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HJ 1226-2021 English PDF

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HJ 1226-2021: Water quality - Determination of sulfide - Methylene blue spectrophotometric method
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Standard similar to HJ 1226-2021

HJ 1347.1   HJ 1346.1   HJ 1217   

Basic data

Standard ID HJ 1226-2021 (HJ1226-2021)
Description (Translated English) Water quality - Determination of sulfide - Methylene blue spectrophotometric method
Sector / Industry Environmental Protection Industry Standard
Word Count Estimation 13,182
Issuing agency(ies) Ministry of Ecology and Environment

HJ 1226-2021: Water quality - Determination of sulfide - Methylene blue spectrophotometric method


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(Water quality Determination of sulfide methylene blue spectrophotometry) National Ecological Environment Standard of the People's Republic of China Determination of Sulfide in Water methylene blue spectrophotometry Water quality-Determination of sulfide -Methylene blue spectrophotometric 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 2021-12-16 2022-03-01 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...4 9 Analysis steps...4 10 Result calculation and representation...5 11 Accuracy...5 12 Quality Assurance and Quality Control...6 13 Waste Disposal...6 14 Notes...6 Appendix A (Normative Appendix) Preparation and Calibration of Sulfide Standard Solution...7 Appendix B (informative) Accuracy of the method...9 Determination of sulfide in water by methylene blue spectrophotometry Warning. The sulfuric acid and hydrochloric acid used in the experiment are highly corrosive, and N,N-dimethyl-p-phenylenediamine hydrochloride and hydrogen sulfide have certain Toxicity, protective equipment should be worn as required during operation to avoid direct contact, and the sample pretreatment process should be carried out in a fume hood.

1 Scope of application

This standard specifies the methylene blue spectrophotometric method for the determination of sulfides in water. This standard applies to the determination of sulfides in surface water, groundwater, domestic sewage, industrial wastewater and seawater. When the sampling volume is.200 ml and a 10 mm optical path cuvette is used, the detection limit of the method is 0.01 mg/L, and the lower detection limit is 0.04 mg/L; When using a 30 mm optical path cuvette, the detection limit of the method was 0.003 mg/L, and the lower limit of determination was 0.012 mg/L. Note. The 30 mm optical path cuvettes are only used for the determination of groundwater or low-concentration seawater below the first class standard, and the pretreatment method should use "acidification-distillation-absorption" Law.

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 442.3 Technical Specifications for Environmental Monitoring in Offshore Seas Part III Water Quality Monitoring in Offshore Seas HJ 493 Technical regulations on preservation and management of water sampling samples

3 Terms and Definitions

The following terms and definitions apply to this standard. 3.1 sulfide Water-soluble inorganic sulfides and acid-soluble metal sulfides, including soluble H2S, -HS, 2-S, and in suspensions of soluble sulfides and acid-soluble metal sulfides.

4 Principles of the method

After the sulfide in the sample is acidified, heated with nitrogen blowing or distilled, the generated hydrogen sulfide is absorbed by sodium hydroxide solution, and the generated sulfide ions are It reacts with N,N-dimethyl-p-phenylenediamine in an acidic solution of ferric ammonium sulfate to generate methylene blue, and its absorbance is measured at 665 nm. The chemical content is proportional to the absorbance value.

5 Interference and cancellation

The main interferent is 2 3SO , 2 2 3S O , SCN-, NO3 -, I-, NO2 -, CN- and some heavy metal ions. Sulfide content is 0.3 mg/L , the maximum permissible content of interfering substances in the sample is 2 3SO  700 mg/L, 2 2 3S O  900 mg/L, SCN- 900 mg/L, NO3 -200 mg/L, - 400 mg/L, CN- 5 mg/L, 2Cu  2 mg/L, 2Pb  25 mg/L, 2Hg  4 mg/L. NO2 - Can react with methylene blue to enable assay The result is low, NO2 - This method is not applicable when the concentration (in N) is higher than 2.0 mg/L.

