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HJ 908-2017

Chinese Standard: 'HJ 908-2017'
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HJ 908-2017English309 Add to Cart Days<=3 Water quality--Determination of chromium(VI)--Flow injection analysis(FIA) and diphenylcarbazide spectrometric method HJ 908-2017 Valid HJ 908-2017
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BASIC DATA
Standard ID HJ 908-2017 (HJ908-2017)
Description (Translated English) Water quality--Determination of chromium(VI)--Flow injection analysis(FIA) and diphenylcarbazide spectrometric method
Sector / Industry Environmental Protection Industry Standard
Word Count Estimation 12,193
Date of Issue 2017-12-29
Date of Implementation 2018-04-01
Drafting Organization Chinese Academy of Environmental Sciences
Administrative Organization Ministry of Environmental Protection
Regulation (derived from) Ministry of Environmental Protection Bulletin 2017 No. 86

HJ 908-2017
People's Republic of China national environmental protection standards
Water quality-Determination of chromium (VI) -Flow injection
analysis (FIA) and diphenylcarbazide spectrometric method
2017-12-29 Posted
2018-04-01 implementation
Directory
Foreword .ii
1 Scope 1
2 Normative references 1
3 method principle 1
4 Interference and elimination .2
5 Reagents and materials .2
6 instruments and equipment
7 samples .3
8 Analysis Step 4
9 Results Calculation and Presentation 4
10 precision and accuracy .5
11 Quality Assurance and Quality Control
12 Waste treatment .6
13 Matters needing attention .6
Appendix A (informative) method of precision and accuracy .7
Foreword
In order to implement the "Law of the People's Republic of China on Environmental Protection" and the "Law of the People's Republic of China on Prevention and Control of Water Pollution", protect the environment,
Protection of human health, standardize the determination of hexavalent chromium in water, the development of this standard.
This standard specifies the determination of surface water, groundwater and domestic wastewater hexavalent chromium flow injection - diphenyl carbazide luminosity
law.
Appendix A of this standard is an informative annex.
This standard is released for the first time.
This standard by the Environmental Protection Department of Environmental Monitoring Division and Science and Technology Standards Division to develop.
This standard was drafted. Fuzhou Environmental Monitoring Center Station.
This standard verification unit. Beijing Environmental Protection Monitoring Center, Fujian Provincial Environmental Monitoring Center Station, Gansu Province, disease prevention
Control Center, Guangzhou City Environmental Monitoring Center Station, Yanqing County Environmental Protection Monitoring Station, Yunnan Provincial Agricultural Environmental Protection Monitoring Station and
Qian'an City Center for Disease Control and Prevention.
This standard MEP approved on December 29,.2017.
This standard since April 1,.2018 come into operation.
This standard is interpreted by the MEP.
Water quality - Determination of hexavalent chromium - Flow injection - diphenylcarbazide spectrophotometric method
Warning. acetone, concentrated sulfuric acid used in the experiment harmful to human health, the reagent preparation process should be carried out in a fume hood,
Operation should be required to wear protective equipment, avoid contact with skin and clothing.
1 scope of application
This standard specifies the determination of hexavalent chromium in water by flow injection - diphenyl carbazide spectrophotometry.
This standard applies to the determination of hexavalent chromium in surface water, groundwater and domestic sewage.
When the detection path length is 10 mm, the detection limit of this standard method is 0.001 mg/L, the lower limit of determination is 0.004 mg/L.
The undiluted sample has an upper limit of 0.600 mg/L, which should be measured after dilution beyond the upper limit of the assay.
2 Normative references
This standard references the following documents or the terms. For undated references, the effective version applies to this book
standard.
HJ/T 91 Technical Specifications for Surface Water and Sewerage Monitoring
HJ/T 164 Groundwater Environmental Monitoring Technical Specifications
3 method principle
In a closed pipeline, a certain volume of sample is injected into the continuous flow of acidic carrier liquid, the sample and reagent in the chemical reaction
The module should be mixed in a specific order and the proportion of non-complete reaction conditions, the sample of hexavalent chromium and diphenylcarbodiimide
Hydrazine generates a purple compound and enters the flow cell for measurement of absorbance at a wavelength of 540 nm. In a certain range,
Sample concentration of hexavalent chromium and its corresponding absorbance showed a linear relationship.
