Method for measuring content of azodicarbonamide in rubber and plastic thermal insulation product

Abstract

The invention relates to the technical field of compound detection, and discloses a method for determining the content of azodicarbonamide in a rubber and plastic thermal insulation product. The method comprises the following steps: 1) preparing a standard solution; 2) drawing a standard curve; 3) accelerated solvent extraction (ASE) treatment is performed on the sample, and specific parameters of the sample ASE treatment are as follows: the extraction solvent is N, N-dimethylformamide (DMF) with the volume of 100%, the extraction pressure is 1500 psi, the solvent flushing volume is 60% of the volume of a pool, the extraction pool is a stainless steel extraction pool with the volume of 34 mL, nitrogen purging is performed for 100 s, the extraction temperature is 65-85 DEG C, the extraction time is 5-15 min, and the cycle index is 1-2 times; (4) the sample is subjected to high performance liquid chromatography (HPLC) determination, and the test conditions of HPLC are as follows: a chromatographic column is ZORBAX SB-Aq (4.6 mm * 250 mm, 5 [mu] m); the column temperature is 30-40 DEG C; the mobile phase comprises the following components in percentage by volume: 80-100% of ultrapure water and 0-20% of methanol; the flow rate is 0.8 to 1.0 mL / min; and the wavelength of a DAD detector is 244 to 275 nm. According to the method, the ASE pretreatment technology is applied, selective extraction and online purification can be achieved through the ASE method, and the content of azodicarbonamide in the rubber and plastic heat preservation product can be accurately detected.

Description

Technical Field

[0001] The invention relates to the technical field of compound detection, and in particular to a method for determining the content of azodicarbonamide in rubber and plastic thermal insulation products. Background Art

[0002] Azodicarbonamide is a non-flammable, odorless yellow powder with strong polarity. It is insoluble in most organic reagents. It will quickly hydrolyze into biurea under heating conditions and release nitrogen, ammonia, carbon monoxide and carbon dioxide. In industrial production processes, azodicarbonamide is a common foaming agent, widely used in food, textiles, leather, rubber and other fields. Studies have found that azodicarbonamide will turn into biurea under moist conditions, and biurea will degrade to form semicarbazide under certain conditions. Semicarbazide belongs to the hydrazine chemical family and is a carcinogen that can damage biological DNA and affect the functioning of the endocrine system and nervous system. Therefore, it is very necessary to detect and monitor azodicarbonamide in products.

[0003] The European Union, Singapore, Japan and other countries have banned the use of azodicarbonamide as a food additive; in 2019, the new test standard of STANDARD 100 of the International Textile and Leather Ecological Research and Testing Association (OEKO-TEX®) requires that the limit value of azodicarbonamide for all product levels must be less than 1000 mg / kg. At present, GB 5009.283-2021 "National Food Safety Standard Determination of Azodicarbonamide in Food" and GB 1886.108-2015 "National Food Safety Standard Food Additive Azodicarbonamide" provide detection methods for azodicarbonamide in food and food additives. So far, there is no report on the detection method of azodicarbonamide in rubber and plastic insulation products. Therefore, it is of great significance to select a suitable pretreatment technology and detection method to determine the content of azodicarbonamide in rubber and plastic insulation products. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a method for determining the content of azodicarbonamide in rubber and plastic insulation products by liquid chromatography. The method uses accelerated solvent extraction (ASE) pretreatment technology. Compared with traditional pretreatment technology, the ASE method can achieve selective extraction and online purification, and has a small amount of solvent, high extraction efficiency, good repeatability, and can accurately detect the content of azodicarbonamide in rubber and plastic insulation products.

[0005] To achieve the above objectives, the present invention provides a method for determining the content of azodicarbonamide in rubber and plastic thermal insulation products, which uses accelerated solvent extraction (ASE) to extract the rubber and plastic thermal insulation product samples, and uses high performance liquid chromatography (HPLC) to detect and analyze the extracts.

[0006] In one embodiment of the present invention, the specific parameters of the accelerated solvent extraction method are: Extraction solvent: 100% volume N,N-dimethylformamide (DMF); Pressure: 1500psi; Extraction temperature: 65-85°C, preferably 70°C; Static extraction time: 5-15min, preferably 10min; Static cycle times: 1-2 times, preferably 2 times; DMF solvent volume for flushing: 60% of the cell volume; Extraction cell volume: 34mL stainless steel extraction cell; Nitrogen purge: 100 s.

