GB/T 23947.1-2009 PDF in English
GB/T 23947.1-2009 (GB/T23947.1-2009, GBT 23947.1-2009, GBT23947.1-2009)
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Inorganic chemicals for industrial use -- General method for determination of arsenic -- Part 1: Silver diethyldithiocarbamate photometric method
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Standards related to (historical): GB/T 23947.1-2009
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GB/T 23947.1-2009: PDF in English (GBT 23947.1-2009) GB/T 23947.1-2009
GB
NATIONAL STANDARD OF THE
PEOPLE'S REPUBLIC OF CHINA
ICS 71.060.01
G 10
Inorganic chemicals for industrial use - General method for
determination of arsenic - Part 1.Silver
diethyldithiocarbamate photometric method
(ISO 2590.1973, MOD)
ISSUED ON. JUNE 2, 2009
IMPLEMENTED ON. FEBRUARY 1, 2010
Issued by. General Administration of Quality Supervision, Inspection and
Quarantine of PRC;
Standardization Administration of PRC.
Table of Contents
Foreword... 3
1 Scope... 5
2 Principle... 5
3 Reagents... 5
4 Apparatus... 6
5 Operation steps... 8
6 Presentation of results... 10
Appendix A (Normative) Use of needle-shaped zinc... 11
Appendix B (Informative) Ions that interfere with the determination... 12
Foreword
GB/T 23947 Inorganic chemicals for industrial use - General method for the
determination of arsenic content is divided into two parts.
-- Part 1.Silver diethyldithiocarbamate photometric method;
-- Part 2.Gutzeit method.
This part is Part 1 of GB/T 23947.
This part was modified in relation to ISO 2590.1973 General method for the
determination of arsenic - Silver diethyldithiocarbamate photometric method (English
version).
This part was drafted according to ISO 2590.1973.The clauses of this standard
correspond to the clauses of the international standard.
Since the international standards cited in ISO 2590.1973 have been abolished, this
standard has been modified when adopting ISO 2590.1973.The technical difference is
that the abolished international standards are not cited.
For ease of use, this part has made the following editorial changes.
-- In order to be consistent with Chinese inorganic chemical product series
standards, "Inorganic chemicals for industrial use" is added to the standard name;
-- The foreword of the international standard is deleted;
-- "This international standard" is replaced with "this standard";
-- The decimal point "." replaces the comma "," that was used as a decimal point;
-- The "Appendix" in the international standard is changed to "Appendix A";
-- Informative Appendix B is added for guidance.
Appendix A of this part is normative and Appendix B is informative.
This part was proposed by China Petroleum and Chemical Industry Association.
This part is under the jurisdiction of the Subcommittee on Inorganic Chemical Industry
of the National Technical Committee on Chemical of Standardization Administration
of China (SAC/TC63/SC1).
Inorganic chemicals for industrial use - General method for
determination of arsenic - Part 1.Silver
diethyldithiocarbamate photometric method
1 Scope
This part of GB/T 23942 specifies the general method for the determination of arsenic
in inorganic chemicals for industrial use -- the silver diethyldithiocarbamate
spectrophotometric method.
This method is applicable to an entire test solution or a test portion taken for
determination with arsenic (As) content of 1 μg~20 μg.
2 Principle
The arsenic is reduced to arsine with zinc in a hydrochloric acid medium, and then the
arsine is absorbed by a silver diethyldithiocarbamate pyridine solution. The purple-red
color produced by the dispersed silver colloid is photometrically measured at the
maximum absorption wavelength (about 540 nm). The reaction equation for the
formation of silver colloid is as follows.
3 Reagents
All reagents, especially zinc, shall contain no arsenic or very little arsenic. The water
used in the experiment shall be distilled water or water of equivalent purity.
3.1 Hydrochloric acid. The density is 1.19 g/mL; the mass fraction is about 38%, or the
concentration is 12 mol/L.
3.2 Silver diethyldithiocarbamate [Ag (DDTC)]. 5 g/L pyridine solution.
Dissolve 1 g of silver diethyldithiocarbamate in pyridine (with a density of about 0.980
g/mL), and dilute the solution to 200 mL with the same pyridine. Store it in a sealed
brown bottle away from light. The shelf life of this solution is two weeks.
3.3 Arsenic standard solution. 0.100 g/L.
Weigh 0.132 g of arsenic trioxide (As2O3), accurate to 0.0001 g, place it in a beaker of
appropriate volume (e.g., 100 mL), and dissolve it in about 2 mL of 50 g/L sodium
hydroxide solution; transfer all of it to a 1000 mL volumetric flask, rinse the beaker
with water several times, transfer the washing liquid to the volumetric flask, dilute with
water to the scale, and mix well.
1 mL of this standard solution contains 100 μg of arsenic (As).
3.4 Arsenic standard solution. 2.50 mg/L.
Pipette 25.0 mL of arsenic standard solution (3.3) into a 1000 mL volumetric flask,
dilute to the volume, and mix well. This solution shall be prepared before use.
