Search result: HJ 550-2015 (HJ 550-2009 Older version)
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Water quality. Determination of cobalt. 5-Cl-PADAB Spectrophotometry
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HJ 550-2015
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| HJ 550-2009 | English | 359 |
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Water quality. Determination of cobalt. 5-CI-PADAB spectrophotometry
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HJ 550-2009
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| Standard ID | HJ 550-2015 (HJ550-2015) | | Description (Translated English) | Water quality. Determination of cobalt. 5-Cl-PADAB Spectrophotometry | | Sector / Industry | Environmental Protection Industry Standard | | Classification of Chinese Standard | Z16 | | Classification of International Standard | 13.060 | | Word Count Estimation | 9,917 | | Date of Issue | 2015-04-03 | | Date of Implementation | 2015-07-01 | | Older Standard (superseded by this standard) | HJ 550-2009 | | Quoted Standard | HJ/T 91 | | Regulation (derived from) | Ministry of Environmental Protection Announcement 2015 No. 20 | | Issuing agency(ies) | Ministry of Environmental Protection | | Summary | This Standard specifies the determination of total dissolved cobalt and cobalt-state 5-chloro-2- (pyridyl) -1, 3-diaminobenzene spectrophotometry. This Standard applies to surface water, industrial wastewater and domestic sewage determination of cobalt. When the sample volume is 20.0ml, method detection limit of 0.009 mg/L, detection limit of 0.036mg/L, measured upper limit is 0.500mg/L. |
HJ 550-2015
Water quality.Determination of cobalt.5-Cl-PADAB Spectrophotometry
National Environmental Protection Standard of the People 's Republic of China
Replacing HJ 550-2009
Determination of water quality Cobalt 5-chloro-2- (pyridylazo)
-1,3-diaminobenzene spectrophotometry
Water quality-Determination of cobalt
-5-Cl-PADAB Spectrophotometry
2015-04-03 released
2015-07-01 implementation
Ministry of Environmental Protection released
I directory
Preface II
1 Scope of application
2 normative reference documents
3 Terms and definitions 1
4 Principle of the method
5 interference and elimination
6 reagents and materials 2
7 instruments and equipment 3
8 Sample 3
9 Analysis steps
The results are calculated and expressed
11 Precision and Accuracy
12 Quality assurance and quality control
13 Waste treatment .5
Preface
In order to implement the Environmental Protection Law of the People's Republic of China and the Law of the People's Republic of China on the Prevention and Control of Water Pollution,
Protect the human health, regulate the monitoring method of cobalt in water, the development of this standard.
This standard is a measure of the determination of total cobalt by 5-chloro-2- (pyridylazo) -1,3-diaminobenzene spectrophotometry (provisional)
(HJ 550-2009).
This standard was first published in.2009, this time for the first revision, this revision mainly on the scope of application of the method,
Methodology, Interference and Elimination, Reagents and Materials, Instruments, Samples, Analytical Steps, Results Calculations and Representations, Precision
Degree and accuracy of the contents of the re-provided. Added normative references to documents, terms and definitions, quality assurance and quality
Control and so on.
From the date of implementation of this standard, "Determination of total cobalt water 5-chloro-2- (pyridylazo) -1,3-diaminobenzene spectrophotometry
(Provisional) "(HJ 550-2009).
This standard is organized by the Ministry of Environmental Protection Science and Technology Standards Division.
The drafting of this standard. Beijing Environmental Protection Monitoring Center.
The standard verification unit. Chaoyang District, Beijing Environmental Protection Monitoring Station, Yanqing County Environmental Protection Monitoring Station, Tsinghua University Ring
Environmental quality testing center, Beijing Kangju environmental testing station, Beijing China measured North Detection Technology Co., Ltd., Beijing Environmental Protection
Monitoring center.
This standard is approved by the Ministry of Environmental Protection on April 03,.2015.
This standard has been implemented since July 1,.2015.
This standard is explained by the Ministry of Environmental Protection.
