Method for simultaneously testing contents of seven preservatives in building water-based interface agent

Abstract

The invention provides a method for simultaneously determining the contents of seven common preservatives in a building water-based interface agent by using a liquid chromatograph. According to the method, the separation degree of seven preservatives including methylisothiazolinone, chloromethylisothiazolinone, benzisothiazolinone, octyl isothiazolinone, dichloro octyl isothiazolinone, iodopropargyl butyl carbamate and zinc pyrithione is good, and the linear correlation coefficient of a standard curve for quantification ranges from 0.99952 to 1.0000; the detection limit is 0.2 to 0.45 mg / kg; the precision is 0.8%-1.5%, and the sample adding standard recovery rate is 94.4%-98.4%. And the method has good stability. Experimental conditions for simply and rapidly determining the content of the preservative in the water-based interface agent for the building are determined, and the experimental efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of analytical chemistry, and particularly relates to a method for simultaneously testing the content of seven preservatives in a water-based interface agent for buildings. BACKGROUND

[0002] A water-based interface agent for buildings is usually composed of high-molecular polymers, surfactants, additives, etc. Its function is to form a protective layer on the surface of a building wall or roof to enhance the waterproof, moisture-proof, durability and other properties, and also to improve the adhesion of paint or coating materials to the surface of the building. It has the advantages of convenient construction, low pollution, economy and practicality, etc. However, the presence of water provides the necessary conditions for the growth of microorganisms, and the presence of various additives promotes the reproduction of microorganisms. In order to prevent the breeding of bacteria, mold and other microorganisms, preservatives are added to solve this problem. Methylisothiazolinone (MIT, CAS No.: 2652-20-4), chloromethylisothiazolinone (CMIT, CAS No.: 26172-55-4), benzisothiazolinone (BIT, CAS No.: 2634-33-5), octylisothiazolinone (OIT, CAS No.: 26530-20-1), dichlorooctylisothiazolinone (DCOIT, CAS No.: 64359-81-5), iodopropynyl butylcarbamate (IPBC, CAS No.: 55406-53-6) and zinc pyrithione (ZPT, CAS No.: 13463-41-7) are commonly used preservatives in water-based interface agents. Since there are many types of bacteria and mold, multiple preservatives need to be used in combination to achieve better bactericidal effect.

[0003] However, preservatives bring us convenience, but also have certain toxicity. Studies have shown that isothiazolinone compounds (MIT, BIT, CMIT) are the most common cause of occupational exposure dermatitis. Because these compounds are volatile, they can cause systemic dermatitis through the air, and in some cases can cause lung disease, asthma symptoms, and even death. OIT has strong skin penetration ability, and the toxicity of OIT to thyroid hormones and development is higher than that of MIT. Although DCOIT is not classified as a skin sensitizer, it can cause endocrine disorders. Some cases of allergic contact dermatitis are related to the use of IPBC, which may be due to the release of free iodine by the preservative. In addition, IPBC can cause damage to the thyroid and general metabolism through interactions with enzymes. People can absorb ZPT through the skin, which can have adverse effects on the liver. In addition, the use of preservatives has the risk of transfer to the environment, which has potential adverse effects on various organisms in the environment. Studies have shown that ZPT has teratogenic effects on fish embryos, and the sublethal concentration of ZPT in Japanese medaka is only 0.003-0.007 mg / L. When juvenile salmon are exposed to water containing IPBC ≥ 1 μg / L, olfactory-mediated behavioral and physiological alarm responses will decrease, affecting migration behavior and leading to population extinction. DCOIT can induce changes in gene expression in shrimp at a concentration of 15 μg / L, and can interfere with the metabolism, growth and survival of shrimp at a concentration of 30 μg / L.

