The determination of calcium and magnesium content in pulp, paper and paperboard, when their respective contents are greater than 200 mg/kg, can be determined by EDTA complexometric titration (referred to as Method A). If an atomic absorption spectrophotometer is available, flame atomic absorption spectrophotometry (referred to as Method B) can also be used. Method B is suitable for the determination of various calcium and magnesium contents in pulp, paper and paperboard. The two determination methods have equal validity. GB 8943.4-1988 Determination of calcium, magnesium and content in pulp, paper and paperboard GB8943.4-1988 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Pulp, paper and board, determination of calcium and magnesium content, Pulppaper and board
Determination of calcium and magnesium GB 8943.4-88
The determination of calcium and magnesium content in pulp, paper and board, when their respective contents are greater than 200 mg/kg, can be determined by EDTA complexometric titration (referred to as Method A). If an atomic absorption spectrophotometer is available, flame atomic absorption spectrophotometry (referred to as Method B) can also be used. Method B is suitable for the determination of various calcium and magnesium contents in pulp, paper and board. The two determination methods have equal validity. This standard refers to the international standards ISO777-1982 "Pulp - Determination of Calcium Content" and ISO9668 "Pulp - Determination of Magnesium Content".
Part I Method A EDTA complexometric titration
Ashe the sample, dissolve the ash in the salt solution, and dilute to a certain volume. Take a portion of the solution and adjust it to pH=12, titrate it with EDTA standard solution as calcium indicator, and calculate the calcium content of the sample by the consumption of standard solution. Take another portion of the solution and adjust it to pH=10 with ammonia buffer. Titrate it with EDTA solution using KB indicator (a mixed indicator of acid chrome blue K), and the volume of EDTA solution consumed is the sum of the consumption of calcium and magnesium. Calculate the magnesium content of the sample by the difference between the total amount and the amount of EDTA consumed by calcium. 1 Reagents
All reagents used in the test must be analytically pure (AR), and the water used in the test must be distilled water or deionized water. 1.1 EDTA standard solution: c (EDTA) = 1/56 mol/L, dissolve 6.635 g of EDTA (GB 1401, CioHuO.N, Na22H, 0) in distilled water and dilute to 1L. 1.2 Zinc standard solution: weigh 1g of chemically pure metal zinc particles (weighed to 0.1mg) in a 150mL conical flask, add 1020mL of 6mol/L hydrochloric acid solution to completely dissolve it, transfer it to a 1L volumetric flask, dilute to the scale with distilled water, and calculate the concentration of the zinc standard solution according to formula (1).
Where '
-concentration of zinc standard solution, mol/L;
-weight of metal zinc particles, g.
Calibration of EDTA standard solution concentration: Pipette 20.00mL zinc standard solution into a 250mL conical flask, add about 50mL of distilled water, add a few drops of ammonia water until a faint ammonia smell is present, then add 10mL of ammonia nitrogen buffer solution and about 0.2g of KB indicator, titrate with EDTA solution until blue under constant shaking, and calculate its concentration; 1.3KB indicator: 1g of acid chrome blue K, 2.5g of naphthol green B and 175g of sodium chloride are evenly ground and stored in a brown bottle; 1.4Calcium red indicator: 1g of calcium red indicator, namely: 2-hydroxy-1-(2-hydroxy-4-sulfonic acid-1-yl)- ）Azo-3-naphthoic acid and 100g sodium sulfate (HGB-123) are ground evenly and stored in a brown bottle; 1.5 Triethanolamine solution: 50mL triethanolamine (京Q/HG10-1255) is diluted with 50mL distilled water; 1.6 Hydroxylamine hydrochloride solution: Dissolve 5g hydroxylamine hydrochloride (HGB3044) and dilute to 250mL with distilled water; .1.7 Potassium hydroxide (HGB3006) solution: about 8mol/1. Store in a polyethylene plastic bottle; Approved by the Ministry of Light Industry of the People's Republic of China on April 12, 1988 and implemented on August 1, 1988
GB 8943.4—88
1.8 Ammonia buffer solution: 54g of ammonium chloride (GI3658) and 350)ml of concentrated ammonia water ((B631) are dissolved and mixed and diluted with 1L of distilled water.
1.9 Hydrochloric acid solution: about c (HCl) = 6mol/L1.10 Nitric acid solution: about c (HNO.) = 5mol/L, measure 325mL of concentrated nitric acid (GB626), P2m1.4g/ml.. and dilute with 500)ml of distilled water.
2 Instruments
2.1 General laboratory instruments.
2.2 Crucible: It needs to be soaked in hydrochloric acid and washed repeatedly. It is best to use a platinum crucible. Its stains should be scrubbed clean with fine sand. 3 Sample collection and preparation
Pulp samples shall be collected in accordance with GB740 "Collection of pulp samples", and paper samples shall be collected in accordance with GB450 "Collection of paper and paperboard samples".
