HJ 535-2009Water Quality - Determination of Ammonia Nitrogen - Nessler Reagent Spectrophotometry (English PDF)

Foreword

This Standard was prepared for the purposes of implementing Environmental

Protection Law of the People's Republic of China, and Water Pollution Prevention and

Control Law of the People's Republic of China, protecting environment, safeguarding

human health, as well as regulating the detection method of ammonia nitrogen in

water.

This Standard specified Nessler's Reagent Spectrophotometry to measure the

ammonia nitrogen in water.

This Standard revised Water Quality - Determination of Ammonium - Nessler's

Reagent Colorimetric Method (GB 7479-87).

This Standard was first-time published in 1987; the drafting organization of the original

standard was Jiangsu Environmental Monitoring Central Station; this is the first-time

revision. The major revised contents are as follows.

--- Standard name was changed FROM Water Quality - Determination of

Ammonium - Nessler's Reagent Colorimetric Method TO Water Quality -

Determination of Ammonia Nitrogen – Nessler's Reagent Spectrophotometry.

--- Add the cuvette's optical path length (10-20mm); reduce the detection limit of

the method; expand the applicable scope of the method. Clearly define the

upper and lower detection limit of the method.

--- Delete the visual colorimetry.

--- Regulate and adjust the structure and format of the standard text.

--- Add the precautions to the key steps such as main reagent preparation and the

sample pretreatment.

--- Combine the calculation formula of the results.

Since the implementation date of this Standard, the Water Quality - Determination of

Ammonium - Nessler's Reagent Colorimetric Method (GB 7479087) that was

approved & published by the original State Environmental Protection Agency on

March 14, 1987 shall be abolished.

This Standard was organized-formulated by Science, Technology and Standard

Division of Ministry of Environmental Protection, Department.

Chief drafting organization of this Standard. Shenyang Environmental Monitoring

Center.

This Standard was approved by Ministry of Environmental Protection on December 31,

Water Quality – Determination of Ammonia Nitrogen –

Nessler's Reagent Spectrophotometry

Warning. Mercuric chloride (HgCl2) and mercuric iodide (HgI2) are highly toxic

substances; avoid the dermal and oral exposure.

1 Scope

This Standard specifies Nessler's reagent spectrophotometry to determine the

ammonia nitrogen in water.

This Standard is applicable to determine the ammonia nitrogen in surface water,

underground water, domestic sewage, and industrial waste water.

When the volume of water sample is 50ml, and 20mm cuvette is used; the detection

limit for this method is 0.025mg/L, the lower determination limit is 0.10mg/L, and the

upper determination limit is 2.0mg/L (calculated as per N).

2 Method Principles

Ammonia nitrogen, existed in the free state of ammonia and ammonium ions, reacts

with Nessler's reagent, and generates light reddish brown complex compound; the

absorbance of such complex compound is proportional to the ammonia nitrogen

contents, then determine the absorbance at the wavelength of 420nm.

3 Interference and Elimination

When water sample contains suspended solids, residual chlorine, metal ions such as

calcium-magnesium, sulfides and organic substances, then they may generate

interference and needs proper treatment, so as to eliminate the influence on the

determination.

If there is residual chlorine in the sample, add proper amount of sodium thiosulfate

solution to remove; use potassium iodide-starch test paper to test whether the

residual chlorine was eliminated completely. When colorization, add proper amount of

potassium sodium tartrate solution, which can eliminate the interference from metal

ions such as calcium-magnesium. If the sample is thick or colorful, it can be treated

with pre-distillation or flocculation methods.

Weigh 20g of hydrochloric acid; dissolve into water; dilute to 1L.

5 Apparatus and Equipment

6 Samples

9 Accuracy and Precision

For the standard solution of which the ammonia nitrogen concentration is

1.21mg/L, the repeatability limit is 0.028mg/L, the reproducibility limit is 0.075mg/L,

and the recovery rate is 94%~104%.

For the standard solution of which the ammonia nitrogen concentration is

1.47mg/L, the repeatability limit is 0.024mg/L, the reproducibility limit is 0.066mg/L,

and the recovery rate is 95%~105%.

10 Quality Assurance & Quality Control