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GB/T 3058-2019 English PDF (GBT3058-2019)

GB/T 3058-2019 English PDF (GBT3058-2019)

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GB/T 3058-2019: Determination of arsenic in coal
This standard specifies the method summary, reagents and materials, instruments and equipment, samples, test procedures, calculation and presentation of results, the precision of the method for the determination of arsenic in coal by arsenic molybdenum blue spectrophotometry and hydride generation-atomic absorption method. Arsenic molybdenum blue spectrophotometry is the arbitration method.
GB/T 3058-2019
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 73.040
D 21
Replacing GB/T 3058-2008
Determination of arsenic in coal
(ISO 11723:2016, Solid mineral fuels - Determination of arsenic and selenium - Eschka's mixture and hydride generation method, NEQ)
ISSUED ON: JUNE 04, 2019
IMPLEMENTED ON: JANUARY 01, 2020
Issued by: State Administration for Market Regulation;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Arsenic molybdenum blue spectrophotometry ... 4
4 Hydride generation-atomic absorption method ... 9
5 Precision ... 14
6 Test report ... 14
Appendix A (Informative) Recovery rate of arsenic measuring device ... 15 Determination of arsenic in coal
1 Scope
This standard specifies the method summary, reagents and materials,
instruments and equipment, samples, test procedures, calculation and
presentation of results, the precision of the method for the determination of arsenic in coal by arsenic molybdenum blue spectrophotometry and hydride generation-atomic absorption method. Arsenic molybdenum blue
spectrophotometry is the arbitration method.
This standard applies to lignite, bituminous coal, anthracite.
2 Normative references
The following documents are essential to the application of this document. For the dated documents, only the versions with the dates indicated are applicable to this document; for the undated documents, only the latest version (including all the amendments) is applicable to this standard.
GB/T 483 General rules for analytical and testing methods of coal
GB/T 2304 Chemical reagent - Zinc granular free from arsenic
3 Arsenic molybdenum blue spectrophotometry
3.1 Method summary
The coal sample is mixed with Eschka reagent and burned. The burned material is dissolved with hydrochloric acid and sulfuric acid. A reducing agent is added to reduce pentavalent arsenic to trivalent arsenic. Add zinc particles to form and release arsenic hydride gas. Use iodine solution to absorb and oxidize it to arsenic acid. Add ammonium molybdate-hydrazine sulfate solution to produce arsenic molybdenum blue. Then use a spectrophotometer to determine it.
3.2 Reagents and materials
Unless otherwise specified, only use reagents and distilled or deionized water or equivalent purity water confirmed to be analytically pure in the analysis. 3.2.1 Arsenic-free zinc metal: In accordance with GB/T 2304, screen out zinc for about 2 hours and dissolve it in 2 mL sodium hydroxide solution (3.2.14). Add about 50 mL of water. Add 2.5 mL sulfuric acid solution (3.2.5) after it is completely dissolved. Use water to dilute it to 1000 mL. The arsenic standard stock solution can also use a commercially available certified arsenic standard material solution.
3.2.16 Arsenic standard working solution: 10 μg/mL. Accurately pipette 50 mL of arsenic standard stock solution (3.2.15) in a 500 mL volumetric flask. Use water to dilute it to the mark. Shake well. Transfer it to a plastic bottle for later use.
3.2.17 Lead acetate cotton: It is replaced each time of the experiment. The absorbent cotton is fully soaked in a lead acetate solution which has a mass concentration of 400 g/L. Take it out and twist it dry. Dry it at 80 °C ~100 °C. Store it in a desiccator for later use.
3.2.18 Porcelain crucible: The capacity is 30 mL. The enamel on the inner surface is intact.
3.3 Instrument and equipment
3.3.1 Arsenic measuring device: The arsenic measuring device shall meet the requirements of Figure 1. For newly-purchased or unused arsenic measuring devices, check whether the size of the arsenic measurement device is qualified before being put into use, whether the grinding holes are tight. Refer to the method in Appendix A to determine the recovery rate of the device. Select the device which has a recovery rate of not less than 90% as an instrument for daily use.
3.3.2 Spectrophotometer: The wavelength range includes 700 nm and 830 nm. 3.3.3 Muffle furnace: It is equipped with a temperature control device. It can be heated from room temperature to (800 ± 10) °C within 2 h, with good ventilation. 3.3.4 Analytical balance: The division value is 0.1 mg.