- 1 -
Determination of water quality Cobalt 5-chloro-2- (pyridylazo)
1,3-diaminobenzene spectrophotometry
1 Scope of application
This standard specifies the determination of dissolved cobalt and total cobalt in water 5-chloro-2- (pyridylazo) -1,3-diaminobenzene spectrophotometry
law.
This standard applies to the determination of cobalt in surface water, industrial waste water and domestic sewage.
When the sampling volume of 20.0ml, the detection limit of 0.009mg/L, the determination of the lower limit of 0.036mg/L, determination of the upper limit
Is 0.500mg/L.
2 normative reference documents
The contents of this standard refer to the terms of the following documents. For those who do not mind the date of the reference file, the valid version applies
In this standard.
Technical specification for surface water and wastewater monitoring
3 terms and definitions
The following terms and definitions apply to this standard.
3.1 dissolved cobalt
Refers to cobalt that has not been acidified after passing through a 0.45 μm pore size filter.
3.2 Total Cobalt
Refers to the sum of the cobalt in two parts of the dissolved and suspended phases of the sample, as measured by the unfiltered sample.
4 principle of the method
Cobalt is reacted with 5-chloro-2- (pyridylazo) -1,3-diaminobenzene (5-Cl-PADAB) to form a magenta complex.
570nm wavelength measured its absorbance, absorbance and cobalt concentration in line with the law of Lang Beibei.
5 interference and elimination
5.1 In 25ml color system, when a single ion interference exists, Fe2 content greater than 0.1mg when there is negative interference, Cr3
Content of more than 0.5μg when there is positive interference, Cr6 content of more than 2μg when there is negative interference, Cu2 content of more than 0.5μg when the negative dry
Disturb. After digestion of the sample, 0.5 ml of sodium pyrophosphate (6.12) was added to remove 0.3 mg of Fe2 interference, 1.5 g of dry
Interference, 4μgCr6 interference, 1.5μgCu2 interference.
- 2 -
5.2 in 25ml color system, Fe3 content of more than 4μg above the positive interference. In the pH = 5 ~ 6 conditions, add the appropriate amount
Sodium pyrophosphate solution to iron brown disappeared, then add 2.5ml sodium pyrophosphate (6.12), can remove 6μgFe3 interference.
5.3 Al3, Cd2, Zn2, Mg2, Ca2, Ni2, SO42-, Cl-, PO43-, NO3-, Br-, ClO4-
Determination.
6 reagents and materials
Unless otherwise stated, analytical reagents conforming to national standards are used for analysis. Experimental water is a newly prepared deionized
Water or distilled water.
6.1 nitric acid. ρ (HNO3) = 1.42g/ml, excellent grade pure.
6.2 perchloric acid. ρ (HClO4) = 1.67g/ml, excellent grade pure.
6.3 Hydrochloric acid. ρ (HCl) = 1.19g/ml, excellent grade pure.
6.4 Sulfuric acid. ρ (H2SO4) = 1.84g/ml, excellent grade pure.
6.5% acetic acid.
6.6 95% ethanol.
6.7 hydrochloric acid solution. 1 1.
6.8 Cobalt trioxide. Spectrum pure.
6.9 Sodium hydroxide. ω (NaOH) = 40%.
Weigh 40.0 g of sodium hydroxide and dissolve in 100 ml of water.
6.10 acetic acid - sodium acetate (HAC-NaAC) buffer solution. pH = 5 ~ 6.
Weigh 21.0g anhydrous sodium acetate, dissolved in a small amount of water, add acetic acid to adjust the pH to 5 to 6, diluted with water to 1000ml,
Is now available.
6.11 5-C1-PADAB Ethanol solution. ω (5-C1-PADAB) = 0.05%.
Weigh 0.05g 5-C1-PADAB, dissolved in 100ml 95% ethanol solution, stored in a brown bottle, is now available.
6.12 Sodium pyrophosphate solution. ω (Na4P2O7 · 10H2O) = 5%.
Weigh 5.0g sodium pyrophosphate, dissolved in water, diluted to 100ml, is now available with.
6.13 cobalt standard stock solution. ρ (Co) = 0.100mg/L.
