The determination of iron content in pulp, paper and paperboard can be carried out by either 1,10-phenanthroline spectrophotometry (referred to as Method A) or flame atomic absorption spectrophotometry (referred to as Method B). These two determination methods have equal validity and can be applied to various pulps, papers and paperboards. GB 8943.2-1988 Determination of iron content in pulp, paper and paperboard GB8943.2-1988 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Determination of iron content in pulp, paper and paperboardPaper ,board and pulp-
Determination of iron contentGB 8943.2-88
Replaces GB8943.2--81
The determination of iron content in pulp, paper and paperboard can be carried out by either 1,10-phenanthroline spectrophotometry (referred to as Method A) or flame atomic absorption spectrophotometry (referred to as Method B). These two determination methods have equal validity and can be applied to various pulps, papers and paperboards. This standard is equivalent to the international standard ISO779-1982 "Pulp-Determination of iron content-1,10-phenanthroline spectrophotometry and flame atomic absorption spectrophotometry". Part I Method A1.10-phenanthroline spectrophotometry 1 Principle
The sample is ashed, and then the ash is dissolved in hydrochloric acid. Hydroxylamine hydrochloride is used to reduce the trivalent iron to divalent iron. Under slightly acidic conditions, the divalent iron forms a red complex with 1,10-phenanthroline. The colored solution is photometrically determined at a wavelength of 510nm by spectrophotometry. 2 Reagents
During analysis, analytically pure reagents and distilled water or water of equal purity must be used. 2.1 Sodium acetate solution: 540g/L, dissolve 540g sodium acetate (NaCOOCH3*3H,O) in distilled water and dilute to 1L; 2.2 Hydroxylamine hydrochloride solution: 20g/L, dissolve 2g hydroxylamine hydrochloride (NH,OH·HCi) in 100mL distilled water; 2.3 Hydrochloric acid 1,10-phenanthroline solution: 10g/L, dissolve 1g hydrochloric acid 1,10-phenanthroline (Ciz2HgN，·HCI·H,O) in 100mL distilled water. This reagent can be replaced by the corresponding amount of 1,10-phenanthroline. This solution should be stored in a brown reagent bottle (note, only use colorless solution),
2.4 Hydrochloric acid solution 6mol/L;
2.5 Standard iron solution I: 0.1g/L, put 0.100g pure iron wire in a 1000mL volumetric flask, dissolve in about 10mL hydrochloric acid with a density of 1.19g/mL, dilute to scale with distilled water, and mix well. 1mL. This standard solution contains 0.01mg iron. 2.6 Standard iron solution I: 0.01g/L, transfer 100mL standard iron solution I to a 1000mL volumetric flask, dilute to scale with distilled water, and mix well. 1mL of this standard solution contains 0.01mg iron. This solution is unstable and should be prepared on the same day it is used. 3 Instruments
General laboratory instruments and
3.1 Spectrophotometer.
4 Sample collection and preparation
Pulp samples shall be collected in accordance with GB740 "Methods for collecting average samples of chemical pulp". The average samples of paper and paperboard shall be collected in accordance with GB450 "Methods for collecting average samples of paper and paperboard and handling samples before inspection". Tear the air-dried samples into pieces of appropriate size, but do not use shearing, punching or other tools that may cause metal contamination to prepare the samples. Approved by the Ministry of Light Industry of the People's Republic of China on April 12, 1988, implemented on August 1, 1988
5 Test procedures
5.1 Drawing of standard curve
5.1.1 Blank reference solution
GB 8943.2-88
At the same time as the test sample, a blank test shall be carried out, following the same test procedures and using the same amount of all reagents as those used in the test sample, but without the sample.
5.1.2 Preparation of standard colorimetric solution
Add standard iron solution II to five 50mL volumetric flasks according to the volume listed in Table 1, then add 10ml hydrochloric acid solution (2.4), 1mL hydroxylamine hydrochloride solution (2.2), 1mL 1,10-phenanthroline hydrochloride solution (2.3), and 15mL sodium acetate solution (2.1). Dilute to the mark with water and shake well. If the solution is turbid, filter it with a glass filter or separate it by centrifugation. Let the colored solution stand for 15 minutes before measuring the absorption value.
Standard solution II
Note: 1) Blank reference solution.
5.1.3 Measurement of absorption value
Equivalent mass of iron
Use a spectrophotometer (3.1) at a wavelength of 510nm, adjust the instrument's absorption value to 0 with a blank reference solution, and then measure its absorption value.
5.1.4 Draw the curve
For example, draw the standard curve with the mass of iron (mg) as the horizontal axis and the corresponding absorption value as the vertical axis. 5.2 Determination of samples
5.2.1 Weigh two samples of 10g (accurate to 0.01g) for each sample. If the iron content of the sample is known to exceed 10mg/kg, only weigh 5g. Weigh two samples at the same time and determine the moisture content of the samples according to GB741 "Determination of moisture content of pulp analysis samples" or GB462 "Determination of moisture content of paper and paperboard".