6 Reagents and Materials

Unless otherwise stated, analytical reagents that meet national standards were used in the analysis, and the experimental water was freshly prepared deionized water or distilled water. 6.1 De-oxygenated deionized water. Deionized water is prepared through an ion exchange column, and nitrogen is passed through at a rate of.200 ml/min to 300 ml/min for about 20 minutes. Saturate the water with nitrogen to remove dissolved oxygen from the water. The prepared deoxygenated deionized water should be immediately sealed and stored in a glass bottle. Instant use. 6.2 Sulfuric acid (H2SO4). ρ=1.84 g/ml. 6.3 Hydrochloric acid (HCl). ρ=1.19 g/ml. 6.4 Sodium Hydroxide (NaOH). 6.5 N,N-Dimethyl-p-phenylenediamine hydrochloride [NH2C6H4N(CH3)2·2HCl]. 6.6 Ferric ammonium sulfate [Fe(NH4)(SO4)2·12H2O]. 6.7 Zinc acetate [Zn(CH3COO)2·2H2O]. 6.8 Ascorbic acid (C6H8O6). 6.9 Disodium EDTA (C10H14O8N2Na2 2H2O). 6.10 Hydrochloric acid solution. Measure 250 ml of hydrochloric acid (6.3) and slowly pour it into 250 ml of water and cool it. 6.11 Zinc acetate solution. c[Zn(CH3COO)2]=1 mol/L. Weigh 220 g of zinc acetate (6.7), dissolve it in 1000 ml of water, and filter it before use if it is cloudy. 6.12 Sodium hydroxide solution. ρ(NaOH)=10 g/L. Weigh 10.0 g of sodium hydroxide (6.4) and dissolve it in 1000 ml of water, shake well. 6.13 Antioxidant solution. Weigh 4.0 g ascorbic acid (6.8), 0.2 g disodium EDTA (6.9), 0.6 g sodium hydroxide (6.4) and dissolve in 100 ml water , shake well and store in a brown reagent bottle. Instant use. 6.14 N,N-dimethyl-p-phenylenediamine solution. ρ[NH2C6H4N(CH3)2·2HCl]=2 g/L. Weigh 2.0 g of N,N-dimethyl-p-phenylenediamine hydrochloride (6.5) and dissolve it in 700 ml of water, slowly add.200 ml of sulfuric acid (6.2), and cool Then dilute to 1000 ml with water and shake well. This solution is stable for 3 months when stored in an airtight amber bottle at room temperature. 6.15 Ferric ammonium sulfate solution. ρ[Fe(NH4)(SO4)2·12H2O]=100 g/L. Weigh 25.0 g of ferric ammonium sulfate (6.6) and dissolve it in 100 ml of water, slowly add 5.0 ml of sulfuric acid (6.2), and dilute with water to 250 ml, shake well. If there is insoluble matter in the solution, it should be used after filtration. 6.16 Sulfide standard solution. you can buy commercially available certified reference materials, or you can prepare it yourself. See Appendix A for the preparation and calibration methods. 6.17 Sulfide standard solution. ρ(S2-)=10.00 mg/L. Transfer a certain amount of sulfide standard solution (6.16) to 2.0 ml of sodium hydroxide solution (6.12) and an appropriate amount of deionized deionized water. (6.1) in a 100 ml brown volumetric flask, dilute to volume with deoxygenated deionized water (6.1), and prepare a sulfur containing sulfur ion concentration of 10.00 mg/L. Chemical standard solution. Instant use. 6.18 Sulfide standard solution. ρ(S2-)=2.00 mg/L. Transfer a certain amount of sulfide standard solution (6.16) to 2.0 ml of sodium hydroxide solution (6.12) and an appropriate amount of deionized deionized water.

