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HJ 1214-2021: Water quality - Determination of adsorbable organically bound halogens (AOX) - Microcoulometric method
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Water quality - Determination of adsorbable organically bound halogens (AOX) - Microcoulometric method
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HJ 1214-2021
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Standard similar to HJ 1214-2021 HJ 1217 HJ 1205 HJ 1204 Basic data | Standard ID | HJ 1214-2021 (HJ1214-2021) | | Description (Translated English) | Water quality - Determination of adsorbable organically bound halogens (AOX) - Microcoulometric method | | Sector / Industry | Environmental Protection Industry Standard | | Word Count Estimation | 11,143 | | Issuing agency(ies) | Ministry of Ecology and Environment | HJ 1214-2021: Water quality - Determination of adsorbable organically bound halogens (AOX) - Microcoulometric method
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(Water Quality Determination of Adsorbable Organic Halogens (AOX) Microcoulometry)
National Ecological Environment Standard of the People's Republic of China
Determination of Adsorbable Organic Halogens (AOX) in Water Quality
Microcoulometry
Water quality-Determination of adsorbable organically bound halogens
(AOX)-Microcoulometric method
This electronic version is the official standard text, which is reviewed and typeset by the Environmental Standards Institute of the Ministry of Ecology and Environment.
Published on 2021-11-29
2022-06-01 Implementation
Released by the Ministry of Ecology and Environment
directory
Foreword...ii
1 Scope...1
2 Normative references...1
3 Terms and Definitions...1
4 Principles of the method...1
5 Interference and cancellation...2
6 Reagents and materials...2
7 Instruments and equipment...3
8 Samples...5
9 Analysis steps...6
10 Result calculation and representation...7
11 Accuracy...7
12 Quality Assurance and Quality Control...8
13 Waste Disposal...8
Determination of Adsorbable Organic Halogens (AOX) in Water Quality by Microcoulometric Method
Warning. The p-chlorophenol and 2-chlorobenzoic acid used in the experiment are toxic chemicals; nitric acid, sulfuric acid and hydrochloric acid are strongly corrosive
The preparation of reagents and sample pretreatment should be carried out in a fume hood; protective equipment should be worn as required during operation to avoid inhalation
respiratory tract or contact with skin and clothing.
1 Scope of application
This standard specifies the microcoulometric method for the determination of organic halides (excluding organic fluorides) that can be adsorbed on activated carbon in water.
This standard applies to the determination of adsorbable organic halogens in surface water, groundwater, domestic sewage and industrial wastewater.
The determination results of this standard include adsorbable organic halogens in suspended solids in water samples.
When the sampling volume is 100 ml, the detection limit of this method is 0.007 mg/L, and the lower limit of determination is 0.028 mg/L.
2 Normative references
This standard refers to the following documents or clauses thereof. For dated references, only the dated version applies to this standard.
For undated references, the latest edition (including all amendments) applies to this standard.
HJ/T 91 Technical Specification for Surface Water and Sewage Monitoring
HJ 91.1 Technical Specification for Wastewater Monitoring
HJ 164 Technical Specification for Groundwater Environmental Monitoring
HJ 493 Technical Regulations for the Preservation and Management of Water Quality Samples
3 Terms and Definitions
The following terms and definitions apply to this standard.
3.1
Adsorbable organically bound halogens (AOX)
Under the test conditions specified in this standard, chlorine, bromine, iodine (not
contains the equivalent total amount of organic fluorides), the results are in chlorine.
3.2
dissolved organic carbon (DOC)
Total organic carbon content in water samples after filtration through a 0.45 m microporous membrane.
4 Principles of the method
The water sample is acidified by nitric acid, adsorbed by activated carbon, and then rinsed with sodium nitrate-nitric acid solution to remove the inorganic halide adsorbed on the activated carbon.
The adsorbed activated carbon is pyrolyzed and burned in the oxygen flow to generate hydrogen halide gas, and the hydrogen halide gas is passed into the micro-coulomb cell, and the micro-coulomb method is used.
