ② Select one of the series of concentration standard solutions of the mixed calibration compound and inject it into the GCMS analyzer for qualitative analysis to determine the elution order of each calibration compound; then, inject the series of concentration standard solutions of the mixed calibration compound into the analyzer for GC-FID analysis, and plot the standard curve of each calibration compound with the content ratio of calibration compound / internal standard compound in the series of concentration standard solutions as the ordinate and the peak area of ​​the corresponding calibration compound / internal standard compound as the abscissa.

[0042] S2. Sample pretreatment:

[0043] Place the cellulose ether powder in a centrifuge tube, add the internal standard diluent, mix well, centrifuge, and filter the supernatant to obtain the sample processing solution.

[0044] S3. Quantitative Analysis:

[0045] The sample solution obtained in step S2 is placed in a quantitative analyzer for quantitative analysis. The content of each component is calculated according to the internal standard curve method, thereby obtaining the VOC content in the cellulose ether powder.

[0046] The order of steps that are not sequentially related to each other is not subject to any special restrictions.

[0047] In this invention, steps that are sequentially related are performed in that order, while steps that are not sequentially related have no special restrictions on their order. "Steps that are not sequentially related" refers to steps that do not necessarily have a sequential relationship. For example, steps (S1-A1) and (S1-A3) are related in that step (S1-A3) uses the calibration compound mother liquor obtained in step (S1-A1). Therefore, step (S1-A1) must be performed before step (S1-A3), meaning they are sequentially related and must be performed in that order. Similarly, steps (S1-A1) and (S1-A2) are not sequentially related, so their order is not particularly restricted. The same applies to other steps, and further examples will not be provided.

[0048] Regarding step S1 :

[0049] According to the present invention, step S1 is to plot the standard curve of the calibration compound, which can be done in two ways: the first is the single calibration compound method SA; the second is the mixed calibration compound method SB.

[0050] [Regarding the Single Calibration Compound Method (SA)]:

[0051] In this invention, the single calibration compound method (SA) includes the following steps: (S1-A1) preparing the calibration compound stock solution → (S1-A2) preparing the internal standard dilution solution → (S1-A3) plotting the standard curve.

[0052] Regarding steps (S1-A1):

[0053] (S1-A1): Preparation of calibration compound stock solution: Weigh a single calibration compound into a volumetric flask, dilute to volume with solvent, and prepare a single calibration compound stock solution.

[0054] In this invention, the calibration compounds correspond to the target components to be detected in the cellulose ethers being tested. The calibration compounds are: ethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol butyl ether, triethylene glycol dimethyl ether, and 1,2-propanediol. In this invention, the purity of the calibration compounds is >99%.

[0055] In this invention, the solvent is preferably acetonitrile. Furthermore, the acetonitrile is preferably of chromatographic grade.

[0056] In this invention, preferably, step (S1-A1) includes: weighing 100 mg of a single calibration compound (preferably accurate to 0.1 mg) into a 20 mL volumetric flask, dissolving it in acetonitrile, and making up to the mark to obtain a single calibration compound stock solution.

[0057] Regarding steps (S1-A2):

[0058] (S1-A2): Preparation of internal standard dilution: Weigh the internal standard compound and place it in a volumetric flask, then dilute to the mark with solvent to obtain the internal standard stock solution; transfer the obtained internal standard stock solution to a volumetric flask, and dilute to the mark with solvent to obtain the internal standard dilution.

[0059] In this invention, the internal standard compound is cyclopropyl methyl ketone. In this invention, the purity of the internal standard compound is ≥99%.

[0060] In this invention, the solvent is preferably acetonitrile. Furthermore, the acetonitrile is preferably of chromatographic grade.

[0061] In this invention, preferably, step (S1-A2) includes: weighing 40 mg of the internal standard compound and placing it in a 20 mL volumetric flask, dissolving it in acetonitrile, and making up to the mark to obtain the internal standard stock solution; then, using a pipette, transferring 1 mL of the internal standard stock solution into a 10 mL volumetric flask, and making up to the mark with acetonitrile to obtain the internal standard diluted solution.

[0062] Regarding steps (S1-A3):

[0063] According to the present invention, steps (S1-A3) include: ① preparing standard solution → ② plotting standard curve.

[0064] Regarding step ①: Weigh the stock solution of the single calibration compound, and use the internal standard diluent and diluent to dilute the stock solution of the single calibration compound into a series of different concentrations to obtain a series of standard solutions of the corresponding calibration compound.

[0065] In this invention, the diluent is preferably acetonitrile.

[0066] In this invention, preferably, step ① includes: transferring 1 mL of the internal standard diluent and 1 mL of the single calibration compound stock solution into a 10 mL volumetric flask, and making up to volume with acetonitrile, which is the first concentration point; then replenishing the internal standard diluent by stepwise dilution to obtain other concentration points in sequence, thereby obtaining a series of concentration standard solutions for the corresponding calibration compound.

[0067] In this invention, the number of concentration points in the series of concentrations is preferably 5. Preferably, the concentration point values ​​in the series of concentrations are selected from 1 to 500 µg / mL.

[0068] In this invention, preferably, the concentration gradient of the series of standard solutions for each calibration compound is as follows:

[0069] Ethylene glycol methyl ether: 1µg / mL, 10µg / mL, 100µg / mL, 250µg / mL, 500µg / mL;

[0070] Diethylene glycol dimethyl ether: 1µg / mL, 10µg / mL, 100µg / mL, 250µg / mL, 500µg / mL;

[0071] Diethylene glycol monomethyl ether: 1µg / mL, 10µg / mL, 100µg / mL, 250µg / mL, 500µg / mL;

[0072] Diethylene glycol butyl ether: 1µg / mL, 10µg / mL, 100µg / mL, 250g / mL, 500µg / mL;

[0073] Triethylene glycol dimethyl ether: 1µg / mL, 10µg / mL, 100µg / mL, 250µg / mL, 500µg / mL;

[0074] 1,2-Propanediol: 2µg / mL, 20µg / mL, 40µg / mL, 200µg / mL, 400µg / mL.

[0075] Regarding step ②: Inject the series of concentration standard solutions into the analyzer for GC-FID analysis. Plot the standard curve of the calibration compound with the ratio of the content of the calibration compound to the internal standard compound in the series of concentration standard solutions as the ordinate and the corresponding peak area ratio of the calibration compound to the internal standard compound as the abscissa.

[0076] In this invention, the analyzer is preferably a gas chromatograph (GC-FID); specifically, it is a gas chromatograph equipped with an FID detector, which can be used for liquid sample injection.

[0077] In this invention, preferably, the conditions for the GC-FID analysis include:

[0078] Capillary column: DB-1301 (60m×0.32mm×1μm);

[0079] Column carrier gas flow rate: 1 mL / min;

[0080] Inlet temperature 250°C;

[0081] FID detector temperature 270°C;

[0082] Column oven temperature program: 50°C for 1 min, then increase to 230°C at 10°C / min, hold for 2 min, then increase to 260°C at 15°C / min, hold for 20 min; injection volume 1 μL, split ratio 20:1.

