1 Subject content and scope of application This standard specifies a method for the determination of sugar components in papermaking raw materials and pulp.
This standard can be applied to various papermaking raw materials and pulps obtained by various pulping methods.
2 Reference standards
GB 741 Pulp analysis moisture determination method
3 Principle Sulfuric acid is used to hydrolyze the cellulose and hemicellulose in the papermaking raw material or pulp into monosaccharides. The monosaccharides are reduced to sugar alcohols by sodium borohydride, and the sugar alcohols and acetic anhydride are esterified into volatile derivatives, which are then analyzed by gas chromatography .
4 Reagent
4.1 Sulfuric acid (AR, GB 625) is prepared with distilled water to a concentration of 72%.
4.2 Inositol (CR), weigh 10g inositol, dissolve in 200mL, distilled water, transfer to 1000mL volumetric flask, dilute to the mark.
4.3 Lead carbonate (CR).
4.4 Sodium borohydride.
4.5 The concentration of acetic acid (AR) is 36%.
4.6 Absolute ethanol (AR, GB 678).
4.7 Acetic anhydride (AR, GB 677).
4.8 Dry acetate (AR, GB 3289).
4.9 Dichloromethane (AR).
4.10 Glucose.
4.11 Galactose.
4.12 Mannose.
4.13 Xylose.
4.14 arabinose.
4.15 Distilled water or deionized water.
5 Instruments General laboratory instruments and the following instruments.
5.1 GC9160 gas chromatograph
5.2 Rotary evaporator: The temperature can be controlled to 75 ° C, and the vacuum can be evacuated to 750mmHg.
5.3 General medical pressure cooker.
5.4 Constant temperature water bath.
5.5 Oven.
6 The raw material for sample preparation is ground to 40-80 mesh, and the pulp is shredded by hand. After air-drying for 24h, take 2 samples of 2g each, and make the absolute dry amount according to GB 741.
7 Test procedure Weigh a sample with an absolute dry weight of 0.3 g (weighed to 0.0005 g) in a 15 mL centrifuge tube and place it in a vacuum desiccator with phosphorus pentoxide. After vacuuming, place it overnight. Take 3mL72% sulfuric acid with a 5mL pipette, add it to a centrifuge tube, insert a pointed glass rod and mix well, and hydrolyze it on a water bath at 30 ± 1 ℃ for 1h. Wash it into 200mL beaker in several times with 66mL of distilled water, add 10mL of internal standard inositol solution, put it in a pressure cooker, and hydrolyze it at 120 ℃ for another 1h. After cooling, use a graduated cylinder to take 10 mL of the clear solution into a 50 mL beaker, add 2 g of lead carbonate, neutralize to pH 5, and filter into a 25 mL beaker. Add 0.2g of sodium borohydride, reduce in a 40 ± 1 ℃ water bath for 0.5h, and then dropwise add 36% acetic acid until no bubbles. Pour this solution into a 10mL graduated cylinder, add distilled water to the 10mL mark, gently stir up and down with a glass rod, use a dropper to take 1mL into the cation exchange column (Appendix A), exchange drops into a 100mL round bottom flask. Place on a rotary evaporator, concentrate to dryness at 55 ° C, add 5 mL of absolute ethanol and evaporate to dryness, then add 5 mL of absolute ethanol and evaporate to dryness. Add 1mL each of acetic anhydride and butyl acetate, and esterify in an oven at 120 ± 1 ℃ for 1.5h. After taking out, add 5mL of distilled water, put it on a rotary evaporator, concentrate to dryness at 75 ° C, then add 1mL of distilled water, and evaporate to dryness. Add 1mL of dichloromethane, and use a micro syringe to take 4μL of inlet gas chromatography analysis (Appendix B)
8 Expression of results The results are reported as the average value of two parallel samples (expressed as a percentage), accurate to 0.01%.
8.1 Calculate the absolute content (%) according to formula (1) and formula (2)
A × Ws
Monosaccharide content (%) = ————— × 100 ………………………… (1)
As × W × K

Glycan content = B × monosaccharide content …………………………………… (2)
In the formula: A-tailing peak of monosaccharide. The former is rare. > Chromatographic peak area, mm2;
As-the area composed of the internal standard chromatographic baseline is called the peak area. A = × σ × h = 2.507σh = 1.064 Wh / 2h> peak area, mm2;
W——The absolute dry weight of the sample, mg;
Ws-weight of internal standard, mg;
B——Conversion coefficient of monosaccharide and glycan. For glucose, galactose, mannose, B = 0.9; for xylose, arabinose, B = 0.88;
K——monosaccharide correction factor. Five standard monosaccharides should be weighed to determine the K value. The weight of each standard monosaccharide should be as close as possible to the actual weight of various monosaccharides in the sample. The general required analysis can be weighed as follows; glucose 0.13g, galactose and arabinose 0.01g each, mannose and xylose 0.03g each.
While measuring the sample, the K value is measured under the same conditions. The K value is calculated according to formula (3):
Ac × W5
K = ———— ……………………………………………… (3)
As × Wc
In the formula: Ac-peak area of ​​standard monosaccharide chromatography, mm2;
Wc——standard monosaccharide weight, mg;
As——Peak area of ​​internal standard chromatography, mm2;
Ws-weight of internal standard, mg.
8.2 Calculate the relative content (%) according to the following formula
Absolute content of monosaccharides Relative content of monosaccharides (%) = —————————— × 100 ………………………… (4)
All monosaccharides absolutely contain

This article is derived from the gas chromatography determination of papermaking raw materials and carbohydrates in pulp | Scientific Instrument Online Text Link:

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