Weigh 0.0703 g of cobalt oxide (6.8), dissolved in 5.0 ml of hydrochloric acid (6.3), transferred to a 500 ml volumetric flask,
Diluted with water to the mark, 4 ℃ can be stored for at least one month. Commercial reference materials may also be used.
6.14 cobalt standard use of liquid. ρ (Co) = 2.00μg/ml.
- 3 -
Absorb 10.00ml cobalt standard stock solution (6.13), into the 500ml volumetric flask, diluted with water to the mark, now use
With
6.15 p-nitrophenol solution. ω (C6H5NO3) = 0.2%.
Weigh 0.20g p-nitrophenol, dissolved in water, diluted to 100ml, is now available with.
6.16 filter. 0.45μm acetate filter.
7 instruments and equipment
Unless otherwise stated, all Class A glass gauges conforming to national standards are used for analysis.
7.1 Visible Spectrophotometer. A cuvette with an optical path of 20mm.
7.2 thousandth of a balance.
7.3 Laboratory equipment and glassware.
8 samples
8.1 Collection and storage of samples
Collect water samples according to HJ/T 91 surface water and wastewater monitoring technical specifications. After the sample was collected, add sulfuric acid (6.4) or nitric acid (6.1)
To pH < 2, stored at 0 ℃ ~ 4 in cold storage for 14 days.
Note 1. When collecting dissolved cobalt, it should be filtered through a 0.45 μm pore size filter before adding acid.
8.2 Preparation of the sample
The samples were prepared by digestion with nitric acid and perchloric acid.
Absorb water samples 2.00 ~ 20.0ml (depending on the water content of cobalt) in 100ml beaker, add l ~ 2ml nitric acid (6.1),
Cover the surface of the dish, in the heating plate to boil for 1 ~ 5min, remove the slightly cold, add l ~ 2ml perchloric acid (6.2) (depending on organic
Subject matter content), continue to heat to smoke thick smoke, and continued until the solution without black residue transparent so far. Remove the cooling
After adding l ~ 2 drops of p-nitrophenol indicator (6.15), add 40% sodium hydroxide solution (6.9) to the solution to yellow,
The total volume can not exceed 5ml, to be measured.
8.3 Preparation of blank sample
Absorb 2.00 ~ 20.0ml distilled water in 100ml beaker, the following steps with (8.2).
9 Analysis steps
9.1 Drawing of working curves
9.1.1 digestion
- 4 -
Respectively, the use of cobalt standard solution (6.14) 0.00,0.25,0.50,1.00,1.50,2.00ml in 100ml beaker,
Distilled water was added to about 5 ml and digested with the same step (8.2).
9.1.2 Draw the working curve
The digested standard solution series (9.1.1) was transferred to 25 ml of a plug colorimetric tube,
Distilled water washed 2 to 3 times, the washing liquid into the colorimetric tube, the total volume can not exceed 8ml. 5.0 ml of acetic acid-acetic acid was added
Sodium buffer solution (6.10), 0.50 ml sodium pyrophosphate solution (6.12), 1.00 ml 5-Cl-PADAB solution (6.11)
Shake well Placed in boiling water bath for 5min, remove, add hot 10ml (1 1) hydrochloric acid solution (6.7), with water dilute
Release to the mark, shake. After cooling, the absorbance was measured with a 20 mm cuvette at a wavelength of 570 nm. To
The calibration curve was plotted against the absorbance of the reagent blank.
9.2 Sample analysis
9.2.1 Determine with the digested water sample (8.2), with the drawing of the working curve step (9.1.2).
Note 2. If the water content of trivalent iron is high, should be appropriate to add sodium pyrophosphate solution, drawing the working curve of sodium pyrophosphate solution should be used with the determination
Water samples are the same.
9.2.2 blank sample analysis
The digested blank sample (8.3) was measured with the step (9.1.2) of drawing the working curve.
