SN/T 4763-2017 English PDF (SNT4763-2017)

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SN/T 4763-2017: Determination of mercury in coal. Direct mercury analyzer with solid sampling
SN/T 4763-2017
SN
ENTRY-EXIT INSPECTION AND QUARANTINE INDUSTRY
STANDARD OF THE PEOPLE’S REPUBLIC OF CHINA
Determination of mercury in coal - Direct mercury analyzer
with solid sampling
ISSUED ON: MAY 12, 2017
IMPLEMENTED ON: DECEMBER 01, 2017
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine of the People's Republic of China
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Method summary ... 4
4 Reagents and materials ... 4
5 Instruments and equipment ... 5
6 Sample preparation ... 6
7 Analysis steps ... 6
8 Result expression ... 6
9 Precision ... 7
Annex A (informative) Working diagram of mercury meter ... 8
Annex B (informative) Reference working conditions for mercury analyzers ... 9
Determination of mercury in coal - Direct mercury analyzer
with solid sampling
1 Scope
This Standard specifies the method for directly injecting samples to determine the
mercury content in coal using a mercury analyzer.
This Standard is applicable to the determination of mercury content in lignite,
bituminous coal, anthracite and coal gangue. The measuring range is: 0.800 × 10-3 μg/g
~10.000 μg/g.
2 Normative references
The following referenced documents are indispensable for the application of this
document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
GB/T 474, Method for preparation of coal sample
GB/T 483, General rules for analytical and testing methods of coal
GB/T 602, Chemical reagent -- Preparations of standard solutions for impurity
GB/T 6682, Water for analytical laboratory use -- Specification and test methods
GB/T 19494.2, Mechanical sampling of coal - Part 2: Method for sample
preparation
3 Method summary
The test coal sample is directly sent to the mercury analyzer. After drying,
decomposition, and oxidation, various forms of mercury are released in the gaseous
state. After amalgamation occurs in the amalgamation tube and is enriched, mercury
atoms are released through rapid heating. The released mercury is measured using an
atomic absorption spectrometer at 253.7 nm.
4 Reagents and materials
Unless otherwise stated, all reagents used are guaranteed reagents, and the experimental
water is grade two water specified in GB/T 6682.
4.1 Nitric acid (ρ=1.42 g/mL).
4.2 Nitric acid: (5+95).
4.3 Certified reference materials for coal: mercury content has been determined.
4.4 Mercury standard stock solution (1000 µg/mL): use national certified standard
solution or prepare according to GB/T 602.
4.5 Mercury standard intermediate solution (100 µg/mL): accurately pipette 10 mL of
mercury standard stock solution (4.4) into a 100 mL volumetric flask. Add 5 mL of
nitric acid (4.1). Add water to dilute to volume. Shake well.
4.6 Mercury standard working solution series 1: absorb mercury standard intermediate
solution (4.5) to prepare: 0 µg/mL, 0.020 µg/mL, 0.050 µg/mL, 0.100 µg/mL, 0.250
µg/mL, 0.500 µg/mL mercury standard working solution. The solvent is nitric acid (4.2).
Prepare when needed.
4.7 Mercury standard working solution series 2: absorb mercury standard intermediate
solution (4.5) to prepare: 0 µg/mL, 0.50 µg/mL, 1.00 µg/mL, 2.00 µg/mL, 5.00 µg/mL,
10.00 µg/mL mercury standard working solution. The solvent is nitric acid (4.2).
Prepare when needed.
5 Instruments and equipment
5.1 Mercury analyzer: equipped with a powder direct sampling device, a thermal
decomposition device, an amalgamation device and an atomic absorption device (see
Annex A).
5.2 Analytical balance: division is 0.1 mg.
5.3 Volumetric flask: grade A, 100 mL.
5.4 Pipette tubes: grade A, 1.0 mL, 5.0 mL, 10.0 mL.
5.5 Pipette: 0 μL~100 μL.
5.6 Sample boat: made of quartz or nickel, suitable for instrument use. The volume is
not less than 150 μL.
5.7 Agate mortar.
5.8 Standard sieve: 116 μm.
5.9 High purity oxygen: purity ≥99.999%.
6 Sample preparation
The general analysis test coal samples prepared according to GB/T 474 or GB/T
19494.2 are ground with an agate mortar until all of them pass the 116 μm standard
sieve, and are set aside.
7 Analysis steps
7.1 Blank test
Do a blank test along with the specimen.
7.2 Sample determination
Accurately weigh 0.09 g±0.01 g of the general analysis test coal sample. Weighing is
accurate to 0.0001 g. Place in the sample boat. Refer to the working conditions in Annex
B for measurement.
7.3 Drawing of working curve
7.3.1 Working curve 1
Adjust the instrument conditions to appropriate working parameters according to the
instrument instructions (see Annex B). In order from low concentration to high
concentration, pipette 100 μL of mercury standard working solution series 1 (4.6) and
add it to the sample boat for measurement. Draw the working curve 1 with the mercury
content in the standard working solution as the abscissa and the absorbance as the
ordinate.
7.3.2 Working curve 2
Determine the mercury standard working solution series 2 (4.7) according to steps 7.3.1.
Draw working curve 2.
7.4 Verification of standard curve
Measure the standard materials with similar contents at the upper and lower ends of
each standard curve, respectively. If the measurement result is within the uncertainty
range of the standard value, the standard curve is valid; otherwise, the cause should be
found and the standard curve should be redrawn.
8 Result expression
The mercury content in general analytical test coal samples is calculated according to
formula (1):