[0004] In view of the environmental and health risks of the use of preservatives, environmental protection organizations at home and abroad have developed a series of preservative limit standards. The European Union's eco-label and the German federal government's blue angel eco-label have clear limit guidance for preservatives MIT, CMIT and BIT in water-based coatings. China's GB / T 35602-2017 standard also has limit requirements for the above preservatives, in addition to IPBC, ZPT, OIT and DCOIT limits, but the standard does not provide a detection method for the content of these preservatives, and only relies on the enterprise to provide a complete list of biological killing agents used as the basis for judgment. This brings risks to the production of raw materials and the control of biological killing agent content in products, so it is very important to establish a high-efficiency detection method for the content of 7 kinds of preservatives commonly used in water-based interface agents for buildings which are limited in amount. SUMMARY

[0005] The purpose of the present application is to provide a method for simultaneously testing the content of 7 kinds of preservatives in water-based interface agents for buildings. The method in the present application can simultaneously determine the content of 7 kinds of preservatives in water-based interface agents for buildings, and has good accuracy, stability and robustness, providing a reliable method for determining the content of preservatives in water-based interface agents for buildings.

[0006] The application provides a method for simultaneously testing the content of seven preservatives in water-based interface agents for buildings, comprising the following steps:

[0007] A) dissolving standard substances of methylisothiazolinone, chloromethylisothiazolinone, benzisothiazolinone, octylisothiazolinone, dichlorooctylisothiazolinone and iodopropynyl butylcarbamate in methanol to obtain a first standard solution;

[0008] dissolving zinc pyrithione in a mixed solution of dimethyl sulfoxide and methanol to obtain a second standard solution;

[0009] mixing the first standard solution and the second standard solution and diluting with methanol to obtain a mixed standard stock solution;

[0010] B) diluting the mixed standard stock solution with methanol to different concentrations to obtain a series of mixed standard solutions with different concentrations, and detecting the series of mixed standard solutions with different concentrations by liquid chromatography to obtain a standard curve;

[0011] The detection conditions of the liquid chromatography are as follows: a C18 reversed-phase chromatographic column, mobile phase A: 0.1% phosphoric acid aqueous solution, and mobile phase B: methanol;

[0012] C) placing a sample to be tested in a centrifugal tube, dissolving with methanol, ultrasonicating, centrifuging, taking the supernatant and filtering to obtain a sample solution to be tested;

[0013] D) detecting the content of the seven preservatives in the sample solution to be tested according to the detection conditions of the liquid chromatography in step B).

[0014] Preferably, in step A), the mass ratio of dimethyl sulfoxide to methanol is 2:(2-4), more preferably 2:3.

[0015] In an embodiment of the application, about 20 mg (accurate to 0.1 mg) of methylisothiazolinone (MIT), 20 mg of chloromethylisothiazolinone (CMIT), 20 mg of benzisothiazolinone (BIT), 20 mg of octylisothiazolinone (OIT) and 20 mg of dichlorooctylisothiazolinone (DCOIT), and 100 mg (accurate to 0.1 mg) of iodopropynyl butylcarbamate (IPBC) are weighed in a 10 mL volumetric flask, dissolved with methanol and diluted to the mark to obtain a first standard solution. About 20 mg of zinc pyrithione (ZPT) (accurate to 0.1 mg) is weighed in a 20 mL volumetric flask, dissolved by adding 8 mL of dimethyl sulfoxide, and then diluted to the mark with methanol, and shaken to obtain a second standard solution. The used preservative standard substances or high-purity reagents have a purity of >95%, and all the used reagents are chromatographically pure.

[0016] Preferably, in the step B), the injection concentration of methylisothiazolinone, chloromethylisothiazolinone, benzisothiazolinone, octylisothiazolinone, dichlorooctylisothiazolinone and zinc pyrithione in the mixed standard solution is 0.5 μg / mL-100.0 μg / mL, and the injection concentration of iodo-propargyl butylcarbamate is 2.5 μg / mL-500.0 μg / mL.