[0007] The extraction temperature, static extraction time and static cycle number of the present invention can directly affect the solvent extraction efficiency. For the extraction of azodicarbonamide, when the extraction temperature is 70° C., the static extraction time is 10 min, and the static cycle number is 2 times, the extraction efficiency is the best and the recovery rate is the highest.

[0008] In one embodiment of the present invention, the test conditions of the high performance liquid chromatography are: Chromatographic column: ZORBAX SB-Aq, specification: 4.6mm×250mm, 5μm; Column temperature: 30~40℃, preferably 30℃; Mobile phase: by volume: 80-100% ultrapure water, 0-20% methanol, preferably 100% ultrapure water; Flow rate: 0.8~1.0mL / min, preferably 0.80mL / min; DAD detector wavelength: 244~275nm, preferably 244nm.

[0009] The column temperature of the present invention can directly affect the column pressure. As the column temperature increases, the column pressure decreases significantly, and the chromatographic peak area remains basically unchanged. When the column temperature is 30°C, the analyte and the solvent peak separation are high, so the preferred column temperature is 30°C. The mobile phase of the present invention can affect the retention of the analyte and the peak shape of the chromatographic peak. When 100% volume of ultrapure water is used as the mobile phase, a regular peak shape, a stable baseline, a chromatographic peak with good reproducibility of peak area and retention time can be obtained, so the preferred mobile phase is 100% volume of ultrapure water. The flow rate of the present invention can affect the retention time, separation and column pressure of the analyte. When the flow rate is 0.8mL / min, the column pressure is low and the separation is good, so the preferred flow rate is 0.8mL / min. The wavelength of the DAD detector of the present invention can affect the retention time and responsiveness of the analyte. When the wavelength of the DAD detector is 244nm, the analyte response is high and the separation degree with the solvent peak is good, so the preferred DAD detector wavelength is 244nm.

[0010] In one embodiment of the present invention, the method for determining the content of azodicarbonamide in the rubber-plastic thermal insulation product comprises the following steps: Step 1: Preparation of standard solution (1) Preparation of standard stock solution: Weigh azodicarbonamide standard sample and dilute it with dilution solvent to obtain a standard stock solution with a concentration of 1000 mg / L; (2) Preparation of standard solution: Pipette a certain amount of azodicarbonamide standard stock solution into a volumetric flask and dilute it to volume with a dilution solvent to obtain multiple standard working solutions of 0.5 to 100 mg / L; Wherein, the diluting solvent is N,N-dimethylformamide.

[0011] Step 2: Drawing of standard curve The plurality of standard working solutions are measured respectively by high performance liquid chromatography to obtain a standard working curve; Step 3: Sample processing Weigh a certain amount of shredded rubber and plastic insulation products and mix them with quartz sand, then put them into the ASE stainless steel extraction pool. The extraction pool is sent into the heating furnace by a conveyor device, heated and pressurized, and static extraction is performed at the set temperature and pressure. DMF solvent for flushing is added to the extraction pool in small amounts for many times. The extract automatically passes through the filter membrane and enters the collection bottle. Nitrogen is purged of the residual solvent in the extraction pool and pipeline to obtain the extract; Among them, the specific parameters of the sample processing ASE extraction method are: Extraction solvent: 100% volume N,N-dimethylformamide (DMF); Pressure: 1500psi; Extraction temperature: 70℃; Static extraction time: 10min; Static cycle times: 2 times; DMF solvent volume for flushing: 60% of the cell volume; Extraction cell volume: 34mL stainless steel extraction cell; Nitrogen purge: 100s; Step 4: Sample determination The extract was fixed to volume with N,N-dimethylformamide (DMF), and the extract was determined by HPLC using an external standard method; Among them, the test conditions of HPLC are: Chromatographic column: ZORBAX SB-Aq, specification: 4.6mm×250mm, 5μm; Column temperature: 30°C; Mobile phase: by volume: 100% ultrapure water; Flow rate: 0.8 mL / min; DAD detector wavelength: 244 nm.

[0012] The method of the present invention has the following advantages: (1) Developed a method for detecting the content of azodicarbonamide in rubber and plastic insulation products using high performance liquid chromatography, filling the gap in the detection of azodicarbonamide in the field of rubber and plastic insulation products; (2) The accelerated solvent extraction method was used for sample pretreatment. Compared with the traditional pretreatment method, the accelerated solvent extraction method can achieve selective extraction and online purification, and has the advantages of low solvent consumption, high extraction efficiency, good repeatability, and taking into account the accuracy, simplicity, and greenness of the pretreatment requirements. It can accurately detect the content of azodicarbonamide in rubber and plastic insulation products. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of accelerated solvent extraction of the present invention; Figure 2 The liquid chromatography spectrum of the standard solution of azodicarbonamide with a concentration of 20 mg / L of the present invention; Figure 3 is the standard working curve of azodicarbonamide of the present invention; DETAILED DESCRIPTION

[0014] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0015] Unless otherwise specified in the present invention, the ratio of each substance in the mobile phase in the embodiments is a volume ratio.

