GB/T 14637-2021 English PDF (GB/T14637-2021)

GB/T 14637-2021: Determination of copper, iron and zinc in industrial circulating cooling water and scale - Atomic absorption spectrometric method
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GB/T 14637-2021
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 71.040.40
CCS G 76
Replacing GB/T 14637-2007
Determination of copper, iron and zinc in industrial
circulating cooling water and scale - Atomic absorption
spectrometric method
ISSUED ON: AUGUST 20, 2021
IMPLEMENTED ON: MARCH 01, 2022
Issued by: State Administration for Market Regulation;
Standardization Administration of the People's Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Terms and definitions ... 6
4 Principle ... 6
5 Reagents or materials ... 6
6 Instruments and equipment ... 7
7 Selection of instrument conditions ... 7
8 Specimen preparation ... 7
9 Determination steps ... 9
10 Result calculation ... 11
11 Allowable difference ... 13
Annex A (normative) Preparation of standard stock solutions ... 14
Bibliography ... 15
Determination of copper, iron and zinc in industrial
circulating cooling water and scale - Atomic absorption
spectrometric method
1 Scope
This document specifies the determination method of copper, iron and zinc content in
industrial circulating cooling water and scale in boiler water system or circulating water
system - atomic absorption spectrometry.
This document is applicable to the determination of copper content of 0.1mg/L~20mg/L,
iron content of 0.1mg/L~20mg/L and zinc content of 0.1mg/L~20mg/L in industrial
circulating cooling water; the determination of copper content ≥ 0.005%, iron content
≥ 0.01%, zinc content ≥ 0.005% in scale.
This document is also applicable to the determination of copper, iron and zinc in boiler
water and the determination of copper, iron and zinc in scale in other industrial water,
raw water and water systems, as well as the determination of zinc content in
phosphorus-zinc pre-film solution for industrial circulating cooling water.
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 4470, Analytical spectroscopic methods. Flame emission, atomic absorption
and atomic fluorescence. Vocabulary
GB/T 6682-2008, Water for analytical laboratory use - Specification and test
methods
DL/T 1151.2, Analytical methods of scale and corrosion products in power plants.
Part 2: Sampling and dissolving method for scale and corrosion products
HG/T 3530, Industrial circulating cooling water. Sampling and production for
sludge and corrosion products
3 Terms and definitions
For the purposes of this document, the terms and definitions defined in GB/T 4470
apply.
4 Principle
The specimen is atomized and sprayed into the air-acetylene flame. Copper, iron, and
zinc are pyrolyzed into ground state atoms. Take copper resonance line 324.7nm, iron
resonance line 248.3nm, and zinc resonance line 213.9nm as analysis lines to measure
the absorbance of copper, iron, and zinc atoms.
5 Reagents or materials
WARNING -- Acetylene gas used in this document is flammable and explosive
when mixed with air. Pay attention to safety. Prevent leakage. Operate strictly
according to the specifications. Strong acids are corrosive, so be careful when using
them. When splashed on body, rinse with plenty of water. Avoid inhalation or
contact with skin.
Reagents used in this document, unless otherwise specified, are only analytically pure
reagents. See GB 6819 for the requirements of acetylene gas used in the test.
5.1 Water: GB/T 6682-2008, grade two.
5.2 Hydrochloric acid.
5.3 Nitric acid.
5.4 Perchloric acid.
5.5 Nitric acid solution: 1+1.
5.6 Nitric acid solution: 1+99.
5.7 Silver nitrate solution: 10g/L.
5.8 Copper, iron, zinc standard stock solution: 1000mg/L. Commercially available or
prepare according to Annex A.
5.9 Copper, iron, zinc standard solution I: 50mg/L. Accurately pipette 5.00mL of
standard stock solutions of copper, iron and zinc respectively. Put each into a 100mL
volumetric flask. Use water to dilute to the scale. Shake well. The solution is valid for
1 month.
5.10 Zinc standard solution II: 5mg/L. Accurately pipette 5.00mL of zinc standard
a) Weigh about 0.2g~0.3g of the prepared scale sample, accurate to 0.1mg. Place it
in a 250mL glass beaker.
b) Add a small amount of water to the beaker to fully wet the scale sample. Slowly
add 15mL of hydrochloric acid and 5mL of nitric acid. Cover with a watch glass.
Shake well. Slowly heat and boil on a hot plate or an adjustable electric stove for
20min. If there is still a brown or brown residue, add 10mL of hydrochloric acid.
