GB/T 11913-1989 PDF EnglishUS$495.00 · In stock · Download in 9 seconds
GB/T 11913-1989: Water quality--Determination of dissolved oxygen--Electrochemical probe method Delivery: 9 seconds. True-PDF full-copy in English & invoice will be downloaded + auto-delivered via email. See step-by-step procedure Status: Obsolete
Similar standardsGB/T 11913-1989: Water quality--Determination of dissolved oxygen--Electrochemical probe method---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GBT11913-1989GB NATIONAL STANDARD OF THE PEOPLE’S REPUBLIC OF CHINA Water Quality - Determination of Dissolved Oxygen - Electrochemical Probe Method APPROVED ON. DECEMBER 25, 1989 Implemented on. JULY 01, 1990 Approved by. State Bureau of Environmental Protection Table of Contents1 Theme Content and Applicable Scope... 3 2 Principle... 4 3 Reagents... 4 4 Instruments... 4 5 Procedures... 5 6 Presentation of Results... 7 7 Test Report... 8 Appendix A (Addition)... 9 Water Quality - Determination of Dissolved Oxygen - Electrochemical Probe Method This Standard equivalently adopts the international standard ISO 5814-1984 Water Quality – Determination of Dissolved Oxygen – Electrochemical Probe Method.1 Theme Content and Applicable Scope1.1 Theme content This Standard specifies a method for measuring dissolved oxygen in water by an electrode that separates the water sample from the electrochemical cell through a gas- permeable membrane. According to the different types of the used probes, the concentration of oxygen (mg/L), or the percentage of oxygen saturation (% dissolved oxygen), or both may be measured. This method may measure dissolved oxygen with a saturation percentage from 0% to 100% in water. However, most instruments can measure supersaturation values higher than 100%. This method may be used not only for determination in the laboratory, but also for on-site determination and continuous monitoring of dissolved oxygen. This method is suitable for the determination of water with high chromaticity and turbidity. It is also suitable for the determination of water containing iron and substances that can interact with iodine. All the above substances shall interfere with the determination by iodometry. Some gases and vapors like chlorine, sulfur dioxide, hydrogen sulfide, amine, ammonia, carbon dioxide, bromine and iodine can diffuse and pass through the membrane. If these substances are present, they shall affect the measured current and cause interference. The presence of other substances in the sample shall cause the membrane blockage, membrane damage or electrode corrosion, and further lead to interfere with the measured current. These substances include solvents, oils, sulfides, carbonates and algae. 1.2 Scope of application This method is applicable to natural water, sewage and salt water. If it is used to measure salt water such as sea water or harbor water, the salt content shall be checked.2 PrincipleThe probe used in this method is composed of a small chamber in which there are two metal electrodes and filled with electrolyte; and the small chamber is sealed by a selective membrane. In fact, water and soluble substance ions cannot pass through this membrane; but oxygen, certain amounts of other gases and hydrophilic substances may pass through this membrane. The probe is immersed in water for dissolved oxygen measurement.3 ReagentsIn the analysis process, only use recognized analytical reagents and distilled water or water of equivalent purity. 3.1 Anhydrous sodium sulfite (Na2SO3) or sodium sulfite heptahydrate (Na2SO3 • 7H2O).4 Instruments4.1 Measuring instruments. It consists of the following components. 4.1.1 Measuring probe. Primary battery type (such as lead/silver) or polarographic type (such as silver, gold); 4.3 Barometer with a scale division of 10Pa.5 ProceduresWhen using the measuring instrument, the instruction manual of the manufacture shall be followed. 5.1 Measurement technology and precautions 5.1.1 Do not touch the active surface of the membrane with hands. 5.1.3 When the probe is immersed in the sample, it shall be ensured that no air bubbles are trapped on the membrane. 5.1.4 When the sample is in contact with the membrane of the probe, a certain flow rate shall be maintained to prevent the dissolved oxygen in the sample at that part from being exhausted at the moment of contact with the membrane, and generating the false readings. It shall be ensured that the flow rate of the sample does not cause the reading to fluctuate. In this regard, refer to the instructions of the instrument manufacturer. 5.2 Calibration The calibration procedures are described in 5.2.1 to 5.2.3; but the instruction manual of the instrument manufacture must be referred. 5.2.1 Adjustment Adjust the electrical zero point of the instrument. Some instruments have compensation zero point, so there is no need to adjust. 5.2.4 Adjust the instrument The probe is immersed in the bottle; and the bottle is completely filled with the sample prepared and calibrated according to the above procedures. Allow the probe to stabilize in the stirred solution for 10min (see 5.2.2 NOTE). 5.3 Determination Determine the water to be tested in accordance with the manufacturer's instruction manual.6 Presentation of Results6.1 The concentration of dissolved oxygen (mg/L) The concentration of dissolved oxygen is expressed in milligrams of oxygen per liter, taking the one digit after the decimal point. 6.2 Dissolved oxygen concentration as a function of temperature and pressure Tables 1 and 2 give the theoretical values of dissolved oxygen concentration. Table 1 gives the values as a function of temperature at standard atmospheric pressure. Table 2 gives the values as a function of temperature and pressure. 6.3 Corrected dissolved oxygen concentration of brine samples The solubility of oxygen in water decreases with the increase of salt content. In practical applications, when the salt content (expressed as total salt) is below 35g/L, it may be reasonably considered that the above relationship is linear. 6.4 Dissolved concentration expressed as saturation percentage This is the actual dissolved oxygen concentration expressed in mg/L, which needs to be temperature corrected if necessary7 Test ReportThe test report includes the following information.Appendix A(Addition) The relationship between the solubility of oxygen in water and temperature, pressure and salt content. A1 Overview The relationship between the solubility of oxygen in water and temperature and pressure is given in the appendix. A2 The solubility of oxygen as a function of temperature and salt content See Table A1 ......Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al. 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