Tear the air-dried sample into pieces of appropriate size. Gloves must be worn when preparing the sample, but the sample shall not be prepared by cutting, perforating or other tools that may cause metal contamination.
4 Test steps
4.1 Weighing and ashing of samples
Weigh 10g (accurate to 0.01g) of each sample and measure the moisture content of the sample in accordance with GB741 "Determination of moisture content of pulp analysis samples" or GB3162 "Determination of moisture content of paper and paperboard". Put the weighed sample in a crucible and ash it into ash in accordance with GB742 "Determination of ash content of pulp" or GB463 "Determination of ash content of paper and paperboard". 4.2 Preparation of test solution
Add about 10mL of water to the ash residue. Then add 3 mL of hydrochloric acid solution (1.9) and heat the crucible on a steam bath for 5 to 1 min. If a brown precipitate of manganese dioxide is produced, filter the contents of the crucible into a 100 mL volumetric flask with filter paper and wash with water. If no insoluble residue is found or the residue is colorless, filtering is not necessary. In this case, the snail contents can be directly washed into a 100 ml volumetric flask with water and diluted to the mark with water. 4.3 Determination of calcium
Use a pipette to transfer a certain amount of test solution (20 ml or 25 ml) into a 250 ml conical flask. Add 5 ml of potassium hydroxide solution (1.7). After 5 min, add 5 ml of triethanolamine solution (1.5), 2 mL of hydroxylamine hydrochloride solution (1.6) and about 0.1 g of calcium red indicator (1.4) while shaking the conical flask from time to time. Use EDTA standard solution (1. 1) Perform titration until the color of the solution changes from wine red to pure blue. Record the volume of EDTA standard solution consumed.
4.4 Determination of magnesium
Use a pipette to transfer a certain amount of test solution (20mL or 25mL) into a 250mL conical flask, add 10ml of ammonia buffer solution (1.8), add 5ml of triethanolamine solution (1.5), 2mL of hydroxylamine hydrochloride solution (1.6) and about (.1 gKB indicator (1.3). Titrate with EDTA standard solution (1.1) until the color of the solution changes from wine red to pure blue, which is l. Record the volume V2 of EDTA standard solution consumed. V is the sum of EDTA standard solutions consumed by calcium and magnesium. Subtract V from V2 to get V, which is the volume of EDTA consumed by magnesium in the test solution.
4.5 Blank determination
While determining the sample, perform a blank test according to the same steps and all reagents used in the determination of the sample, with the sample solution replaced by the same volume of distilled water. The volume of EDTA standard solution consumed in the blank test is V for calcium determination and Vs for magnesium determination.
5 Expression of results
The content is expressed in mg/kg and calculated according to formula (2): 474
Calcium content (mg/kg)
Magnesium content (mg/kg)
武:t
GB 8943.4 --- 88
(V. V) :c× 40. 08 × 10
(V:—Vs).c× 24.31 × 10
The volume of EDTA standard solution consumed when determining calcium, mL; The volume of EDTA standard solution consumed when determining magnesium, mL; The volume of EDTA standard solution consumed when determining magnesium blank, mL; The concentration of EDTA standard solution, mol/L; The absolute dry weight of the sample is ·
The average value of the results of the lake chain is reported according to the provisions of Table 1. Table 1
Average value of results
≤100
≥100~500
5.1 Porcelain crucibles can be used for routine testing, and platinum crucibles should be used for arbitration of controversial samples. Reported precise units
5.2 Hydrochloric acid (1.9) or nitric acid (1.10) can be used to dissolve the ash of the sample. For samples with high manganese content, nitric acid is better, which can separate the manganese oxide precipitate. It helps to eliminate the interference of manganese in titration. 5.3 When the copper content in the sample exceeds 0.03 mg, the indicator will not change significantly or even fail. In this case, 5 mL of 1g/l potassium hydroxide solution can be added during titration to mask the copper present. Or add 2g/l.5 ml of sodium sulfide solution is added to make copper form copper sulfide precipitation to eliminate the interference of copper.