Put the weighed samples in a porcelain evaporating dish (preferably an evaporating dish with a lid and handle) or a porcelain crucible, and burn the pulp samples according to GB742 "Determination of ash content of chemical pulp" and the paper and paperboard samples according to GB463 "Determination of ash content of paper and paperboard" into ash. 5.2.2 Dissolution of ash and preparation of test solution Carefully add 5 mL of hydrochloric acid solution (2.4) to the evaporating dish (5.2.1) and evaporate to dryness on a steam bath. Repeat this operation 10 times and then treat the residue with 5 mL of hydrochloric acid solution and heat on a steam bath for 5 min. Transfer the contents of the evaporating dish to a 50 mL volumetric flask with distilled water. Add 5 mL of hydrochloric acid solution to the residue in the evaporating dish and heat on a steam bath. Transfer this last part of the contents to the volumetric flask with distilled water. Rinse the evaporating dish 3 times with a small amount of water and pour the washings into the volumetric flask.
Add 1 mL of hydroxylamine hydrochloride solution (2.2), 1 mL of 1,10-phenanthroline hydrochloride solution (2.3) and 15 ml of sodium acetate solution (2.1) to the volumetric flask, dilute to the mark with water and shake well. If the solution is turbid, filter it with a glass filter or separate it with a centrifuge. Let the colored solution stand for 15 min and then measure the absorbance.
5.2.3 Measurement of absorption value
Pour a certain amount of test solution (5.2.2) into the colorimetric instrument III with a light distance of 1 cm, and adjust the absorption value of the instrument to ) with a blank reference solution. Then measure the absorption value of the test solution according to the provisions of 5.1.3. 466
6 Calculation of results
GB 8943.2--88
The iron content X of the sample is expressed in mg/kg and is calculated according to formula (1): X=㎡×100
The iron content of the test solution obtained from the standard curve (5.1.4), mg; where: mr
-absolute dry weight of the sample, g.
Use the average value of two measurements and report the result with decimal places. Part II Method B Flame Atomic Absorption Spectrophotometry 7 Principle
Ash the sample and dissolve the ash in hydrochloric acid. Inhale the test solution into an air-acetylene flame. Measure the absorption value of the 248.3nm spectrum emitted by the iron hollow cathode lamp.
8 Reagents
Analytically pure reagents and distilled water or water of equal purity must be used during analysis. 8.1 Hydrochloric acid (GB622) solution: about 6 mol/L; 8.2 Standard iron solution 1: 0.1 g/L, prepared according to the provisions of 2.5 in Method A. 8.3
Standard iron solution I1: 0.01 g/L, prepared according to the provisions of 2.6 in Method A. 9 Instruments
General laboratory instruments and
9.1 Atomic absorption spectrophotometer, equipped with an air-acetylene burner; iron hollow cathode lamp.
10 Sample collection and preparation
Perform according to 4 in Method A.
Test steps
11.1 Drawing of standard curve
11.1.1 Preparation of standard comparison solution
Add 10.mL of saline solution (8.1) and one volume of standard iron solution II listed in Table 2 to five 50mL volumetric flasks respectively, then dilute to scale with distilled water and mix well. Table 2bZxz.net
Standard iron solution 11
11.1.2 Calibration of instrument
Equivalent iron mass
Install the iron hollow cathode lamp on the lamp holder of the atomic absorption spectrophotometer, start the instrument according to the operating steps specified by the instrument, turn on the current 467
GB 8943.2-88
and stabilize the current. According to the conditions for measuring iron in the instrument, adjust and fix the wavelength to 248.3nm, and then adjust the current, sensitivity, slit, burner head height, gas/fuel ratio, air flow rate and suction volume, etc. 11.1.3 Absorption value measurement
After the instrument is normal and the flame is burning stably, suck the standard comparison solution into the flame in turn and measure the absorption value of each solution. When measuring, use the blank test solution as a control, adjust the absorption value of the instrument to 0, and then measure the remaining solutions to be tested. During the entire process of preparing the standard curve:, pay attention to keeping the instrument under constant conditions. Spray water through the burner for cleaning after each measurement. 11.1.4 Plotting the curve
Plot the standard curve with the mass of iron (mg) as the horizontal axis and the corresponding absorption value as the vertical axis. 11.2 Determination of samples
11.2.1 Weighing and ashing of the sample
Perform according to 5.2.1 of Method A.
11.2.2 Dissolution of ash and preparation of sample solution After performing according to 5.2.2 of Method A, dilute to the scale with distilled water and mix evenly. If the solution contains suspended matter, wait for it to sink and then use the clear solution to measure the absorption value.
11.2.3 Calibration of instrument
The calibration instrument is the same as that in 11.1.2.
11.2.4 Measurement of absorption value
The measurement of absorption value is the same as that in 11.1.3.
12 Calculation of results
The iron content X of the sample, expressed in mg/kg, is calculated according to formula (2): X=㎡2×1000
Where: m2—
—iron content of the test solution obtained from the standard curve, mg; absolute dry sample volume, g.
Use the average value of two measurements, round to
one decimal place, and report the result.
Additional remarks:
This standard is under the jurisdiction and drafted by the Paper Industry Research Institute of the Ministry of Light Industry of the People's Republic of China. This standard was first promulgated on September 15, 1961 and revised for the first time on August 1, 1981. 468
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