8 samples

8.1 Sample Collection and Storage Samples were collected in accordance with the relevant regulations of HJ/T 91, HJ 91.1, HJ 164, HJ 442.3 and HJ 493. When sampling, first add zinc acetate solution (6.11) to the sampling bottle (7.1), add water sample to the near full bottle, and then add sodium hydroxide solution in sequence. solution (6.12) and antioxidant solution (6.13), leaving no headspace after stoppering. Usually 2 ml of zinc acetate solution (6.11), 1 ml sodium hydroxide solution (6.12) and 2 ml antioxidant solution (6.13). When the sulfide content is high, the zinc acetate solution should continue to be added dropwise (6.11) until the precipitation is complete. The samples were determined within 4 days after fixation. Replace the water sample with experimental water at the sampling site, and add zinc acetate solution (6.11), sodium hydroxide solution (6.12) and After the oxidant solution (6.13), take it back to the laboratory as a full procedure blank. Note 1.When determining soluble sulfide, the sample should be fixed after filtration through a 0.45 µm filter. Note 2.Multiple parallel samples can be collected for high concentration sample dilution, field parallel samples and sample matrix spiking. 8.2 Preparation of test specimens 8.2.1 "Acid-Blow-Absorption" Method Take.200 ml of mixed water sample, or dilute an appropriate amount of sample with deoxygenated deionized water (6.1) to.200 ml, and quickly transfer to 500 ml for reaction Into the bottle, add 5 ml of antioxidant solution (6.13) and shake gently. Measure 20.0 ml of sodium hydroxide solution (6.12) into a 100 ml absorption tube (7.5) as the absorption liquid, insert the airway to below the liquid level of the absorption liquid to ensure complete absorption. Connect the device and turn on the water bath The temperature rose to 60°C to 70°C. Switch on nitrogen (6.19), adjust the flow to 300 ml/min, and turn off the gas source after 5 min. Turn off acid addition The funnel piston, open the top cover of the separating funnel, add 10 ml of hydrochloric acid solution (6.10), cover tightly, slowly unscrew the piston, switch on nitrogen (6.19), The reaction flask was placed in a water bath apparatus. Maintain the nitrogen flow at 300 ml/min, blow air continuously for 30 min, remove the reaction bottle, disconnect the air tube, close the Close the air source. Flush the airway with a small amount of deoxygenated deionized water (6.1), add it to the absorption solution, add deoxygenated deionized water (6.1) to about 60 ml, To be tested. 8.2.2 "Acidation-distillation-absorption" method Measure.200 ml of mixed water sample, or dilute an appropriate amount of sample with deoxygenated deionized water (6.1) to.200 ml, and quickly transfer to 500 ml for distillation Into the bottle, add 5 ml of antioxidant solution (6.13), shake gently, and add a few glass beads. Measure 20.0 ml of sodium hydroxide solution (6.12) Use the 100 ml absorbing tube (7.5) as the absorbing solution, and insert the distillate conduit to the level below the absorbing solution to ensure complete absorption. Turn on condensation Water, quickly add 10 ml of hydrochloric acid solution (6.10) to the distillation flask, immediately close the stopper, turn on the temperature-controlled electric furnace, and adjust to an appropriate heating temperature. degree, distilled at a distillation rate of 2 ml/min to 4 ml/min. When the volume of the solution in the absorption tube reaches about 60 ml, remove the distillation bottle and remove the Absorber tube, stop distillation. Rinse the distillate conduit with a small amount of deoxygenated deionized water (6.1) and incorporate it into the absorption solution to be tested. 8.3 Preparation of blank samples Substitute the experimental water for the actual sample, and follow the same steps as the preparation of the sample (8.2) for the preparation of the laboratory blank sample.