[0017] In an embodiment of the present application, the injection concentration of methylisothiazolinone, chloromethylisothiazolinone, benzisothiazolinone, octylisothiazolinone, dichlorooctylisothiazolinone and zinc pyrithione in the mixed standard solution is 0.5 μg / mL, 1.0 μg / mL, 5.0 μg / mL, 10.0 μg / mL, 20.0 μg / mL, 50.0 μg / mL, 100.0 μg / mL, and the injection concentration of iodo-propargyl butylcarbamate is 2.5 μg / mL, 5.0 μg / mL, 25.0 μg / mL, 50.0 μg / mL, 100.0 μg / mL, 250.0 μg / mL, 500.0 μg / mL; further, the injection concentration of methylisothiazolinone in the mixed standard solution with a series of concentrations is 0.5 μg / mL, 1.0 μg / mL, 5.0 μg / mL, 10.0 μg / mL, 20.0 μg / mL, 50.0 μg / mL, 100.0 μg / mL, the injection concentration of chloromethylisothiazolinone is 0.5 μg / mL, 1.0 μg / mL, 5.0 μg / mL, 10.0 μg / mL, 20.0 μg / mL, 50.0 μg / mL, 100.0 μg / mL, the injection concentration of benzisothiazolinone is 0.5 μg / mL, 1.0 μg / mL, 5.0 μg / mL, 10.0 μg / mL, 20.0 μg / mL, 50.0 μg / mL, 100.0 μg / mL, the injection concentration of octylisothiazolinone is 0.5 μg / mL, 1.0 μg / mL, 5.0 μg / mL, 10.0 μg / mL, 20.0 μg / mL, 50.0 μg / mL, 100.0 μg / mL, the injection concentration of dichlorooctylisothiazolinone is 0.5 μg / mL, 1.0 μg / mL, 5.0 μg / mL, 10.0 μg / mL, 20.0 μg / mL, 50.0 μg / mL, 100.0 μg / mL, and the injection concentration of zinc pyrithione is 0.5 μg / mL, 1.0 μg / mL, 5.0 μg / mL, 10.0 μg / mL, 20.0 μg / mL, 50.0 μg / mL, 100.0 μg / mL.

[0018] Preferably, in step B), the mixed standard stock solution is diluted with methanol to obtain an intermediate solution with the concentrations of methylisothiazolinone, chloromethylisothiazolinone, benzisothiazolinone, octylisothiazolinone, dichlorooctylisothiazolinone and zinc pyrithione all being 500 μg / mL and the concentration of iodopropynyl butylcarbamate being 2500 μg / mL, and then the intermediate solution is diluted with methanol to obtain a series of mixed standard solutions with different concentrations.

[0019] In one embodiment of the present application, a volume of mixed standard stock solution of MIT, CMIT, BIT, OIT, DCOIT, IPBC and ZPT is measured in a 10 mL volumetric flask, and diluted with methanol to obtain an intermediate solution containing 7 preservatives with the concentrations of MIT, CMIT, BIT, OIT, DCOIT and ZPT all being 500 μg / mL and the concentration of IPBC being 2500 μg / mL. A volume of the intermediate solution is removed and diluted to prepare a series of standard solutions with different concentrations, in which the concentrations of MIT, CMIT, BIT, OIT, DCOIT and ZPT are all 0.5 μg / mL, 1.0 μg / mL, 5.0 μg / mL, 10.0 μg / mL, 20.0 μg / mL, 50.0 μg / mL, 100.0 μg / mL, and the concentration of IPBC is 2.5 μg / mL, 5.0 μg / mL, 25.0 μg / mL, 50.0 μg / mL, 100.0 μg / mL, 250.0 μg / mL, 500.0 μg / mL.

[0020] Preferably, in step B), the liquid chromatography detection conditions further comprise:

[0021] Column temperature: 35°C

[0022] Column flow rate: 1 mL / min

[0023] Injection volume: 20 μL

[0024] Detector wavelength: MIT / ZPT / CMIT / OIT / DCOIT: 280 nm; IPBC: 230 nm; BIT: 318 nm.

[0025] Preferably, in the liquid chromatography detection, the elution gradient program is:

[0026] Time (min) Flow phase A (%) Flow phase B (%) 0 75 25 13 75 25 15 30 70 20 10 90 24 10 90 27 75 25 32 75 25 .

[0027] Preferably, in step C), the frequency of ultrasonic is switched between 45 kHz and 80 KHz with an interval of 20 s, the time of ultrasonic is 10-30 min, and the temperature of ultrasonic is 20-30°C.

[0028] Preferably, in step C), the temperature of centrifugation is 20-30℃, and the rotation speed of centrifugation is 12000-27000r / min.

[0029] Preferably, in step C), the supernatant is filtered by a 0.22μm microporous filter after centrifugation to obtain the sample solution to be detected.

