HJ 491-2019 English PDF (HJ491-2019)

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HJ 491-2019: Soil and sediment - Determination of copper, zinc, lead, nickel and chromium - Flame atomic absorption spectrophotometry
HJ 491-2019
HJ
NATIONAL ENVIRONMENTAL PROTECTION STANDARD
OF THE PEOPLE’S REPUBLIC OF CHINA
Replacing HJ 491-2009
Soil and sediment - Determination of copper, zinc, lead,
nickel and chromium - Flame atomic absorption
spectrophotometry
ISSUED ON: MAY 12, 2019
IMPLEMENTED ON: SEPTEMBER 01, 2019
Issued by: Ministry of Ecology and Environment
Soil and sediment - Determination of copper, zinc, lead,
nickel and chromium - Flame atomic absorption
spectrophotometry
Warning: Since the perchloric acid and nitric acid used in the experiment are
highly oxidizing and corrosive, and the hydrochloric acid and hydrofluoric acid
are highly volatile and highly corrosive, reagent preparation and sample digestion
shall be carried out in a fume hood; during the operation, protective equipment
shall be wore as required to avoid inhalation into respiratory tract or contact with
skin and clothing.
1 Scope of application
This Standard specifies the flame atomic absorption spectrophotometry for the
determination of copper, zinc, lead, nickel and chromium in soil and sediment.
This Standard applies to the determination of copper, zinc, lead, nickel and chromium
in soil and sediment.
When the sample volume is 0.2 g and the constant volume after digestion is 25 ml, the
method detection limits for copper, zinc, lead, nickel and chromium are 1 mg/kg, 1
mg/kg, 10 mg/kg, 3 mg/kg and 4 mg/kg, respectively, and the lower limits of
determination are 4 mg/kg, 4 mg/kg, 40 mg/kg, 12 mg/kg and 16 mg/kg, respectively.
2 Normative references
This standard refers to the following documents or clauses therein. For undated
references, the valid edition applies to this Standard.
GB 17378.3, The specification for marine monitoring - Part 3: Sample collection
storage and transportation
GB 17378.5, The specification for marine monitoring - Part 5: Sediment analysis
HJ 494, Water quality - Guidance on sampling techniques
HJ 613, Soil - Determination of dry matter and water content - Gravimetric method
HJ 832, Soil and sediment - Digestion of total metal elements - Microwave assisted
acid digestion method
HJ/T 166, Technical specification for soil environmental monitoring
3 Principle of the method
After the soil and sediment are digested by acid, the copper, zinc, lead, nickel and
chromium in the sample are atomized in the air-acetylene flame, and the ground state
atoms have selective absorption of the characteristic spectral lines of copper, zinc, lead,
nickel and chromium respectively; the absorption intensity is proportional to the
concentration of copper, zinc, lead, nickel and chromium within a certain range.
4 Interference and elimination
4.1 Iron below 1 000 mg/L does not interfere with the determination of zinc.
4.2 Potassium, sodium, magnesium, iron and aluminum below 2 000 mg/L, as well as
calcium below 1 000 mg/L, do not interfere with the determination of lead.
4.3 When using 232.0 nm as the absorption line to measure nickel, it is influenced by
the nickel three-line spectrum of similar wavelength, and the selection of 0.2 nm
spectral passband can reduce the influence.
4.4 Under the conditions of this Standard, when using a reducing flame, the common
elements coexisting in soil and sediment do not interfere with the determination of
chromium.
5 Reagents and materials
Unless otherwise stated, use guaranteed reagents that meet national standards in the
analysis, and use freshly prepared deionized water as the experimental water.
5.1 Hydrochloric acid: ρ(HCl) = 1.19 g/ml.
5.2 Nitric acid: ρ(HNO3) = 1.42 g/ml.
5.3 Hydrofluoric acid: ρ(HF) = 1.49 g/ml.
5.4 Perchloric acid: ρ(HClO4) = 1.68 g/ml.
5.5 Metal copper: spectral pure.
5.6 Metal zinc: spectral pure.
5.7 Metal lead: spectral pure.
5.8 Metal nickel: spectral pure.
5.9 Metal chromium: spectral pure.
Accurately pipette 10.00 ml of zinc standard stock solution (5.14) into a 100 ml
volumetric flask; use nitric acid solution (5.12) to dilute to the mark; shake well. Store
in a polyethylene bottle; refrigerate below 4 ℃, valid for one year.