3.3.5 Balance: The division value is 0.1 g.
3.3.6 Balance: The division value is 0.01 g.
3.3.7 Single marking line pipette: The capacity is 1 mL, 2 mL, 3 mL, 5 mL. (3.2.16). Place it into the round flask of the arsenic determination device. First add 10 mL of sulfuric acid solution (3.2.5). Then add 20 mL of hydrochloric acid solution (3.2.4). Use water to dilute it to 50 mL.
3.5.1.2 Add 2 mL of potassium iodide solution (3.2.7), 1 mL of stannous chloride solution (3.2.8). Shake it uniformly. Place it at room temperature for 15 min. 3.5.1.3 Use a pipette to add 3 mL of iodine solution (3.2.9), 1 mL of sodium bicarbonate solution (3.2.13), 6 mL of water to the absorber of the arsenic determination device. Insert the absorber into the absorber casing which contains lead acetate cotton (3.2.17).
3.5.1.4 Add 5.0 g of arsenic-free zinc metal (3.2.1) to the round flask. Immediately connect the absorber casing to the flask. After confirming that there is no air leakage at the instrument interfaces, let the generation process continue for 1 h.
3.5.1.5 Take out the absorber. Add 5 mL of ammonium molybdate-hydrazine sulfate mixed solution (3.2.12). Use ear wash balls to pump in air via the side hole of the absorber about 10 times, to make the absorption liquid fully mixed evenly. Heat the absorber in a boiling water bath for 20 minutes. Take it out. Cool to room temperature. This is the working curve solution.
3.5.1.6 On the spectrophotometer, use a 10 mm cuvette, at 700 nm (or 830 nm) wavelength; use a standard blank solution as a reference, to measure the absorbance of the working curve. When the arsenic content in coal is low, the absorbance shall be measured at a wavelength of 830 nm.
3.5.1.7 Draw a working curve with the mass of arsenic [micrograms (μg)] as the abscissa and the corresponding absorbance as the ordinate. Proceed it
simultaneously with the analysis of the coal sample.
3.5.2 Sample determination
3.5.2.1 Weigh 2 g of aldrin agent in a porcelain crucible (accurate to 0.01 g). Then weigh 0.99 g ~ 1.01 g (accurate to 0.0002 g) of coal sample for general analysis test which has a particle size of less than 0.2 mm. Use a glass rod to stir it uniformly. Then use 1 g (accurate to 0.01 g) of Aldrin to evenly cover the mixed coal sample (no black coal particles can be seen). When the ash content in the coal sample is greater than 40%, or the arsenic content is greater than 50 μg/g or the total sulfur content is greater than 8%, the sample weight is 0.50 g.
3.5.2.2 Put the crucible into the muffle furnace. Slowly heat from room temperature to (800 ± 10) °C within about 2 h. Keep it at this temperature for 2 h ~ 3 h. Take out the crucible and cool to room temperature.
The coal sample is mixed with aldrin and burned. The burned material is dissolved by hydrochloric acid. The pentavalent arsenic is reduced to trivalent arsenic by potassium iodide. Then the trivalent arsenic is reduced to arsenic hydride by sodium borohydride. The nitrogen is used as the carrier gas; it is introduced into a quartz tube atomizer and measured by atomic absorption method.
4.2 Reagents and materials
Unless otherwise specified, only use reagents and distilled or deionized water or equivalent purity water confirmed to be analytically pure in the analysis. 4.2.1 Aldrin: Same as 3.2.2.
4.2.2 Hydrochloric acid: Same as 3.2.3.
4.2.3 Sodium hydroxide solution: 5 g/L. Weigh 5.0 g of sodium hydroxide and dissolve it in 1 L of water.
4.2.4 Sodium borohydride solution: 18 g/L. Weigh 18.0 g of sodium borohydride and dissolve it in 1 L of sodium hydroxide solution (4.2.3). Prepare it immediately before use.
4.2.5 Potassium iodide solution: 300 g/L. Dissolve 300.0 g of potassium iodide in 1 L of water.
4.2.6 Sodium thiosulfate solution: Saturated solution.
4.2.7 Arsenic standard stock solution: 100 μg/mL, same as 3.2.15.
4.2.8 Arsenic standard intermediate solution: 10 μg/mL, same as 3.2.16. 4.2.9 Arsenic standard working solution: 0.2 μg/mL. Pipette 1 mL of arsenic standard intermediate solution (4.2.8) in a 50 mL volumetric flask. Use blank solution (4.5.2.2) to dilute it to the mark. Shake well.
