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HJ 1147-2020 English PDF

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HJ 1147-2020: (Determination of pH value of water quality Electrode method)
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Basic data

Standard ID: HJ 1147-2020 (HJ1147-2020)
Description (Translated English): (Determination of pH value of water quality Electrode method)
Sector / Industry: Environmental Protection Industry Standard
Classification of Chinese Standard: Z16
Word Count Estimation: 11,154
Date of Issue: 2020-11-26
Date of Implementation: 2021-06-01
Regulation (derived from): Ministry of Ecology and Environment Announcement No. 56 (2020)
Issuing agency(ies): Ministry of Ecology and Environment

HJ 1147-2020: (Determination of pH value of water quality Electrode method)

---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order.
(Determination of pH value of water quality Electrode method) National Environmental Protection Standards of the People's Republic of China Electrode method for the determination of pH value of water quality Water quality-Determination of pH-Electrode method 2020-11-26 release 2021-06-01 implementation Issued by the Ministry of Ecology and Environment i table of contents Foreword...ii 1 Scope of application...1 2 Normative references...1 3 Principles of the method...1 4 Interference and cancellation...1 5 Reagents and materials...1 6 Instruments and equipment...2 7 Sample...2 8 Analysis steps...3 9 Results presentation...4 10 Precision and accuracy...4 11 Quality Assurance and Quality Control...4 12 Waste disposal...4 13 Precautions...5 Appendix A (informative appendix) Standard buffer solution...6 Appendix B (informative appendix) Common temperature compensation methods...9

Foreword

To implement the Environmental Protection Law of the People’s Republic of China and the Water Pollution Prevention Law of the People’s Republic of China, and protect the ecology The environment, to protect human health, regulate the method for measuring pH in water, and formulate this standard. This standard specifies the electrode method for determining the pH value of surface water, groundwater, domestic sewage and industrial wastewater. Compared with the "Glass Electrode Method for the Determination of pH Value of Water Quality" (GB 6920-86), the main differences between this standard are as follows. -The name was revised to "The Electrode Method for the Determination of pH Value of Water Quality"; --Modified the scope of application of the method, the principle of the method and the sample storage conditions; --Deleted the definition part; --Improved the requirements of standard buffer solution and experimental water; --Detailed contents such as calibration, sample determination and result presentation; --Added the terms of sample collection, quality assurance and quality control, and precautions. Since the implementation of this standard, the original National Environmental Protection Agency approved and issued the "Water Quality pH Value" on October 10, 1986. "Glass Electrode Method" (GB 6920-86) is implemented in the corresponding environmental quality standards and pollutant emission (control) standards. Stop execution during implementation. Appendix A and Appendix B of this standard are informative appendices. This standard was formulated by the Department of Ecological Environment Monitoring and the Department of Regulations and Standards of the Ministry of Ecology and Environment. Drafting organization of this standard. Tianjin Ecological Environment Monitoring Center. Verifiers of this standard. China National Environmental Monitoring Center, National Environmental Analysis and Testing Center, Beijing Ecological Environment Monitoring Center Center, Dalian Ecological Environment Monitoring Center of Liaoning Province, Hunan Ecological Environment Monitoring Center and Sichuan Provincial Ecological Environment Monitoring Center. This standard was approved by the Ministry of Ecology and Environment on November 26, 2020. This standard shall come into effect on June 1, 2021. This standard is interpreted by the Ministry of Ecology and Environment.

1 Electrode method for measuring pH value of water quality

1 Scope of application

This standard specifies the electrode method for determining the pH value of water. This standard applies to the determination of pH values in surface water, groundwater, domestic sewage and industrial wastewater. The measurement range is 0-14.

2 Normative references

This standard quotes the following documents or their clauses. For undated reference documents, their valid versions are applicable to this standard. GB/T 27501 Preparation method of buffer solution for pH value determination HJ 91.1 Technical Specification for Wastewater Monitoring HJ/T 91 Technical specification for surface water and sewage monitoring HJ/T 164 Technical Specification for Groundwater Environmental Monitoring

3 Principles of the method

The pH value is obtained by measuring the electromotive force of the battery. The battery usually consists of a reference electrode and a hydrogen ion indicator electrode. Solution For every change of 1 pH unit, the change of the potential difference at the same temperature is constant, so the pH value is directly read on the instrument. Said.