10 results are calculated and expressed
10.1 Result calculation
The mass concentration of cobalt in the sample is calculated according to equation (1)
BV
Ay
BV
Ay 001 (Co) (1)
Where. ρ (Co) - mass concentration of cobalt in the sample, mg/L;
1 ü - mass concentration of cobalt in the sample from the working curve, mg/L;
0 £ - mass concentration of cobalt in blank samples taken from the working curve, mg/L;
Y - the absorbance value of the test sample;
0y - measure the absorbance of the blank sample;
B - the slope of the working curve;
A - the intercept of the working curve, μg;
V - water sample volume, ml.
- 5 -
10.2 results are shown
When the measurement result is less than 1 mg/L, the result is retained to three decimal places; when the measurement result is greater than or equal to 1 mg/L
, The result retains three significant digits.
11 precision and accuracy
11.1 precision
Six laboratories carried out uniform standard samples with a concentration of 0.400mg/L, 2.00mg/L and 3.60mg/L respectively
Parallel test. the relative standard deviation in the laboratory were. 0.7% ~ 4.0%, 0.9% ~ 1.4%, 0.3% ~ 1.2%; experiment
The relative standard deviations were 5.3%, 0.4%, 0.3%, and the repeatability r was 0.034 mg/L, 0.070 mg/L, 0.070
Mg/L; reproducibility limit R was 0.068 mg/L, 0.073 mg/L, 0.074 mg/L, respectively.
11.2 Accuracy
6 laboratories were used to determine the concentration of 0.141 ± 0.013mg/L, 1.15 ± 0.08mg/L standard samples were.
The relative errors in the laboratory were -2.1% ~ 3.6%, - 0.9% ~ 1.7%, respectively. The relative errors were 0.5%
0.04%, 0.3% ± 0.03%.
Six laboratories were on the surface water, domestic sewage, industrial wastewater samples were measured by the standard recovery. laboratory
The recoveries were 99.7% ~ 101%, 94.3% ~ 98.6% and 94.7% ~ 106%, respectively.
The values were 99.5% ± 2.0%, 97.3% ± 4.6% and 98.7% ± 8.2%, respectively.
12 quality assurance and quality control
12.1 each batch of samples should be at least a full blank test and laboratory blank test, the determination of the results should be lower than the method
The detection limit.
12.2 The correlation coefficient of the working curve should be ≥0.999.
12.3 per batch of samples should be analyzed calibration curve intermediate point concentration standard solution, the determination of the results and calibration curve of the middle point of concentration
The relative deviation of the degree should be ≤ 10%, otherwise, need to re-draw the calibration curve.
12.4 each batch of samples should be done spike recovery determination, spike recovery rate should be 90% to 110% range.
12.5 Each sample of 10 samples should be tested in parallel, with less than 10 samples, at least once
Parallel sample determination, the two parallel sample analysis results relative deviation should be less than 10%.
13 Waste treatment
During the course of the experiment, the waste liquid should be placed in a suitable container for centralized storage and handled by a qualified unit.
......
HJ 550-2009
Water quality.Determination of cobalt.5-CI-PADAB spectrophotometry
National Environmental Protection Standard of the People's Republic
Determination of total cobalt in water
Spectrophotometry (tentative)
Water quality-Determination of cobalt
-5-Cl-PADAB spectrophotometry
Released.2009-12-30
2010-04-01 Implementation
Ministry of Environmental Protection released
Ministry of Environmental Protection
announcement
No. 74 of.2009
In order to implement the "Environmental Protection Law of the People's Republic of China", protect the environment, and protect human health, we now approve the lead gas of fixed pollution sources.
The four standards, such as the determination of flame atomic absorption spectrophotometry (tentative), are national environmental protection standards and are released.
The standard name and number are as follows.