[0016] Figure 1The accelerated solvent extraction schematic diagram of the present invention comprises the following steps: loading the sample into an extraction cell and placing it on a disc conveyor; setting the extraction conditions (temperature, pressure, time, solvent, etc.) on the instrument operation panel; the disc conveyor conveys the extraction cell into a heating furnace chamber and connects it to a relatively numbered collecting bottle; a pump conveys the extraction solvent into the extraction cell; the extraction cell is heated and pressurized in the heating furnace; static extraction is performed at the set temperature and pressure; a flushing solvent is added to the extraction cell in small amounts multiple times; the extract automatically passes through a filter membrane into the collecting bottle; the extraction cell and the pipeline are purged with N2; and all the extract enters the collecting bottle for analysis.

[0017] Figure 2 It is a liquid chromatography spectrum of the azodicarbonamide standard solution with a concentration of 20 mg / L of the present invention, the abscissa is the retention time, the ordinate is the peak intensity value, wherein 4.971 min is the peak time of the analyte azodicarbonamide, and 5.861 min is the peak time of the solvent peak (N,N-dimethylformamide).

[0018] Figure 3 For the azodicarbonamide standard working curve of the present invention, standard series solutions with concentrations of 0.50, 1.00, 5.00, 10.00, 20.00, 50.00, and 100.00 mg / L are injected in sequence from low concentration to high concentration, and a linear regression is performed with the target concentration (mg / L) as the abscissa and the external standard peak area as the ordinate to draw a standard curve.

[0019] Example 1: Determination of azodicarbonamide content in rubber and plastic insulation products This embodiment provides a method for determining the content of azodicarbonamide in a rubber and plastic thermal insulation product, the method comprising the following steps: (1) Preparation of standard solution Standard stock solution: Weigh 0.1 g (accurate to 0.0001 g) of azodicarbonamide standard sample into a 100 mL volumetric flask, dilute to volume with N,N-dimethylformamide, and shake well to obtain a standard stock solution with a concentration of 1000 mg / L.

[0020] Preparation of standard solutions: Pipette 0.05, 0.10, 0.50, 1.00, 2.00, 5.00, and 10.00 mL of the standard stock solution into seven 100 mL volumetric flasks, dilute to volume with diluent, shake well, and obtain seven standard working solutions of 0.50 to 100 mg / L.

[0021] (2) Drawing of standard curve The plurality of standard working solutions are measured respectively by high performance liquid chromatography (HPLC) to obtain a standard working curve; (3) Sample processing At room temperature, weigh 1.0g (accurate to 0.0001g) of shredded rubber and plastic insulation products, put them into a stainless steel extraction cell, add quartz sand to mix with the sample, and fill the empty space on the top with quartz sand to save solvent consumption. Put the stainless steel extraction cell into the ASE instrument and perform heating, pressurization and static extraction according to the extraction method. The extract is automatically filtered into the collection bottle with the solvent, and the filtrate in the collection bottle is fixed to 50mL with DMF to obtain the sample to be tested.

[0022] Among them, the specific parameters of the sample processing ASE extraction method are: Extraction solvent: 100% volume N,N-dimethylformamide (DMF); Extraction solvent dosage: 40mL Pressure: 1500psi; Extraction temperature: 70℃; Static extraction time: 10min; Static cycle times: 2 times; The volume of DMF solvent used for washing: 60% of the cell volume; Extraction cell volume: 34mL stainless steel extraction cell; Nitrogen purge: 100 s.

[0023] (4) Sample measurement Under the same conditions as in step 2, the sample to be tested is injected into a liquid chromatograph for HPLC determination, and the external standard method is used for quantification. The peak area is substituted into the standard curve to obtain the concentration of azodicarbonamide in the sample to be tested. The mass of azodicarbonamide obtained by conversion divided by the mass of the sample is the content of azodicarbonamide in the sample; Among them, the test conditions of HPLC are: Chromatographic column: ZORBAX SB-Aq, specification: 4.6mm×250mm, 5μm; Column temperature: 30°C; Mobile phase: by volume: 100% ultrapure water, Flow rate: 0.8 mL / min DAD detector wavelength: 244 nm.