1 mL of this standard solution contains 2.5 μg of arsenic (As).
3.5 Lead acetate absorbent cotton.
Dissolve 50 g of lead acetate trihydrate [Pb(C2H3O2)2 • 3H2O] in 250 mL of water. Soak
the absorbent cotton with this solution, remove the excess solution, and dry it under a
vacuum at room temperature.
Store it in an airtight container.
3.6 Potassium iodide solution. 150 g/L.
Dissolve 15 g of potassium iodide in water and dilute to 100 mL, then mix well.
3.7 Stannous chloride. hydrochloric acid solution.
Dissolve 40 g of stannous chloride dihydrate (SnCl2 • 2H2O) in a mixed solution of 25
mL of water and 75 mL of hydrochloric acid (3.1).
3.8 Zinc particles. 0.5 mm~1 mm; or any shape of zinc that has been proven through
tests to produce the same results under the specified test conditions (see Appendix A).
4 Apparatus
Glass containers used for arsenic determinations shall be rinsed with hot concentrated
sulfuric acid (be careful when doing this), then rinsed with water and dried completely.
4.1 Glassware with a ground glass joint for arsenic release and total absorption.
The apparatus is shown in Figure 1 and consists of the following parts.
4.1.1 Conical flask. 100 mL; it is used for arsenic release.
4.1.2 Connecting pipe. It is used for absorbing hydrogen sulfide.
4.1.3 15-ball absorber.
4.2 Spectrophotometer.
4.3 Photoelectric absorption meter. It is equipped with a filter with a maximum
transmittance at 520 nm~560 nm.
5 Operation steps
WARNING -- Since pyridine is toxic and has a foul odor, it is recommended to
handle it with caution in a fume hood.
5.1 Weighing samples and preparing test solutions
Weigh the specimen according to the amount specified in the standard of the product to
be tested, and treat the specimen according to the following conditions to obtain the test
solution.
In general, the total volume of the test solution prepared or the volume of the test
solution taken for determination is 40 mL, containing 1 μg~20 μg of arsenic and 10 mL
of hydrochloric acid (3.1). Before the potassium iodide solution is added, the acidity of
the test solution shall be 3 mol/L. Nitrate ions must not be present in the test solution.
In addition, certain elements (cobalt, mercury, silver, copper, molybdenum, cesium, etc.)
will affect the formation of arsine. If necessary, the operating steps shall indicate how
to take into account the effects of their presence.
NOTE. When the test solution is sulfuric acid medium, the acidity of 40 mL test solution shall be 1.9
mol/L~2 mol/L (including 10 mL of about 7.5 mol/L sulfuric acid solution).
5.2 Blank test
Simultaneously with the determination, a blank test is performed using the same
procedure and the same amounts of all reagents.
5.3 Drawing of working curve
The working curve shall be re-plotted whenever a new batch of zinc is used or a freshly
prepared silver diethyldithiocarbamate solution is used.
5.3.1 Preparation of standard reference solution when using 1 cm cuvette for
photometric measurement.
Add arsenic standard solution (3.4) into 6 conical flasks (4.1.1) according to the
volumes shown in Table 1.
Table 1 -- Volume of arsenic standard solution and corresponding arsenic mass
Add 10 mL of hydrochloric acid (3.1) to each conical flask, add water to about 40 mL,
add 2 mL of potassium iodide solution (3.6) and 2 mL of stannous chloride solution
(3.7), shake well, and then let them stand for 15 min.
NOTE. When the test solution is sulfuric acid, 10 mL of about 7.5 mol/L sulfuric acid solution must be
used to replace 10 mL of hydrochloric acid.
Place some lead acetate absorbent cotton (3.5) in the connecting pipe (4.1.2) to absorb
the hydrogen sulfide released along with the arsine.
Apply grease that is insoluble in pyridine to the ground glass joint. Pipette 5.0 mL of
silver diethyldithiocarbamate solution (3.2) and place it in the absorber (4.1.3). Connect
the absorber to the connecting pipe (4.1.2) with a safety clip.
After standing for 15 min, add 5 g of zinc (3.8) into the conical flask using a funnel and
immediately assemble the instrument as shown in the figure.
The reaction takes about 45 min.
Remove the absorber (4.1.3), shake it to dissolve the red precipitate formed at the
bottom, and mix the solution thoroughly.
The color of the solution is stable within 2 hours in the absence of light and the
measurement shall be carried out within this time range.
5.3.2 Photometric measurement
Use a spectrophotometer (4.2) at the wavelength of about 540 nm or a photoelectric
absorption meter (4.3) equipped with a corresponding filter to make photometric
measurements after the absorbance of the instrument is adjusted to zero with the reagent
blank solution.
5.3.3 Drawing of working curve
Volume of arsenic standard solution (3.4)/mL
a Reagent blank solution.
Corresponding arsenic mass/μg
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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