I. Determination of lead in fixed pollution sources - Flame atomic absorption spectrophotometry (tentative) (HJ 538-2009);
2. Determination of lead in ambient air by graphite furnace atomic absorption spectrophotometry (tentative) (HJ 539-2009);
III. Determination of arsenic in ambient air and exhaust gases - Spectrophotometric method of silver diethyldithiocarbamate (interim) (HJ 540-2009);
4. Determination of gaseous arsenic in the production of yellow phosphorus - Determination of silver diethyldithiocarbamate spectrophotometry (interim) (HJ 541-2009);
V. Determination of mercury in ambient air - Enrichment of sulfhydryl cotton - Cold atomic fluorescence spectrophotometry (interim) (HJ 542-2009);
6. Determination of mercury in fixed pollution sources - Cold atomic absorption spectrophotometry (provisional) (HJ 543-2009);
VII. Determination of Sulfuric Acid Fog of Fixed Pollution Sources by Ion Chromatography (Provisional) (HJ 544-2009);
VIII. Determination of gaseous total phosphorus in fixed pollution sources - Determination of quinolinol ketone capacity (provisional) (HJ 545-2009);
IX. Determination of Phosphorus Pentoxide in Ambient Air Ascorbic Acid Reduction - Molybdenum Blue Spectrophotometry (Provisional) (HJ 546-2009);
X. Determination of chlorine gas from fixed pollution sources, iodometric method (provisional) (HJ 547-2009);
XI. Determination of hydrogen chloride in fixed source pollution. Silver nitrate capacity method (provisional) (HJ 548-2009);
12. Determination of hydrogen chloride in ambient air and exhaust gas Ion chromatography (interim) (HJ 549-2009);
14. Determination of Chlorine Dioxide in Water Quality Iodometric Method (Provisional) (HJ 551-2009).
The above standards have been implemented since April 1,.2010 and published by the China Environmental Science Press. The standard content can be found on the website of the Ministry of Environmental Protection.
Special announcement.
December 30,.2009
Content
Foreword..iv
1 Scope..1
2 Method principle..1
3 interference and elimination.1
4 Reagents and materials.1
5 instruments and equipment. 2
6 samples.3
7 Analysis steps..3
8 result calculation..4
9 precision and accuracy..4
Foreword
To protect the environment and protect the human body in order to implement the Environmental Protection Law of the People's Republic of China and the Law of the People's Republic of China on Water Pollution Prevention and Control
To develop and standardize the monitoring methods for cobalt in water.
This standard specifies the 5-chloro-2-(pyridylazo)-1,3-diaminobenzene spectrophotometric method for the determination of total cobalt in water.
This standard was formulated by the Science and Technology Standards Department of the Ministry of Environmental Protection.
This standard was drafted. Beijing Environmental Protection Monitoring Center.
This standard was approved by the Ministry of Environmental Protection on December 30,.2009.
This standard has been implemented since April 1,.2010.
This standard is explained by the Ministry of Environmental Protection.
Iv
Determination of total cobalt in water
5-Chloro-2-(pyridylazo)-1,3-diaminobenzene spectrophotometry (interim)
1 Scope of application
This standard specifies the 5-chloro-2-(pyridylazo)-1,3-diaminobenzene spectrophotometric method for the determination of total cobalt in water.
This standard applies to the determination of total cobalt in surface water, groundwater, industrial wastewater and domestic sewage.
Without pre-enrichment, when the sampling volume is 10 ml, the method detection limit is 0.007 mg/L, the lower limit of determination is 0.02 mg/L, and the upper limit of determination is
0.16 mg/L. After pre-enrichment, the method detection limit can be reduced by 50 times.
2 Principle of the method
Cobalt and 5-chloro-2-(pyridylazo)-1,3-diaminobenzene (5-Cl-PADAB) in a pH-to-sodium acetate-sodium acetate buffer medium
The reaction produces a purple-red complex, and its absorbance is measured by a spectrophotometer at a wavelength of 570 nm. The molar absorptivity is 1.03×105 L/
(mol·cm), the mass concentration of cobalt in the range of 0.02 to 0.16 mg/L in accordance with Lambert Beer's law.
When the cobalt content in water is less than 0.02 mg/L, it is pre-enriched with sulfhydryl cotton or XAD-2 macroporous reticulated resin, and then color measurement is carried out.
Its sensitivity can be increased by 5 to 50 times.