[0024] The following describes the results of measurements using the measurement method of the present invention.

[0025] 1) Linear correlation coefficient of azodicarbonamide The test of 7 standard working solutions in step (2) showed that azodicarbonamide showed a good linear relationship in the range of 0.50 to 100 mg / L, with a correlation coefficient greater than 0.999. The results are shown in Table 1 and the liquid chromatogram is shown in Figure 2 , the linear regression equation is shown in Figure 3 .

[0026] Table 1 Retention time, linear equation and correlation coefficient of azodicarbonamide

[0027] 2) Detection limit The blank rubber and plastic insulation samples with a spiked concentration of 0.50 mg / L were processed and measured, and the standard deviation of n=7 parallel measurements was calculated. When the degree of freedom was 6 and the confidence level was 99%, the t value was 3.143. The summary of the method detection limit and the lower limit of determination is shown in Table 2. After calculation, the detection limit of azodicarbonamide concentration was 0.10 mg / L, and the lower limit of determination was 0.40 mg / L. When the sample size was 1.000 g and the fixed volume was 50 mL, the detection limit was 5 mg / kg and the lower limit of determination was 20 mg / kg.

[0028] Table 2 Test data of method detection limit and determination lower limit of azodicarbonamide

[0029] 3) Spike recovery experiment Three rubber and plastic insulation samples were taken and the standard addition method was used to quantitatively add azodicarbonamide to each sample. Six parallel samples were tested at each concentration, and the spike recovery rate was calculated. The results are shown in Table 2. It was calculated that the spike recovery rate of azodicarbonamide was 86.0%~101.5%.

[0030] Table 3 Data table of spiked recovery of azodicarbonamide

[0031] 4) Precision experiment The blank matrix rubber and plastic insulation samples with spiked concentrations of 0.50g / kg, 2.00g / kg and 5.00g / kg were spiked as low, medium and high concentration blank matrix samples, and 6 parallel samples were tested for each concentration, and their average value, standard deviation, relative standard deviation, etc. were calculated, and their precision data were statistically analyzed. It can be seen from the calculation that the relative deviation of azodicarbonamide is between 1% and 2%, the deviation is small, and the measurement result is highly accurate.

[0032] Table 4 Precision data of azodicarbonamide

[0033] Example 2 In this embodiment, the content of azodicarbonamide in the rubber and plastic thermal insulation product is determined in the same manner as in Example 1, with the only difference being that in the ASE extraction method of this embodiment, the extraction temperature is 70° C., the extraction time is 15 min, the extraction times are 2 times, and the other conditions are the same as in Example 1.

[0034] Example 3 In this embodiment, the content of azodicarbonamide in the rubber and plastic thermal insulation product is determined in the same manner as in Example 1, with the only difference being that the extraction temperature in the ASE extraction method of this embodiment is 65° C., the extraction time is 5 min, the extraction number is 1, and the other conditions are the same as in Example 1.

[0035] Example 4 In this embodiment, the content of azodicarbonamide in the rubber and plastic thermal insulation product is determined in the same manner as in Example 1, with the only difference being that the extraction temperature in the ASE extraction method of this embodiment is 65° C., the extraction time is 10 min, the extraction times are 2 times, and the other conditions are the same as in Example 1.

[0036] Example 5 In this embodiment, the content of azodicarbonamide in the rubber and plastic thermal insulation product is determined in the same manner as in Example 1, with the only difference being that the extraction temperature in the ASE extraction method of this embodiment is 85° C., the extraction time is 10 min, the extraction times are 2 times, and the other conditions are the same as in Example 1.

[0037] Example 6 In this embodiment, the content of azodicarbonamide in the rubber and plastic thermal insulation product is determined in the same manner as in Example 1, with the only difference being that the extraction temperature in the ASE extraction method of this embodiment is 85° C., the extraction time is 15 min, the extraction times are 2 times, and the other conditions are the same as in Example 1.

[0038] Example 7 This example uses the same method as Example 1 to determine the content of azodicarbonamide in rubber and plastic thermal insulation products, except that the HPLC chromatographic conditions in this example are: Column temperature: 30°C Mobile phase: by volume: 100% ultrapure water Flow rate: 0.8 mL / min DAD detector wavelength: 275nm Other conditions are the same as in Example 1.

[0039] Example 8 This example uses the same method as Example 1 to determine the content of azodicarbonamide in rubber and plastic thermal insulation products, except that the HPLC chromatographic conditions in this example are: Column temperature: 40°C Mobile phase: by volume: 80% ultrapure water, 20% methanol Flow rate: 1.0mL / min DAD detector wavelength: 244nm Other conditions are the same as in Example 1.

