GB 8943.1-1988 Determination of copper content in pulp, paper and paperboard
Some standard content:
National Standard of the People's Republic of China
Pulp, paper and paperboard
Determination of copper content
Paper, board and pulp
Determination of copper contentGB 8943.1--88
Replaces GB8943.179
The copper content in pulp, paper and paperboard can be determined by either the sodium diethyldithiocarbamate spectrophotometric method (referred to as Method A) or the flame atomic absorption spectrophotometric method (referred to as Method B). The two methods have equal validity and can be applied to various pulps, papers and paperboards.
This standard equivalently adopts the international standard 1SO778-1982 "Pulp-Determination of copper content-Extractive photometric method and flame atomic absorption spectrophotometric method".
Part I Method A Sodium diethyldithiocarbamate spectrophotometry 1 Principle
The sample is ashed, and then the ash is dissolved in hydrochloric acid. In an ammonia solution, copper ions react with sodium diethyldithiocarbamate to form a yellow-brown colloidal complex, the color depth of which is proportional to the concentration of copper ions. Starch is used as a protective colloid to form this yellow-brown colloidal complex - a stable colloidal suspension. The colored solution is photometrically determined at a wavelength of 435nm by spectrophotometry. 2 Reagents
Analytically pure reagents and distilled water or water of equal purity must be used during analysis. The copper content of distilled water must be less than 0.01mg/kg. 2.1 Standard copper solution l: 0.1g/L, 0.100g of pure electrolytic copper metal is dissolved in about 5ml of nitric acid with a density of 1.4g/ml. The solution is boiled to remove nitrous fumes. After cooling, transfer the solution quantitatively into a 100mL volumetric flask, dilute to the mark with distilled water, and mix well. 1mL of this standard solution contains 0.1mg copper. 2.2 Standard copper solution II: 0.01g/L, transfer 100mL of standard copper solution I into a 1000ml volumetric flask, dilute to the mark with distilled water and mix well. 1ml. This standard solution contains 0.01mg copper. This solution is unstable, so prepare it on the day it is used. 2.3 Sodium diethyldithiocarbamate solution: about 1 g/L, dissolve 0.1g of sodium diethyldithiocarbamate [(C,H),NCSSNa·3H2O} in 100mL of distilled water (if turbid, filter it). Store in a brown glass bottle and store in a dark place. This solution can remain unchanged for about a week.
2.4 Potassium sodium tartrate solution: about 50g/L, dissolve 50g sodium tartrate in water and dilute to 1000ml. 2.5 Starch solution: about 2.5g/L, dissolve 0.25g soluble starch in 100ml distilled water, boil and cool for later use. 2.6 Hydrochloric acid solution: about 6mol/L.
2.7 Ammonia water: 1:5 ammonium hydroxide solution. Mix 1 volume of concentrated ammonia water (density 0.91g/ml.) with 5 volumes of water. 3 Instruments
General laboratory instruments and
3.1 Spectrophotometer.
Approved by the Ministry of Light Industry of the People's Republic of China on April 12, 1988 460
Implemented on August 1, 1988
4 Sample collection and preparation
GB 8943.1--88
Pulp samples shall be collected in accordance with the provisions of GB740 "Collection of pulp samples". The collection of average samples of paper and paperboard shall be carried out in accordance with the provisions of GB450 "Collection of average samples of paper and paperboard and treatment of 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 samples. 5 Test steps
5.1 Drawing of standard curve
5.1.1 Blank reference solution
At the same time as the test sample, a blank test shall be carried out, following the same test steps and using the same amount of all reagents as those used in the test sample, but without adding the sample.
5.1.2 Preparation of standard colorimetric solution
Inject 20mL of hydrochloric acid solution (2.6) into five 100mL beakers respectively, add concentrated ammonia water (density 0.91g/mL) until neutral, heat and concentrate to about 20mL, then transfer to five 50mL volumetric flasks respectively, and rinse the beakers with a small amount of distilled water, and pour the washing liquid into the volumetric flasks. Add standard copper solution I to each volumetric flask according to the volume listed in Table 1, mix, add 1mL of potassium sodium tartrate solution (2.4), 5mL of ammonia water (2.7), and 1mL of newly prepared starch solution (2.5), mix well, add 5mL. Sodium diethyldithiocarbamate solution (2.3), dilute to the scale with water, and shake well. Pour a certain amount of solution into a colorimetric dish with an optical distance of 1cm, and immediately measure the absorbance value. Table 1
Standard copper solution I
Note: 1) Blank reference solution.