9 Analysis steps

9.1 Establishment of standard curve Take 6 absorption tubes (7.5), add 20 ml of sodium hydroxide absorption solution (6.12) to each, and measure 0.00 ml, 0.50 ml, 1.00 ml, 2.00 ml, 4.00 ml and 7.00 ml of sulfide standard use solution (6.17) are transferred into the absorption tube (7.5), add deoxygenated deionized water (6.1) to about 60 ml, along the Slowly add 10 ml of N,N-dimethyl-p-phenylenediamine solution (6.14) to the wall of the absorption tube, immediately cap the stopper and slowly invert once. Cork, along the absorber tube Slowly add 1 ml of ferric ammonium sulfate solution (6.15) to the wall, immediately stopper and shake well. After standing for 10 min, use deoxygenated deionized water (6.1). Make up to the marked line, shake well. Measure the absorbance at a wavelength of 665 nm using a 10 mm pathlength cuvette with deoxygenated deionized water (6.1) as a reference. Take the content of sulfide (μg) as the abscissa and the absorbance value after deducting the zero concentration point as the ordinate to establish a high-concentration standard curve. Measure 0.00 ml, 1.00 ml, 2.50 ml, 5.00 ml, 7.50 ml, and 10.00 ml of sulfide standard solution (6.18) respectively, and press the above Step, use a 30 mm optical path cuvette for colorimetry to establish a low-concentration standard curve. 9.2 Determination of samples Measure the absorbance of sample 8.2 according to the same steps as the establishment of the standard curve (9.1). 9.3 Blank test Measure the absorbance of blank sample 8.3 according to the same procedure as the measurement of sample (9.2). 10 Result calculation and presentation 10.1 Result calculation The concentration of sulfide in the sample is calculated according to formula (1). 10.2 Result representation The determination result shall retain up to 3 significant figures, and the number of digits after the decimal point is consistent with the detection limit. 11 Accuracy 11.1 Precision When the sampling volume was.200 ml and a 10 mm optical path cuvette was used, the six laboratories were Blank spiked samples at 0.10 mg/L, 0.30 mg/L and 3 actual samples spiked at 0.10 mg/L (surface water, domestic sewage and (industrial waste water) were repeated for 6 times, and the relative standard deviations in the laboratory were 13% to 19%, 5.5% to 13%, 2.8% to 7.7%, 6.6% to 13%. When the sampling volume was.200 ml and a 30 mm optical path cuvette was used, the 6 laboratories added standard concentrations of 0.01 mg/L, 0.01 mg/L, Two actual samples (groundwater and seawater) of 0.05 mg/L and 0.09 mg/L were tested for 6 replicates, and the relative standard deviation in the laboratory was divided into 11% to 14%, 6.2% to 12%, 3.8% to 9.8%, respectively. Precision data are shown in Table B.1 and Table B.2 in Appendix B. 11.2 Correctness When the sampling volume was.200 ml and a 10 mm optical path cuvette was used, the six laboratories were Blank spiked samples at 0.10 mg/L, 0.30 mg/L and 3 actual samples spiked at 0.10 mg/L (surface water, domestic sewage and (industrial wastewater) were repeated for 6 times, and the recovery rates of standard addition were 62.8%-69.4%, 77.3%-95.7%, 80.1%-99.4%, 72.3% to 110%. When the sampling volume was.200 ml and a 30 mm optical path cuvette was used, the 6 laboratories added standard concentrations of 0.01 mg/L, 0.01 mg/L, Two actual samples (groundwater and seawater) of 0.05 mg/L and 0.09 mg/L were tested in 6 replicates, and the recovery rates of standard additions ranged from 63.2%～69.8%, 75.7%～85.3%, 87.2%～94.8%. For accuracy data, see Table B.3 and Table B.4 in Appendix B. 12 Quality Assurance and Quality Control 12.1 For each batch of samples, at least one full procedure blank sample should be collected and one laboratory blank sample should be prepared. out of limit. 12.2 The correlation coefficient of the standard curve should be ≥ 0.999.Each batch of samples should be measured at the middle point of the standard curve, and the measurement results should be consistent with the standard curve. The relative error of the concentration should be within ±10%. 12.3 At least 10% of the parallel double samples should be measured for each batch of samples. When the number of samples is less than 10, at least one parallel double sample should be measured. The relative deviation of the results should be within 30%. 12.4 At least 10% of the matrix spiked samples should be measured for each batch of samples. When the number of samples is less than 10, at least one matrix spiked sample should be measured. The recovery rate of the standard addition should be between 60% and 120%. 13 Waste Disposal The waste generated in the experiment should be collected by classification, stored in a centralized manner, and marked accordingly, and entrust a qualified unit to deal with it according to law. 14 Notes 14.1 The interface of glassware should be designed with ground mouth, and each connecting pipe should preferably be connected by glass pipe. When using a silicone tube connection, add The recovery rate of the standard is significantly reduced and should be replaced immediately. 14.2 During the preparation of the sample, attention should be paid to check the air tightness of the blowing or distillation device to prevent the occurrence of gas leakage and cause the volatilization of hydrogen sulfide. Ruofa If there is a gas leak, the sample should be re-sampled for analysis.

