GB/T 4499-1997 Determination of antioxidants in vulcanized rubber - Thin layer chromatography

This standard specifies the determination method of antioxidants in vulcanized rubber and compounded rubber. This standard is applicable to the determination of antioxidants in vulcanized rubber or compounded rubber by thin layer chromatography. GB/T 4499-1997 Determination of antioxidants in vulcanized rubber by thin layer chromatography GB/T4499-1997 Standard download decompression password: www.bzxz.net

GB/T 4499—1997
This standard adopts ISO4645:1984 "Determination of antioxidants in raw rubber, mixed rubber and vulcanized rubber by thin layer chromatography" in a non-equivalent manner. This standard is simpler than ISO4645-1984 in sample pretreatment. ISO.4645:1984 requires the use of a chromatographic column to remove oil from samples with excessive oil content, while this standard improves this method by using ethanol for extraction, taking the ethanol layer for spotting, or first developing and drying the thin layer plate after spotting in petroleum ether, and then developing and developing in the required developing agent, which simplifies the experimental operation. ISO4645:1984 stipulates that different antioxidants use different developing agents and coloring agents, including method A and method B, which are cumbersome and difficult to master, while the developing agents and coloring agents used in this standard are applicable to all types of antioxidants and are simple and easy to use. ISO4645:1984 only specifies one specification for glass plates, which is easy to cause waste when there are few samples. In this standard, there are three different specifications of glass plates. In the experiment, different specifications of thin layer plates can be selected according to the number of samples. This standard basically follows the content of the original standard GB4499--84, corrects the errors in the previous version, emphasizes that the ambient temperature during the development of thin layer chromatography should not be lower than 18℃, and makes appropriate supplements to relevant technical issues. From the date of entry into force, this standard will replace GB4499-84. This standard is proposed by the Ministry of Chemical Industry of the People's Republic of China. This standard is under the jurisdiction of the Beijing Rubber Industry Research and Design Institute of the Ministry of Chemical Industry. The drafting unit of this standard: Beijing Rubber Industry Research and Design Institute. The main drafters of this standard: Qiu Jianmin and Kang Li. This standard was first issued in June 1984.
This standard is entrusted to the Beijing Rubber Industry Research and Design Institute for interpretation. 641bZxz.net
National Standard of the People's Republic of China
Determination of antidegradant content in vulcanized rubber
Thin layer chromatography
Vuicanized rubber-Determinationof antidegradant content-Thin layerchromatographic method
Safety statement recommended for use in this committee test method standard: GB/T 4499-1997
neqIsO4645:1984
Replaces GB4499--84
Warning Personnel using this standard should be familiar with regular laboratory operating procedures. This standard does not purport to cover all safety issues that may arise from the use of this standard. It is the user's responsibility to establish appropriate safety and health systems and ensure compliance with relevant national regulations. 1 Scope
This standard specifies the method for the determination of antioxidants in vulcanized rubber and compounded rubber. This standard is applicable to the determination of antioxidants (aldehyde amines, ketone amines, secondary amines, p-phenylenediamines, bisphenols, polyphenols and phosphates) in vulcanized rubber or compounded rubber by thin layer chromatography. 2 Referenced standards
The provisions contained in the following standards constitute the provisions of this standard by reference in this standard. When this standard is published, the versions shown are valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T3516-94 Determination of solvent extracts in rubber 3 Principle
During the thin layer chromatography process, due to the different chemical structures of antioxidants, the distribution coefficients in the liquid-solid phase are different, thereby achieving the purpose of separation. Spotting, development and color development are carried out on a glass plate coated with silica gel. Then the corresponding antioxidant is determined according to the color, shape and relative shift value R of the spots in the spectrum.
4 Reagents
In the experiment, except for special provisions, only analytical reagents and distilled water or water of equal purity should be used. All recognized health and safety precautions should be effective when conducting this test. 4.1 Developing agent (all in volume ratio)
4.1.1 Toluene + anhydrous ethanol + ammonia water = 100 + 0.5 + 0.05. 4.1.2 Toluene + acetone + ammonia water = 100 + 10 + 0.2. 4.2 Color developer
4.2.1 2.6-Dichloroaldehyde chloroimide ethanol solution: 0.2% (m/m) (prepare before use or store in a refrigerator after preparation). 4.2.2 Buffer spray (used in conjunction with 4.2.1): 23.4g sodium tetraborate and 3.5g sodium hydroxide are dissolved in 1000mL distilled water. 4.3 Thin layer plate adsorbent: silica gel-G (for thin layer chromatography). 4.4 Thin layer adhesive: 0.1%~0.2% (m/m) sodium carboxymethyl cellulose solution, prepared the day before, take the clear solution when using. Approved by the State Bureau of Technical Supervision on September 26, 1997 642
Implementation on April 1, 1998
5 Instruments
GB/T4499—1997
5.1 Glass plate: Glass plates with specifications of 200mm×50mm, 200mm×70mm, and 200mm×200mm can be selected. 5.2 Coating device: A device that can evenly coat a silica gel layer with a thickness of 0.2mm~0.3mm on the glass plates of the above specifications 5.3 Oven: The temperature can be controlled at (110±5)℃. 5.4 Spotter: Glass capillary or micro-syringe. 5.5 Chromatographic development cylinder: Select a suitable sealed glass cylinder. 5.6 Extraction device; according to GB/T3516.