5.1.3 Measurement of absorbance value
Equivalent copper mass
Use a spectrophotometer (3.1) at a wavelength of 435nm, use a blank reference solution to adjust the instrument's absorbance value to 0, and then measure its absorption respectively. 5.1.4 Plotting a curve
For example, plot a standard curve with the mass of copper (mg) as the horizontal axis and the corresponding absorbance value as the vertical axis. 5.2 Determination of samples
5.2.1 Weighing and ashing of samples
Weigh two 10g portions of each sample (accurate to 0.01g). If the copper 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 sample in a porcelain evaporator III (preferably an evaporator with a lid and handle) or a crucible. Burn the pulp sample into ash according to GB742 "Determination of ash content of pulp" and the paper and paperboard sample into ash according to GB463 "Determination of ash content of paper and paperboard". 5.2.2 Ash dissolution and preparation of test solution Carefully add 5mL of hydrochloric acid solution (2.6) to the evaporator (5.2.1) and evaporate to dryness on a steam bath. Repeat this operation once, then treat the residue with 20mL of hydrochloric acid solution (2.6) and heat on a steam bath for 5 minutes. Cool slightly, and slowly add ammonia water (density 0.91g/mL) until it becomes slightly alkaline. At this time, iron should be precipitated as iron hydroxide and the solution should be colorless. Filter with filter paper, wash with hot water 6-7 times, collect the filtrate and washing liquid in a beaker, evaporate and concentrate to about 20mL, transfer to a 50mL volumetric flask, rinse the beaker with a small amount of water 3 times, and pour the washing liquid into a 461
volumetric flask.
GB 8943.188
Add 1mL potassium sodium tartrate solution (2.4), 5mL ammonia water (2.7) and 1mlL newly prepared starch solution (2.5) to the volumetric flask, mix well, add 5mL sodium diethyldithiocarbamate solution (2.3), dilute to the scale with water, and shake well. 5.2.3 Measurement of absorption value
Pour a certain amount of test solution (5.2.2) into 1cm colorimetric III, adjust the absorption value of the instrument to 0 with blank reference solution, and immediately measure the absorption value of the test solution according to the provisions of 5.1.3. 6 Calculation of results
The copper content X of the sample is expressed in mg/kg and is calculated according to formula (1): X=㎡×1 000bzxZ.net
Where: m,
The copper content of the test solution obtained from the standard curve (5.1.4), mg; the absolute dry weight of the sample, g.
Use the average of two determinations and report the result with one decimal place. Part II Method B Flame Atomic Absorption Spectrophotometry 7 Principle
·(1))
Ashe the sample and dissolve the ash in hydrochloric acid. Absorb the test solution into a NO-acetylene or air-acetylene flame. Measure the absorption value of the 324.7nm spectral line emitted by the copper hollow cathode lamp. 8 Reagents
Analytical reagents and distilled water or water of equal purity must be used during analysis. The copper content of distilled water must be less than 0.01mg/kg. 8.1 Hydrochloric acid solution is about 6mol/L.
: 8.2 Standard copper solution I: 0.1 g/L, prepared as specified in 2.2 of Method A. 8.3 Standard copper solution II: 0.01 g/L, prepared as specified in 2.3 of Method A. 9 Apparatus
General laboratory instruments and
9.1 Atomic absorption spectrophotometer, equipped with N,O-acetylene burner or air-acetylene burner. 9.2 Copper hollow cathode lamp.
Sample collection and preparation
Carry out as in Method A.
11 Test procedures
11.1 Drawing of standard curve
11.1.1 Preparation of standard comparison solution
Add 10 mL of hydrochloric acid solution (8.1) and the standard copper solution Il of a certain volume as shown in Table 2. Then dilute to the mark with distilled water and mix well. 462
11.1.2 Calibration of instrument
Standard copper solution
GB 8943.1--88
Equivalent copper mass
Install the copper 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 and stabilize the current. According to the conditions for measuring copper in the instrument, adjust and fix the wavelength to 324.7nm, and then adjust the current, sensitivity slit, burner head height, gas/fuel ratio, air flow velocity and suction volume, etc. If N2O-acetylene is used, special attention should be paid to safety to prevent explosion. N,O-acetylene burner should be used. Before connecting N,O-acetylene, the burner must be ignited with air-acetylene.
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 test solutions. During the entire process of preparing the standard curve, pay attention to keeping the instrument under constant conditions. After each measurement, spray water through the burner for cleaning. 11.1.4 Plotting the curve
Plot the standard curve with the mass of copper (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 well. If the solution contains suspended matter, wait for it to sink and use the clear solution to measure the absorption value.
11.2.3 Calibration 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 copper content X is expressed in mg/kg and is calculated according to formula (2): X=m2×100
Formula: m-
The copper content of the test solution obtained from the standard curve, mg; the amount of the absolute dry sample, g.
Use the average value of two measurements, take a decimal place, and report the result. .(2)
Additional remarks:
GB8943.1—88
This standard is proposed by the Ministry of Light Industry of the People's Republic of China. This standard was drafted by the Paper Industry Research Institute of the Ministry of Light Industry. This standard was first issued on September 15, 1961 and first revised on August 1, 1979.
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