[0083] Based on the above GC-FID analysis, a standard curve for the single calibration compound was plotted with the ratio of the calibration compound to the internal standard compound in the series of concentration standard solutions as the ordinate and the peak area of ​​the corresponding calibration compound / internal standard compound as the abscissa.

[0084] In this invention, each calibration compound is processed according to steps (S1-A1) to (S1-A3) to obtain a standard curve for each calibration compound. The calibration compounds are: ethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol butyl ether, triethylene glycol dimethyl ether, and 1,2-propanediol. The concentration distribution of each calibration compound in the preparation of the standard solution in steps (S1-A3) is as described above. Furthermore, the calibration compounds are: ethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol butyl ether, triethylene glycol dimethyl ether, 1,2-propanediol, propylene glycol methyl ether, (2S)-2-methoxy-1-propanol, 1-(2-methoxy-1-methylethoxy)isopropanol, and ethylene glycol.

[0085] [Regarding the hybrid calibration compound method (SB)]:

[0086] In this invention, the mixed calibration compound method SB includes the following steps: (S1-B1) preparing the calibration compound stock solution → (S1-B2) preparing the internal standard dilution solution → (S1-B3) plotting the standard curve.

[0087] Regarding steps (S1-B1):

[0088] (S1-B1): Preparation of calibration compound stock solution: Weigh each calibration compound into the same volumetric flask, dilute to volume with solvent, and prepare a mixed calibration compound stock solution.

[0089] In this invention, each calibration compound corresponds to the target component to be detected in the cellulose ether being tested. The calibration compounds are: ethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol butyl ether, triethylene glycol dimethyl ether, and 1,2-propanediol. In this invention, the purity of the calibration compounds is >99%.

[0090] In this invention, the solvent is preferably acetonitrile. Furthermore, the acetonitrile is preferably of chromatographic grade.

[0091] In this invention, preferably, step (S1-B1) includes: weighing 100 mg (preferably accurate to 0.1 mg) of each calibration compound and placing them in the same 20 mL volumetric flask, dissolving them in acetonitrile, and making up to the mark to obtain a mixed calibration compound mother solution.

[0092] Regarding steps (S1-B2):

[0093] (S1-B2): Preparation of internal standard dilution: Weigh the internal standard compound and place it in a volumetric flask, then dilute to the mark with solvent to obtain the internal standard stock solution; transfer the obtained internal standard stock solution to a volumetric flask, and dilute to the mark with solvent to obtain the internal standard dilution.

[0094] In this invention, the internal standard compound is cyclopropyl methyl ketone. In this invention, the purity of the internal standard compound is ≥99%.

[0095] In this invention, the solvent is preferably acetonitrile. Furthermore, the acetonitrile is preferably of chromatographic grade.

[0096] In this invention, preferably, step (S1-B2) includes: weighing 40 mg of the internal standard compound and placing it in a 20 mL volumetric flask, dissolving it in acetonitrile, and making up to the mark to obtain the internal standard stock solution; then, using a pipette, transferring 1 mL of the internal standard stock solution into a 10 mL volumetric flask, and making up to the mark with acetonitrile to obtain the internal standard diluted solution.

[0097] Regarding steps (S1-B3):

[0098] According to the present invention, step (S1-B3) includes: ① preparing standard solution → ② plotting standard curve.

[0099] Regarding step ①: Weigh the mixed calibration compound stock solution, and use the internal standard diluent and diluent to dilute the mixed calibration compound stock solution into a series of different concentrations to obtain a series of concentration standard solutions of the mixed calibration compound.

[0100] In this invention, the diluent is preferably acetonitrile.

[0101] In this invention, preferably, step ① includes: transferring 1 mL of the internal standard diluent and 1 mL of the mixed calibration compound stock solution into a 10 mL volumetric flask, and making up to volume with acetonitrile, which is the first concentration point; then replenishing the internal standard diluent by stepwise dilution to obtain other concentration points in sequence, thereby obtaining a series of concentration standard solutions of the mixed calibration compound.

[0102] In this invention, the number of concentration points in the series of concentrations is preferably 5. Preferably, the concentration point values ​​in the series of concentrations are selected from 1 to 500 µg / mL.

[0103] In this invention, preferably, the concentration gradient of each calibration compound in the series of concentration standard solutions of the mixed calibration compounds is as follows:

[0104] Ethylene glycol methyl ether: 1µg / mL, 10µg / mL, 100µg / mL, 250µg / mL, 500µg / mL;

[0105] Diethylene glycol dimethyl ether: 1µg / mL, 10µg / mL, 100µg / mL, 250µg / mL, 500µg / mL;

[0106] Diethylene glycol monomethyl ether: 1µg / mL, 10µg / mL, 100µg / mL, 250µg / mL, 500µg / mL;

[0107] Diethylene glycol butyl ether: 1µg / mL, 10µg / mL, 100µg / mL, 250g / mL, 500µg / mL;

[0108] Triethylene glycol dimethyl ether: 1µg / mL, 10µg / mL, 100µg / mL, 250µg / mL, 500µg / mL;

[0109] 1,2-Propanediol: 2µg / mL, 20µg / mL, 40µg / mL, 200µg / mL, 400µg / mL;

[0110] In the series of standard solutions: (1) In the first standard solution (first concentration point): ethylene glycol methyl ether concentration is 500µg / mL, diethylene glycol dimethyl ether concentration is 500µg / mL, diethylene glycol monomethyl ether concentration is 500µg / mL, diethylene glycol butyl ether concentration is 500µg / mL, triethylene glycol dimethyl ether concentration is 500µg / mL, and 1,2-propanediol concentration is 400µg / mL; (2) In the second standard solution (second concentration point): ethylene glycol methyl ether concentration is 500µg / mL, diethylene glycol monomethyl ether concentration is 500µg / mL, and 1,2-propanediol concentration is 400µg / mL; The concentrations of ethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol butyl ether, triethylene glycol dimethyl ether, and 1,2-propanediol were 250 µg / mL, 250 µg / mL, 250 µg / mL, 250 µg / mL, and 200 µg / mL, respectively. (3) In the third standard solution (third concentration point): the concentrations of ethylene glycol methyl ether and diethylene glycol dimethyl ether were 100 µg / mL, 100 µg / mL, and 200 µg / mL, respectively. / mL, diethylene glycol monomethyl ether concentration of 100µg / mL, diethylene glycol butyl ether concentration of 100µg / mL, triethylene glycol dimethyl ether concentration of 100µg / mL, 1,2-propanediol concentration of 40µg / mL; (4) in the fourth standard solution (fourth concentration point): ethylene glycol methyl ether concentration of 10µg / mL, diethylene glycol dimethyl ether concentration of 10µg / mL, diethylene glycol monomethyl ether concentration of 10µg / mL, diethylene glycol butyl ether concentration of 10µg / mL (5) In the fifth standard solution (fifth concentration point): the concentration of ethylene glycol methyl ether is 1µg / mL, the concentration of diethylene glycol dimethyl ether is 1µg / mL, the concentration of diethylene glycol monomethyl ether is 1µg / mL, the concentration of diethylene glycol butyl ether is 1µg / mL, the concentration of triethylene glycol dimethyl ether is 1µg / mL, and the concentration of 1,2-propanediol is 2µg / mL.