Note: Potassium fluoride is an extremely toxic drug. When using it, you must follow the relevant safety precautions. Part II Method B Flame Atomic Absorption Spectrophotometry Ash the pulp sample and dissolve the ash in hydrochloric acid. After adding strontium ions (or lanthanum ions) to suppress certain interfering substances, absorb the test solution into N. ()-acetylene or air-acetylene flame. Measure the absorption value of the 422.7nm spectral line emitted by the calcium hollow cathode lamp and the absorption value of the 285.2nm spectral line emitted by the magnesium hollow cathode lamp. 6 Reagents
All reagents used in the test should be analytically pure (AR) The water used in the test should be distilled water or deionized water. 6.1 Hydrochloric acid solution: about c (HCl) 6 mol/L; 6.2 Strontium chloride (HGB1073) solution 5%, weigh 152.14g strontium chloride (SrCl. · 6H.)) (AR or high-grade pure) and put it in a 250ml beaker. Dissolve it with water and transfer it to a 1000ml volumetric flask, dilute it with water to the scale, and mix it evenly; 6.3 Lanthanum oxide solution: about 50g/L, moisten 59g lanthanum oxide (1.az0) with water. Slowly and carefully add 250)ml concentrated hydrochloric acid (p1.19g/cm). Dissolve the lanthanum oxide. Dilute to scale with water in a 1000ml volumetric flask and mix well; 475
GB 8943.4--88
6.4 Standard calcium solution I: Each liter contains 500mg calcium. Weigh 1.2400g of calcium carbonate that has been dried at a temperature not exceeding 200C and place it in a 1000ml volumetric flask. Add 50ml of water, then drop by drop the minimum volume of hydrochloric acid (about 10ml) that can completely dissolve the calcium carbonate, dilute to scale with water and mix well. 1ml. This standard solution contains 0.500mg calcium; 6.5 Standard calcium solution I: Each liter contains 50.mg calcium. Take 100mL of standard calcium solution and put it into a 1000ml volumetric flask, dilute to the mark with water and mix well.
1ml This standard solution contains 0.050mg calcium; 6.6 Standard magnesium solution l: Each liter contains 500mg magnesium. Weigh 0.5000g of magnesium bar and put it into a 1000ml volumetric flask, add 50ml6 mol/L hydrochloric acid, (1.1) dissolved, and diluted with water to the scale and mixed evenly. 1mL of this standard solution contains 0.500mg magnesium; 6.7 Standard magnesium solution II: Each liter contains 10mg magnesium, transfer 20mL of standard magnesium solution into a 1000ml volumetric flask, and dilute with water to the scale and mix evenly.
1ml of this standard solution contains 0.01mg magnesium.
7 Instruments
7.1 General laboratory instruments and atomic absorption spectrophotometer, equipped with N20-acetylene burner or air-acetylene burner. 7.2 Calcium and magnesium hollow cathode lamps.
7.3 Tower crucible: required Soak in hydrochloric acid and wash repeatedly. It is best to use a platinum crucible, and its stains should be scrubbed clean with fine sand. 8 Sample collection and preparation
Same as 3 in Method A.
Tear the air-dried sample into pieces of appropriate size. Gloves must be worn when preparing samples, but samples must not be prepared using shearing, punching or other tools that may cause metal contamination.
9 Test steps
9.1 Sample weighing and ashing
Same as 4.1 in Method A.
9.2 Sample ash treatment
First, add a few drops of distilled water to the ash (9.1) to moisten it, then add 5 ml of hydrochloric acid solution (6 .1) and evaporate to dryness on a steam bath. Repeat this process once, then treat the residue with 5 ml of hydrochloric acid solution and heat on a steam bath for 5 min. Transfer the contents into a 100 ml volumetric flask with water. To ensure complete extraction, add 5 ml of hydrochloric acid solution (6.1) to the residue in each crucible and heat on a steam bath. Transfer this last portion of the contents into a volumetric flask with water. Combine with the main sample solution, dilute to the mark with water and mix well. 9.3 Preparation of standard comparison solution
Add 4 ml or 20 ml of 5% strontium chloride solution (6.2) to each of the six 100 ml volumetric flasks. l. Lanthanum solution (6.3) and 10ml hydrochloric acid solution (6.1), then add calcium standard solution II or magnesium standard solution II according to the volume shown in Table 2. 476
Volume, ml.
GB8943.4—88
Calcium standard solution II
Equivalent calcium, mg
Note: 1) Reagent blank test for calibration curve. 9.4 Preparation of test solution
Volume, mL
Magnesium standard solution H
Equivalent calcium.mg
Use a pipette to transfer a certain volume V of test solution (9.2) into a 50mL volumetric flask. Make sure that the calcium or magnesium content meets the specified range in Table 2. If the calcium and magnesium content of the sample is unknown, V, it can be measured in advance by atomic absorption, such as transferring 1.0mL, 2.0mL or 5.0mL to make a preliminary measurement together with the standard comparison solution, or transferring 20mL to determine the approximate content by method A and then adding 2ml of 5% strontium chloride solution (6.2) or 10mL of lanthanum solution (6.3) 5mL of hydrochloric acid solution and diluting to the scale with water. If the solution contains suspended matter, wait until the suspended matter sinks before measuring the spectrum. 9.5 Calibration of the instrument
Install the calcium (or magnesium) hollow cathode lamp on the lamp holder of the atomic absorption spectrophotometer, turn on the instrument according to the operating steps specified by the instrument, connect the current and stabilize the current. Adjust the wavelength according to the instrument measurement conditions. Calcium is at 422.7nm and magnesium is at 285.2nm, and adjust to the maximum absorption value within their wavelength range.