The amount of halide ions was measured, and the result was expressed as the mass concentration of chlorine.
5 Interference and cancellation
5.1 The free chlorine in the water sample can lead to high AOX measurement results, and sodium sulfite solution (6.14) should be added immediately after sampling to eliminate dryness.
disturb.
5.2 When the inorganic chloride concentration in the sample is greater than 1 g/L, it should be diluted and measured; the sample with a lower AOX value contains more than 1 g/L
Chloride ions may lead to high determination results. Adding the same concentration of chloride ions (such as NaCl) to laboratory blank samples can eliminate dryness.
disturb.
5.3 Inorganic bromide and iodide in water samples will lead to high determination results.
5.4 When the DOC in the sample exceeds 10 mg/L, it should be diluted and measured.
5.5 The organic bromide and organic iodide in the sample generate high-valence oxides of bromine and iodine during the combustion process, and this part of AOX cannot
be measured, which will result in a low measurement result.
5.6 Alcohols, aromatic compounds and hydroxy acids can cause low results.
5.7 For samples containing living cells (such as microorganisms, algae, etc.), the determination results are high due to their own chloride content.
Add nitric acid to acidify the water sample, destroy the algae and microbial cells, dissolve the chloride contained in the water sample, and then go through the elution step to eliminate the interference.
6 Reagents and Materials
Unless otherwise specified, analytical reagents that meet national standards were used in the analysis. The experimental water was distilled water or pure water without AOX.
6.1 Nitric acid. ρ=1.42 g/ml.
6.2 Hydrochloric acid. ρ=1.19 g/ml.
6.3 Sulfuric acid. ρ=1.84 g/ml.
6.4 Sodium nitrate (NaNO3).
6.5 Sodium sulfite (Na2SO3).
6.6 p-Chlorophenol (C6H5ClO).
6.7 2-Chlorobenzoic acid (C7H5ClO2).
6.8 Potassium iodide (KI).
6.9 Soluble starch.
6.10 Nitric acid solution. c(HNO3)=0.02 mol/L.
Measure 1.36 ml of nitric acid (6.1) and dilute to 1000 ml with water.
6.11 Hydrochloric acid solution. c(HCl)=0.010 mol/L.
Measure 0.83 ml of hydrochloric acid (6.2) and dilute to 1000 ml with water.
6.12 Sodium nitrate-nitric acid solution. c=0.2 mol/L.
Weigh 17.00 g of sodium nitrate (6.4) and dissolve it in water, add 25 ml of nitric acid (6.1), and dilute to 1000 ml with water. Sodium nitrate - nitric acid solution
The liquid can be stored for 3 months in the amber glass bottle.
6.13 Sodium nitrate-nitric acid eluent. c=0.01 mol/L, pH≈1.7.
Take 50 ml of sodium nitrate-nitric acid solution (6.12) and dilute to 1000 ml with water. Sodium nitrate-nitric acid eluent is safe in amber glass vials
Save 1 month.
6.14 Sodium sulfite solution. c(Na2SO3)=1 mol/L.
Weigh 126 g of sodium sulfite (6.5), dissolve it in water, and dilute to 1000 ml with water. This solution is refrigerated at 4 °C and can be stored for 1
moon.
6.15 p-chlorophenol stock solution. ρ(Cl)=200 μg/ml.
Accurately weigh 0.0725 g of p-chlorophenol (6.6) and dissolve it in water, transfer it to a 100 ml volumetric flask, and dilute to the mark with water. p-chlorophenol storage
The prepared solution is stored in a glass bottle and refrigerated at 4°C for 1 month. Commercially available certified standard solutions can also be used, refer to standard solutions
The certificate is saved.
6.16 p-chlorophenol intermediate solution. ρ(Cl)=10.0 μg/ml.
