BS 6068-2.11:1984

National foreword
Method
1. Scope and field of application
2. Reference
3. Principle
4. Reagents
5. Apparatus
6. Sampling and samples
7. Procedure
8. Expression of results
9. Interferences
10. Special cases
11. Notes on procedure
12. Test report
Annexes
A. The effect of other substances on pN
B. Typical absorbance values for blank and standard
    solutions
Tables
1. Volumes of standard solution for use in the
    calibration series
2. Conversion table
3. Repeatability and reproducibility standard deviations

Applicable to the determination of ammoniacal nitrogen in drinking and waste waters in the range 0.01 to l mg/l.

1.1 Substance determined

This part of ISO 7150 specifies a manual spectrometric method for the determination of ammonium in water.

NOTE An automated spectrometric method for the determination of ammonium will form the subject of ISO 7150/2.

1.2 Type of sample

The method is applicable to the analysis of potable water, and most raw and waste waters. Application to excessively coloured or saline waters shall be preceded by distillation (see clause 10). For interferences, see clause 9.

1.3 Range

An ammonium nitrogen concentration, ϱ_N of up to 1 mg/l, using the maximum test portion of 40 ml, can be determined. Much higher concentrations can be determined by taking smaller test portions.

1.4 Limit of detection¹)

When using cells of optical path length 40 mm and a 40 ml test portion, the limit of detection lies within the range ϱ_N = 0,003 to 0,008 mg/l.

1.5 Sensitivity¹)

Using a 40 ml test portion and a cell of optical path length 40 mm, ϱ_N = 0,200 mg/l gives an absorbance of about 0,69 units.

Using a 40 ml test portion and a cell of optical path length 10 mm, ϱ_N = 0,750 mg/l gives an absorbance of about 0,65 units.