Appendix A

(normative appendix) Preparation and Calibration of Sulfide Standard Solutions A.1 Soluble starch [(C6H10O5)n]. A.2 Iodine (I2). A.3 Potassium iodide (KI). A.4 Sodium thiosulfate (Na2S2O3 5H2O). A.5 Anhydrous sodium carbonate (Na2CO3). A.6 Sodium sulfide (Na2S·9H2O). A.7 Potassium dichromate (K2Cr2O7). reference reagent. Take an appropriate amount of potassium dichromate in a weighing bottle, place it in an oven at 105 °C for 2 h, and cool it in a desiccator for later use. A.8 Sulfuric acid solution. Measure 20.0 ml of sulfuric acid (6.2) and slowly pour it into 100 ml of water and cool it. A.9 Starch solution. ρ[(C6H10O5)n]=10 g/L. Weigh 1.0 g of soluble starch (A.1), make a paste with a small amount of water, slowly pour 50 ml of boiling water, continue to boil until the solution is clear, Make up to 100 ml and store in a reagent bottle after cooling. Instant use. A.10 Potassium dichromate standard solution. c(1/6K2Cr2O7)=0.1000 mol/L. Accurately weigh 4.9032 g of potassium dichromate (A.7) and dissolve it in 100 ml of water, transfer it to a 1000 ml volumetric flask, make up to the mark, and shake well. A.11 Iodine standard solution. c(1/2 I2)≈0.1 mol/L. Accurately weigh 12.7 g of iodine (A.2) and dissolve it in 100 ml of water, then add 40.0 g of potassium iodide (A.3), dissolve it and add water to make up to 1 L, Store in reagent bottles. Instant use. A.12 Standard solution of sodium thiosulfate. c(Na2S2O3)≈0.1 mol/L. Weigh 24.8 g of sodium thiosulfate (A.4) and dissolve it in water, add 1 g of anhydrous sodium carbonate (A.5), dilute to 1 L with water, store in a reagent bottle, The exact concentration was calibrated after a week of storage. If the solution is cloudy, it must be filtered. Calibration method. in a 250 ml iodine volumetric flask, add 1 g potassium iodide (A.3) and 50 ml water, add 15.00 ml potassium dichromate standard solution (A.10), After shaking until completely dissolved, add 5 ml of sulfuric acid solution (A.8), immediately stopper and shake well. After standing in the dark for 5 min, use the thiocyanate to be calibrated. When the sodium sulfate standard solution is dropped until the solution is pale yellow, add 1 ml of starch solution (A.9), and continue to titrate until the blue color just disappears as the end point. Record Dosage of sodium thiosulfate standard solution, and make blank titration at the same time. The concentration of sodium thiosulfate standard solution is calculated according to formula (A.1). (NaSO) .. VV (A.1) In the formula. c(Na2S2O3)--concentration of sodium thiosulfate standard solution, mol/L; 0.1000--Concentration of potassium dichromate standard solution, mol/L; 15.00--Volume of potassium dichromate standard solution, ml; V1--the volume of sodium thiosulfate standard solution consumed by titration of potassium dichromate standard solution, ml; V0--the volume of standard solution of sodium thiosulfate consumed by titration blank solution, ml. A.13 Sulfide standard solution. ρ(S2-)≈100 mg/L. Take a certain amount of crystalline sodium sulfide (A.6) in a Buchner funnel beaker and rinse with water to remove surface impurities. After absorbing the water with dry filter paper, Weigh about 0.75 g and dissolve it in a small amount of water, dilute to 100 ml with water, and calibrate the exact concentration after shaking well. Calibration method. In a 250 ml iodine flask, add 10 ml sodium hydroxide solution (6.12) and 10.00 ml sulfide standard solution to be calibrated (6.16) and 20.00 ml of iodine standard solution (A.11). Dilute with water to about 60 ml, add 5 ml sulfuric acid solution (A.8), immediately stopper and seal Shake well. After standing in the dark for 5 min, titrate with sodium thiosulfate standard solution (A.12) until the solution is pale yellow, add 1 ml of starch solution (A.9), continue to titrate until the blue color just disappears as the end point. Record the amount of sodium thiosulfate standard solution (A.12), and replace it with 10 ml of water. Instead of sulfide standard solution, make blank titration.

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