[0030] In one embodiment of the present application, a certain amount of methanol is added to a centrifuge tube, 0.5-2g of uniform sample (accurate to 0.1mg) is weighed into the centrifuge tube, and the volume is made up to 20mL with methanol. The sample is shaken thoroughly on a vortexer to disperse uniformly. The sample is placed in an ultrasonic cleaner and ultrasonically treated for 10min at 25℃. Then, the sample is centrifuged for 30min using a centrifuge, the centrifugation temperature is set at 20℃, and the rotation speed is set at 27000r / min. The supernatant is filtered by a 0.22μm microporous filter, 0.5mL-1mL of the filtrate is transferred to a 2mL vial and sealed.

[0031] Preferably, the detection limit of the method for simultaneously testing the content of 7 preservatives in water-based interface agents for building is 0.2-0.45mg / kg, the precision is 0.8%-1.5%, and the accuracy is 94.4%-98.4%.

[0032] The present application provides a method for simultaneously testing the content of 7 preservatives in water-based interface agents for building, comprising the following steps: A) dissolving standard substances of methylisothiazolinone, chloromethylisothiazolinone, benzisothiazolinone, octylisothiazolinone, dichlorooctylisothiazolinone and iodo-propargyl butylcarbamate in methanol to obtain a first standard solution; dissolving zinc pyrithione in a mixed solution of dimethyl sulfoxide and methanol to obtain a second standard solution; mixing the first standard solution and the second standard solution and diluting with methanol to obtain a mixed standard stock solution; B) diluting the mixed standard solution with methanol to different concentrations to obtain a series of mixed standard solutions with different concentrations, and detecting the different concentrations of standard solutions by liquid chromatography to obtain a standard curve; the detection conditions of the liquid chromatography are as follows: C18 reversed-phase chromatographic column, mobile phase A: 0.1% phosphoric acid aqueous solution, mobile phase B: methanol; C) dissolving the sample to be detected in a centrifuge tube with methanol, ultrasonically treating, centrifuging, filtering the supernatant to obtain a sample solution to be detected; D) detecting the content of 7 preservatives in the sample solution to be detected according to the detection conditions of the liquid chromatography in step B).

[0033] Compared with the prior art, the present application has the following advantages:

[0034] (1) The present application can simultaneously quantify the content of 7 commonly used preservatives in water-based interface agents for building, and the analysis time is short and the efficiency is high.

[0035] (2) The application uses methanol as a solvent to extract preservatives in the sample during pretreatment, which is less toxic and easy to operate.

[0036] (3) The application uses phosphoric acid aqueous solution as the mobile phase to improve the tailing phenomenon of preservative peak shape, which is less harmful to the instrument than triethylamine and ammonium acetate solutions.

[0037] (4) The detection limit of the 7 preservatives in the application is between 0.2mg / kg and 0.45mg / kg.

[0038] (5) The precision of the 7 preservatives in the application is between 0.8% and 1.5%, with good repeatability.

[0039] (6) The recovery rate of the 7 preservatives in the application is 94.4% to 98.4%, with accurate quantification.

[0040] (7) The application has high stability, and different ultrasonic time (10min, 20min, 30min), centrifugal speed (12000r, 20000r, 27000r), and centrifugal temperature (20℃, 25℃, 30℃) have no significant difference on the quantitative results. BRIEF DESCRIPTION OF DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are only embodiments of the application, and those skilled in the art can obtain other drawings according to the provided drawings without creative labor.

[0042] Figure 1 MIT, CMIT, BIT, OIT and DCOIT peak positions under the analysis conditions of Table 2;

[0043] Figure 2 IPBC and ZPT peak positions under the analysis conditions of Table 2;

[0044] Figure 3 MIT, CMIT, BIT, IPBC and ZPT peak positions under the analysis conditions of Table 3;

[0045] Figure 4 Liquid chromatogram of 7 preservative standard solutions;

[0046] Figure 5 Chromatogram of preservative content in water-based interfacial agent sample;

[0047] Figure 6 Effect of different ultrasonic time on the content of 7 preservatives;

[0048] Figure 7 Effects of different centrifugal temperature on the content of 7 preservatives;

[0049] Figure 8 Effects of different centrifugal speed on the content of 7 preservatives. DETAILED DESCRIPTION

[0050] In order to further illustrate the present application, the following embodiments are described in detail for the method for simultaneously testing the content of 7 preservatives in water-based interface agent for building provided by the present application, but it cannot be understood as limiting the protection scope of the present application.