Reference workflow shown in Figure 1.
1. Peristaltic pump; 2. Injection valve; 3. Reaction loop; 4. Detection cell (540 nm); S. Sample; C. Carrier liquid; R. Color developer;
Figure 1 flow injection - diphenyl carbazide spectrophotometric determination of hexavalent chromium reference workflow
4 Interference and elimination
4.1 Sample turbidity or color, interference hexavalent chromium determination, zinc salt precipitation separation method can be used after pretreatment. Such as
After the separation of zinc salt, there is still color, color correction is required.
4.2 Part of the metal ions interfere with determination of hexavalent chromium. When the hexavalent chromium content of 0.1 mg/L, the use of zinc salt precipitation pre-separation
Ni2 ≤.200 mg/L, Mo6 ≤ 160 mg/L, Hg2 ≤ 160 mg/L, V5 ≤ 2.0 mg/L,
Fe3 ≤200 mg/L, Cu2 ≤100 mg/L, Co2 ≤60 mg/L do not interfere with the determination.
4.3 water reducing substances and oxidizing substances interfere with determination of hexavalent chromium. When the hexavalent chromium content of 0.1 mg/L, the sample
Reducing substances S2O32-≤5.0 mg/L, Fe2 ≤0.20 mg/L, S2-≤2.0 mg/L, SO32-≤2.0 mg/L do not interfere with the determination,
Oxidizing substances Active chlorine ≤ 0.7 mg/L does not interfere with the determination.
4.4 When the sample metal ions, reducing substances and oxidizing substances and other interfering substances concentration exceeds the range of 4.2 and 4.3,
Other methods should be used for analysis.
5 Reagents and materials
Unless otherwise specified, the analysis of the use of analytical reagents in line with national standards, experimental water for the newly prepared deionized
Water or distilled water.
5.1 Sodium hydroxide (NaOH).
5.2 Diphenylcarbazide (C13H14N4O).
5.3 Zinc sulfate (ZnSO4 · 7H2O).
5.4 Acetone (C3H6O).
5.5 Sulfuric acid. ρ (H2SO4) = 1.84 g/ml, excellent grade pure.
5.6 Phosphate. ρ (H3PO4) = 1.69 g/ml, excellent grade pure.
5.7 potassium dichromate (K2Cr2O7). excellent grade pure.
After drying at 110 ℃ 2 h, placed in a desiccator cooled standby.
5.8 Sodium hydroxide solution. ρ (NaOH) = 4 g/L.
5.9 Sodium hydroxide solution. ρ (NaOH) ≈50 g/L.
5.10 hexavalent chromium standard stock solution. ρ = 100 mg/L.
Weigh accurately 0.1415 g potassium dichromate (5.7), dissolved in water, dissolved and then transferred to 500 ml volumetric flask, with water
Set the volume to mark, shake well. The solution at 1 ℃ ~ 5 ℃ closed refrigeration, can be stable for 1 year. Or buy directly from the market
Standard solution.
5.11 hexavalent chromium standard solution. ρ = 1.00 mg/L.
Appropriate amount of hexavalent chromium standard stock solution (5.10) diluted step by step to 1.00 mg/L. The solution is sealed at 1 ° C to 5 ° C
Frozen, stable 5 d.
5.12 developer.
Slowly add 40 ml of sulfuric acid (5.5) and 40 ml of phosphoric acid (5.6) to 700 ml of water. Weigh 0.40 g
Diphenylcarbazide (5.2) is dissolved in.200 ml of acetone (5.4), stirred until it is completely dissolved, and added to the above sulfuric acid-
Phosphoric acid mixed solution, moved to 1000 ml volumetric flask, the volume of water to mark, shake, stored in a brown bottle. The solution in
1 ℃ ~ 5 ℃ closed refrigeration storage, stable for 1 month, can not be used after discoloration.
5.13 color correction solution.
Except not add the color reagent diphenylcarbazide (5.2), the amount of other reagents and the preparation method with the developer (5.12). Formulation when needed.
5.14 zinc sulfate solution. ρ (ZnSO4 · 7H2O) ≈ 100 g/L.