4 Interference and elimination

4.1 Water color, turbidity, colloidal substances, oxidizing agents and reducing agents do not interfere with the measurement. 4.2 In a strong acid solution with a pH value of less than 1, an acid error will occur; in a strong alkaline solution with a pH value greater than 10, Will produce sodium difference. It can be measured with an acid and alkali-resistant pH electrode, or you can choose a standard buffer that is similar to the pH value of the measured solution The solution calibrates the instrument to counteract interference. 4.3 When measuring samples with low electrolyte, a pH electrode suitable for low ionic strength should be used; For samples with a temperature greater than 5‰), a pH electrode suitable for high ionic strength should be used for measurement. 4.4 When measuring acidic samples with high concentration of fluorine, use a hydrofluoric acid-resistant pH electrode for measurement. 4.5 Temperature affects the electrode potential and the ionization balance of water, the instrument should have a temperature compensation function, and the temperature compensation range is based on Instrument manual.

5 Reagents and materials

Unless otherwise specified, analytical reagents that meet national standards are used for analysis. 25.1 Experimental water. newly prepared distilled water to remove carbon dioxide. Pour the water into the beaker, boil for 10 minutes, cover and leave to cool. Temporarily use the current system. 5.2 Potassium hydrogen phthalate (C8H5KO4). Dry for 2 h at 110℃～120℃, and store in a desiccator for later use. 5.3 Anhydrous disodium hydrogen phosphate (Na2HPO4). Dry for 2 h at 110℃～120℃, and store in a desiccator for later use. 5.4 Potassium dihydrogen phosphate (KH2PO4). Dry for 2 h at 110℃～120℃, and store in a desiccator for later use. 5.5 Sodium tetraborate (Na2B4O7·10H2O). Place it in a desiccator with saturated sodium bromide (or sodium chloride and sucrose) solution (room temperature) for 48 hours to make sodium tetraborate The crystal remains stable. 5.6 Standard buffer solution. 5.6.1 Standard buffer solution I. c (C8H5KO4) = 0.05 mol/L, pH = 4.00 (25°C). Weigh 10.12 g of potassium hydrogen phthalate (5.2), dissolve in water (5.1), transfer to a 1 L volumetric flask and dilute to Marking. You can also buy a commercially available qualified standard buffer solution and use it according to the instructions. 5.6.2 Standard buffer solution II. c(Na2HPO4)=0.025 mol/L, c(KH2PO4)=0.025 mol/L, pH=6.86 (25°C). Weigh 3.53 g of anhydrous disodium hydrogen phosphate (5.3) and 3.39 g of potassium dihydrogen phosphate (5.4) and dissolve in water (5.1), Transfer to a 1 L volumetric flask and dilute to the mark. You can also buy a commercially available qualified standard buffer solution and use it according to the instructions. 5.6.3 Standard buffer solution III. c (Na2B4O7) = 0.01 mol/L, pH = 9.18 (25°C). Weigh 3.80 g of sodium tetraborate (5.5), dissolve it in water (5.1), transfer to a 1 L volumetric flask, and dilute to the mark. Sealed and stored in a polyethylene bottle. You can also buy a commercially available qualified standard buffer solution and use it according to the instructions. Note 1.The above pH standard buffer solution can be stored for 2 to 3 months under refrigeration below 4°C. When turbidity, mold or precipitation is found, Cannot continue to use. Note 2.When the pH value of the tested sample is too high or too low, other standard buffer solutions with similar pH values can be selected. Refer to Appendix A for details. 5.7 pH extensive test paper.

6 Apparatus and equipment

6.1 Sampling bottle. polyethylene bottle. 6.2 Acidity meter. The accuracy is 0.01 pH unit, with temperature compensation function, and the pH value measurement range is 0-14. 6.3 Electrode. split pH electrode or composite pH electrode. 6.4 Thermometer. 0℃～100℃. 6.5 Beaker. polyethylene or hard glass material. 6.6 Commonly used instruments and equipment in general laboratories.

7 samples

Collect samples in accordance with the relevant regulations of HJ 91.1, HJ/T 91 and HJ/T 164, and measure them on site; or collect samples in sampling Among the 3 bottles (6.1), the container is immediately sealed when the sample is filled, and the measurement is completed within 2 hours.