[0051] Example 1: information of standard substance and reagent

[0052] The reagents include methanol (chromatographic pure), phosphoric acid (mass fraction 85%, chromatographic pure) and dimethyl sulfoxide (chromatographic pure). The ultrapure water is provided by MILI-Q instrument company.

[0053] Table 1 general information of target compounds

[0054]

[0055] Example 2: configuration of standard solution and standard curve

[0056] About 20 mg (accurate to 0.1 mg) of MIT, CMIT, BIT, OIT and DCOIT, 100 mg (accurate to 0.1 mg) of IPBC were weighed in a 10 mL volumetric flask, dissolved with methanol, and diluted to the mark. About 20 mg of ZPT (accurate to 0.1 mg) was weighed in a 20 mL volumetric flask, 8 mL of dimethyl sulfoxide was added for dissolution, and then methanol was used for dilution to the mark, and then shaken well.

[0057] 5 mL of MIT, CMIT, BIT, OIT, DCOIT, IPBC mixed standard solution and 2.5 mL of ZPT solution were measured in a 10 mL volumetric flask, diluted to the mark with methanol, and 7 mixed standard solutions with MIT, CMIT, BIT, OIT, DCOIT and ZPT concentration of 500 μg / mL and IPBC concentration of 2500 μg / mL were obtained. A certain volume of 7 mixed standard solutions was removed, and diluted to prepare standard curve solutions with MIT, CMIT, BIT, OIT, DCOIT and ZPT concentration of 0.5 μg / mL, 1.0 μg / mL, 5.0 μg / mL, 10.0 μg / mL, 20.0 μg / mL, 50.0 μg / mL, 100.0 μg / mL, and IPBC concentration of 2.5 μg / mL, 5.0 μg / mL, 25.0 μg / mL, 50.0 μg / mL, 100.0 μg / mL, 250.0 μg / mL, 500.0 μg / mL.

[0058] Pre-treatment of the sample of Example 3

[0059] A certain amount of methanol was added into a centrifuge tube, 2 g of the uniform sample (accurate to 0.1 mg) was weighed into the centrifuge tube, and the volume was made up to 20 mL with methanol. The sample was shaken well on a vortexer to disperse uniformly. The sample was placed in an ultrasonic cleaner and ultrasonically treated for 10 min, controlled at 25°C. Then, the sample was centrifuged for 30 min using a centrifuge, the centrifuge temperature was set at 20°C, and the rotation speed was set at 27000 r / min. The supernatant was filtered with a 0.22 μm microporous filter membrane, and 0.5 mL to 1 mL of the filtrate was transferred into a 2 mL liquid bottle and sealed.

[0060] Example 4: Instrument model and test conditions

[0061] Centrifuge: rotation speed up to 27000 r / min, temperature controllable (Sorvall Lynx 6000, Thermo Fisher)

[0062] Balance: accuracy 0.1 mg (SQP, Sartorius)

[0063] Liquid chromatograph: Agilent 1260 liquid chromatograph equipped with a DAD detector.

[0064] The liquid chromatograph conditions are as follows:

[0065] Chromatographic column: C18 reversed-phase column (length 150 mm*inner diameter 4.6 mm, 5 μm);

[0066] Mobile phase A: water (0.1% phosphoric acid); mobile phase B: methanol

[0067] Column temperature: 35°C

[0068] Column flow rate: 1 mL / min

[0069] Injection volume: 20 μL

[0070] Detector wavelength: MIT / ZPT / CMIT / OIT / DCOIT: 280 nm; IPBC: 230 nm; BIT: 318 nm.

[0071] Elution gradient program:

[0072] Table 2 Elution gradient degree

[0073]

[0074]

[0075] The following examples are all based on the processing method and liquid chromatography conditions in Examples 1-4.