4.2.10 Nitrogen: Purity above 99.9%.
4.2.11 Porcelain crucible: Same as 3.2.18.
4.2.12 Porcelain evaporating dish: The capacity is 100 mL. The enamel on the inner surface is intact.
4.3 Instrument and equipment
4.3.1 Atomic absorption spectrophotometer: It has the functions of absorption peak area integration and peak height measurement.
raise the temperature to (800 ± 10) °C. Burn it for 3 h. Remove the evaporating dish. Cool it to room temperature.
4.5.2.2 Transfer the burned aldrin into a 400 mL beaker which contains 100 mL to 150 mL of hot water. Use 25 mL of hydrochloric acid (4.2.2) to dissolve the residue in the dish. Transfer it into the beaker. Use water to rinse all the residues into the beaker. Then use 75 mL of hydrochloric acid to rinse the evaporating dish three times (25 mL each time). Transfer the solution to the beaker. Stir to completely dissolve the Aldrin. Cool to room temperature. Transfer to a 500 mL volumetric flask. Use water to dilute it to the mark. Shake well. Transfer to a plastic bottle as a blank solution for storage.
4.5.3 Preparation and pre-reduction of standard series solution
4.5.3.1 Take six 100 mL volumetric flasks. Respectively add 0.0 mL, 1.0 mL, 2.0 mL, 3.0 mL, 4.0 mL, 5.0 mL of arsenic standard working solution (4.2.9). Then add 5 mL, 4 mL, 3 mL, 2 mL, 1 mL, 0 mL of blank solution (4.5.2.2), respectively. Shake well.
4.5.3.2 In the above series of solutions. Add 10 mL of hydrochloric acid (4.2.2) to each. Mix it uniformly. Then add 5 mL of potassium iodide solution (4.2.5). Use water to dilute it to about 50 mL. Place for 30 min. Add saturated sodium thiosulfate solution (4.2.6) to the bottle until the iodine fades. Use water to dilute it to the mark. Shake well.
4.5.4 Hydride generation-atomic absorption determination
4.5.4.1 Instrument preparation
Install the atomizer of the hydride generator on the burner of the atomic absorption spectrophotometer according to the instrument instructions, so that the quartz tube is located directly above the burner slit. Adjust the up and down, front and rear positions and rotation angle of the burner, to make the axis of the quartz tube coincide with the main optical axis of the atomic absorption spectrophotometer. Connect the gas path.
4.5.4.2 Selection of working parameters of atomic absorption
spectrophotometer
The parameter selection is as follows:
a) Measurement method: Absorption peak area integration or peak height; b) Flame: Air-acetylene flame;
c) Light source: Arsenic hollow cathode lamp or arsenic electrodeless
discharge lamp, monochromator's wavelength is 193.7 nm. According to
Appendix A
(Informative)
Recovery rate of arsenic measuring device
A.1 Method summary
Add a certain amount of arsenic standard working solution to each measuring device to make determination according to the arsenic hydride generation step. Then compare it with the determination result of direct color development without the arsenic hydride generation step. Determine the recovery rate of the arsenic measurement device based on the ratio of the two absorbance.
A.2 Operation steps
A.2.1 With arsenic hydride generation steps
A.2.1.1 Take two newly purchased or long-term unused arsenic measurement devices, one of which is marked as No.0, which is used as a standard blank solution without adding arsenic standard working solution. For the other one, use a single-line pipette to draw 1.0 mL or 2.0 mL of 10 μg/mL arsenic standard working solution in the round flask of the arsenic determination device. First add 10 mL sulfuric acid solution (3.2.5). Then add 20 mL of hydrochloric acid solution (3.2.4). Use water to dilute it to 50 mL.
A.2.1.2 The rest of the operation steps are the same as 3.5.1.2 ~ 3.5.1.6, to determine the absorbance A1.
A.2.2 Without arsine hydride generation steps
A.2.2.1 In the above two arsenic determination devices, the device marked as No.0 is not added with the arsenic standard working solution as the standard blank solution. For the other one, use a single-line pipette to draw 1.0 mL or 2.0 mL of 10 μg/mL arsenic standard working solution in the absorber of the arsenic measuring device.
A.2.2.2 Use a pipette to add 3 mL of iodine solution, 1 mL of sodium bicarbonate solution. Add 6 mL of water to the standard blank solution. Add 5 mL or 4 mL of water to the other device. Insert the absorber into the absorber casing. A.2.2.3 The rest of the operation steps are the same as 3.5.1.5 ~ 3.5.1.6, to determine the absorbance A2.
A.3 Result calculation
The recovery rate of the arsenic measuring device is calculated according to
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