5.15 carrier liquid. experimental water.
5.16 Nitrogen. Purity ≥99.99%.
5.17 Helium. Purity ≥99.99%.
5.18 aqueous microporous membrane. pore size 0.45 μm.
6 instruments and equipment
6.1 Flow Injection. Includes autosampler, chemical reaction module (injection valve, reaction channel and flow cell)
Peristaltic pump and data processing system.
6.2 analytical balance. a sense of the amount of 0.0001 g.
6.3 ultrasonic cleaner. ultrasonic frequency 40 kHz, ultrasonic power 500 W.
6.4 Syringe. 20 ml.
6.5 Microfiltration Membrane. 0.45 μm aqueous microfiltration membrane (5.18) is installed.
6.6 General laboratory equipment and equipment.
7 samples
7.1 Sample Collection and Storage
Collect and store samples according to HJ/T 91 and HJ/T 164 regulations. The volume of sample collected should not be less than 250 ml.
After sample collection, add the appropriate amount of sodium hydroxide solution (5.8), adjust the sample pH to 8 to 9, and measured within 24 h after the acquisition.
7.2 Sample Preparation
7.2.1 for non-suspended solids, colorless samples can be directly measured.
7.2.2 for suspended solids, colored samples, zinc salt precipitation separation pretreatment. Take a 50.0 ml sample in 150 ml
Beaker, add 0.1 ml zinc sulfate solution (5.14) Shake well, add 0.05 ml sodium hydroxide solution (5.9), shake
After standing. After the flocculent sediment produced by the sample settles, filter it with a microporous membrane filter (6.5), discard the initial filtrate and concentrate
Set follow-up filtrate placed in the sample tube to be tested. If no precipitation can be properly increased zinc sulfate and sodium hydroxide solution (volume ratio of 2.1).
Note. If the filtrate is colored, enough samples should be retained for color correction.
7.3 Blank sample preparation
Take the experimental water instead of the sample, according to the preparation of the sample (7.2) the same procedure for the preparation of laboratory blank samples.
8 Analysis steps
8.1 Instrument debugging
Experimental water, carrier and developer must be degassed on the machine. Nitrogen (5.16) or helium (5.17) purge can be used
Degassing, but also the reagent bottle placed in the ultrasonic cleaner (6.3) ultrasonic degassing 20 min ~ 30 min. Press the instrument manual
Install the analysis system, set the working parameters, operate the instrument. After boot, first with experimental water instead of developer (5.12), seized
Check the entire analysis of the confinement of the flow path and liquid flow smoothly until the baseline is stable, the experimental water is replaced by a color reagent
(5.12), until the baseline stabilized again, the 8.2 ~ 8.4 operation.
8.2 Calibration
Respectively, remove the appropriate amount of hexavalent chromium standard solution (5.11) to 100 ml volumetric flask, the water volume to mark, shake,
The preparation of standard series of solutions, hexavalent chromium concentrations were. 0 mg/L, 0.005 mg/L, 0.010 mg/L, 0.050 mg/L,
0.200 mg/L, 0.400 mg/L, 0.600 mg/L. Measure the amount of standard series of solutions, were placed in the sample tube, according to set
The instrument conditions (8.1) from low concentration to high concentration followed by determination of different concentrations of hexavalent chromium absorbance (peak surface
product). The standard series of solutions of hexavalent chromium concentration (mg/L) as the abscissa, with its corresponding absorbance (peak surface
Product) for the vertical axis, the establishment of the calibration curve.
8.3 Sample Determination
8.3.1 The determination of sample (7.2) is carried out in accordance with the same measurement conditions as in the calibration curve (8.2). If the sample is thick
Degree higher than the highest point of the calibration curve, the sample should be diluted.
8.3.2 After the sample 7.2.2 pretreatment there is color, the need for chromaticity correction. Replace with colorimetric correction fluid (5.13)
Color (5.12), until the baseline after the determination of stable samples.
8.4 Blank test
The laboratory blank sample (7.3) is measured according to the same procedure as the sample test (8.3).
9 results calculated and expressed
9.1 Calculation Results
The concentration of hexavalent chromium in the sample (mg/L), calculated according to equation (1).