Take 5.00 ml of the p-chlorophenol stock solution (6.15), transfer it to a 100 ml volumetric flask, dilute to the mark with water, and prepare for immediate use.
6.17 Use solution of p-chlorophenol. ρ(Cl)=1.00 μg/ml.
Take 10.00 ml of p-chlorophenol intermediate solution (6.16), transfer it into a 100 ml volumetric flask, dilute to the mark with water, and prepare for immediate use.
6.18 2-Chlorobenzoic acid stock solution. ρ(Cl)=250 μg/ml.
Accurately weigh 0.1104 g of 2-chlorobenzoic acid (6.7), dissolve it in water, transfer it to a 100 ml volumetric flask, and make up to the mark with water. 2-Chloro
The benzoic acid stock solution is stored in a glass bottle and refrigerated at 4°C for 1 month.
6.19 2-chlorobenzoic acid intermediate solution. ρ(Cl)=10.0 μg/ml.
Take 4.00 ml of 2-chlorobenzoic acid stock solution (6.18), transfer it into a 100 ml volumetric flask, dilute to the mark with water, and prepare for immediate use.
6.20 2-chlorobenzoic acid working solution. ρ(Cl)=1.00 μg/ml.
Take 10.00 ml of the 2-chlorobenzoic acid intermediate solution (6.19), transfer it into a 100 ml volumetric flask, dilute to the mark with water, and prepare for immediate use.
Note. 2-Chlorobenzoic acid is difficult to dissolve in water and can be prepared 1 day in advance.
6.21 Check solution.
Accurately pipette 1.00 ml, 5.00 ml, 10.0 ml, 20.0 ml and 30.0 ml of p-chlorophenol working solution (6.17) or 2-chlorobenzoic acid, respectively
Use liquid (6.20) into a 100 ml volumetric flask, and make up to the mark with water. The concentrations of AOX contained in this verification solution are. 0.010 mg/L,
0.050 mg/L, 0.100 mg/L, 0.200 mg/L and 0.300 mg/L, ready for immediate use.
6.22 Starch indicator. ρ=10 g/L.
Weigh 1.0 g of soluble starch (6.9), make a paste with a small amount of water, slowly add 100 ml of warm water, and continue to cook until the solution is clear and cooled.
After use, it is ready for immediate use.
6.23 Activated carbon. iodine value ≥ 1050, chloride content < 0.0015%, particle size of activated carbon for vibration adsorption is about 10 μm ~ 50 μm, column
The particle size of activated carbon for adsorption is about 50 μm to 100 μm.
Note. Activated carbon easily adsorbs compounds in the air, and activated carbon will lose its activity after being exposed to the air for 5 days. In order to reduce the blank value of activated carbon, take 1.5 g ~ 2.0 g
(Consumption of the day) Qualified activated carbon is stored in a sealed glass bottle for future use. Once the activated carbon in the airtight bottle is opened, it must be used up on the same day.
The rest can no longer be used.
6.24 Filter membrane. diameter ≤25 mm, pore size 0.45 μm, polycarbonate material.
6.25 Ceramic wool.
6.26 Quartz wool.
6.27 Oxygen. purity ≥99.9%.
7 Instruments and equipment
7.1 Sampling container
Rigid glass bottle, 500 ml.
7.2 Adsorbable organic halogen analyzer
7.2.1 Instrument composition
The main components of the instrument should include burners, detectors and drying tubes, and a complete set of commercial adsorbable organic halogen analyzers can also be used.
7.2.2 Burners
7.2.2.1 Combustion furnace. the heating temperature is adjustable, the maximum temperature is not lower than 950 ℃, both horizontal furnace and vertical furnace can be used.
7.2.2.2 Combustion tube. a quartz tube with a diameter of 2 cm to 4 cm and a length of about 30 cm.
7.2.3 Detector
Microcoulometer, capable of detecting 1 g Cl- with a relative standard deviation of < 10%.