3 interference and elimination
Alkali metals and alkaline earth metals do not interfere with the determination without pre-enrichment treatment. When the Fe3 content is greater than 0.006 mg, the Cr3 content is greater than 0.001 mg
Positive interference occurs. The interference of Fe3 can be added to the sodium pyrophosphate solution at pH=5~6 until the iron brown disappears, then add 2.5 m1.
Masking; Cr3 interference can be removed by digestion with HNO3-HCl-HClO4. Some heavy metal ions and 5-Cl-PADAB coloration interfere with cobalt
Determination, but after the color development is completed, add HCl to strong acid to decompose and discolor to eliminate the interference, while the cobalt complex is very stable, not
Affected.
A large amount of Fe2 and Cr6 may cause negative interference, and may also be digested with HNO3-HCl-HClO4, respectively, by oxidation, masking and volatilization.
Remove.
SO42−, Cl−, PO43−, NO3−, Br−, ClO4−, tartarate, etc. do not interfere with the determination. The citrate makes the cobalt color incomplete.
If pre-enrichment is carried out with sulfhydryl cotton, adding appropriate amount of tartrate can prevent manganese and iron from hydrolyzing to form colloid at pH=9, and the remaining metal is separated.
The sub-series can be separated and removed without interference. Organic complexing agents such as citric acid and cysteine do not affect the adsorption of Co2.
If the XAD-2 type macroporous reticulated resin is pre-enriched, the interference and elimination methods are the same as those without pre-enrichment treatment.
4 reagents and materials
Unless otherwise stated, analytically pure reagents that meet national standards were used for the analysis. The experimental water is freshly prepared deionized water or distilled water.
4.1 Nitric acid. ρ (HNO3) = 1.42 g/ml, excellent grade pure.
4.2 Perchloric acid. ρ (HClO4) = 1.67 g/ml, excellent grade pure.
4.3 Hydrochloric acid. ρ (HCl) = 1.19 g/ml, excellent grade pure.
4.4 Sulfuric acid. ρ (H2SO4) = 1.84 g/ml, excellent grade pure.
4.5 thioglycolic acid.
4.6 Acetic anhydride.
4.7 36% acetic acid.
4.8 95% ethanol.
4.9 Ammonia. pH=10.
4.10 Hydrochloric acid solution. 1 1.
4.11 Hydrochloric acid solution. c (HCl) = 3 mol/L.
4.12 Hydrochloric acid solution. c (HCl) = 1 mol/L.
4.13 Sodium hydroxide. w (NaOH) = 20%.
Weigh 20.0 g of sodium hydroxide and dissolve in 100 ml of water.
4.14 Ammonium tartrate solution. w (C4H12N2O6) = 10%.
Weigh 10.0 g of ammonium tartrate, dissolve in water, and dilute to 100 ml.
4.15 sodium thiosulfate solution. w (Na2S2O7·5H2O) = 20%.
Weigh 20.0 g of sodium thiosulfate, dissolve in water, and dilute to 100 ml.
4.16 Ammonium chloride-ammonia (NH4Cl-NH4OH) buffer solution. pH = 10.
Weigh 20.0 g of ammonium chloride (NH4Cl), dissolve it in 100 ml of concentrated ammonia water, close it, and store it in the refrigerator.
4.17 Acetic acid-sodium acetate (HAC-NaAC) buffer solution. pH = 5-6.
Weigh 21.0 g of anhydrous sodium acetate, dissolve in a small amount of water, add acetic acid to adjust the pH to 5-6, and dilute with water to 1 000 ml.
4.18 5-Cl-PADAB Ethanol solution. w(5-Cl-PADAB) = 0.1%.
0.10 g of 5-Cl-PADAB was weighed, dissolved in a 95% ethanol solution, and diluted to 100 ml. Store in brown bottles.
4.19 Sodium pyrophosphate solution. w(Na4P2O7·10H2O) = 5%.
Weigh 5.0 g of sodium pyrophosphate, dissolve in water, and dilute to 100 ml.
4.20 Cobalt standard stock solution. ρ (Co) = 100 μg/ml.
Weigh 0.035 15 g of the reference reagent cobalt dioxide, add 2.5 ml of hydrochloric acid (4.3) to dissolve, transfer to a 250 ml volumetric flask, and use water.