Then adjust the current, sensitivity, slit, burner head height, gas/fuel ratio, air flow velocity, suction volume, etc. to the specified test conditions according to the instrument characteristics (each instrument provides test reference conditions). If N,-acetylene is used, special attention should be paid to safety. To prevent explosion, use N,O-acetylene burner, and be sure to ignite it with air-acetylene burner before connecting N2O-acetylene.
9.6 Absorption value measurement
Wait for the instrument to be normal and the flame to burn stably, and then suck the standard comparison solution into the flame in turn. And measure the absorption value of each solution. When measuring, a blank test solution should be used as a control, and the absorption value of the instrument should be adjusted to zero, and then the remaining samples should be measured. During the entire process of preparing the calibration curve, it is important to keep the instrument conditions constant. After each measurement, spray water through the burner for cleaning. The determination of the absorption value of the calibration curve series must be carried out simultaneously with the determination of the absorption value of the sample solution to overcome the error caused by changes in experimental conditions.
9.7 Drawing the curve
Use the weight of calcium or magnesium (in mg) (per 100 mL of the standard comparison solution) as the abscissa and the corresponding absorption value as the ordinate to draw the calibration curve.
10 Calculation of results
The corresponding weight of calcium or magnesium (in mg) is obtained from the absorption value of the sample solution on the calibration curve, and its content is calculated by the following formula, expressed in mg/kg.
Formula: 50 000-
Calcium content = 50000×vm
Magnesium content = 50 000×m
is the sample release and conversion factor;
(5)
GB8943.4—88
is the calcium or magnesium content of the test solution obtained from the calibration curve, mg; is the volume of the sample solution to be transferred for absorption value measurement, mL; is the absolute dry weight of the sample, g.
Use the average of the two determinations and report the results according to the provisions of Table 3. Table 3
Average value of results
≥100～500
Additional notes:
This standard is drafted by the Paper Industry Research Institute of the Ministry of Light Industry. 478
Precise units reported3 Lanthanum oxide solution: about 50g/L, moisten 59g lanthanum oxide (1.az0) with water. Slowly and carefully add 250ml concentrated hydrochloric acid (p1.19g/cm). Dissolve the lanthanum oxide. Dilute to scale with water in a 1000ml volumetric flask and mix well; 475
GB 8943.4-88
6.4 Standard calcium solution I: Contains 500mg calcium per liter, weigh 1.2400g of calcium carbonate that has been dried at a temperature not exceeding 200C and place it in a 1000mL volumetric flask. Add 50ml of water, then add the minimum volume of hydrochloric acid (about 10 ml) that can completely dissolve the calcium carbonate drop by drop, dilute to scale with water and mix well. 1ml. This standard solution contains 0.500mg calcium; 6.5 Standard calcium solution I: Each liter contains 50.mg calcium. Take 100mL of standard calcium solution and put it into a 1000ml volumetric flask, dilute to the mark with water and mix well.
1ml This standard solution contains 0.050mg calcium; 6.6 Standard magnesium solution l: Each liter contains 500mg magnesium. Weigh 0.5000g of magnesium bar and put it into a 1000ml volumetric flask, add 50ml6 mol/L hydrochloric acid, (1.1) dissolved, and diluted with water to the scale and mixed evenly. 1mL of this standard solution contains 0.500mg magnesium; 6.7 Standard magnesium solution II: Each liter contains 10mg magnesium, transfer 20mL of standard magnesium solution into a 1000ml volumetric flask, and dilute with water to the scale and mix evenly.
1ml of this standard solution contains 0.01mg magnesium.
7 Instruments
7.1 General laboratory instruments and atomic absorption spectrophotometer, equipped with N20-acetylene burner or air-acetylene burner. 7.2 Calcium and magnesium hollow cathode lamps.
7.3 Tower crucible: required Soak in hydrochloric acid and wash repeatedly. It is best to use a platinum crucible, and its stains should be scrubbed clean with fine sand. 8 Sample collection and preparation
Same as 3 in Method A.
Tear the air-dried sample into pieces of appropriate size. Gloves must be worn when preparing samples, but samples must not be prepared using shearing, punching or other tools that may cause metal contamination.
9 Test steps
9.1 Sample weighing and ashing
Same as 4.1 in Method A.
9.2 Sample ash treatment
First, add a few drops of distilled water to the ash (9.1) to moisten it, then add 5 ml of hydrochloric acid solution (6 .1) and evaporate to dryness on a steam bath. Repeat this process once, then treat the residue with 5 ml of hydrochloric acid solution and heat on a steam bath for 5 min. Transfer the contents into a 100 ml volumetric flask with water. To ensure complete extraction, add 5 ml of hydrochloric acid solution (6.1) to the residue in each crucible and heat on a steam bath. Transfer this last portion of the contents into a volumetric flask with water. Combine with the main sample solution, dilute to the mark with water and mix well. 9.3 Preparation of standard comparison solution
Add 4 ml or 20 ml of 5% strontium chloride solution (6.2) to each of the six 100 ml volumetric flasks. l. Lanthanum solution (6.3) and 10ml hydrochloric acid solution (6.1), then add calcium standard solution II or magnesium standard solution II according to the volume shown in Table 2. 476
Volume, ml.
