GB/T 2677.9-1994 Determination of polypentose content in papermaking raw materials
Some standard content:
National Standard of the People's Republic of China
Fibrous raw material-Determination of pentosan1 Subject content and scope of application
This standard specifies the method for determining the content of pentosan in papermaking raw materials. This standard is applicable to various wood and non-wood plant fiber papermaking raw materials. 2 Reference standards
GB/T2677.1 Sampling of samples for analysis of papermaking raw materials GB/T2677.2 Determination of moisture content in papermaking raw materials 3 Principle
GB/T 2677.9--94
Replaces GB 2677.9-81
This determination method is to heat the sample with 12% (m/m) hydrochloric acid to convert the pentosan in the sample into furfural. The furfural content distilled out is quantitatively determined by volumetric method or colorimetric method, and then converted into pentosan content. 4 Reagents
4.112% (m/m) hydrochloric acid solution: Measure 307mL hydrochloric acid (p2o=1.19g/mL), dilute to 1000mL with water, add acid or water to adjust to P2o=1.0570g/mL.
4.21,3-dihydroxytoluene [CH;CH(OH), solution: Weigh 0.400g 1,3-dihydroxytoluene and 0.500g ferric chloride (FeCl3·6H,O), dissolve in 1000mL 11mol/L hydrochloric acid solution, this solution is prepared by diluting 915mL hydrochloric acid (p20=1.19g/mL) with water to 1 000mL. Note that the prepared solution should be stored in the refrigerator, and it needs to be prepared separately if it exceeds two weeks. 4.3 Sodium bromate-sodium bromide solution: weigh 2.5g sodium bromate and 12.0g sodium bromide (or weigh 2.8g potassium bromate and 15.0g potassium bromide), dissolve in a 1000mL volumetric flask, and dilute to scale. 4.4 Sodium thiosulfate standard solution [Ec(Na2S,O.)=0.1000mo1/L]: weigh 25.0g sodium thiosulfate (NazS.O:·5H,0) and 0.1g NazCO,, dissolve in 1000mL of freshly boiled and cooled distilled water, shake well and let stand for a week, filter, and calibrate its concentration. 4.5 Acetic aniline solution: measure 1mL of freshly distilled aniline in a small beaker, add 9mL of glacial acetic acid and stir evenly. 4.61 mol/L sodium hydroxide solution.
4.70.1% phenolic acid indicator: dissolve 0.1g phenolphthalein in 100mL.50% ethanol. 4.810% potassium iodide solution.
4.90.5% starch solution.
4.1095% ethanol.
4.11 Sodium chloride.
4.12 Xylose (C.H1oO.).
5 ApparatusbZxz.net
5.1 Furfural distillation apparatus (as shown), its components are as follows: Approved by the State Administration of Technical Supervision on September 24, 1994 216
Implemented on March 1, 1995
5.1.1500mL round bottom flask.
5.1.2 Serpentine condenser.
GB/T 2677.9 ---94
Diagram of furfural distillation apparatus
1 Round bottom flask; 2- Condenser; 3- Separating funnel; 4- Receiving flask 5.1.3 Separating funnel with a capacity of 60mL.
5.1.4 500mL receiving flask with 30mL interval scale. 5.2 Temperature-controlled electric furnace.
5.3 Temperature-controlled porous water bath.
5.4 Spectrophotometer.
5.5 Volumetric flask: 50mL and 500mL.
5.6 Conical flask with stopper: 500mL and 1000mL. 6 Sampling and treatment
Sampling and treatment shall be carried out in accordance with the provisions of GB/T2677.1. 7 Test steps and result calculation
7.1 Volumetric method
7.1.1 Distillation of furfural
Weigh the sample (0.5 g if the polypentose content in the sample is higher than 12%, and 1 g if it is lower than 12%), accurate to 0.1 mg, (while weighing another sample to determine the water content according to GB/T2677.2), and place it in a 500 mL round-bottom flask (5.1.1). Add 10 g of sodium chloride (4.11), install a condenser (5.1.2) and a separatory funnel (5.1.3), pour a certain amount of 12% hydrochloric acid into the separatory funnel, adjust the temperature of the electric furnace to make the contents of the round-bottom flask boil, and control the distillation rate to distill 30 mL of distillate every 10 minutes. After that, whenever 30 mL is distilled out, add 30 ml of 12% hydrochloric acid from the separating funnel to the flask. When a total of 300 mL of distillate is distilled out, use acetic acid aniline solution (4.5) to check whether the furfural is completely distilled. For this purpose, collect 1 mL of distillate from the lower end of the condenser with a test tube, add 1 to 2 drops of phenolic acid indicator (4.7), drop into 217
GB/T 2677.9 --94
1mol/L sodium hydroxide solution (4.6) to neutralize until it just turns slightly red, then add 1 mL of newly prepared acetic acid aniline solution. If it turns red after standing for 1 minute, it proves that the furfural has not been completely distilled and distillation must be continued. If it does not turn red, it means that the distillation is complete. After the distillation of furfural is completed, transfer the distillate in the receiving bottle (5.1.4) into a 500mL volumetric flask (5.5), rinse the receiving bottle with a small amount of 12% hydrochloric acid, and pour all the washing liquid into the volumetric flask, then add 12% hydrochloric acid to the scale, shake well to obtain distillate A. 7.1.2 Determination of furfural and calculation of results
7.1.2.1 Dibromination method
Use a pipette to draw 200mL of distillate A into a 1000mL conical flask (5.6), add 250g of crushed ice made of distilled water, and when the distillate drops to 0℃, add 25.0mL of sodium bromate-sodium bromide solution (4.3), quickly plug the bottle, and place it in a dark place for 5min. At this time, the solution temperature should be maintained at 0℃.