Dilute to the mark.
4.21 Cobalt standard use solution. ρ (Co) = 2 μg/ml.
Pipette 10.00 ml of cobalt standard stock solution (4.20), transfer to a 500 ml volumetric flask, and dilute to the mark with water.
4.22 p-Nitrophenol solution. w(C6H5NO3) = 0.2%.
Weigh 0.20 g of p-nitrophenol, dissolve in water, and dilute to 100 ml.
4.23 巯 base cotton
4.23.1 Add 100 ml of analytically pure thioglycolic acid (4.5), 60 ml of acetic anhydride (4.6), 40 ml of 36% acetic acid (4.7), and then to the grinding bottle.
0.3 ml of sulfuric acid (4.4), mix well. After cooling to room temperature, add 30 g of absorbent cotton, completely submerge, capped, and baked at 40 ° C
Remove in the box for 2 to 4 days, filter by suction, wash with distilled water until neutral, and dry at 30 °C. Put it into the grinding bottle, cover it in the dark and store it at low temperature.
Save for 3 months.
4.23.2 Sulfhydryl cotton can also be prepared by adding 70 ml of thioglycolic acid (4.5), 0.4 ml of sulfuric acid (4.4), and shaking in a small jar.
uniform. Add 10 g of cotton wool to completely submerge, cover and leave at room temperature for 24 h. The following steps are the same as 4.23.1.
4.24 XAD-2 Macroporous Resin
The XAD-2 resin was soaked in methanol (submerged resin) for 24 h, then filtered and washed several times with 3 mol/L hydrochloric acid (4.11) solution.
Rinse several times with ammonia water (4.9) and finally wash with distilled water until neutral.
5 Instruments and equipment
Unless otherwise stated, the analysis uses a Class A glass gauge that complies with national standards.
5.1 Visible spectrophotometer. equipped with a cuvette with an optical path of 20 mm.
5.2 Enrichment unit. A solid phase extraction column with a diameter of 1 cm is filled with 0.25 g of sulfhydryl cotton (4.23) or 0.5 g of resin (4.24).
6 samples
6.1 Sample collection and preservation
Depending on the amount of cobalt in the water sample, 250 ml to 2 L of water is collected. After sample collection, add sulfuric acid or hydrochloric acid to pH< 2, complex on the substrate
The mixed wastewater sample should have an acidity of about 1% and be stored at 0 to 4 °C.
6.2 Preparation of samples
6.2.1 Nitric acid-perchloric acid digestion
For surface water and sewage containing high quality, take 2-20 ml of water sample (depending on the cobalt content in the water sample) in a 100 ml beaker.
Add 2 ml of nitric acid (4.1), cover with a watch glass, heat and boil on a hot plate for 1 to 5 minutes, remove slightly cold, add 1 to 2 ml of perchloric acid (4.2)
(Depending on the amount of organic matter), continue to heat until thick white smoke, and continue until the solution is free of black residue. After taking off the cooling, turn
Move to a 25 ml plug colorimetric tube, add 1 to 2 drops of p-nitrophenol indicator (4.22), add 20% sodium hydroxide solution (4.13) to the solution.
Rendered yellow, to be tested.
6.2.2 Pre-enrichment
6.2.2.1 For samples containing less than 0.02 mg/L of cobalt, pre-enrichment is required. If the water sample contains organic matter or other impurities, it should be
Digestion is performed and pre-enrichment is performed.
6.2.2.2 Pre-enrichment of sulphur-based cotton method
Take 500 ml of water (depending on the amount of cobalt in the water sample), add 2.5 ml of 10% ammonium tartrate solution (4.14), 2.5 ml of 20% thiosulfate
Sodium (4.15), adjust the pH to 8.5-9.5, add 10 ml ammonium chloride-ammonia buffer solution (4.16), pass at a flow rate of 1-4 ml/min
The adsorption device is enriched. After the water sample is finished, it is eluted twice with 4 ml of 1 mol/L hydrochloric acid (4.12) at a flow rate of 1-4 ml/min.