7.2.4 Drying tube
For drying gas, the absorption tube is filled with sulfuric acid (6.3), and the volume accounts for about 20% of the volume of the tube. When the liquid level in the drying tube rises significantly, it should be
Replace the sulfuric acid (6.3) in the drying tube.
7.3 Activated carbon adsorption device
7.3.1 Oscillating adsorption device
7.3.1.1 Horizontal oscillator. a horizontal oscillator with a fixed conical flask clamp, the oscillation frequency is 150 times/min～250 times/min, and the amplitude is 4 cm～
10 cm.
7.3.1.2 Suction filtration equipment. a filter funnel with a diameter of 25 mm and a volume of 150 ml can be installed. A complete set of commercial pre-treatment equipment can also be used
ready.
7.3.1.3 Erlenmeyer flask. 250 ml glass Erlenmeyer flask.
7.3.2 Column adsorption device
Each activated carbon adsorption column is filled with 50 mg of activated carbon (6.23), and the activated carbon is separated by ceramic wool (6.25) or quartz wool (6.26) at both ends.
The particles are immobilized in a quartz column. The activated carbon adsorption column and the test column are vertically connected in series, and the piston pump and the activated carbon adsorption tube are connected by a PTFE tube.
The inner diameter of the activated carbon column adsorption device is about 2 mm to 3 mm, and the column length is about 40 mm to 50 mm.
A complete set of commercial column adsorption system and activated carbon adsorption column can be used. The specifications of activated carbon column and adsorption system refer to the phase provided by the manufacturer.
related information.
7.4 Commonly used laboratory instruments and equipment
A-grade glass measuring device and general glassware in line with national standards.
8 samples
8.1 Collection and storage of samples
Collect and save water samples according to the relevant regulations of HJ/T 91, HJ 91.1, HJ 164 and HJ 493.Sampling, transportation and storage of water samples
Glassware should be used for storage, and the sampling volume should be ≥500 ml.
To avoid oxidizing agents such as free chlorine in the sample, add 10 ml of sodium sulfite solution (6.14) per liter of water sample immediately after sampling.
Note. To test whether the water sample contains free chlorine. take a small amount of water sample into a clean test tube, add a small amount of potassium iodide (6.8), and then add 3 to 5 drops of starch to indicate
(6.22), if it shows blue, it proves that there is free chlorine in the water, and starch-potassium iodide test paper can also be used to test.
After sampling, add 2 ml of nitric acid (6.1) per liter of water to make pH < 2.If it cannot be reached, an appropriate amount can be added. The glass bottle should be filled with water
so that no air bubbles remain. If there are microorganisms, it should be placed for 8 hours before the determination.
If it cannot be analyzed as soon as possible after sampling, the water sample should be acidified with nitric acid (6.1) to make the pH < 2, and it can be stored for 3 days under refrigeration below 4 °C.
8.2 Preparation of test specimens
8.2.1 Pretreatment of specimens
Measure the sample according to the optimal measurement range of the instrument specification, and the high concentration sample can be diluted and measured. For chloride ion concentrations over 1 g/L
The water sample is measured after dilution with nitric acid solution (6.10).
After the sample has been brought to room temperature, take 100 ml of a well-mixed water sample or diluted water sample, add 5 ml of sodium nitrate-nitric acid solution (6.12),
The adsorption method can be oscillating adsorption (8.2.2) or column adsorption (8.2.3).
8.2.2 Oscillation adsorption and purification
Place the water sample (8.2.1) in a 250 ml conical flask (7.3.1.3), add 50 mg of activated carbon (6.23), place the conical flask in the water
On the flat shaker (7.3.1.1), the shaking frequency is based on the slight shaking of the water sample in the conical flask, shake for 1 h, filter through the filter membrane (6.24), and use
About 25 ml of sodium nitrate-nitric acid eluent (6.13) wash the activated carbon on the filter several times to keep the activated carbon moist and avoid the activated carbon filter cake
Prolonged exposure to air results in higher results. Transfer the filter membrane and activated carbon particles after shaking adsorption to a quartz vessel, and use ceramic wool.