[0111] Regarding step ②: Select one of the series of concentration standard solutions of the mixed calibration compounds and inject it into the GCMS analyzer for qualitative analysis to determine the elution order of each calibration compound; then, inject the series of concentration standard solutions of the mixed calibration compounds into the analyzer for GC-FID analysis, and plot the standard curve of each calibration compound with the content ratio of the calibration compound / internal standard compound in the series of concentration standard solutions as the ordinate and the peak area of ​​the corresponding calibration compound / internal standard compound as the abscissa.

[0112] In this invention, one standard solution is first randomly selected from the series of concentration standard solutions of the mixed calibration compounds and injected into a GCMS analyzer for qualitative analysis to determine the elution order of each calibration compound (i.e., selecting one concentration point for qualitative analysis is sufficient). The GCMS is a gas chromatography-mass spectrometry coupling technique, where GC serves as the injection system and MS as the mass spectrometry detector. GCMS combines GC and MS instruments to form a combined technique for separation and qualitative analysis. This invention first uses GCMS analysis to determine the elution order of each calibration compound in the series of concentration standard solutions of the mixed calibration compounds to achieve qualitative analysis.

[0113] Preferably, the qualitative analysis conditions of the GCMS include:

[0114] Capillary column: DB-1301 (60m×0.32mm×1μm);

[0115] Column carrier gas flow rate: 1 mL / min;

[0116] Inlet temperature 250°C;

[0117] MS detector (i.e., mass spectrometry conditions): SCAN mode, scan range 30~400 m / z;

[0118] Column oven temperature program: 50°C for 1 min, then increase to 230°C at 10°C / min, hold for 2 min, then increase to 260°C at 15°C / min, hold for 20 min; injection volume 1 μL, split ratio 20:1.

[0119] In this invention, after GCMS, a series of concentration standard solutions of the mixed calibration compounds are injected into the analyzer for GC-FID analysis. The analyzer is preferably a gas chromatograph; specifically, it is a gas chromatograph equipped with an FID detector, capable of liquid sample injection.

[0120] Preferably, the conditions for the GC-FID analysis include:

[0121] Capillary column: DB-1301 (60m×0.32mm×1μm);

[0122] Column carrier gas flow rate: 1 mL / min;

[0123] Inlet temperature 250°C;

[0124] FID detector temperature 270°C;

[0125] Column oven temperature program: 50°C for 1 min, then increase to 230°C at 10°C / min, hold for 2 min, then increase to 260°C at 15°C / min, hold for 20 min; injection volume 1 μL, split ratio 20:1.

[0126] Based on the above GC-FID analysis, standard curves for each calibration compound were plotted with the ratio of calibration compound to internal standard compound in the series of concentration standard solutions as the ordinate and the peak area of ​​the corresponding calibration compound / internal standard compound as the abscissa.

[0127] Regarding step S2 :

[0128] S2. Sample pretreatment: Place the cellulose ether powder in a centrifuge tube, add the internal standard diluent, mix well, then centrifuge, and filter the supernatant to obtain the sample pretreatment solution.

[0129] In this invention, preferably, the sampling method for the cellulose ether powder includes: quickly removing the cellulose ether powder sample from the large packaging and immediately sealing it in a container for testing. The container is one with good sealing properties. More preferably, the sampling method for the cellulose ether powder includes: using a clean stainless steel single-slot quantitative powder sampler, puncturing the large packaging bag of the cellulose ether, quickly pouring an appropriate amount of powder into a container, filling it completely, and sealing it with a lid featuring a sealing gasket. Preferably, the container is a glass container.

[0130] In this invention, after removing the cellulose ether powder, a certain amount of cellulose ether powder is weighed and placed in a centrifuge tube, the internal standard diluent is added, mixed well, and then centrifuged. The supernatant is then filtered to obtain the sample processing solution. Preferably, the above process includes: weighing 1g of cellulose ether powder (preferably accurate to 0.1mg) into a 15mL centrifuge tube, adding 10mL of the internal standard diluent, sealing the centrifuge tube and mixing well, then centrifuging, and filtering 0.5~1mL of the supernatant into a 2mL liquid sample bottle using a syringe and needle filter.

[0131] The mixing method is selected from the following two: (1) ultrasonic treatment; (2) ultrasonic treatment first, followed by vortex mixing and then ultrasonic treatment again. Specifically, ultrasonic treatment is performed first. If the sample can be mixed evenly, the mixing is stopped (i.e., the first method). If a good mixing effect cannot be obtained after ultrasonic treatment, vortex mixing can be continued before ultrasonic treatment (i.e., the second method). The ultrasonic treatment temperature is preferably ≤30℃, more preferably 20±3℃, and the ultrasonic treatment time is preferably 20±10min to prevent the diluent and the analyte from evaporating due to temperature rise during ultrasonic treatment. The sample is extracted by the above ultrasonic treatment so that the components in the cellulose ether sample are fully extracted into the organic phase. In this invention, the centrifugation speed is preferably 12000r / min, the centrifugation temperature is preferably 15℃~30℃, more preferably 20℃±3℃, and the centrifugation time is preferably 10min. If a clear liquid cannot be obtained, the centrifugation time can be extended. In this invention, the needle filter is preferably an organic needle filter with a diameter of 0.22μm or 0.45μm, and its material is preferably nylon.

[0132] Regarding step S3 :

[0133] S3. Quantitative analysis: The sample solution obtained in step S2 is placed in a quantitative analyzer for quantitative analysis. The content of each component is calculated according to the internal standard curve method, thereby obtaining the VOC content in the cellulose ether powder.

[0134] In this invention, the quantitative analysis is preferably performed as follows: (1) For samples with VOC content ≥100 mg / kg, GC-FID quantitative analysis is performed (i.e., the analyzer is a gas chromatograph equipped with an FID detector); (2) For samples with VOC content <100 mg / kg, GC-MS quantitative analysis is performed (i.e., the analyzer is a gas chromatograph-mass spectrometer equipped with a mass spectrometer detector). This invention mainly uses GC-FID analysis. However, for samples with low VOC content, GC-FID may not be able to detect them. In this case, GCMS quantification is used, which has a lower detection limit than GC-FID analysis. However, the SIM mode of GCMS quantification is required. Therefore, it is divided into the above two cases (1) and (2).

[0135] (1) The conditions for the GC-FID quantitative analysis include:

[0136] Capillary column: DB-1301 (60m×0.32mm×1μm);

[0137] Column carrier gas flow rate: 1 mL / min;

[0138] Inlet temperature 250°C;

[0139] FID detector temperature 270°C;

[0140] Column oven temperature program: 50°C for 1 min, then increase to 230°C at 10°C / min, hold for 2 min, then increase to 260°C at 15°C / min, hold for 20 min; injection volume 1 μL, split ratio 20:1.

