HG/T 2157-1991 Determination of ammonium in industrial circulating cooling water by potentiometric method HG/T2157-1991 Standard download decompression password: www.bzxz.net

Chemical Industry Standard of the People's Republic of China
Determination of ammonium in industrial circulating cooling water
This standard adopts the international standard ISO6778-84 "Water quality-Determination of ammonium-1 Content and scope of application
HG/T 2157-91
-Potentiometric analysis"
This standard specifies the determination of ammonium content in industrial circulating cooling water by potentiometric method. This standard is applicable to the determination of ammonium (in terms of N) in industrial circulating cooling water with a content of 0.50 mg/L. This standard is not applicable to industrial circulating cooling water samples with a urine content exceeding 100 μg/L, because urine has a positive interference with this method. 2. Reference standard
GB603, Preparation of preparations and products used in chemical reagent test methods 3 Method summary
In alkaline medium (about pH 12), ammonium ions in water are converted into ammonia water. When an ammonia-sensitive membrane electrode that can respond to the partial pressure of ammonia in the solution is inserted into the solution, the content of ammonia is calculated according to the Nernst equation, E, E-2.3RT
igc(NH
In order to mask the gold ions that may be complexed with ammonia in the water sample, ethylenediaminetetraacetic acid dihydrate is added to the alkaline medium. Sodium salt can be used to eliminate interference. 4 Reagents and Materials
In the analytical method, unless otherwise specified, only analytically pure reagents and water that meets the requirements of 4.1 can be used. 4.1 Water: Water should be ammonium-free and prepared by one of the following methods. 4.1.1: Ion exchange method: Steam water through a strong cation exchange resin (hydrogen type) column, collect the effluent water in a glass bottle equipped with a sealed ground-mouth stopper, and add 10 μL of the same resin to each liter of effluent water to facilitate storage. 4.1.2. Steaming pot method: 0.10 μL vegetable acid (G3 625) to 1000 μL of distilled water, and then distill again in a full glass container, discard the first 50% of the effluent water, and then collect the effluent water in a glass bottle equipped with a sealed ground stopper. Add 10g of strong acid cation exchange resin (hydrogen type) per liter of distilled water. 2 Alkaline buffer solution
Weigh 40% sodium hydroxide (GB.629) and 37.2% disodium ethylenediaminetetraacetic acid (GB1401) in 800 μL of water (4.1), dilute to 1, and store in a polyethylene bottle. For low To determine the concentration of ammonium (p(N) 0.5m/L), boil the buffer solution for 20 minutes, cool it down and dilute it. 4.3. Ammonium chloride: (GB658). 5.4/L solution; 4.4: Prepare the solution according to the standard: P(N) = 1000mg/L Weigh 3.8190 mg of ammonium chloride (GB658) dried at 105°C for more than 2 hours in a 200mL beaker: Dissolve it with water (4.1) Ministry of Chemical Industry of the People's Republic of China 1991-09-16 Approved 1992-01-01 After implementing
HG / T 2157 — 91
, transfer to a 1L volumetric bottle, dilute to the mark with water (4.1), mix well, the solution is valid for 1 month. 4.5 Ammonium standard solution: p(N)=100 mg/L; Use a pipette to accurately pipette 100.0mL of ammonium standard solution (4.4) into a 1L volumetric flask, dilute to the mark with water (4.1), mix well, the solution is valid for 1 week. 5 Instruments and equipment
5.1 Ammonia membrane electrode;
3.2 pH/millivoltmeter: graduation value 0.2 mV;5.3 Magnetic stirrer and stirrer wrapped with polytetrafluoroethylene, 6 Sampling
6.1 The sampling bottle should be polytetrafluoroethylene or glass narrow-necked bottle with threaded cap. After washing, rinse with water (4.1) respectively. 6.2 For open circulating cooling water system, sampling is usually carried out in the return water channel before entering the cooling tower; for direct current water system, sampling is carried out at the outlet pipe; for sealed closed-circuit system, sampling is carried out at a low position. 6.3 To ensure the representativeness of sampling, all parts of the pipeline should be kept full of water. Before formal sampling; first drain some, take out the sample from the pressurized pipeline to clean the sampling bottle, and finally fill the sampling bottle with the sample, tighten the lid, and analyze as soon as possible, otherwise it should be stored for 6 hours under 2s,
7 Analysis steps
7.1 Drawing of calibration curve
7.1.1 Prepare at least three ammonium calibration drops, and their concentration range should include the concentration of the sample to be tested. 。 If the concentration range of the sample to be tested is very large, pipette 50.0, 5.00.50mL of the standard solution (4.5) into a 100mL volumetric flask, dilute to the mark with water (4.1), and the liquid concentrations are 50.0, 5.0 and 0.5mL/L (in N) respectively. b. If the concentration range of the sample to be tested is very small, the standard solution (4.5) should be appropriately diluted to make its concentration as close as possible to the concentration range of the sample to be tested.