Boil until the solution is clear.
c) Remove the beaker. Add 10mL of perchloric acid when the beaker is slightly
cooled. Reheat until it starts to emit thick white smoke. Move the watch glass slightly.
Continue to heat slowly for 15min~20min. Never evaporate the solution to dryness.
d) Remove the beaker. Add 10mL of nitric acid solution (5.6) while the breaker is
hot. Stir well to dissolve the salt on the wall of the beaker.
e) If the scale sample is completely dissolved, transfer the solution to a 100mL
volumetric flask. Use a straw to absorb the nitric acid solution (5.6) to wash the inner
wall of the beaker (not less than 3 times). Collect the washing solution together in a
100mL volumetric flask. Add nitric acid solution (5.6) to dilute to the scale. Shake
well. It shall be the scale sample test solution. If the dissolved solution contains white
suspended matter, use medium-speed quantitative filter paper to filter. Use nitric acid
solution (5.6) (about 10mL each time) to wash the beaker wall and the sediment and
filter paper attached to the wall several times (not less than 5 times). The filtrate and
washings are collected together in a volumetric flask. Add nitric acid solution (5.6)
to dilute to the scale. Shake well. It shall be the scale sample test solution.
8.2.3 Dissolve scale samples by microwave digestion. Do as follows:
a) Weigh 0.2g~0.3g of the prepared scale sample, accurate to 0.1mg. Place in the
digestion inner tank of microwave digestion instrument. Moisten with a few drops
of water. Slowly add 6mL of hydrochloric acid and 2mL of nitric acid. Shake the
digestion inner tank. Let the gas run out (if a large amount of gas is generated, pre-
digest the inner tank on the electric heating plate at 100°C for 20min, and then add
the same proportion of digestion solution to about 10mL). Cover the tank tightly and
put it in the outer tank. Put the digestion tank into the microwave digester. Digest
the scale sample according to the instrument instructions.
b) After the digestion is complete, transfer the solution in the tank to a 250mL glass
beaker. Wash the digestion tank and lid with a small amount of nitric acid solution
(5.6) and pour it into a beaker. Add 10mL of perchloric acid. Place beaker on hot
plate or adjustable hotplate. Slowly heat until white smoke is emitted for
15min~20min. Never evaporate the solution to dryness. Remove the beaker from hot
plate or adjustable hotplate. Add 10mL of nitric acid solution (5.6) while the breaker
is hot. Stir well to dissolve the salt on the wall of the beaker.
c) If the scale sample is completely dissolved, transfer the solution to a 100mL
volumetric flask. Use a straw to absorb the nitric acid solution (5.6) to wash the inner
wall of the beaker (not less than 3 times). Collect the washing solution together in a
100mL volumetric flask. Add nitric acid solution (5.6) to dilute to the scale. Shake
well. It shall be the scale sample test solution. If the dissolved solution contains white
suspended matter, filter it with medium-speed quantitative filter paper. Use nitric
acid solution (5.6) (about 10mL each time) to wash the beaker wall and the sediment
and filter paper attached to the wall several times (not less than 5 times). The filtrate
and washings are collected together in a volumetric flask. Add nitric acid solution
(5.6) to dilute to the scale. Shake well. It shall be the scale sample test solution.
8.2.4 Except that the scale sample is not added, follow the same operation as in 8.2.2
or 8.2.3 to prepare the scale sample test solution to prepare a dissolved sample blank
solution.
9 Determination steps
9.1 Determination of copper content
9.1.1 Drawing of copper calibration curve
Accurately pipette 0.00mL (blank), 0.50mL, 1.00mL, 1.50mL, 2.00mL of copper
standard solution I. Respectively place in 50mL volumetric flasks. Use nitric acid
solution (5.6) to dilute to the scale. Shake well. The copper content of this series of
calibration solutions is 0.00 mg/L, 0.50 mg/L, 1.00mg/L, 1.50mg/L, 2.00mg/L. Under
the best working conditions of the instrument, at a wavelength of 324.7nm, zero with
reagent blank. Measure its absorbance. Take the measured absorbance as the ordinate,
and the corresponding copper content (mg/L) as the abscissa, to draw a calibration curve
or calculate a regression equation. The linear correlation coefficient of the calibration
curve shall be greater than 0.999, otherwise it shall be redrawn.
9.1.2 Determination of water samples
Accurately pipette an appropriate amount of specimen solution (8.1). Place in a 50mL
volumetric flask. Use nitric acid solution (5.6) to dilute to the scale. Shake well.