[0141] (2) The conditions for the GC-MS quantitative analysis include:

[0142] Capillary column: DB-1301 (60m×0.32mm×1μm);

[0143] Column carrier gas flow rate: 1 mL / min;

[0144] Inlet temperature 250°C;

[0145] Column oven temperature program: 50°C for 1 min, then increase to 230°C at 10°C / min, hold for 2 min, then increase to 260°C at 15°C / min, hold for 20 min; injection volume 1 μL, split ratio 20:1;

[0146] The preferred mass spectrometry conditions were: SIM scan, quantitative and qualitative ions are shown in Table 3; ion source: Xtr high-sensitivity ion source, 230℃; quadrupole temperature: 150°C; timing events: detector off at 6.5 min, detector on at 8.5 min; gain factor: 1.0.

[0147] Table 3: Retention times and selected ion information for each calibration compound and internal standard compound

[0148]

[0149] This invention obtains the peak area of ​​each compound through the above quantitative analysis, and calculates the content of each compound in the sample according to the internal standard curve method, thus obtaining the VOC content in the cellulose ether powder. Preferably, this invention further includes: calculating the peak areas of all compounds, treating uncalibrated compounds as internal standard compounds, and summing them to obtain the TVOC content in the cellulose ether powder.

[0150] In this invention, preferably, if other uncalibrated compounds are detected in the quantitative analysis results of step S3, GCMS qualitative analysis is first performed to confirm the uncalibrated compounds. Then, the confirmed uncalibrated compounds are added to the list of calibrated compounds, and steps S1-S3 are repeated to obtain the VOC content in the cellulose ether powder. The process of qualitative analysis to confirm uncalibrated compounds preferably includes: injecting the standard solution obtained in step (S1-A3) or step (S1-B3) into the analyzer, using the same chromatographic conditions as in step (S1-A3) or step (S1-B3), changing the detector to a mass spectrometer, and using GCMS to perform qualitative analysis on the sample to confirm the information of the uncalibrated compounds. The preferred GCMS qualitative conditions are:

[0151] Capillary column: DB-1301 (60m×0.32mm×1μm);

[0152] Column carrier gas flow rate: 1 mL / min;

[0153] Inlet temperature 250°C;

[0154] MS detector: Scan mode, scan range 30~400 m / z;

[0155] Column oven temperature program: 50°C for 1 min, then increase to 230°C at 10°C / min, hold for 2 min, then increase to 260°C at 15°C / min, hold for 20 min; injection volume 1 μL, split ratio 5:1.

[0156] This invention provides a method for determining the VOC content in cellulose ethers, used to simultaneously determine the content of IVOCs (invisible ions) and TVOCs (total volatile organic compounds) in cellulose ethers, including ethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol butyl ether, triethylene glycol dimethyl ether, 1,2-propanediol, propylene glycol methyl ether, (2S)-2-methoxy-1-propanol, 1-(2-methoxy-1-methylethoxy)isopropanol, and ethylene glycol. This method ensures accuracy and stability, providing a reliable approach for determining VOC content in cellulose ethers. It also provides an evaluation standard for product quality control by cellulose ether manufacturers, the development of environmentally friendly building materials, and the screening of raw materials. Addressing the volatility of low-boiling-point, high-vapor-pressure VOC components in powder samples, this invention solves the problem of VOC content differences between laboratory samples and production tonnes through reasonable sampling and storage methods, making the test results significant for raw material screening and quality control. This invention proposes for the first time a method for detecting TVOC and VOC in solid powdered cellulose ethers. By combining ultrasonication and vortex mixing, it solves the problems of difficult pretreatment and poor stability of powder samples. This invention employs an internal standard method (using cyclopropyl methyl ketone as an internal standard) combined with gas chromatography (DB-1301 capillary column) to optimize separation conditions, achieving efficient separation of 10 IVOCs, including ethylene glycol methyl ether. The linear correlation coefficient (0.99995~1) and precision (RSD≤1.1%) are significantly better than existing external standard methods. This invention systematically verifies the effects of extraction time, sample weight, and storage time on the results, finding that storage time is a key interfering factor, filling the gap in existing research on the stability analysis of VOC content detection in cellulose ethers.

[0157] Key aspects of this invention include: Cellulose ethers, as dry powder materials, readily volatilize low-boiling-point, high-vapor-pressure VOC components under small-scale laboratory sampling conditions. However, in industrial production, factors such as large-batch storage and sealed mixing make VOC components difficult to volatilize. To accurately determine the VOC content in cellulose ethers, this invention uses a stainless steel single-slot quantitative powder sampler to extract samples from the batch and stores the samples in glass sample vials with sealed septa. Simultaneously, this invention selects acetonitrile, a suitable solvent with low toxicity, and employs a suitable pretreatment method for powdered cellulose ether samples (ultrasonic extraction followed by vortex mixing) to effectively extract various VOC components from the cellulose ethers. Furthermore, this invention selects a low- to medium-polarity chromatographic column and, with appropriate chromatographic separation conditions, achieves effective and complete separation of 10 target IVOCs, enabling accurate quantitative analysis using general-purpose GCFID instruments.

[0158] The present invention has the following beneficial effects:

[0159] (1) The present invention can simultaneously quantify the VOC and TVOC content in cellulose ethers, with short analysis time and high efficiency;

[0160] (2) In the pretreatment process, the present invention uses acetonitrile as a solvent to extract the sample, which has low toxicity and is easy to operate;

[0161] (3) The chromatographic conditions of the present invention provide good separation of common VOCs in cellulose ethers, such as ethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol butyl ether, triethylene glycol dimethyl ether, and 1,2-propanediol, with linear correlation coefficients between 0.99995 and 1.

[0162] (4) The detection limits of VOC and TVOC in this invention are low, with the detection limit of VOC being about 10 mg / kg and the detection limit of TVOC being <100 mg / kg;

[0163] (5) The precision of VOC and TVOC content in this invention is ≤1.1%, and the repeatability is good;

[0164] (6) The recovery rate of VOC and TVOC content in this invention is 92%~106%, and the quantification is accurate;

[0165] (7) This invention proposes for the first time a method for determining the VOC and TVOC content in cellulose ethers, and proposes a technical solution for accurately determining the VOC content, thereby controlling the VOC release of building materials, providing evaluation standards for the development of environmentally friendly building materials and the screening of raw materials;

[0166] (8) This invention verified the effects of extraction time, sample weight, and sample placement time on the VOC content of cellulose ethers through experiments. It was found that extraction time and sample weight had no significant effect on the VOC and TVOC content, while placement time had a significant effect on the content of ethylene glycol methyl ether, diethylene glycol dimethyl ether, and TVOC. This fills the gap in the existing research on the stability analysis of VOC content detection in cellulose ethers and provides guidance for the accurate determination of VOC content in cellulose ethers.