7.1.2 Pipette 50.0mL of the calibration solution (7.1.1) into a 100mL dry beaker, stir slowly with a magnetic stirrer (5.3) (speed of about 300 min-), and carefully place the top of the electrode (5.1) into the sample, paying attention to the electrode (5. 1) The end of the electrode cannot be covered with bubbles. Then add 5.0 mL of alkaline buffer (4.2). When the potential of the electrode (5.1) is constant at 0.2-0.3 mV within 30 °C, record the electrode potential. Take out the electrode (5.1) from the sample and rinse it with water (4.1). The time for each measurement of the electrode potential should be consistent. Use the more concentrated calibration solution (7.1.1) in turn and repeat the above procedure. 7.1.3 Check the calibration curve every 1-2 hours with one or two calibration solutions (7.1.1). The temperature difference between the calibration solution (7.1.1) and the sample should not be greater than ±1
7. 1.4 Draw a standard curve between the measured electrode potential (expressed in mV) and the logarithm (base 10) of the ammonium concentration (in N/L) of the corresponding calibration solution (7.1.1). Note: At room temperature, the slope of the two calibration lines should be 58.5 ± 2 mV for every 10-fold change in ammonium concentration. If it is lower than 50 mV, the electrode is considered old and should be replaced with a new one.
7.1.5 Storage of electrodes
Between two measurements, store the electrode (5.1) in a calibration solution (7.1.1) treated with an alkaline buffer solution (4.2). If the storage time is more than 12 hours, the top of the electrode (5.1) should be immersed in an ammonium chloride solution (4.3). Before use, rinse the tip of the electrode (5.1) repeatedly with water (4.1) to reach the potential specified in the instruction manual of the electrode. 7.2 Determination
Use a pipette to draw 50.0 m2 L of sample and place it in a dry 100 mL beaker. Perform the analysis according to the steps described in 7.1.2. 6
8 Expression of analysis results
HG / T 2iST -
8.1 The ammonium content (in terms of N) in the sample expressed in g/L is calculated according to formula (2): YAntiiY
- the logarithm of the ammonium concentration (in terms of N) found on the calibration curve (base 10), mg/L. In the formula: IzY-
9 Allowable difference
The water content X is linearly related to the repeatability. r-0.074+0.051x
There is a linear equation relationship between the ammonium content X, in water and the reproducibility R, R= 0. 52+0. 24 X,
HG /T 2157 — 91
Convert according to oxygen concentration
(Supplementary Material)
The determination result can be expressed by the mass concentration of nitrogen p(N), the mass concentration of nitrogen p(NH) or the concentration of ammonium ions c(NH) (μmol/L). The conversion factor between them is engraved below: mass concentration of oxygen
p(N, mg/L
P(N) -1/L
p(NH,) 1mg/ L
P(NH) 1m&/ L
mol / L
Mass concentration of ammonia
P(NH4), mg/L
For example, 1 mg/L ammonium ion concentration is equivalent to 0.777 mg/L nitrogen concentration. Additional remarks:
This standard is issued by the Science and Technology Department of the Ministry of Chemical Industry of the People's Republic of China. This standard is under the technical supervision of Tianjin Chemical Research Institute and drafted by Beijing Institute of Chemical Technology. The main drafters of this standard are Long Ezi, Guan Hui and Ni Meitong. Ion concentrationwwW.bzxz.Net
p(NH4, mg/L
Ammonium ion micromolar density
e(NH4), μtmol /L
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