8 Analysis steps

8.1 Preparation before measurement Activate and maintain the electrode (6.3) according to the instruction manual, and confirm that the instrument is working normally. On-site measurement should understand On-site environmental conditions and the source and nature of the samples, preliminary judgments whether there are strong acid, high electrolyte, low electrolyte, high Interference with fluoride, etc., and prepare accordingly. 8.2 Instrument calibration 8.2.1 Calibration solution Use pH extensive test paper (5.7) to roughly measure the pH value of the sample, and choose two suitable calibrations according to the pH value of the sample Use standard buffer solution (5.6). The difference in pH between the two standard buffer solutions is about 3 pH units. The sample pH value should be as low as possible Between the two standard buffer solutions pH value range, if it exceeds the range, the sample pH value is at least one of the standard buffer solutions The difference in pH value does not exceed 2 pH units. 8.2.2 Temperature compensation Manual temperature compensation instrument, adjust the temperature of the standard buffer solution to be consistent with the actual temperature of the sample, use the temperature The meter (6.4) measures and records the temperature. During calibration, set the temperature compensation knob of the acid meter (6.2) to this temperature. With For the instrument with automatic temperature compensation, it is not necessary to keep the standard buffer solution and the sample at the same temperature, follow the instrument instructions operating. See Appendix B for common temperature compensation methods. Note. The instrument with automatic temperature compensation function must be used for on-site measurement. 8.2.3 Calibration method Use two-point calibration method, select the calibration mode according to the instrument manual, first use neutral (or weak acid, weak base) standard buffer Solution, and then calibrated with acidic or alkaline standard buffer solution. Refer to the attached table for the pH value of various standard buffer solutions at different temperatures A.2. a) Immerse the electrode (6.3) in the first standard buffer solution and stir slowly horizontally to avoid air bubbles. Wait until the reading is stable. After setting, adjust the display value of the instrument to be consistent with the pH value of the standard buffer solution. b) Rinse the electrode (6.3) with distilled water and absorb the moisture on the electrode surface with the edge of the filter paper, and immerse the electrode (6.3) in the second In a standard buffer solution, stir slowly and horizontally to avoid air bubbles. After the reading is stable, adjust the value of the instrument Consistent with the pH value of the standard buffer solution. c) Repeat a) operation, after the reading is stable, the difference between the displayed value of the instrument and the pH value of the standard buffer solution should be ≤0.05 pH unit, otherwise repeat steps a) and b) until qualified. Note 1.Multi-point calibration method can also be used. Follow the instrument manual. When measuring actual samples, it is necessary to use similar pH values (not large Verification of certified reference samples or reference materials at 3 pH units. Note 2.The reading of the pH meter within 1 min changes less than 0.05 pH units to be regarded as stable. 48.3 Sample determination Rinse the electrode with distilled water and use the edge of the filter paper to absorb the moisture on the surface of the electrode. Take an appropriate amount according to the instrument used during on-site measurement Sample or direct measurement; in the laboratory, pour the sample into the beaker (6.5) along the wall of the cup, and immediately dip the electrode into the sample. Stir slowly and horizontally to avoid air bubbles. After the reading is stable, write down the pH value. The instrument with automatic reading function can directly Read the data. Rinse the electrode with distilled water after each sample is measured.

9 Results presentation

The measurement result keeps one decimal place, and the temperature of the sample is indicated. When the measurement result exceeds the measurement range (0～ 14) When it is reported as "strong acid, out of measuring range" or "strong base, out of measuring range". 10 Precision and accuracy 10.1 Precision The six laboratories tested drinking water source water, landscape surface water, and landscape water with pH values of 8.2, 7.5, 8.3, 8.6, 2.1, and 10.2, respectively. The unified samples of groundwater, domestic sewage and two kinds of industrial wastewater were subjected to 6 repeated determinations. the range in the laboratory was all 0.1; The range between laboratories is 0.1～0.2. 10.2 Accuracy The six laboratories have tested 3 uniform certified standards with pH values of 4.13±0.04, 7.33±0.06 and 9.09±0.07, respectively The sample was tested for 6 times. the error ranges were -0.04～0.02, -0.05～0.04 and -0.05～0; the final error The values are -0.02±0.06, -0.03±0.08 and -0.04±0.04, respectively. 11 Quality Assurance and Quality Control 11.1 The instrument should be calibrated before the determination of each batch of samples. When the pH value of the sample changes significantly or the monitoring site changes New calibration. 11.2 For every 20 consecutive samples or batches (≤20 samples/batch), 1 certified standard sample or standard should be analyzed Quality, the measurement result should be within the guaranteed value range, otherwise it should be re-calibrated and re-measure the batch of samples. 11.3 Every 20 samples or every batch (≤20 samples/batch) should analyze 1 parallel sample. When the pH value is between 6-9 The allowable difference is ±0.1 pH units; when the pH value is less than or equal to 6 or the pH value is ≥9, the allowable difference is ±0.2 pH units. The measurement result is the first measurement value. 12 Waste treatment The waste generated during the experiment should be collected separately, properly kept, and entrusted to a qualified unit for disposal according to law. 513 Note 13.1 The pH meter (6.2) should be used and maintained according to the instrument manual. 13.2 The electrode (6.3) should be used and maintained according to the instructions. 13.3 In order to reduce the dissolution of acid and alkaline gases in the air, or the volatilization of corresponding substances in the sample, the sampling should not be opened before the determination. Sample bottle (6.1). 13.4 When measuring strongly alkaline samples with a pH value greater than 10, a polyethylene beaker (6.5) should be used. 13.5 The used standard buffer solution is not allowed to be poured back into the original bottle. 13.6 If there are special needs, the number of significant digits of the result can be determined according to the needs and the accuracy of the instrument. 13.7 If you choose higher-precision instruments and equipment, you need to use a higher-precision standard buffer solution. The accuracy should meet the requirements of the instrument, see Appendix A for details.