According to the same instrument conditions in the preparation of the calibration curve,
adjust to zero with reagent blank. Measure its absorbance. Find out the corresponding
copper content from the calibration curve. If the copper content is lower than the lower
limit of detection or exceeds the range of the calibration curve, the dilution factor can
be adjusted and measured again.
9.1.3 Determination of scale samples
Accurately pipette appropriate amount of scale sample test solution (8.2.2 or 8.2.3) and
dissolved sample blank solution (8.2.4). Place in a 50mL volumetric flask. Use nitric
acid solution (5.6) to dilute to the scale. Shake well. According to the same instrument
conditions in the preparation of the calibration curve, zero with reagent blank. Measure
the absorbance of the dissolved sample blank solution and the scaled sample solution
after diluting to constant volume, respectively. Find out the corresponding copper
content from the calibration curve. If the copper content is lower than the lower limit
of detection or exceeds the range of the calibration curve, the dilution factor can be
adjusted and measured again.
9.2 Determination of iron content
9.2.1 Preparation of iron calibration curve
Accurately pipette 0.00mL (blank), 1.00mL, 2.00mL, 4.00mL, 6.00mL of iron standard
solution I. Respectively place in 50mL volumetric flasks. Use nitric acid solution (5.6)
to dilute to the scale. Shake well. The iron content of this standard series is 0.00 mg/L,
1.00 mg/L, 2.00 mg/L, 4.00 mg/L, 6.00 mg/L, respectively. Under the best working
conditions of the instrument, at a wavelength of 248.3nm, zero with reagent blank.
Measure its absorbance. Take the measured absorbance as the ordinate, and the
corresponding iron content (mg/L) as the abscissa, to draw a calibration curve or
calculate a regression equation. The linear correlation coefficient of the calibration
curve shall be greater than 0.999, otherwise it shall be redrawn.
9.2.2 Determination of water samples
Accurately pipette an appropriate amount of specimen solution (8.1). Put in a 50mL
volumetric flask. Use nitric acid solution (5.6) to dilute to the scale. Shake well.
According to the same instrument conditions in the preparation of the calibration curve,
the reagent blank is used for zero adjustment. Measure its absorbance. Find out the
corresponding iron content from the calibration curve. If the iron content is lower than
the lower limit of detection or exceeds the range of the calibration curve, the dilution
factor can be adjusted and re-measured.
9.2.3 Determination of scale samples
Respectively and accurately pipette appropriate amount of scale sample test solution
(8.2.2 or 8.2.3) and dissolved sample blank solution (8.2.4). Place in 50mL volumetric
flasks (choose the appropriate dilution factor according to the scale source and scale
type. Generally, the scale sample mainly composed of calcium and magnesium scale is
diluted by about 10 times to 100 times. The scale sample mainly composed of iron oxide
scale is diluted by about 100 times to 500 times. Dissolved sample blank solution and
scale test solution use the same dilution factor). Use nitric acid solution (5.6) to dilute
to the scale. Shake well. According to the same instrument conditions in the preparation
of the calibration curve, the reagent blank is used for zero adjustment. Measure the
absorbance of the dissolved sample blank solution and the scaled sample solution after
diluting to constant volume, respectively. Find out the corresponding iron content from
the calibration curve. If the iron content is lower than the lower limit of detection or
exceeds the range of the calibration curve, the dilution factor can be adjusted and re-
measured.
9.3 Determination of zinc content
9.3.1 Drawing of zinc calibration curve
Accurately pipette 0.00mL (blank), 2.00mL, 4.00mL, 6.00mL, 8.00mL of zinc standard
solution II. Place in 50mL volumetric flasks, respectively. Use nitric acid solution (5.6)
to dilute to the scale. The zinc content of this standard series is 0.00mg/L, 0.20mg/L,
0.40mg/L, 0.60mg/L, 0.80mg/L. Under the optimal conditions of the instrument, at a
wavelength of 213.9nm, zero with reagent blank. Measure its absorbance. Take the
measured absorbance as the ordinate, and the corresponding zinc content (mg/L) as the
abscissa, to draw a calibration curve or calculate a regression equation. The linear
correlation coefficient of the calibration curve shall be greater than 0.999, otherwise it
shall be redrawn.
9.3.2 Determination of water samples
Accurately pipette an appropriate amount of sample solution (8.1). Put it into a 50mL