(6.25) or quartz wool (6.26). The shaking adsorption step can also be completed by using a complete set of commercial shaking adsorption pretreatment devices.
Note. When the sample contains suspended solids, the vibration method should be used for activated carbon adsorption, which can effectively avoid the blockage of the pipeline in the pretreatment method of column adsorption.
8.2.3 Column adsorption and purification
Connect adsorption columns and test columns in series, each adsorption column is filled with 50 mg of activated carbon (6.23), and the water sample (8.2.1) is filtered at a speed of 3 ml/min.
Elute with 25 ml of sodium nitrate-nitric acid eluent (6.13) at 3 ml/min and keep the activated carbon column wet. If the water contains particles
particulate matter, ensuring that the particulate matter is retained at the top of the adsorption column. The column adsorption step can also be completed using a complete set of commercial column adsorption pretreatment devices.
Note. For samples with chloride concentration close to 1 g/L, the pretreatment method of column adsorption should be used; for samples that may contain volatile organic halides, it should be
The pretreatment method of column adsorption was adopted to avoid the loss of AOX caused by oscillation adsorption.
8.3 Preparation of blank samples
Substitute the sample with 100 ml of nitric acid solution (6.10) and follow the same procedure as in the preparation of the sample (8.2) for the laboratory blank
preparation.
9 Analysis steps
9.1 Instrument Reference Conditions
9.1.1 Adjust the temperature of the combustion furnace (7.2.2.1) not to be lower than 950 °C.
9.1.2 Adjust the flow rate of oxygen (6.27) to about 150 ml/min. If a complete set of commercial instruments is used, refer to the information provided by the instrument manufacturer for relevant parameters.
material.
9.2 Calibration of the Microcoulomb Counter
Before measurement, check whether the instrument is in normal working condition, and use at least one of the following methods to check.
a) Directly inject 50 l～100 l hydrochloric acid solution (6.11) or the calibration sample specified by the instrument manufacturer into the coulomb cell, and measure its concentration
9.3 Determination
9.3.1 Sample determination
Connect the combustion pipe (7.2.2.2) and the drying pipe (7.2.4), and inject sulfuric acid (6.3) into the drying pipe. The prepared sample (8.2.2 or
8.2.3) Push it into the heating zone in the combustion tube, and titrate and count by Coulomb cell.
Note. Relevant factors in the experiment may affect the measurement results, such as. the amount of activated carbon, sample volume, combustion furnace volume, residence time, combustion temperature and gas
If the relevant parameters are changed, the performance and status of the instrument should be checked according to 12.2.1.
9.3.2 Blank test
Carry out the determination of the blank sample (8.3) according to the same procedure as the sample determination (9.3.1).
10 Result calculation and presentation
10.1 Result calculation
The mass concentration (mg/L) of AOX in the sample is expressed as the mass concentration of chlorine, and is calculated according to formula (4).
10.2 Result representation
The number of decimal places of the measurement results is consistent with the detection limit of the method, and the maximum number of significant figures is 3.
Note. If the water sample is filtered, the test result only indicates the AOX concentration in the filtered water, which should be stated in the test report.
11 Accuracy
11.1 Precision
The 6 laboratories determined the concentrations of AOX in the range of 0.016 mg/L to 0.017 mg/L, 0.016 mg/L to 0.038 mg/L,
0.033 mg/L～5.63 mg/L, 0.043 mg/L～8.63 mg/L and 0.016 mg/L～0.879 mg/L of surface water, groundwater and sewage
The actual samples of the effluent from the processing plant, pulp and papermaking wastewater and textile dyeing and finishing wastewater were repeatedly determined for 6 times.
The relative standard deviation ranges in the laboratory are. 2.0%-4.3%, 3.6%-9.4%, 2.8%-9.2%, 2.3%-7.8%, 1.2%-
9.3%.
