HJ 537-2009Water quality. Determination of ammonia nitrogen. Distillation-neutralization titration (English PDF)

Foreword

To protect the environment and protect the human body in order to implement the Environmental Protection Law of the People's Republic of China and the Law of the People's Republic of China on Water Pollution Prevention and Control to develop and standardize the monitoring methods for ammonia nitrogen in water.

This standard specifies the distillation-neutralization titration method for the determination of ammonia nitrogen in water.

This standard is a revision of the "Determination of Distillation and Titration of Ammonium Water" (GB 7478-87).

This standard was first published in 1987. The original standard drafting unit was the Jiangsu Provincial Environmental Monitoring Station. This is the first revision.

The main contents of this revision are as follows.

-- Revised the name of the standard, modified from "Determination of Water Ammonium by Distillation and Titration" to "Determination of Ammonia Nitrogen in Water Quality" - Neutralization titration.

-- In the scope of application, the sensitivity is eliminated; the method detection limit is clarified.

-- Added calibration method for hydrochloric acid standard solution.

-- Modified the preparation method of the mixed indicator.

-- A table of conversion factors for the mass concentration of various forms of nitrogen has been eliminated.

-- Added quality assurance and quality control provisions.

As of the date of implementation of this standard, the former National Environmental Protection Agency approved and issued the "Distillation of Ammonium Water" approved by the National Environmental Protection Agency on March 14, 1987.

And the titration method (GB 7478-87) is abolished.

This standard was formulated by the Science and Technology Standards Department of the Ministry of Environmental Protection.

This standard is mainly drafted by. Shenyang Environmental Monitoring Center Station.

This standard was approved by the Ministry of Environmental Protection on December 31, 2009.

This standard has been implemented since April 1, 2010.

This standard is explained by the Ministry of Environmental Protection.

Water quality - Determination of ammonia nitrogen - Distillation - Neutralization titration

1 Scope of application

This standard specifies the distillation-neutralization titration method for the determination of ammonia nitrogen in water.

This standard applies to the determination of ammonia nitrogen in domestic sewage and industrial wastewater.

When the sample volume is 250 ml, the detection limit of the method is 0.05 mg/L (both in N).

2 Principle of the method

The pH of the water sample is adjusted to 6.0 to 7.4, and light magnesium oxide is added to make it slightly alkaline, and the ammonia released by distillation is absorbed by the boric acid solution. Take A Base red-methylene blue is an indicator, and the ammonia nitrogen (in N) in the distillate is titrated with a hydrochloric acid standard solution.

3 Interference and elimination

Substances that can be distilled under the conditions specified in this standard and which are capable of reacting with an acid interfere with the measurement. For example, urea, volatile amines and Chloramine in chlorinated samples, etc.

4 Reagents and materials

Unless otherwise stated, the reagents used in the analysis were analyzed analytical reagents in accordance with national standards, and the experimental water was prepared according to 4.1.

water.

4.1 No ammonia water, prepared in one of the following ways in an ammonia-free environment (see 10.1 for inspection without ammonia).

5 Instruments and equipment

5.1 Ammonia Nitrogen Distillation Unit. consists of 500 ml Kay flask, nitrogen ball, straight condenser and conduit. The end of the condenser can be connected for a suitable period.

The length of the dropper is such that the tip of the outlet is immersed under the surface of the absorbing liquid. A distillation flask can also be used.

5.2 Acid burette. 50 ml.

6 Samples

8 Calculation of results

The concentration of ammonia nitrogen in the water sample is calculated by equation (2).

N 14.01 1000

VV c

rho -= × × × (2)

Where. rhoN--the concentration of ammonia nitrogen in the water sample (in N), mg/L;

V--the volume of the sample, ml;

Vs--the volume of hydrochloric acid standard titration solution consumed by the titration sample, ml;

Vb--the volume of hydrochloric acid standard titration solution consumed by titration blank, ml;

C--concentration of hydrochloric acid standard solution for titration, mol/L;

14.01--Atom atomic weight, g/moL.

9 Accuracy and precision

Table 1 Accuracy and precision of standard and actual samples

Sample ammonia nitrogen content/(mg/L) Repeatability limit r/(mg/L) Reproducibility limit R/(mg/L) relative error /% Standard 1 2.76 0.106 0.146 0.73 Standard 2 23.8 0.641 1.39 -0.42 Surface water 6.60 0.109 0.515 -Domestic sewage 21.4 0.694 3.09 -Note. Five laboratories participated in the validation, and each laboratory repeated the number of measurements for each sample six times.

10 Quality Assurance and Quality Control

10.1 Inspection without ammonia. 250 ml of water should be titrated with hydrochloric acid standard solution (4.14). The volume of the standard solution for consumption of hydrochloric acid should not be greater than 0.04 ml.

10.2 Distillator cleaning. Add 350 ml of water to the distillation flask, add several glass beads (4.15), install the instrument, and distill to at least collect.

After 100 ml of water, the distillate and the residual liquid in the bottle were discarded.

10.3 Pre-distillation. At the beginning of the distillation, the ammonia gas is evaporated faster, and the heating cannot be too fast, otherwise the water sample will be bumped and the distillate temperature will rise.

High, ammonia absorption is incomplete, and the distillate rate should be kept at about 10 ml/min. If residual chlorine is present in the water sample, a few more crystalline sulfur should be added.

Sodium sulfate (Na2S2O3 or Na2S2O3·5H2O) was removed.

10.4 When calibrating the standard titration solution of hydrochloric acid, at least 3 times of parallel titration, the maximum allowable deviation of parallel titration is not more than 0.05 ml.