GB8943.4—88
Calcium standard solution II
Equivalent calcium, mg
Note: 1) Reagent blank test for calibration curve. 9.4 Preparation of test solution
Volume, mL
Magnesium standard solution H
Equivalent calcium.mg
Use a pipette to transfer a certain volume V of test solution (9.2) into a 50mL volumetric flask. Make sure that the calcium or magnesium content meets the specified range in Table 2. If the calcium and magnesium content of the sample is unknown, V, it can be measured in advance by atomic absorption, such as transferring 1.0mL, 2.0mL or 5.0mL to make a preliminary measurement together with the standard comparison solution, or transferring 20mL to determine the approximate content by method A and then adding 2ml of 5% strontium chloride solution (6.2) or 10mL of lanthanum solution (6.3) 5mL of hydrochloric acid solution and diluting to the scale with water. If the solution contains suspended matter, wait until the suspended matter sinks before measuring the spectrum. 9.5 Calibration of the instrument
Install the calcium (or magnesium) hollow cathode lamp on the lamp holder of the atomic absorption spectrophotometer, turn on the instrument according to the operating steps specified by the instrument, connect the current and stabilize the current. Adjust the wavelength according to the instrument measurement conditions. Calcium is at 422.7nm and magnesium is at 285.2nm, and adjust to the maximum absorption value within their wavelength range.
Then adjust the current, sensitivity, slit, burner head height, gas/fuel ratio, air flow velocity, suction volume, etc. to the specified test conditions according to the instrument characteristics (each instrument provides test reference conditions). If N,-acetylene is used, special attention should be paid to safety. To prevent explosion, use N,O-acetylene burner, and be sure to ignite it with air-acetylene burner before connecting N2O-acetylene.
9.6 Absorption value measurement
Wait for the instrument to be normal and the flame to burn stably, and then suck the standard comparison solution into the flame in turn. And measure the absorption value of each solution. When measuring, a blank test solution should be used as a control, and the absorption value of the instrument should be adjusted to zero, and then the remaining samples should be measured. During the entire process of preparing the calibration curve, it is important to keep the instrument conditions constant. After each measurement, spray water through the burner for cleaning. The determination of the absorption value of the calibration curve series must be carried out simultaneously with the determination of the absorption value of the sample solution to overcome the error caused by changes in experimental conditions.
9.7 Drawing the curve
Use the weight of calcium or magnesium (in mg) (per 100 mL of the standard comparison solution) as the abscissa and the corresponding absorption value as the ordinate to draw the calibration curve.
10 Calculation of results
The corresponding weight of calcium or magnesium (in mg) is obtained from the absorption value of the sample solution on the calibration curve, and its content is calculated by the following formula, expressed in mg/kg.
Formula: 50 000-
Calcium content = 50000×vm
Magnesium content = 50 000×m
is the sample release and conversion factor;
(5)
GB8943.4—88
is the calcium or magnesium content of the test solution obtained from the calibration curve, mg; is the volume of the sample solution to be transferred for absorption value measurement, mL; is the absolute dry weight of the sample, g.
Use the average of the two determinations and report the results according to the provisions of Table 3. Table 3
Average value of results
≥100～500
Additional notes:
This standard is drafted by the Paper Industry Research Institute of the Ministry of Light Industry. 478
Precise units reported3 Lanthanum oxide solution: about 50g/L, moisten 59g lanthanum oxide (1.az0) with water. Slowly and carefully add 250ml concentrated hydrochloric acid (p1.19g/cm). Dissolve the lanthanum oxide. Dilute to scale with water in a 1000ml volumetric flask and mix well; 475
GB 8943.4-88
6.4 Standard calcium solution I: Contains 500mg calcium per liter, weigh 1.2400g of calcium carbonate that has been dried at a temperature not exceeding 200C and place it in a 1000mL volumetric flask. Add 50ml of water, then add the minimum volume of hydrochloric acid (about 10 ml) that can completely dissolve the calcium carbonate drop by drop, dilute to scale with water and mix well. 1ml. This standard solution contains 0.500mg calcium; 6.5 Standard calcium solution I: Each liter contains 50.mg calcium. Take 100mL of standard calcium solution and put it into a 1000ml volumetric flask, dilute to the mark with water and mix well.
1ml This standard solution contains 0.050mg calcium; 6.6 Standard magnesium solution l: Each liter contains 500mg magnesium. Weigh 0.5000g of magnesium bar and put it into a 1000ml volumetric flask, add 50ml6 mol/L hydrochloric acid, (1.1) dissolved, and diluted with water to the scale and mixed evenly. 1mL of this standard solution contains 0.500mg magnesium; 6.7 Standard magnesium solution II: Each liter contains 10mg magnesium, transfer 20mL of standard magnesium solution into a 1000ml volumetric flask, and dilute with water to the scale and mix evenly. bzxZ.net
1ml of this standard solution contains 0.01mg magnesium.
