GB/T 9104.9-1988 Test method for industrial stearic acid Determination of composition GB/T9104.9-1988 standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Test methods for industrial stearic acids-Determination of components
1 Subject content and scope of application
This standard specifies the method for determining the composition of industrial stearic acid by gas-liquid chromatography. This standard is applicable to the determination of the composition of industrial stearic acid. 2 Principle
UDC 668.1.012
：543.06
GB 9104.9--88
This method adopts gas-liquid chromatography. After industrial stearic acid is methylated, it is separated in a chromatographic column. The content of fatty acids with different carbon numbers is calculated by the normalized method based on the area of ​​the obtained chromatogram.
3 Reagents
3.1 Standard fatty acids, chromatographically pure C16 and C18 saturated fatty acids3.2 Anhydrous methanol
3.3 Sulfuric acid (GB 625), density 1.84 g/mL. 3.4 Ether (HG 3-1002)
4 Instruments
4.1 Chromatograph, equipped with the following units
4.1.1 Filling column 2~~3m long, 3~4mm inner diameter, filled with stationary phase (such as DEGS coated on 80~100 mesh white carrier), chromatographic peaks of fatty acids with different carbon numbers should be well separated. 4.1.2 Flame ionization detector.
4.1.3 Electronic integrator or integrator
When these two instruments are not available, the peak area can be calculated by multiplying the peak height by the half peak width. 4.1.4 Recorder
4.1.5 Microsyringe 1μL or 10μL. 4.2 Volumetric flask 5mL.
5 Test procedure
5.1 Methylation
Take about 0.1% of the sample in a 5mL volumetric flask and add 2~3mL of anhydrous methanol. After heating and dissolving in a water bath, add 5~8 drops of concentrated sulfuric acid, shake well, let stand for about 10 minutes, add 3~4mL of distilled water and 0.5~1mL of ether, shake vigorously and extract for 1min, let stand and separate, and take the upper ether phase for chromatographic analysis. Approved by the Ministry of Light Industry of the People's Republic of China on April 30, 1988 116
Implemented on October 1, 1988
Standard fatty acids are methylated in the same way. 5.2 Chromatographic analysis
5.2.1 Chromatographic instrument settingswww.bzxz.net
5.2.1.1 Injection port, temperature is 300℃. 5.2.1.2 Column temperature
single. Constant temperature
GB9104.9—88
According to the column used, the temperature of DEGS column is 180℃. b. Program temperature rise
The starting temperature is between 150～~180℃, and the temperature is increased at a rate of 3~～5℃/min to a final temperature of 200～240℃. 5.2.1.3 Carrier gas
According to the diameter and length of the column, the flow rate can be 30～50mL/min. 5.2.1.4 Identifier temperature, greater than 250℃. 5.2.2 Introduction of the sample
Use a syringe (4.1.5) to take about 0.5μL of the solution (5.1) and inject it into the injection port of the chromatogram, so that the obtained chromatogram peak height is appropriate. A typical chromatogram is shown in the figure below
Stearic acid chromatogram
5.3 Inspection of the chromatogram
5.3.1 Qualitative analysis
Compare the sample chromatogram with the chromatogram of the methyl ester of the standard fatty acid (3.1) to identify the composition of the sample. 5.3.2 Quantitative analysis
Use an electronic integrator or a quadrature meter (4.1.3) to determine the peak area of ​​each carbon number of fatty acid and calculate the total peak area. 117
Calculation of results
Where: B: --- the percentage of the fatty acid with carbon number i, %, A-- the peak area of ​​the chromatogram of the fatty acid with carbon number i: A-- the sum of the peak areas of the fatty acids with carbon number i. 7 Precision
GB9104.9-88
For C16 and C18 fatty acids, the standard deviation of this method is less than ±0.306Additional remarks:
This standard is proposed by the Ministry of Light Industry of the People's Republic of China. This standard is under the technical jurisdiction of the Daily Chemical Industry Scientific Research Institute of the Ministry of Light Industry. This standard was drafted by the Daily Chemical Industry Scientific Research Institute of the Ministry of Light Industry. The main drafter of this standard is Xu Shuyi.
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