[0076] Example 5: Chromatography condition optimization

[0077] ① Elution procedure

[0078] The different chemical properties of the seven preservatives pose a great challenge to their effective separation. In order to achieve effective separation of the seven preservatives, different gradient ratios of mobile phase were tested. First, according to the range of mobile phase ratio provided in GB / T 37363.1-2019 "Determination of biocidal agents content in coatings Part 1: Determination of isothiazolinone content", the specific ratio of mobile phase was determined by experiment (see Table 3), which realized the separation of MIT, CMIT, BIT, OIT and DCOIT components (see Figure 1 ), but under this experimental condition, ZPT and IPBC had close retention time and could not be effectively separated, and ZPT peak shape was poor with baseline fluctuation moving up (see Figure 2 ). According to the peak time of each compound, it was found that MIT, CMIT, BIT, IPBC and ZPT were greatly affected by the ratio of mobile phase and eluted during the gradient change of mobile phase, while OIT and DCOIT were eluted under the condition of constant mobile phase ratio (mobile phase A (%): mobile phase B (%) = 10:90), therefore, the ratio of mobile phase A (water) was extended to keep time (see Table 4), so that the peak time of compounds MIT, CMIT, BIT, IPBC and ZPT was moved forward and eluted at the stable baseline, and the analysis time was shortened. Under this condition, MIT, CMIT, BIT, IPBC and ZPT were effectively separated (see Figure 3 ), but IPBC eluted late, so the ratio of mobile phase was further adjusted to shorten the analysis time, and the final liquid chromatography condition is shown in Example 4. In addition, ZPT had peak tailing phenomenon during the test, which led to its close retention time to CMIT. Therefore, it was tried to improve the peak tailing phenomenon by adding 0.1% phosphoric acid in water phase, which realized the effective separation of ZPT and CMIT. Of course, buffer salt or triethylamine can also be added to the mobile phase, but it is relatively harmful to the chromatographic column and instrument.

[0079] Table 3 Test-1 of mobile phase ratio for determination of content of 7 preservatives

[0080]

[0081]

[0082] Table 4 Test-2 of mobile phase ratio for determination of content of 7 preservatives

[0083] Time (min) Flow phase A (%) Flow phase B (%) 0 75 25 13 75 25 15 30 70

[0084] ②Extraction solvent

[0085] The extraction solvent is an important factor affecting the extraction efficiency of preservatives in the sample. Based on the demulsification ability of the solvent in the sample and the ability to fully disperse the sample matrix, methanol and acetonitrile were selected for the extraction of preservative content. Since the water-based interface agent for construction was not fully dissolved when extracted with acetonitrile, the preservative determination results were significantly lower than the actual preservative content added in the sample (see Table 5), so methanol was selected for extraction. Methanol has strong demulsification ability for the sample, and a large amount of polymer dissolution leads to column plugging, so different proportions of methanol aqueous solution were selected for sample extraction research. The results showed that under the condition of 100% methanol dissolution, the preservative content in the sample was closest to the added amount in the sample (see Table 6). Therefore, 100% methanol was selected for sample treatment, and a high-speed centrifuge was selected to solve the problem of column plugging.

[0086] Table 5: Effect of different extraction solvents on preservative content in the sample

[0087] MIT content (mg / kg) CMIT content (mg / kg) Acetonitrile 2.8 17.0 Methanol 7.1 20.2 Sample actual addition 7.0 21.0

[0088] Table 6: Preservative content in the sample under different proportions of methanol aqueous extraction conditions

[0089]

[0090] Example 6: Standard curve, detection limit, precision and accuracy verification process

[0091] ①Standard curve

[0092] The standard working solution of different concentrations in Example 2 was determined according to the conditions in Example 4. The standard working curve was drawn with the peak area as the ordinate and the corresponding concentration as the abscissa, as shown in Table 7.

[0093] Table 7: Regression equation and correlation coefficient of 7 preservatives

[0094]

[0095] ②Detection limit

[0096] About 2 g of water-based interface agent sample (accurate to 0.1 mg) was taken in a centrifuge tube, and a certain amount of MIT, CMIT, BIT, OIT, DCOIT, ZPT and IPBC was added, and then diluted to 20 mL with methanol. According to the method in Example 3, the sample was treated, and 10 parallel determinations were made, and the standard deviation S of the 10 determination results was calculated. The detection limit of the method was calculated as 3 times the standard deviation.