7 Instruments
7.1 General laboratory instruments and atomic absorption spectrophotometer, equipped with N20-acetylene burner or air-acetylene burner. 7.2 Calcium and magnesium hollow cathode lamps.
7.3 Tower crucible: required Soak in hydrochloric acid and wash repeatedly. It is best to use a platinum crucible, and its stains should be scrubbed clean with fine sand. 8 Sample collection and preparation
Same as 3 in Method A.
Tear the air-dried sample into pieces of appropriate size. Gloves must be worn when preparing samples, but samples must not be prepared using shearing, punching or other tools that may cause metal contamination.
9 Test steps
9.1 Sample weighing and ashing
Same as 4.1 in Method A.
9.2 Sample ash treatment
First, add a few drops of distilled water to the ash (9.1) to moisten it, then add 5 ml of hydrochloric acid solution (6 .1) and evaporate to dryness on a steam bath. Repeat this process once, then treat the residue with 5 ml of hydrochloric acid solution and heat on a steam bath for 5 min. Transfer the contents into a 100 ml volumetric flask with water. To ensure complete extraction, add 5 ml of hydrochloric acid solution (6.1) to the residue in each crucible and heat on a steam bath. Transfer this last portion of the contents into a volumetric flask with water. Combine with the main sample solution, dilute to the mark with water and mix well. 9.3 Preparation of standard comparison solution
Add 4 ml or 20 ml of 5% strontium chloride solution (6.2) to each of the six 100 ml volumetric flasks. l. Lanthanum solution (6.3) and 10ml hydrochloric acid solution (6.1), then add calcium standard solution II or magnesium standard solution II according to the volume shown in Table 2. 476
Volume, ml.
GB8943.4—88
Calcium standard solution II
Equivalent calcium, mg
Note: 1) Reagent blank test for calibration curve. 9.4 Preparation of test solution
Volume, mL
Magnesium standard solution H
Equivalent calcium.mg
Use a pipette to transfer a certain volume V of test solution (9.2) into a 50mL volumetric flask. Make sure that the calcium or magnesium content meets the specified range in Table 2. If the calcium and magnesium content of the sample is unknown, V, it can be measured in advance by atomic absorption, such as transferring 1.0mL, 2.0mL or 5.0mL to make a preliminary measurement together with the standard comparison solution, or transferring 20mL to determine the approximate content by method A and then adding 2ml of 5% strontium chloride solution (6.2) or 10mL of lanthanum solution (6.3) 5mL of hydrochloric acid solution and diluting to the scale with water. If the solution contains suspended matter, wait until the suspended matter sinks before measuring the spectrum. 9.5 Calibration of the instrument
Install the calcium (or magnesium) hollow cathode lamp on the lamp holder of the atomic absorption spectrophotometer, turn on the instrument according to the operating steps specified by the instrument, connect the current and stabilize the current. Adjust the wavelength according to the instrument measurement conditions. Calcium is at 422.7nm and magnesium is at 285.2nm, and adjust to the maximum absorption value within their wavelength range.
Then adjust the current, sensitivity, slit, burner head height, gas/fuel ratio, air flow velocity, suction volume, etc. to the specified test conditions according to the instrument characteristics (each instrument provides test reference conditions). If N,-acetylene is used, special attention should be paid to safety. To prevent explosion, use N,O-acetylene burner, and be sure to ignite it with air-acetylene burner before connecting N2O-acetylene.
9.6 Absorption value measurement
Wait for the instrument to be normal and the flame to burn stably, and then suck the standard comparison solution into the flame in turn. And measure the absorption value of each solution. When measuring, a blank test solution should be used as a control, and the absorption value of the instrument should be adjusted to zero, and then the remaining samples should be measured. During the entire process of preparing the calibration curve, it is important to keep the instrument conditions constant. After each measurement, spray water through the burner for cleaning. The determination of the absorption value of the calibration curve series must be carried out simultaneously with the determination of the absorption value of the sample solution to overcome the error caused by changes in experimental conditions.
9.7 Drawing the curve
Use the weight of calcium or magnesium (in mg) (per 100 mL of the standard comparison solution) as the abscissa and the corresponding absorption value as the ordinate to draw the calibration curve.
10 Calculation of results
The corresponding weight of calcium or magnesium (in mg) is obtained from the absorption value of the sample solution on the calibration curve, and its content is calculated by the following formula, expressed in mg/kg.
Formula: 50 000-
Calcium content = 50000×vm
Magnesium content = 50 000×m
is the sample release and conversion factor;
(5)
GB8943.4—88
is the calcium or magnesium content of the test solution obtained from the calibration curve, mg; is the volume of the sample solution to be transferred for absorption value measurement, mL; is the absolute dry weight of the sample, g.