6 Appendix A

(Informative appendix) Standard buffer solution A.1 Composition of standard buffer solution There are 6 kinds of standard buffer solutions, and their composition and the quality of standard substances required to prepare 1 L solution are listed in Table A.1. Table A.1 Composition of standard buffer solution A.2 Preparation and storage of standard buffer solution A.2.1 Experimental water. newly prepared distilled water to remove carbon dioxide. Pour water into the flask, boil for 10 minutes, cover and let it cool. Temporarily use the current system. A.2.2 Potassium tetraoxalate (KH3C4O8·2H2O). Dry for 4 h at 51℃～57℃, store in a desiccator for later use. A.2.3 Potassium hydrogen tartrate (KH5C4O6). A.2.4 Potassium hydrogen phthalate (C8H5KO4). Dry for 2 h at 110℃～120℃, and store in a desiccator for later use. A.2.5 Anhydrous disodium hydrogen phosphate (Na2HPO4). Dry for 2 h at 110℃～120℃, and store in a desiccator for later use. A.2.6 Potassium dihydrogen phosphate (KH2PO4). Dry for 2 h at 110℃～120℃, and store in a desiccator for later use. A.2.7 Sodium tetraborate (Na2B4O7·10H2O). Place it in a desiccator with saturated sodium bromide (or sodium chloride and sucrose) solution (room temperature) for 48 hours to make sodium tetraborate 7 The crystal remains stable. A.2.8 Calcium hydroxide [Ca(OH)2]. A.2.9 Standard buffer solution B1.c (KH3C4O8·2H2O)=0.05 mol/L, pH=1.680 (25°C). Weigh 12.61 g of potassium tetraoxalate (A.2.2), dissolve in water (A.2.1), transfer to a 1 L volumetric flask at 25°C and Set the volume to the marking line. You can also buy a commercially available qualified standard buffer solution and use it according to the instructions. A.2.10 Standard buffer solution B3.KH5C4O6 saturated solution, pH=3.559 (25°C). Weigh about 7 g of potassium hydrogen tartrate (A.2.3), dissolve it in water (A.2.1), and place it in a ground glass bottle at 22℃～28℃ Dilute to 1 L, shake vigorously for 20 minutes to 30 minutes, after the solution is clear, take the clear liquid by decantation method for use. You can also buy the city Qualified standard buffer solutions are sold and used in accordance with the instructions. A.2.11 Standard buffer solution B4.c (C8H5KO4)=0.05 mol/L, pH=4.003 (25℃). Weigh 10.12 g of potassium hydrogen phthalate (A.2.4), dissolve in water (A.2.1), and transfer to 1 L volume at 25°C Fill the bottle and dilute to the mark. You can also buy a commercially available qualified standard buffer solution and use it according to the instructions. A.2.12 Standard buffer solution B6.c(Na2HPO4)=0.025 mol/L, c(KH2PO4)=0.025 mol/L, pH=6.864 (25°C). Weigh 3.533 g anhydrous disodium hydrogen phosphate (A.2.5) and 3.387 g potassium dihydrogen phosphate (A.2.6), and dissolve in water (A.2.1) Transfer to a 1 L volumetric flask at 25°C and dilute to the mark. You can also buy commercially available qualified standard buffer solutions, according to Instructions for use. A.2.13 Standard buffer solution B9.c (Na2B4O7) = 0.01 mol/L, pH = 9.182 (25°C). Weigh 3.80 g of sodium tetraborate (A.2.7), dissolve in water (A.2.1), transfer to a 1 L volumetric flask at 25°C and determine Fill it up to the marking line and seal it in a polyethylene bottle. You can also buy a commercially available qualified standard buffer solution and use it according to the instructions. A.2.14 Standard buffer solution B12.Ca(OH)2 saturated solution, pH=12.460 (25℃). Weigh ......
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