[0097] Table 8: Detection limit determination results

[0098]

[0099]

[0100] Take about 2 g of water-based interface agent sample (accurate to 0.1 mg) in a centrifuge tube, and use methanol to make up to 20 mL. Process according to the method in sample preparation in Example 3, measure 10 times in parallel, and calculate the relative standard deviation S of the 10 measurement results, which is the precision of the method.

[0101] Table 9 Precision test results

[0102]

[0103] (4) Accuracy

[0104] The accuracy verification uses the method of standard addition recovery. Select 2 g of water-based interface agent sample for standard addition experiment, process according to the method in sample preparation in Example 3, measure 2 times in parallel, and calculate the recovery rate. The results are shown in Table 9.

[0105] Table 9 Accuracy test results

[0106]

[0107] Example 7: Influencing factors of preservative content determination

[0108] During the determination of this method, the ultrasonic time, centrifugation temperature and centrifugation rate are crucial to the determination of preservative content. Short ultrasonic time may cause insufficient extraction of preservatives, and too long ultrasonic time will affect the experimental efficiency. Studies have shown that when the temperature is lower than 20℃, high concentration of ZPT solution may exist in the form of precipitation. The centrifugation rate affects the separation effect of the matrix and the target compound, thereby affecting the content determination. Therefore, gradient experiments are set up for ultrasonic time, centrifugation temperature and centrifugation rate respectively, in order to verify their influence on the content of preservatives, and the results are as follows.

[0109] Ultrasonic time: select water-based interface agent according to the method in sample preparation in Example 3, select different ultrasonic time (10 min, 20 min, 30 min) to process it, and the results are as Figure 6 From Figure 6 it can be seen that after ultrasonic treatment for 10 min, 20 min and 30 min, the preservative content of the sample has no significant change (p<0.05). The relative standard deviation is between 0.00% and 1.41%, which is less than the repeatability limit requirement (10% / 2.8=3.57%). Therefore, the ultrasonic time has no significant effect on the preservative content in this method. In order to improve the detection efficiency, the final ultrasonic time in the experiment is set to 10 min.

[0110] Centrifugation temperature: The centrifugation temperature is an important factor affecting the determination of preservative content. Different preservatives have different tolerance to temperature. Studies have shown that when the temperature is lower than 20℃, high concentration of ZPT solution may precipitate. However, high temperature conditions can lead to IPBC degradation, and when the ultrasonic temperature is 40℃, the accuracy of the analysis results will be seriously affected. According to the method in the sample preparation in Example 3, different centrifugation temperatures (20℃, 25℃ and 30℃) were selected to treat the samples, and the results are shown in Table 3. Figure 7 Figure 7 It can be seen that there is no obvious change in the content of preservatives under different centrifugation temperatures, and the relative standard deviation is between 0.00% and 2.62%, which is less than the repeatability limit requirement (10% / 2.8=3.57%). Therefore, the centrifugation temperature has no significant effect on the content of preservatives in this method.

[0111] Centrifugation rate: It was found that a large amount of polymers in the sample were dissolved when methanol was used as the solvent. At a centrifugation speed of 10000r, the polymers and preservatives were not completely separated, which affected the stability of the experimental results. Therefore, a high-speed centrifuge was selected to centrifuge the sample. According to the method in the sample preparation in Example 3, different centrifugation speeds (12000r, 20000r, 27000r) were selected to treat the samples, and the results are shown in Table 4. Figure 8 Figure 8 It can be seen that there is no obvious change in the content of preservatives under different centrifugation rates, and the relative standard deviation is between 0.00% and 3.11%, which is less than the repeatability limit requirement (10% / 2.8=3.57%). Therefore, the centrifugation rate has no significant effect on the content of preservatives in this method. However, in order to protect the chromatographic column and the instrument, the final centrifugation speed is set to 27000r in the experiment.