[0167] In this invention, the cellulose ethers include hydroxypropyl methylcellulose (HPMC), hydroxyethyl cellulose (HEC), methylcellulose (MC), and other types of cellulose ethers. That is, the determination method of this invention is applicable to the determination of VOC and TVOC content in various cellulose ethers. Attached Figure Description

[0168] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0169] Figure 1GCMS qualitative spectra under the column oven temperature programs recommended in GB / T 23986-2009 and GB / T 23986.2-2023;

[0170] Figure 2 This is a GCMS qualitative spectrum under the column oven heating program of this invention. Detailed Implementation

[0171] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0172] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0173] Reagents and consumables:

[0174] (1) Acetonitrile: chromatographic grade;

[0175] (2) Disposable consumables: disposable syringe (2mL); 2mL liquid sample vial; 0.22μm microporous filter membrane (organic phase);

[0176] (3) Internal standard compound: cyclopropylmethyl ketone (purity 99%);

[0177] (4) Calibration compounds: ethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol butyl ether, triethylene glycol dimethyl ether, 1,2-propanediol; analytical grade;

[0178] instrument:

[0179] (1) Balance: accuracy 0.1 mg and 0.01 g;

[0180] (2) Measuring instruments: volumetric flasks, pipettes;

[0181] (3) High-speed centrifuge: speed up to 1200r / min, temperature controllable;

[0182] (4) Ultrasonic cleaning machine with temperature control;

[0183] (5) Chromatograph for quantitative analysis: Gas chromatograph equipped with FID detector;

[0184] (6) Qualitative analysis gas chromatography-mass spectrometry: gas chromatography-mass spectrometry is equipped with a mass spectrometer detector and an FID detector, and can be used for liquid injection.

[0185] Example 1: Method for determining VOC content in cellulose ethers

[0186] S1. Plot the standard curve for the calibration compound:

[0187] (S1-A1) Preparation of calibration compound stock solution:

[0188] Weigh 100 mg of a single calibration compound (accurate to 0.1 mg) into a 20 mL volumetric flask, dissolve it in acetonitrile, and dilute to the mark to obtain a single calibration compound stock solution.

[0189] (S1-A2) Prepare the internal standard diluent:

[0190] Weigh 40 mg of the internal standard compound (cyclopropyl methyl ketone) into a 20 mL volumetric flask, dissolve it in acetonitrile, and dilute to the mark to obtain the internal standard stock solution; then, use a pipette to transfer 1 mL of the internal standard stock solution into a 10 mL volumetric flask, and dilute to the mark with acetonitrile to obtain the internal standard diluted solution.

[0191] (S1-A3) Plot the standard curve:

[0192] ①Preparation of standard solution:

[0193] Transfer 1 mL of the internal standard diluent and 1 mL of the single calibration compound stock solution to a 10 mL volumetric flask, and dilute to volume with acetonitrile. This is the first concentration point. Then, the internal standard diluent is added by serial dilution to obtain other concentration points in sequence, thereby obtaining a series of concentration standard solutions for the corresponding calibration compounds.

[0194] ②Draw the standard curve:

[0195] The series of concentration standard solutions were injected into the analyzer for GC-FID analysis. The standard curve of the calibration compound was plotted with the ratio of the content of the calibration compound to the internal standard compound in the series of concentration standard solutions as the ordinate and the corresponding peak area ratio of the calibration compound to the internal standard compound as the abscissa.

[0196] in,

[0197] The analyzer is a gas chromatograph equipped with an FID detector.

[0198] The analysis and testing conditions are as follows:

[0199] Capillary column: DB-1301 (60m×0.32mm×1μm);

[0200] Column carrier gas flow rate: 1 mL / min;

[0201] Inlet temperature 250°C;

[0202] FID detector temperature 270°C;

[0203] Column oven temperature program: 50°C for 1 min, then increase to 230°C at 10°C / min, hold for 2 min, then increase to 260°C at 15°C / min, hold for 20 min; injection volume 1 μL, split ratio 20:1.

[0204] Each calibration compound was processed according to steps (S1-A1) to (S1-A3) to obtain a standard curve for each compound. The calibration compounds were: ethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol butyl ether, triethylene glycol dimethyl ether, and 1,2-propanediol. The concentration distribution of each calibration compound in the standard solution preparation in step (S1-A3) is shown in Table 4. The standard curve information for each calibration compound is shown in Table 5. The correlation coefficients of all linear regression equations were greater than 0.99, meeting the requirements of standard GB / T 27417-2017 "Guideline for Conformity Assessment and Validation of Chemical Analysis Methods" (not less than 0.99).

[0205] S2. Sample pretreatment:

[0206] Weigh 1 g (accurate to 0.1 mg) of the pre-preserved cellulose ether powder into a 15 mL centrifuge tube, add 10 mL of the internal standard diluent obtained in step S2, seal the centrifuge tube, and mix thoroughly. The mixing method is as follows: ultrasonic extraction at 20°C for 20 min, followed by vortex mixing, and then ultrasonic treatment again (under the same conditions as the previous ultrasonic treatment). After mixing, centrifuge (12000 r / min, centrifugation temperature 20°C, time 10 min), and then filter 1 mL of the supernatant into a 2 mL liquid sample vial using a syringe and a 0.22 μm organic needle filter.

[0207] The pre-preserved cellulose ether powder is obtained by the following method: using a clean stainless steel single-slot quantitative powder sampler, puncturing the large packaging bag of cellulose ether, taking out an appropriate amount of powder, quickly pouring it into a glass container, filling it, and sealing it with a lid with a sealing gasket.

[0208] S3. Quantitative Analysis:

[0209] The sample solution obtained in step S2 is placed in a quantitative analyzer for quantitative analysis. The content of each component is calculated according to the internal standard curve method to obtain the VOC content in the cellulose ether powder. The peak areas of all compounds are counted, and the uncalibrated compounds are calculated as internal standard compounds. The contents are summed to obtain the TVOC content in the cellulose ether powder.

[0210] in:

[0211] The quantitative analyzer is a gas chromatograph equipped with an FID detector.

[0212] The analysis and testing conditions are as follows:

[0213] Capillary column: DB-1301 (60m×0.32mm×1μm);

[0214] Column carrier gas flow rate: 1 mL / min;

[0215] Inlet temperature 250°C;

[0216] FID detector temperature 270°C;

[0217] Column oven temperature program: 50°C for 1 min, then increase to 230°C at 10°C / min, hold for 2 min, then increase to 260°C at 15°C / min, hold for 20 min; injection volume 1 μL, split ratio 20:1.

[0218] Table 4: Concentration gradient of series of standard solutions for each calibration compound

[0219]

[0220] Table 5: Standard curves and linear correlation coefficients of each calibration compound

[0221]

[0222] Commercially available ethylene glycol methyl ether standard solution (1ST000071-100M-S101507) was used for quality control. The standard solution recovery rate was 94.0%, which meets the requirements of 90%~110% in GB / T 27417-2017.

[0223] Example 2: Repeatability

[0224] The cellulose ether E sample was tested 10 times according to the test method in Example 1. The results of ethylene glycol methyl ether, diethylene glycol dimethyl ether, and TVOC content were statistically analyzed, as shown in Table 6. The test results show that the coefficient of variation (i.e., relative standard deviation RSD) of TVOC content is 1.1%, which meets the requirements described in GB / T 27417-2017 and GB / T 23986.2-2023: when the content of the analyte is on the order of 1%, the in-laboratory coefficient of variation is ≤2.7%, proving that the determination method of this invention has high precision.