11.2 Correctness
Six laboratories carried out six repeated tests on standard samples containing AOX concentrations of 0.050 mg/L, 5.00 mg/L and 15.0 mg/L.
Certainly.
The relative errors of the oscillation adsorption method are. -14.8%~9.6%, -7.6%~0.7%, -6.7%~12.0%;
The final values of the relative errors of the oscillation adsorption method are. -1.9%±16.4%, -4.0%±5.4%, -1.0%±12.8%;
The relative errors of the column adsorption method are. -8.0% to 1.8%, -8.4% to 1.2%, and -10.7% to 0;
The final values of the relative errors of the column adsorption method were. -2.6%±8.1%, -3.2%±7.2%, -3.8%±7.2%.
The 6 laboratories determined the concentrations of AOX in the range of 0.016 mg/L to 0.017 mg/L, 0.016 mg/L to 0.038 mg/L,
0.033 mg/L～5.63 mg/L, 0.043 mg/L～8.63 mg/L and 0.016 mg/L～0.879 mg/L surface water
0.050 mg/L and 0.100 mg/L), groundwater (0.050 mg/L and 0.100 mg/L for spiking), sewage treatment plant effluent (spiking for 0.100 mg/L)
1.00 mg/L and 3.00 mg/L), pulp and papermaking wastewater (5.00 mg/L and 10.0 mg/L spiked), textile dyeing and finishing wastewater (spiked
5.00 mg/L and 10.0 mg/L) the actual samples were determined in 6 replicates.
The recovery rates of standard additions ranged from 88.6% to 99.6%, 89.6% to 102%, 88.0% to 103%, 83.0% to 102%, and 81.7% to
104%, 81.2%～101%, 82.0%～105%, 80.8%～101%, 82.4%～103%, 81.8%～109%.
12 Quality Assurance and Quality Control
12.1 Blank test
1 laboratory blank test is performed for every 10 consecutive samples or each batch (≤10 samples/batch), and the blank value should be lower than
Otherwise, the adsorption step, the combustion step and the determination of microcoulombs should be checked separately.
12.2 Calibration
12.2.1 When the instrument is turned on continuously, the whole process measurement of the verification solution (6.21) shall be carried out once a month, and the measurement results shall be subjected to regression analysis.
The correlation coefficient should be greater than or equal to 0.999, and the slope should be in the range of 0.95 to 1.05.The full process determination of the verification solution is only used for instrument performance and condition
inspection.
12.2.2 Each batch of samples should be checked for the intermediate point of a standard solution, or a standard solution with a similar AOX concentration to the sample to be tested should be prepared
The whole process measurement is carried out at the point, and the relative error between the measurement result and the standard solution concentration should be within ±10%.
12.3 Parallel samples
Measure 10% of the parallel samples for each batch of samples. When the number of samples is less than 10, at least one parallel sample should be measured. Sample determination result ≥ 0.100 mg/L
When the measurement result of the parallel sample is less than ±10%, the relative deviation of the measurement result of the parallel sample should be within ±10%; when the measurement result of the sample is less than 0.100 mg/L, the measurement result of the parallel sample is absolutely
The difference should be < 0.010 mg/L.
12.4 Matrix spikes
Every 10 samples or every batch (≤10 samples/batch) should be 1 matrix spiked sample, and the matrix spiked recovery rate should be 80% to 120%
between.
12.5 Adsorption performance verification
One sample with the highest concentration was selected from each batch of samples for verification of adsorption performance.
Oscillation adsorption method. take samples of different volumes (such as 50 ml and 100 ml) and test them separately. When the sample determination result is ≥ 0.100 mg/L,
If the relative deviation of the AOX values of the two samples is within ±10%, it means that the adsorption is complete; when the sample measurement result is less than 0.100 mg/L, the two samples
The absolute difference of the fixed result < 0.010...
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