After the specified time, add 10 mL of 10% potassium iodide solution (4.8), quickly plug the bottle, shake well, place in the dark for 5 minutes, and titrate with 0.1000 mol/L sodium thiosulfate standard solution (4.4). When the solution turns light yellow, add 2-3 mL of 0.5% starch solution (4.9) and continue titrating until the blue disappears. Draw 200 mL of 12% hydrochloric acid solution (4.1) and perform a blank test according to the above operation. The furfural content X (%) is calculated according to formula (1):
X=-V5: 048 × 500 × 100
Wherein: V-the volume of 0.1000mol/L sodium thiosulfate standard solution consumed in the blank test, mL; V2——the volume of 0.1000mol/L sodium thiosulfate standard solution consumed in the sample, mL; c—the concentration of sodium thiosulfate standard solution, mol/L; m-
—the absolute dry mass of the sample, g,
·(1)
0.048——the mass of furfural equivalent to 1.0mL sodium thiosulfate standard solution [c(Na2S2O3)=0.1000mol/L], g. 7.1.2.2 Tetrabromination method
Use a pipette to draw 200 mL of distillate A into a 500 mL conical flask (5.6), then draw 25.0 mL of sodium bromate-sodium bromide solution into the conical flask, quickly plug the bottle, and place it in a dark place for 1 hour. At this time, the solution temperature is controlled at 20-25°C. After the specified time, add 10 mL of 10% potassium iodide solution (4.8), quickly plug the bottle, shake well, place it in a dark place for 5 minutes, and titrate with 0.1000 mol/L sodium thiosulfate standard solution (4.4). When the solution turns light yellow, add 2-3 mL of 0.5% starch solution (4.9) and continue to titrate until the blue disappears. Pipette 200 mL of 12% hydrochloric acid solution (4.1) and perform a blank test according to the above operation. The furfural content X (%) is calculated according to formula (2):
X = VV)c0. 024 × 500 × 100200m
Wherein: V1—the volume of 0.1000mol/L sodium thiosulfate standard solution consumed in the blank test, mL; V,—the volume of 0.1000mol/mL sodium thiosulfate standard solution consumed in the sample, mL; c——the concentration of sodium thiosulfate standard solution, mol /L; m
—the absolute dry mass of the sample, g;
(2)
the mass of furfural equivalent to 1.0mL sodium thiosulfate standard solution [c(NazS,0,)=0.1000mol/L], g. 7.1.2.3 Calculation of polypentose
The polypentose content Y (%) in the sample is calculated according to formula (3): 218
GB/T 2677.9-94
a coefficient. When the sample is wood plant fiber, K=1.88; When the sample is non-wood plant fiber, K=1.38. Where: K-
7.2 Colorimetric method
7.2.1 Distillation of furfural
Same as test step 7.1.1.
7.2.2 Determination of furfural and calculation of results
(3)
Pipette 5mL of distillate A and 25mL of 1,3-dihydroxytoluene solution into a 50ml volumetric flask (5.5), shake well, place in a constant temperature water bath at 25±1℃, take out after 60±5min, add 95% ethanol (4.10) to the scale, and place in a constant temperature water bath at 25±1℃ to cool down. When the temperature of the volumetric flask drops to 25±1℃, add an appropriate amount of 95% ethanol to the scale. Starting from the first addition of ethanol, 60 ± 5 minutes later, use a spectrophotometer (5.4) at 630nm, use a blank solution to adjust the instrument's absorption value to zero, and then measure the absorption value of the solution to be tested. To prevent acid mist from corroding the instrument during measurement, the colorimetric cell should be covered. According to the measured absorption value, find the mass a (mg) of polypentose in the standard curve. Use 5mL of 12% hydrochloric acid solution (4.1) to replace the distillate A, and prepare a blank solution according to the above operation. The polypentose Y (%) in the sample is calculated according to formula (4): Y
The mass of polypentose found from the standard curve, mg; where: a——
m—absolute dry mass of the sample, g;
K—coefficient, when the sample is wood plant fiber, K=0.73; when the sample is non-wood plant fiber, K=1. (4)
7.2.3 Drawing of standard curve: Weigh about 40.80, 120, 160, and 200 mg of xylose, accurate to 0.1 mg, and distill and determine furfural according to the colorimetric method in the above test step 7.2 to obtain a series of absorption values of the distillate. Convert the mass of xylose to the mass of polypentose, polypentose (mg) = xylose (mg) × 0.88. Draw a standard curve with the mass of polypentose (mg) as the horizontal axis and the corresponding absorption value as the vertical axis. 7.3 Perform two determinations at the same time, and take their arithmetic mean as the determination result. The determination result is calculated to the second decimal place. The difference between the calculated values of the two determinations should not exceed 0.40%.
Test report
a. The number of this national standard;
Indicate the determination method used (volume method or colorimetry); b.
Test results and necessary explanations;
Any abnormal phenomena observed during the test; d.
Any operation that is not specified in this national standard or the referenced standard and may affect the results. Additional notes:
This standard is proposed by the China Light Industry General Association.
This standard is under the jurisdiction of the National Technical Committee for Standardization of Paper Industry. This standard was drafted by the Paper Industry Scientific Research Institute of the Ministry of Light Industry. The main drafters of this standard were Chen Qizhao, Zhu, and Zhang Guilan. This standard was first published in 1961 and revised for the first time in 1981. This standard refers to the American Pulp and Paper Association standard TAPPIT223cm-84 "Polypentoses in Wood and Pulp". 219
Tip: This standard content only shows part of the intercepted content of the complete standard. If you need the complete standard, please go to the top to download the complete standard document for free.