[0225] Table 6: Summary of Repeated Determination Results of Cellulose Ethers

[0226]

[0227] Example 3: Detection Limit

[0228] The TVOC content of cellulose ether F is approximately 700 mg / kg, which is close to the detection limit of 100 mg / kg specified in the similar standard GB / T 23986.2-2023. Therefore, the detection limit of ethylene glycol methyl ether and diethylene glycol dimethyl ether for this type of product was evaluated by measuring the VOC values ​​of the sample 10 times. The specific values ​​are shown in Table 7. According to the method for determining the detection limit in GB / T27417-2017 "Guideline for Conformity Assessment Chemical Analysis Methods Validation and Verification", 0+3s was used as the method detection limit, and the final result was rounded. The detection limit of ethylene glycol methyl ether and diethylene glycol dimethyl ether was 10 mg / kg, and the detection limit of TVOC content was 70 mg / kg. The detection limit is better than the 50 mg / kg specified in the similar standard GB / T 23986.2-2023.

[0229] Table 7: Summary of TVOC content from 10 repeated determinations of cellulose ether F

[0230]

[0231] Example 4: Accuracy

[0232] The accuracy of the method was verified by spike recovery using ethylene glycol methyl ether standard solution and diethylene glycol dimethyl ether standard solution, respectively. Since cellulose ether is a solid powder, the standard solution was added to the sample extracted with internal standard dilution solution for determination. Low, medium, and high concentrations of mixed ethylene glycol methyl ether and diethylene glycol dimethyl ether standard solutions were added to cellulose ether A, cellulose ether B, and cellulose ether C, respectively. The spike recovery results are shown in Table 8, and the spike recovery rate meets the requirements of Table A.1 of standard GB / T 27417-2017.

[0233] Table 8: Recovery data of ethylene glycol methyl ether and diethylene glycol dimethyl ether standard solutions

[0234]

[0235] Example 5: Influencing Factors

[0236] The effects of solvent soaking time, sample weight, and sample placement time on the VOC content determination results were verified through experiments.

[0237] (5.1) Solvent soaking time

[0238] The method was implemented according to Example 1, except that the continuous operation in step S2, "mixing (ultrasonic extraction for 20 min), then centrifuging, and filtering the supernatant to obtain the sample treatment solution," was changed to "mixing (ultrasonic extraction for 20 min), then allowing it to stand for 24 hours, then centrifuging, and filtering the supernatant to obtain the sample treatment solution." The test results were compared between soaking without additional soaking time and soaking with additional solvent for 24 hours, as shown in Table 9. It can be seen that there was no significant difference in the VOC and TVOC contents obtained under both soaking times, proving that soaking time has no significant effect on the VOC and TVOC contents.

[0239] Table 9: VOC data measured at different extraction times

[0240]

[0241] (5.2) Sample weight

[0242] Different amounts of a certain cellulose ether sample were weighed and tested according to the determination method in Example 1. The results are shown in Table 10. It can be seen that the relative standard deviation (RSD) of the ethylene glycol methyl ether content and TVOC content determination results in the six tests was 2.2%, which meets the requirement of Table B.1 of GB / T 27417-2017 that the coefficient of variation in the laboratory should be ≤3.8% when the content of the analyte is in the range of 1000 mg / kg. Therefore, when the sample weight is in the range of 0.2 g to 1.0 g and the volume of the dilution solution is 10 mL, the sample weight has no significant effect on the VOC content of the cellulose ether.

[0243] Table 10: VOC data measured under different sample sizes

[0244]

[0245] (5.3) Sample placement time

[0246] Three cellulose ethers (A, B, and C) were selected and stored (sealed in self-sealing bags) for approximately 20 days. Their VOC content was determined according to the method in Example 1, and the results are shown in Table 10. Table 11 shows that with increasing storage time, the contents of ethylene glycol methyl ether, diethylene glycol dimethyl ether, and TVOC all decreased to some extent. This indicates that storage time has a significant impact on the contents of ethylene glycol methyl ether, diethylene glycol dimethyl ether, and TVOC.

[0247] Table 11: VOC data measured at different placement times

[0248]

[0249] Based on the above factors, storing cellulose ethers in sealed glass bottles (at room temperature) can reduce the impact of storage time on the results.

[0250] Example 6: Method Application

[0251] Quantitative analysis was performed on cellulose ether samples commonly used in building materials. The results are shown in Table 12.

[0252] Table 12: Detection results of different cellulose ether samples

[0253]

[0254] The above TVOC content does not have an integration endpoint. The calibration compounds are ethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol monomethyl ether, triethylene glycol dimethyl ether, diethylene glycol butyl ether, and 1,2-propanediol. Other VOCs are calculated using the internal standard compound cyclopropyl methyl ketone. ND means not detected (<10 mg / kg).

[0255] Comparative Example 1: Gas Chromatography Conditions Recommended in GB / T 23986.2-2023

[0256] The column oven temperature program recommended in Appendix B of GB / T 23986.2-2023 "Determination of Volatile Organic Compounds (VOCs) and / or Semi-Volatile Organic Compounds (SVOCs) in Paints and Varnishes - Part 2: Gas Chromatography" was as follows: initial temperature 100℃, hold for 1 min, increase to 260℃ at a rate of 20℃ / min, hold for 16 min, run for 25 min (the run time can be extended if necessary). Cellulose ethers were detected and qualitatively analyzed by GC-MS. Results are shown in [link to GC-MS documentation]. Figure 1 It can be seen that the internal standard compound cyclopropyl methyl ketone (CAS No.: 765-43-5, retention time 7.8158 min) co-elutes with ethylene glycol (CAS No.: 107-21-1, retention time 7.8718 min), 2,3-dimethoxyprop-1-ol (CAS No.: 40453-77-8, retention time 9.2780 min) co-elutes with diethylene glycol dimethyl ether (CAS No.: 111-96-6, retention time 9.3650 min), and 1-(2-methoxypropoxy)-2-propanol (CAS No.: 13429-07-7, retention time 10.1306 min) co-elutes with diethylene glycol (CAS No.: 111-46-6, retention time 10.1937 min). This indicates that the target compounds interfere with and affect the accurate quantification of VOC and TVOC content in cellulose ethers.

[0257] The column oven temperature program of this invention is as follows: hold at 50°C for 1 min, then increase the temperature to 230°C at 10°C / min, hold for 2 min, then increase the temperature to 260°C at 15°C / min, hold for 20 min. The GCMS qualitative spectrum for the detection of cellulose ethers is shown below. Figure 2As shown, under the column oven heating program of this invention, the internal standard compound cyclopropyl methyl ketone (CAS No.: 765-43-5, retention time 12.0379 min) is completely separated from ethylene glycol (CAS No.: 107-21-1, retention time 12.4283 min), 2,3-dimethoxyprop-1-ol (CAS No.: 40453-77-8, retention time 15.5749 min) is completely separated from diethylene glycol dimethyl ether (CAS No.: 111-96-6, retention time 15.8498 min), and 1-(2-methoxypropoxy)-2-propanol (CAS No.: 13429-07-7, retention time 17.3234 min) is completely separated from diethylene glycol (CAS No.: 111-46-6, retention time 17.4419 min), which can accurately determine the VOC and TVOC content in cellulose ethers.