The eluate was taken up in a 25 ml plug colorimetric tube, and 1 to 2 drops of p-nitrophenol (4.22) was added to the eluent, and 20% sodium hydroxide solution (4.13) was added dropwise.
The solution appears yellow and is to be tested.
6.2.2.3 XAD-2 type resin pre-enrichment
Take 500 ml of water (depending on the amount of cobalt in the water sample), adjust the pH to 5-6, and add 10 ml of acetic acid-sodium acetate buffer solution (4.17).
1.5 ml of 5-Cl-PADAB solution (4.18), heated on a boiling water bath (or directly heated to near boiling) for 5 min. Dissolve with 20% NaOH after cooling
The liquid (4.13) is adjusted to pH 10 and is enriched by an adsorption device at a flow rate of 1 to 2 ml/min using 10 ml of 95% ethanol (4.8) solution.
The elution was performed in two portions, and the eluate was taken up in a 50 ml beaker. After elution, place it on a water bath or a low temperature electric heating plate and evaporate to about 5 ml.
Remove the cooling. Add 10 ml (1 1) HCl solution (4.10), transfer to a 25 ml plug colorimetric tube, dilute to the mark with water, shake well.
To be tested.
7 Analysis steps
7.1 Drawing of the calibration curve
Absorb cobalt standard solution (4.21) 0.00, 0.25, 0.50, 1.00, 1.50, 2.00 ml in 25 ml plug color tube, cobalt
The contents are in order. 0.00, 0.50, 1.00, 2.00, 3.00, 4.00 μg. Add 5.0 ml of acetic acid-sodium acetate buffer solution (4.17),
0.50 ml sodium pyrophosphate solution (4.19), 1.0 ml 5-Cl-PADAB solution (4.18), dilute with water to about 10 ml, shake well. Placed
Heat on a boiling water bath for 5 min, remove, cool to room temperature, add 10 ml (1 1) HCl solution (4.10), dilute to the mark with water.
Shake well. The absorbance was measured with a 20 mm cuvette at a wavelength of 570 nm using water as a reference. Absorbing cobalt corresponding to the reagent blank
The content is plotted against a calibration curve.
7.2 Sample Analysis
7.2.1 Pipette 2 to 10 ml of clean water (depending on the amount of cobalt in the water sample) in a 25 ml plug colorimetric tube. The following steps are the same as (7.1).
7.2.2 Using the digested sample (6.2.1) or the sample pre-enriched with the sulphur-based cotton method (6.2.2.2), the following procedure is the same as (7.1).
Note. If the iron content in the water sample is high, the sodium pyrophosphate solution should be added as appropriate. When preparing the calibration curve, the amount of sodium pyrophosphate solution should be the same as that of the measured water sample.
7.2.3 Samples pre-enriched with XAD-2 resin (6.2.2.3), directly with the colorimetric conditions of the calibration curve for absorbance determination.
7.3 Blank test
The sample was replaced with 10 ml of water and the absorbance was measured in the same manner as in the sample measurement (7.2).
8 Calculation of results
The total cobalt content ρ in the sample is calculated according to formula (1).
0(Co)
AA a
bV
ρ − −= (1)
Where. ρ (Co)--the total cobalt content in the water sample, mg/L;
A--the absorbance of the water sample;
A0--the absorbance of the blank test;
A--the intercept of the calibration curve;
B--the slope of the calibration curve;
V--water sample volume, ml.
9 Precision and accuracy
9.1 precision
Six laboratories use different pre-treatment methods for groundwater, surface water and industrial waste with a cobalt concentration of 0.001 to 0.130 mg/L.
The water uniform sample was measured, and the relative standard deviation between the laboratories was 0.2% to 23.0%.
9.2 Accuracy
Six laboratories use different pre-treatment methods for groundwater, surface water and industrial waste with a cobalt concentration of 0.001 to 0.130 mg/L.
The unified sample of water was spiked and the recovery rate was 90%-120%.
Six laboratories measured a cobalt concentration of 0.099 mg/L of reference material with a relative error of −5% to 2%.
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