5.20 Lead standard working solution: ρ(Pb) = 100 mg/L.
Accurately pipette 10.00 ml of lead standard stock solution (5.15) into a 100 ml
volumetric flask; use nitric acid solution (5.12) to dilute to the mark; shake well. Store
in a polyethylene bottle; refrigerate below 4 ℃, valid for one year.
5.21 Nickel standard working solution: ρ(Ni) = 100 mg/L.
Accurately pipette 10.00 ml of nickel standard stock solution (5.16) into a 100 ml
volumetric flask; use nitric acid solution (5.12) to dilute to the mark; shake well. Store
in a polyethylene bottle; refrigerate below 4 ℃, valid for one year.
5.22 Chromium standard working solution: ρ(Cr) = 100 mg/L.
Accurately pipette 10.00 ml of chromium standard stock solution (5.17) into a 100 ml
volumetric flask; use nitric acid solution (5.12) to dilute to the mark; shake well. Store
in a polyethylene bottle; refrigerate below 4 ℃, valid for one year.
5.23 Gas: acetylene, purity ≥99.5%.
5.24 Supporting gas: air, where water, oil and other impurities shall be removed before
entering the burner.
6 Instruments and apparatuses
6.1 Flame atomic absorption spectrophotometer.
6.2 Light source: sharp line source or continuous light source of copper, zinc, lead,
nickel and chromium elements.
6.3 Electrothermal digestion device: temperature-controlled electric heating plate or
graphite electrothermal digestion instrument, with a temperature control accuracy of
±5 °C.
6.4 Microwave digestion device: power 600 W ~ 1 500 W, equipped with microwave
digestion tank.
6.5 Polytetrafluoroethylene crucible or polytetrafluoroethylene digestion tube: 50 ml.
6.6 Analytical balance: sensitivity 0.1 mg.
6.7 Utensils and equipment commonly used in general laboratories.
7 Sample
7.1 Sample collection and storage
Soil samples shall be collected and stored in accordance with the relevant requirements
of HJ/T 166; sediment samples shall be collected and stored in accordance with the
relevant requirements of GB 17378.3 or HJ 494.
7.2 Sample preparation
Remove foreign matter (such as sticks, leaves, stones) in the sample; in accordance with
the requirements of HJ/T 166 and GB 17378.3, air-dry, crush, and sieve the collected
samples in the laboratory, and save them for future use.
7.3 Determination of moisture
Measure the dry matter content of soil samples according to HJ 613; determine the
moisture content of sediment samples according to GB 17378.5.
7.4 Preparation of test pieces
7.4.1 Electrothermal digestion method
7.4.1.1 Hot plate digestion method
Weigh 0.2 g ~ 0.3 g (accurate to 0.1 mg) of the sample (7.2) into a 50 ml
polytetrafluoroethylene crucible (6.5); use water to wet it; then, add 10 ml of
hydrochloric acid (5.1); put it on the electric heating plate in the fume hood at 90 ℃ ~
100°C to decompose the sample initially; when the digestion solution evaporates to
about 3 ml remaining, add 9 ml of nitric acid (5.2); cover and heat until there are no
obvious particles; add 5 ml ~ 8 ml of hydrofluoric acid (5.3); uncover the lid; heat to
remove silicon at 200 ℃ for 30 minutes; cool slightly; add 1 ml of perchloric acid (5.4);
heat at 150 ℃ ~ 170 ℃ until white smoke comes out; shake the crucible frequently
during heating. If there are black carbides on the crucible wall, add 1 ml of perchloric
acid (5.4); cover and continue to heat until the black carbides disappear; then, uncover;
heat to rem...