Use the average of the two determinations and report the results according to the provisions of Table 3. Table 3
Average value of results
≥100～500
Additional notes:
This standard is drafted by the Paper Industry Research Institute of the Ministry of Light Industry. 478
Precise units reported1 Weighing and ashing of the sample
Same as 4.1 in Method A.
9.2 Treatment of the sample ash
First add a few drops of distilled water to the ash (9.1) to moisten it, then add 5 ml of hydrochloric acid solution (6.1) and evaporate to dryness on a steam bath. Repeat this once, then treat the residue with 5 ml of hydrochloric acid solution and heat it on a steam bath for 5 minutes. Transfer the contents to a 100 mL volumetric flask with water. To ensure complete extraction, add 5 mL of hydrochloric acid solution (6.1) to the residue in each crucible and heat it on a steam bath. Transfer this last part of the contents to a volumetric flask with water. Combine it with the main sample solution, dilute to the mark with water and mix well. 9.3 Preparation of standard comparison solution
Add 4 mL of 5% strontium chloride solution (6.2) or 20 mL of lanthanum solution (6.3) and 10 mL of hydrochloric acid solution (6.1) to six 100 mL volumetric flasks, and then add calcium standard solution II or magnesium standard solution II according to the volume shown in Table 2. 476
Volume, ml.
GB8943.4—88
Calcium standard solution II
Equivalent calcium, mg
Note: 1) Reagent blank test for calibration curve. 9.4 Preparation of test solution
Volume, mL
Magnesium standard solution H
Equivalent calcium. mg
Use a pipette to transfer a certain volume V of test solution (9.2) into a 50 mL volumetric flask. Make sure that the calcium or magnesium content meets the specified range in Table 2. If the calcium and magnesium content of the sample is unknown, V, it can be measured in advance by atomic absorption, such as transferring 1.0mL, 2.0mL or 5.0mL to make a preliminary measurement together with the standard comparison solution, or transferring 20mL to determine the approximate content by method A and then adding 2ml of 5% strontium chloride solution (6.2) or 10mL of lanthanum solution (6.3) 5mL of hydrochloric acid solution and diluting to the scale with water. If the solution contains suspended matter, wait until the suspended matter sinks before measuring the spectrum. 9.5 Calibration of the instrument
Install the calcium (or magnesium) hollow cathode lamp on the lamp holder of the atomic absorption spectrophotometer, turn on the instrument according to the operating steps specified by the instrument, connect the current and stabilize the current. Adjust the wavelength according to the instrument measurement conditions. Calcium is at 422.7nm and magnesium is at 285.2nm, and adjust to the maximum absorption value within their wavelength range.
Then adjust the current, sensitivity, slit, burner head height, gas/fuel ratio, air flow velocity, suction volume, etc. to the specified test conditions according to the instrument characteristics (each instrument provides test reference conditions). If N,-acetylene is used, special attention should be paid to safety. To prevent explosion, use N,O-acetylene burner, and be sure to ignite it with air-acetylene burner before connecting N2O-acetylene.
9.6 Absorption value measurement
Wait for the instrument to be normal and the flame to burn stably, and then suck the standard comparison solution into the flame in turn. And measure the absorption value of each solution. When measuring, a blank test solution should be used as a control, and the absorption value of the instrument should be adjusted to zero, and then the remaining samples should be measured. During the entire process of preparing the calibration curve, it is important to keep the instrument conditions constant. After each measurement, spray water through the burner for cleaning. The determination of the absorption value of the calibration curve series must be carried out simultaneously with the determination of the absorption value of the sample solution to overcome the error caused by changes in experimental conditions.
9.7 Drawing the curve
Use the weight of calcium or magnesium (in mg) (per 100 mL of the standard comparison solution) as the abscissa and the corresponding absorption value as the ordinate to draw the calibration curve.
10 Calculation of results
The corresponding weight of calcium or magnesium (in mg) is obtained from the absorption value of the sample solution on the calibration curve, and its content is calculated by the following formula, expressed in mg/kg.
Formula: 50 000-
Calcium content = 50000×vm
Magnesium content = 50 000×m
is the sample release and conversion factor;
(5)
GB8943.4—88
is the calcium or magnesium content of the test solution obtained from the calibration curve, mg; is the volume of the sample solution to be transferred for absorption value measurement, mL; is the absolute dry weight of the sample, g.
Use the average of the two determinations and report the results according to the provisions of Table 3. Table 3
Average value of results
≥100～500
Additional notes:
This standard is drafted by the Paper Industry Research Institute of the Ministry of Light Industry. 478
Precise units reported1 Weighing and ashing of the sample
Same as 4.1 in Method A.