- The mass concentration of hexavalent chromium in the sample obtained from the calibration curve, mg/L;
- When chromaticity is corrected, the sample chromaticity obtained from the calibration curve corresponds to the mass concentration of hexavalent chromium and is not carried out
When chroma correction, the value is 0, mg/L;
9.2 results indicated
When the test result is less than 1.00 mg/L, keep three decimal places; when the test result is greater than or equal to 1.00 mg/L,
Keep three significant figures.
10 precision and accuracy
10.1 Precision
Seven laboratories on hexavalent chromium concentrations of 0.005 mg/L, 0.300 mg/L and 0.540 mg/L of a unified sample (with standard
Solution preparation) were repeated 6 times, the relative standard deviation of the laboratory were 3.7% to 5.1%, 0.2% to 0.9%, respectively,
0.1% ~ 0.9%. The relative standard deviations (RSDs) were 8.4%, 2.5% and 1.8%, respectively. The repeatability limit was 0.004 mg/L,
0.004 mg/L and 0.008 mg/L, reproducibility limits of 0.004 mg/L, 0.022 mg/L and 0.029 mg/L.
Seven laboratories of hexavalent chromium concentration of 0.002 mg/L ~ 0.226 mg/L of surface water, groundwater, sewage of the real
The relative standard deviations (RSDs) were 0.5% ~ 7.7%, 1.1% ~
9.1%, 1.1% ~ 3.3%.
See Appendix A for precision data.
10.2 Accuracy
The concentrations of hexavalent chromium in seven laboratories were (0.0603 ± 0.0042) mg/L, (0.130 ± 0.005) mg/L and (0.396
± 0.013) mg/L, the relative standard deviation was -3.5% ~ 5.0%, -1.5% ~
2.3% and -1.5% -2.0%, respectively. The final relative error values were (0.5 ± 6.0)%, (0.3 ± 2.6)% and (0.2 ± 2.4)%, respectively.
Seven laboratories for hexavalent chromium concentration of 0.003 mg/L ~ 0.064 mg/L, did not detect ~ 0.008 mg/L,
0.003 mg/L ~ 0.120 mg/L of the surface water, groundwater, domestic sewage samples were spiked, spiked recovery
The results showed that the final recovery rates were 92.0% ~ 118%, 88.0% ~ 108% and 93.0% ~ 113%
8.2)%, (98.4 ± 9.2)% and (103 ± 5.0)%.
See Appendix A for accuracy data.
11 Quality Assurance and Quality Control
11.1 Blank test
Each batch of samples to determine at least two laboratory blank, the measured value shall not exceed the method detection limit.
11.2 Calibration
Each batch of sample analysis need to establish a calibration curve, the calibration curve correlation coefficient ≥ 0.999.
Each analysis of 10 samples required a calibration curve of the intermediate concentration solution for calibration verification, the measured value and the standard value
The relative error should be within ± 5%, otherwise the calibration curve should be re-established.
11.3 Parallel samples
Each batch of sample analysis should be measured at least 10% of the parallel double sample, the sample number is less than 10, should be measured at least one group
Double row. When the sample concentration of hexavalent chromium ≤ 0.01 mg/L, the difference between the measured results should be ≤ 0.003 mg/L; when the hexavalent chromium concentration
> 0.01 mg/L, the relative deviation of the measurement results should be ≤ 10%.
11.4 Substrate spiking
At least 10% of the spiked samples should be tested for each batch of samples and at least one spiked sample should be measured for fewer than 10 samples.
Spike recovery should be between 80% to 120%.
12 Waste treatment
The waste liquid generated in the experiment should be collected centrally, stored in a unified way, properly labeled, and entrusted to qualified units for processing.
13 Precautions
13.1 All glassware shall not be washed with chromic acid. Available nitric acid, sulfuric acid mixture or synthetic detergent, washed to rinse.
13.2 After the analysis is finished daily, clean the instrument pipeline with the experimental water, and the filter should be stored in the dryer.
13.3 Instrument parameter setting Refer to the instrument manual, the calibration curve and other quality control indicators must meet the requirements of this standard.
Related standard: HJ 471-2020    HJ 519-2020