[0258] Comparative Example 2: GB 18582-2020 "Limits of Hazardous Substances in Wall Coatings for Building Use"

[0259] GB 18582-2020, section 6.2.1.2, references GB / T 23986-2009 for the VOC content detection method. The recommended column oven temperature program is: initial temperature 100℃, hold for 1 min, increase to 260℃ at a rate of 20℃ / min, hold for 21 min. Similar to "Comparative Example 1," this temperature program also suffers from poor separation of the target compound. Furthermore, the calibration compounds in GB 18582-2020 include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, triethylamine, dimethylethanolamine, 2-amino-2-methyl-1-propanol, ethylene glycol, 1,2-propanediol, diethanol, and 2,2,4-trimethyl-1,3-pentanediol. Only the target compound 1,2-propanediol in the cellulose ether VOCs of this invention is included. The test results of the two methods are shown in Table 13 below.

[0260] Table 13: Test results of the two methods

[0261]

[0262] The determination of VOC content in cellulose ethers according to GB 18582-2020 6.2.1.2 method has several drawbacks. Firstly, the separation is poor. Secondly, due to the lack of correction compounds, the VOC content is calculated based on internal standard compounds. As a result, the measured values ​​of ethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol monomethyl ether, triethylene glycol dimethyl ether, and TVOC content are all lower than the actual values, making it impossible to accurately determine the VOC and TVOC content in cellulose ethers.

[0263] Comparative Example 3: GB 30981.1-2025 "Limits of Hazardous Substances in Coatings - Part 1: Architectural Coatings" 6.2.1.3

[0264] GB 30981.1-2025 references GB / T 23986.2-2023 for the detection method of VOC content. Like "Comparative Example 1", it also has the problem of poor separation of the target compound by the temperature program. In addition, the calibration compounds specified in the above standard are missing diethylene glycol monomethyl ether and 1,2-propanediol in cellulose ether VOC. The test results of the two methods are shown in Table 14 below.

[0265] Table 14: Test results of the two methods

[0266]

[0267] The determination of VOC content in cellulose ethers according to GB 30981.1-2025 method has several drawbacks. Firstly, the separation is poor. Secondly, due to the lack of correction compounds diethylene glycol monomethyl ether and 1,2-propanediol, the VOC content is calculated based on the internal standard compounds. As a result, the measured values ​​of diethylene glycol monomethyl ether content, 1,2-propanediol content, and TVOC content are all lower than the actual values, making it impossible to accurately determine the VOC content and TVOC content in cellulose ethers.

[0268] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely to aid in understanding the method and core ideas of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for determining the VOC content of a cellulose ether, characterized in that Comprising the following steps: S1, draw calibration compound standard curve: Draw the standard curve by single calibration compound method SA or mixed calibration compound method SB; Wherein, The single calibration compound method SA comprises: (S1-A1): Preparation of calibration compound stock solution: Weigh a single calibration compound into a volumetric flask, dilute to volume with solvent, and prepare a single calibration compound stock solution; (S1-A2): Preparation of internal standard diluent: Weigh the internal standard compound into a volumetric flask, dilute to volume with solvent to the mark, and obtain the internal standard stock solution; Transfer the obtained internal standard stock solution to a volumetric flask, dilute to volume with solvent to the mark, and obtain the internal standard diluent; Wherein, the internal standard compound is cyclopropyl methyl ketone; (S1-A3): Draw the standard curve: ① Weigh the single calibration compound stock solution, dilute the single calibration compound stock solution into a series of different concentrations using the internal standard diluent and diluent, and obtain a series of concentration standard solutions corresponding to the calibration compound; ② Take the series of concentration standard solutions into the analyzer for GC-FID analysis, take the content ratio of the calibration compound / internal standard compound in the series of concentration standard solutions as the vertical coordinate, and take the corresponding peak area ratio of the calibration compound / internal standard compound as the horizontal coordinate. Draw the standard curve of the calibration compound; Each calibration compound is executed according to the above steps (S1-A1)-(S1-A3) respectively, so as to obtain the standard curve of each calibration compound; each calibration compound is: ethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol butyl ether, triethylene glycol dimethyl ether, 1,2-propanediol; The mixed calibration compound method SB comprises: (S1-B1): Preparation of calibration compound stock solution: Weigh each calibration compound into the same volumetric flask, dilute to volume with solvent, and prepare a mixed calibration compound stock solution; The calibration compounds are respectively: ethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol butyl ether, triethylene glycol dimethyl ether, 1,2-propanediol; (S1-B2): Preparation of internal standard diluent: Weigh the internal standard compound into a volumetric flask, dilute to volume with solvent to the mark, and obtain the internal standard stock solution; Transfer the obtained internal standard stock solution to a volumetric flask, dilute to volume with solvent to the mark, and obtain the internal standard diluent; Wherein, the internal standard compound is cyclopropyl methyl ketone; (S1-B3): Draw the standard curve: ① Weigh the mixed calibration compound stock solution, dilute the mixed calibration compound stock solution into a series of different concentrations using the internal standard diluent and diluent, and obtain a series of concentration standard solutions of the mixed calibration compound; ② From the series of concentration standard solutions of the mixed calibration compound, select one to inject into the analyzer GCMS for qualitative analysis to determine the peak order of each calibration compound; then, take the series of concentration standard solutions of the mixed calibration compound into the analyzer for GC-FID analysis, take the content ratio of the calibration compound / internal standard compound in the series of concentration standard solutions as the vertical coordinate, and take the corresponding peak area ratio of the calibration compound / internal standard compound as the horizontal coordinate. Draw the standard curve of each calibration compound; S2, sample pretreatment: Put the cellulose ether powder into a centrifuge tube, add the internal standard diluent, mix well, then centrifuge, take the supernatant for filtration to obtain a sample treatment liquid; S3, quantitative analysis: Put the sample treatment liquid obtained in step S2 into a quantitative analyzer for quantitative analysis, calculate the content of each component according to the internal standard standard curve method, so as to obtain the content of each VOC in the cellulose ether powder; In the above steps, the steps have no special restrictions on the order.

2. The assay method according to claim 1, characterized in that, The solvent is acetonitrile.

3. The assay method according to claim 1, characterized by, In ② of step (S1-A3), the conditions of GC-FID analysis include: Capillary column: DB-1301; Chromatographic column carrier gas flow rate: 1 mL / min; Injection port temperature 250°C; FID detector temperature 270°C; Column oven temperature program: 50°C for 1 min, then 10°C / min to 230°C, hold for 2 min, then 15°C / min to 260°C, hold for 20 min; injection volume 1 μL, split ratio 20:

1.

4. The assay method according to claim 1, characterized by, In ② of step (S1-B3), the qualitative analysis conditions of GCMS include: Capillary column: DB-1301; Chromatographic column carrier gas flow rate: 1 mL / min; Injection port temperature 250°C; MS detector: SCAN mode, scan range 30~400 m / z; Column oven temperature program: 50°C for 1 min, then 10°C / min to 230°C, hold for 2 min, then 15°C / min to 260°C, hold for 20 min; injection volume 1 μL, split ratio 20:1; In ② of step (S1-B3), the conditions of GC-FID analysis include: Capillary column: DB-1301; Chromatographic column carrier gas flow rate: 1 mL / min; Injection port temperature 250°C; FID detector temperature 270°C; Column oven temperature program: 50°C for 1 min, then 10°C / min to 230°C, hold for 2 min, then 15°C / min to 260°C, hold for 20 min; injection volume 1 μL, split ratio 20:

1.