[0040] Comparative Example 1 The difference between this comparative example and Example 1 is that the sample is processed by ultrasonic extraction method, and the ultrasonic conditions are: ultrasonic power 400W, ultrasonic time 30min, ultrasonic temperature 50°C, and other conditions are the same as Example 1.

[0041] Experimental Example 1 The same product in this embodiment and the comparative example was tested for the peak time of the target azodicarbonamide, the extraction rate (the percentage of the extracted target content in the sample amount) and the precision. The test results of the embodiment and the comparative example are compared in Table 5.

[0042] Table 5: Extraction rate and precision data of azodicarbonamide in the examples and comparative examples

[0043] As shown in Table 5, the method for determining the content of azodicarbonamide in a rubber and plastic thermal insulation product of the present invention can obtain a chromatogram of an analyte with a regular peak shape and a stable baseline by optimizing the sample pretreatment method and liquid chromatography conditions. It can be seen from the comparison results of Example 1 with Examples 2-7 that the extraction rate of azodicarbonamide under the preferred conditions is higher and the repeatability is better. It can be seen from the comparison results of Example 1 with Example 8 that changing the volume ratio and flow rate of the HPLC mobile phase will affect the peak time of the analyte. It can be seen from the comparison results of Examples 1-8 with Comparative Example 1 that, compared with the traditional ultrasonic extraction method, the extraction rate and relative standard deviation of the pretreatment method of the present invention are better than those of Comparative Example 1.

[0044] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A method for determining the content of azodicarbonamide in rubber and plastic thermal insulation products, characterized in that: The rubber-plastic thermal insulation product sample is extracted by accelerated solvent extraction (ASE), and the extract is detected and analyzed by high performance liquid chromatography (HPLC).

2. The method for determining the content of azodicarbonamide in rubber and plastic thermal insulation products according to claim 1, wherein: The accelerated solvent extraction method is carried out at an extraction temperature of 65-85° C. for 5-15 minutes.

3. The method for determining the content of azodicarbonamide in rubber and plastic thermal insulation products according to claim 2, wherein: The extraction temperature is 70°C.

4. The method for determining the content of azodicarbonamide in rubber and plastic thermal insulation products according to claim 3, wherein: The extraction time is 10 min.

5. The method for determining the content of azodicarbonamide in rubber and plastic thermal insulation products according to claim 1, wherein: The test conditions of the high performance liquid chromatography are: Column temperature: 30~40℃; Mobile phase: by volume: 80~100% ultrapure water, 0~20% methanol; Flow rate: 0.8~1.0mL / min; DAD detector wavelength: 244~275nm.

6. The method for determining the content of azodicarbonamide in rubber and plastic thermal insulation products according to claim 5, wherein: The column temperature was 30°C.

7. The method for determining the content of azodicarbonamide in rubber and plastic thermal insulation products according to claim 5, wherein: The mobile phase is composed of 100% ultrapure water by volume.

8. The method for determining the content of azodicarbonamide in rubber and plastic thermal insulation products according to claim 5, wherein: The flow rate was 0.8 mL / min.

9. The method for determining the content of azodicarbonamide in rubber and plastic thermal insulation products according to claim 5, wherein: The DAD detector wavelength is 244 nm.

10. The method for determining the content of azodicarbonamide in rubber and plastic thermal insulation products according to claim 1, wherein: The steps include: (1) Preparation of standard solution Use N,N-dimethylformamide as a diluent to prepare multiple standard working solutions of 0.5 to 100 mg / L of azodicarbonamide; (2) Drawing of standard curve The plurality of standard working solutions are measured respectively by high performance liquid chromatography to obtain a standard working curve; (3) Sample processing The ASE extraction method was used for sample processing. The specific parameters of the sample processing ASE extraction method were as follows: Extraction solvent: 100% volume N,N-dimethylformamide (DMF); Pressure: 1500psi; Extraction temperature: 70℃; Static extraction time: 10min; Static cycle times: 2 times; The volume of DMF solvent used for washing: 60% of the cell volume; Extraction cell volume: 34mL stainless steel extraction cell; Nitrogen purge: 100s; (4) Sample measurement Determined by HPLC, quantified by external standard method; Among them, the test conditions of HPLC are: Chromatographic column: ZORBAX SB-Aq, specification: 4.6mm×250mm, 5μm; Column temperature: 30°C; Mobile phase: by volume: 100% ultrapure water; Flow rate: 0.8 mL / min; DAD detector wavelength: 244 nm.

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