5.7 Spray bottle: glass spray bottle or medical throat sprayer. 6 Preparation of thin layer plate and developing cylinder
6.1 Preparation of thin layer plate: Mix 4.3 and 4.4 in a ratio of 1:2 (m/m) to make a paste, and apply the paste silica gel on the glass plate with an applicator. Let it dry at room temperature until the silica gel solidifies. The coating thickness should be kept at 0.2mm~0.3mm. Then put it in an oven and dry and activate it at (100±5)℃ for 1.5h~2h.
The activated thin layer plate should be stored in a desiccator, but not more than 4d, otherwise it should be activated again before use. 6.2 Preparation of developing cylinder: Add the developing agent selected for the test into the developing cylinder, and the liquid level should be 15mm~20mm from the bottom of the cylinder. Stir it slightly and let it stand for use. The developing agent can be reused several times. 7.1. Preparation of the sample
7.1.1 Weigh 2.5g~3.0g of the sample cut into 1mm2, wrap it with filter paper and put it into the extractor, extract it with acetone or anhydrous ethanol for 2h~~4h, and concentrate the extract to about 5mL at a temperature below 50℃ for standby use. Other methods can also be used to avoid thermal decomposition of the antioxidant. For example, soak it in acetone or anhydrous ethanol at room temperature overnight. It can also be soaked in chloroform at room temperature for 30min, and the clear liquid is taken for testing. 7.1.2 If the oil content in the sample is too high and affects the results, it can be extracted with anhydrous ethanol. After concentration and cooling, the oil and ethanol are separated into layers, and the ethanol layer is taken for testing, or the thin layer plate with the sample extract is first developed in petroleum ether to the top of the thin layer plate, and the thin layer plate is taken out and dried naturally in a ventilated place, and then developed and colored in the required developer. 7.2 Spotting
7.2.1 The best chromatogram can be obtained when the spotting volume is about 0.005mL, and it should not exceed 0.01mL at most. If the volume is too large, the spots after development are not easy to concentrate. For this reason, the concentration of the extract can be appropriately adjusted to obtain the best chromatogram within the limited spotting volume. 7.2.2 Lightly draw a baseline 25mm away from one end of the thin layer plate, and lightly draw an upper limit line 150mm away from the baseline. Use a capillary or micro-syringe to spot on the baseline. The spotting spot should be as small as possible, and the maximum diameter should not exceed 6mm. Too large will affect the separation effect. Several sample spots can be spotted on the same plate, and the interval between each spot should not be less than 15mm. After the spotting spot is slightly dry, it can be developed. 7.3 Development
Place the thin layer plate with the sample extract spotted with the end of the spot facing down in the cylinder. In order to ensure that the cylinder is saturated with the vapor of the developing agent during development, a piece of filter paper can be attached to the inner wall of the development cylinder. Do not open the cover of the development cylinder during development. When the developing agent rises to the upper limit, take out the plate and dry it for color development. The ambient temperature should not be lower than 18°C ​​during development, otherwise the resolution will be affected. 7.4 Color development
Spray the developed thin layer plate with 4.2.1, dry it and then spray it with 4.2.2, and the spot color will appear. Identify it after the color development is stable (about 30 minutes).
8 Experimental results
8.1 The ratio shift value R is calculated according to formula (1):
GB/T4499-1997
Where: a—the distance from the baseline to the center of the spot, mm; A-the distance from the baseline to the upper limit, mm.
（1）
8.2 Result judgment: Compare the standard spectrum of each laboratory with the sample spectrum, and preliminarily determine the category of antioxidant according to the color, shape and R value of the spots. Then use the predicted antioxidant to select a suitable solvent to dissolve and prepare a solution. On the same thin layer plate, the sample extract and the estimated antioxidant are sampled, developed, and color-developed according to the above method for comparison, and the result can be finally determined. 9 Standard spectrum
9.1 Take the raw antioxidant as the standard sample, dissolve it with a suitable solvent, and prepare a solution with a concentration of 1 to 10 mg/mL. Sample, develop, and color according to the above method. Record the obtained spectrum with color photography or colored pens. 9.2 Because many complex antioxidants contain different components and have a variety of spot shapes, some even have tailing strips, etc. Therefore, accurate graphics and photos are more important than using only a single color and R value. The color and shape of the spots are more helpful for result judgment. 61
GB/T4499—1997
Appendix A
(Suggestive Appendix)
The choice of developing agent and color developer depends on the specific situation encountered by the analyst. The following developing agents and color developers are for reference. A1Developing agent (all by volume ratio)
A1.1n-heptane + ethyl acetate = 90 + 10.
A1.2 Toluene.
A1.3 Toluene + ethyl acetate = 95 + 5.
A1.4 Cyclohexane + diethylamine = 75 + 25.
A1.5 Toluene + n-heptane 50 + 50.
A2 Color developer
A2.11g diazotized p-aminobenzenesulfonic acid, 1g p-aminobenzenesulfonic acid and 1g potassium nitrite are dissolved in 200mL 1mol/L hydrochloric acid. A2.2 Benzoyl peroxide toluene solution 40g/L (for use on the same day). A2.3 Toulon's reagent: Mix 0.5mL 5% silver nitrate solution and 2 drops of 2mol/L sodium hydroxide solution. Add 2% nitrogen aqueous solution (V/V) to the precipitate until the precipitate disappears, and add an equal volume of 95% (V/V) ethanol solution. A2.4 Bismuth nitrate solution: Dissolve 7.5g anhydrous bismuth nitrate in a mixture of 1mL nitric acid and 150mL water. A2.5 0.1% (m/m) 2.6-dichloroquinone chloroimide ethanol solution. A2.6 Buffered spray used together with 2.5: Dissolve 23.4g sodium tetraborate decahydrate and 3.3g sodium hydroxide in 1000mL water.
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