5. The assay method according to claim 1, characterized by, In step S3, the quantitative analysis is as follows: (1) For samples with VOC content ≥100 mg / kg, perform GC-FID quantitative analysis; (2) For samples with VOC content <100 mg / kg, perform GC-MS quantitative analysis.

6. The assay method according to claim 5, characterized in that, In step S3: The conditions of GC-FID quantitative analysis include: Capillary column: DB-1301; Chromatographic column carrier gas flow rate: 1 mL / min; Injection port temperature 250°C; FID detector temperature 270°C; Column oven temperature program: 50°C for 1 min, then 10°C / min to 230°C, hold for 2 min, then 15°C / min to 260°C, hold for 20 min; injection volume 1 μL, split ratio 20:1; The conditions of GC-MS quantitative analysis include: Capillary column: DB-1301; Chromatographic column carrier gas flow rate: 1 mL / min; Injection port temperature 250°C; Column oven temperature program: 50°C for 1 min, then ramped at 10°C / min to 230°C, hold for 2 min, then ramped at 15°C / min to 260°C, hold for 20 min; injection volume 1 μL, split ratio 20:1; The mass spectrometry conditions are as follows: SIM scan, quantitative ions and qualitative ions are as shown in the table; ion source: Xtr high sensitivity ion source, 230°C; quadrupole temperature: 150°C; timing event: 6.5 min detector off, 8.5 min detector on; gain factor: 1.0; 。 7. The assay method according to claim 1, characterized by, In step S2, the sampling mode of the cellulose ether powder comprises: using a clean stainless steel single-slot quantitative powder sampler, piercing the cellulose ether large packaging bag, taking out an appropriate amount of powder, quickly pouring it into a container, and filling it, covering it with a sealed cover with a sealing gasket, and sealing and storing it.

8. The assay method of claim 1, wherein In step S2, the mixing mode is selected from the following two modes: (1) ultrasonic treatment; (2) ultrasonic treatment first, then vortex mixer mixing, and then ultrasonic treatment again; The temperature of the ultrasonic treatment is ≤30°C, and the time is 20±10 min. In step S2, the temperature of the centrifugation is 15-30°C. In ① of step (S1-A3), the concentration point values of each calibration compound in the series of concentration standard solutions are selected from 1-500 µg / mL. In ① of step (S1-B3), the concentration point values of each calibration compound in the mixed calibration compound series of concentration standard solutions are selected from 1-500 µg / mL. Step S3 further comprises: summing the peak areas of all compounds, and adding the uncalibrated compounds to obtain the TVOC content in the cellulose ether powder.

9. The assay method according to claim 1 or 8, characterized by, In ① of step (S1-A3), the concentration gradient of each calibration compound in the series of concentration standard solutions is as follows: Ethylene glycol methyl ether: 1 µg / mL, 10 µg / mL, 100 µg / mL, 250 µg / mL, 500 µg / mL; Diethylene glycol dimethyl ether: 1 µg / mL, 10 µg / mL, 100 µg / mL, 250 µg / mL, 500 µg / mL; Diethylene glycol monomethyl ether: 1 µg / mL, 10 µg / mL, 100 µg / mL, 250 µg / mL, 500 µg / mL; Diethylene glycol butyl ether: 1 µg / mL, 10 µg / mL, 100 µg / mL, 250 µg / mL, 500 µg / mL; Triethylene glycol dimethyl ether: 1 µg / mL, 10 µg / mL, 100 µg / mL, 250 µg / mL, 500 µg / mL; 1,2-Propanediol: 2 µg / mL, 20 µg / mL, 40 µg / mL, 200 µg / mL, 400 µg / mL; In ① of step (S1-B3), the concentration gradient of each calibration compound in the mixed calibration compound series of concentration standard solutions is as follows: Ethylene glycol methyl ether: 1 µg / mL, 10 µg / mL, 100 µg / mL, 250 µg / mL, 500 µg / mL; Diethylene glycol dimethyl ether: 1 µg / mL, 10 µg / mL, 100 µg / mL, 250 µg / mL, 500 µg / mL; Diethylene glycol monomethyl ether: 1 µg / mL, 10 µg / mL, 100 µg / mL, 250 µg / mL, 500 µg / mL; Diethylene glycol monomethyl ether: 1 µg / mL, 10 µg / mL, 100 µg / mL, 250 µg / mL, 500 µg / mL; Diethylene glycol monomethyl ether: 1 µg / mL, 10 µg / mL, 100 µg / mL, 250 µg / mL, 500 µg / mL; 1,2-Propanediol: 2 µg / mL, 20 µg / mL, 40 µg / mL, 200 µg / mL, 400 µg / mL.

10. The assay method of claim 1, wherein Step (S1-A1) comprises: weighing 100 mg of a single calibration compound into a 20 mL volumetric flask, dissolving with acetonitrile, and diluting to the calibration mark to obtain a single calibration compound stock solution; Step (S1-A2) comprises: weighing 40 mg of an internal standard compound into a 20 mL volumetric flask, dissolving with acetonitrile, and diluting to the calibration mark to obtain an internal standard stock solution; then, using a pipette, transferring 1 mL of the internal standard stock solution into a 10 mL volumetric flask, and diluting to the calibration mark with acetonitrile to obtain an internal standard dilution; Step (S1-A3) ① comprises: respectively transferring 1 mL of the internal standard dilution and 1 mL of the single calibration compound stock solution into a 10 mL volumetric flask, and diluting with acetonitrile, which is the first concentration point; then, using a step-by-step dilution method to supplement the internal standard dilution, sequentially obtaining other concentration points, thereby obtaining a series of concentration standard solutions corresponding to the calibration compound; Step (S1-B1) comprises: weighing 100 mg of each calibration compound into the same 20 mL volumetric flask, dissolving with acetonitrile, and diluting to the calibration mark to obtain a mixed calibration compound stock solution; Step (S1-B2) comprises: weighing 40 mg of an internal standard compound into a 20 mL volumetric flask, dissolving with acetonitrile, and diluting to the calibration mark to obtain an internal standard stock solution; then, using a pipette, transferring 1 mL of the internal standard stock solution into a 10 mL volumetric flask, and diluting to the calibration mark with acetonitrile to obtain an internal standard dilution; Step (S1-B3) ① comprises: respectively transferring 1 mL of the internal standard dilution and 1 mL of the mixed calibration compound stock solution into a 10 mL volumetric flask, and diluting with acetonitrile, which is the first concentration point; then, using a step-by-step dilution method to supplement the internal standard dilution, sequentially obtaining other concentration points, thereby obtaining a series of concentration standard solutions of the mixed calibration compound; If other uncalibrated compounds are detected in the quantitative analysis results of step S3, first perform GCMS qualitative analysis to confirm the uncalibrated compounds, then supplement the confirmed uncalibrated compounds to the calibration compound list, and repeat steps S1-S3, thereby obtaining the content of each VOC in the cellulose ether powder.

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