[0112] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, which should also be considered as the protection scope of the present application.​​

Claims

1. A method for simultaneously testing the content of seven preservatives in a water-based interface agent for building applications, comprising the following steps: A) Dissolve the standard substances of methylisothiazolinone, chloromethylisothiazolinone, benzisothiazolinone, octylisothiazolinone, dichlorooctylisothiazolinone and iodopropynyl butylcarbamate in methanol to obtain the first standard solution. Zinc pyrithione was dissolved in a mixed solution of dimethyl sulfoxide and methanol to obtain a second standard solution; The first and second standard solutions were mixed and diluted with methanol to obtain a mixed standard mother liquor; B) Dilute the mixed standard mother liquor with methanol to obtain a series of mixed standard solutions of different concentrations, and perform liquid chromatography detection on the mixed standard solutions of different concentrations to obtain a standard curve; The detection conditions for the liquid chromatography are: C18 reversed-phase column, mobile phase A: 0.1% aqueous phosphoric acid solution, mobile phase B: methanol; C) Place the sample to be tested in a centrifuge tube, dissolve it in methanol, sonicate and centrifuge, take the supernatant and filter it to obtain the sample solution to be tested; D) The content of the seven preservatives in the sample solution to be tested is detected according to the detection conditions of liquid chromatography in step B).

2. The method for simultaneously testing the content of seven preservatives in a water-based interface agent for building applications according to claim 1, characterized in that, In step A), the mass ratio of dimethyl sulfoxide to methanol is 2:(2-4).

3. The method for simultaneously testing the content of seven preservatives in water-based interface agents for building applications according to claim 1, characterized in that, In step B), the injection concentrations of methylisothiazolinone, chloromethylisothiazolinone, benzisothiazolinone, octylisothiazolinone, dichlorooctylisothiazolinone, and zinc pyridinethione in the mixed standard solution are all 0.5 μg / mL to 100.0 μg / mL, and the injection concentration of iodopropynyl butylcarbamate is 2.5 μg / mL to 500.0 μg / mL.

4. The method for simultaneously testing the content of seven preservatives in a water-based interface agent for building applications according to claim 3, characterized in that, In step B), the mixed standard mother liquor is first diluted with methanol to obtain an intermediate solution with a concentration of 500 μg / mL for methylisothiazolinone, chloromethylisothiazolinone, benzisothiazolinone, octylisothiazolinone, dichlorooctylisothiazolinone, and zinc pyridinium ketone, and a concentration of 2500 μg / mL for iodopropynyl butylcarbamate. The intermediate solution is then diluted with methanol to obtain a series of mixed standard solutions with different concentrations.

5. The method for simultaneously testing the content of seven preservatives in a water-based interface agent for building applications according to claim 1, characterized in that, In step B), the liquid chromatography detection conditions further include: Column temperature: 35℃ Column flow rate: 1 mL / min Injection volume: 20 μL Detector wavelengths: MIT / ZPT / CMIT / OIT / DCOIT: 280nm; IPBC: 230nm; BIT: 318nm.

6. The method for simultaneously testing the content of seven preservatives in a water-based interface agent for building applications according to claim 1, characterized in that, In the liquid chromatography detection, the elution gradient program is as follows: 。 7. The method for simultaneously testing the content of seven preservatives in a water-based interface agent for building applications according to claim 1, characterized in that, In step C), the ultrasonic frequency is switched between 45kHz and 80kHz with a switching interval of 20s, the ultrasonic time is 10-30min, and the ultrasonic temperature is 20-30℃.

8. The method for simultaneously testing the content of seven preservatives in a water-based interface agent for building applications according to claim 1, characterized in that, In step C), the centrifugation temperature is 20–30°C, and the centrifugation speed is 12,000–27,000 r / min.

9. The method for simultaneously testing the content of seven preservatives in a water-based interface agent for building applications according to claim 1, characterized in that, In step C), after centrifugation, the supernatant is filtered through a 0.22 μm microporous membrane to obtain the sample solution to be tested.

10. The method for simultaneously testing the content of seven preservatives in a water-based interface agent for building applications according to claim 1, characterized in that, The method for simultaneously testing the content of seven preservatives in water-based interface agents for building materials has a detection limit of 0.2–0.45 mg / kg, a precision of 0.8%–1.5%, and an accuracy of 94.4%–98.4%.

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