9.2 Treatment of the sample ash
First add a few drops of distilled water to the ash (9.1) to moisten it, then add 5 ml of hydrochloric acid solution (6.1) and evaporate to dryness on a steam bath. Repeat this once, then treat the residue with 5 ml of hydrochloric acid solution and heat it on a steam bath for 5 minutes. Transfer the contents to a 100 mL volumetric flask with water. To ensure complete extraction, add 5 mL of hydrochloric acid solution (6.1) to the residue in each crucible and heat it on a steam bath. Transfer this last part of the contents to a volumetric flask with water. Combine it with the main sample solution, dilute to the mark with water and mix well. 9.3 Preparation of standard comparison solution
Add 4 mL of 5% strontium chloride solution (6.2) or 20 mL of lanthanum solution (6.3) and 10 mL of hydrochloric acid solution (6.1) to six 100 mL volumetric flasks, and then add calcium standard solution II or magnesium standard solution II according to the volume shown in Table 2. 476
Volume, ml.
GB8943.4—88
Calcium standard solution II
Equivalent calcium, mg
Note: 1) Reagent blank test for calibration curve. 9.4 Preparation of test solution
Volume, mL
Magnesium standard solution H
Equivalent calcium. mg
Use a pipette to transfer a certain volume V of test solution (9.2) into a 50 mL volumetric flask. Make sure that the calcium or magnesium content meets the specified range in Table 2. If the calcium and magnesium content of the sample is unknown, V, it can be measured in advance by atomic absorption, such as transferring 1.0mL, 2.0mL or 5.0mL to make a preliminary measurement together with the standard comparison solution, or transferring 20mL to determine the approximate content by method A and then adding 2ml of 5% strontium chloride solution (6.2) or 10mL of lanthanum solution (6.3) 5mL of hydrochloric acid solution and diluting to the scale with water. If the solution contains suspended matter, wait until the suspended matter sinks before measuring the spectrum. 9.5 Calibration of the instrument
Install the calcium (or magnesium) hollow cathode lamp on the lamp holder of the atomic absorption spectrophotometer, turn on the instrument according to the operating steps specified by the instrument, connect the current and stabilize the current. Adjust the wavelength according to the instrument measurement conditions. Calcium is at 422.7nm and magnesium is at 285.2nm, and adjust to the maximum absorption value within their wavelength range.
Then adjust the current, sensitivity, slit, burner head height, gas/fuel ratio, air flow velocity, suction volume, etc. to the specified test conditions according to the instrument characteristics (each instrument provides test reference conditions). If N,-acetylene is used, special attention should be paid to safety. To prevent explosion, use N,O-acetylene burner, and be sure to ignite it with air-acetylene burner before connecting N2O-acetylene.
9.6 Absorption value measurement
Wait for the instrument to be normal and the flame to burn stably, and then suck the standard comparison solution into the flame in turn. And measure the absorption value of each solution. When measuring, a blank test solution should be used as a control, and the absorption value of the instrument should be adjusted to zero, and then the remaining samples should be measured. During the entire process of preparing the calibration curve, it is important to keep the instrument conditions constant. After each measurement, spray water through the burner for cleaning. The determination of the absorption value of the calibration curve series must be carried out simultaneously with the determination of the absorption value of the sample solution to overcome the error caused by changes in experimental conditions.
9.7 Drawing the curve
Use the weight of calcium or magnesium (in mg) (per 100 mL of the standard comparison solution) as the abscissa and the corresponding absorption value as the ordinate to draw the calibration curve.
10 Calculation of results
The corresponding weight of calcium or magnesium (in mg) is obtained from the absorption value of the sample solution on the calibration curve, and its content is calculated by the following formula, expressed in mg/kg.
Formula: 50 000-
Calcium content = 50000×vm
Magnesium content = 50 000×m
is the sample release and conversion factor;
(5)
GB8943.4—88
is the calcium or magnesium content of the test solution obtained from the calibration curve, mg; is the volume of the sample solution to be transferred for absorption value measurement, mL; is the absolute dry weight of the sample, g.
Use the average of the two determinations and report the results according to the provisions of Table 3. Table 3
Average value of results
≥100～500
Additional notes:
This standard is drafted by the Paper Industry Research Institute of the Ministry of Light Industry. 478
Precise units reported4—88
Calcium or magnesium content of the test solution obtained from the calibration curve, mg; is the volume of the sample solution to be transferred for absorption value measurement, mL; is the absolute dry weight of the sample, g.
Use the average of the two determination results and report the results according to the provisions of Table 3. Table 3
Average value of the results
≥100～500
Additional remarks:
This standard is under the jurisdiction and drafted by the Paper Industry Science Research Institute of the Ministry of Light Industry. 478
Precise units for reporting4—88
Calcium or magnesium content of the test solution obtained from the calibration curve, mg; is the volume of the sample solution to be transferred for absorption value measurement, mL; is the absolute dry weight of the sample, g.
Use the average of the two determination results and report the results according to the provisions of Table 3. Table 3
Average value of the results
≥100～500
Additional instructions:
This standard is under the jurisdiction and drafted by the Paper Industry Science Research Institute of the Ministry of Light Industry. 478
Precise units for reporting
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