BS EN 16169:2012 pdf download
BS EN 16169:2012 pdf download.Sludge, treated biowaste and soil —Determinationof Kjeldahl nitrogen.
Heat the digestion mixture until the sulfuric acid condenses on the wall of the tube and the brown colour has disappeared; then continue heating for at least another 60 mm. Avoid digestion block temperatures exceeding 400 °C to avo.d losses of nitrogen The use of a temperature programme that ensures gentle heating before reaching me boiling point is recommended, espeoally for liquid samples or samples with high content of organic matter.
NOTE 2 The boiling time may vary and depends on the wnple material. The sc&ibon should be clear at the end of boiling,
NOTE 3 The amouns of test material and added chemicals and catalysts may be changed adherlig to the ratio descnbed in the manufacti.wer’s instructions.
NOTE 4 The secm-rmcro and the macro versions 04 the Kjeldahl procedure are suitable tar some materials.
9.3 Titration
After completion of the digestion step, allow the flask or tube to cool and add 20 ml of water (6.1) slowly while shaking. Then swirl the flask or tube to bring any insoluble material into suspension and transfer the contents to the distillation apparatus (7.3). Rinse three times with water (6.1) to complete the transfer.
Add 50 ml of boric acid sokition (6.5) 10 a 200 ml conical flask and place the flask under the condenser of the distillation apparatus m such a way that the end of the condenser dips into the solution. Add 20 ml of sodium hydroxide (6.4) to the funnel of the apparatus and run the alkali slowly into the distillation chamber.
NOTE 1 Modem Kjeidahl apparatuses use the digestion tubes for disaltation and the addition of chemicals is prograxnnied. The distillation is done automatically. A potentiornstnc titration is possible.
NOTE 2 The best way of detillalion is steam distillation. A rate of L4) to 25 ml’,iiI, is applicable.
Stop the distillation when 100 ml of distillate have been collected (for quantitative results, the amount ot the distillate depends on the dimensions of the apparatus). rinse the end of the condenser, add a few drops of mixed indicator (6.6) to the distillate and titrate with sullunc or hydrochloric acid solution (6.7) to a violet endpoint.
The concentration of the sulfuric or hydrochloric acid solution (6.7) shall be chosen according to the expected amount that is consumed in titration of different sample matrices. For sludges and treated biowasle the use of c(H.) = 0.5 moM Is recommended, due to nitrogen contents >0,5 %. For soil samples the use of other acid concentrations decreases analytical error but care shall be taken on the contamination of titration acids by carbon dioxide, which changes the acid concentration arid therefore reduces its stability.
NOTE 3 The final determination can be done by olher validated methods than titration spectropl iotometric determination 04 ammonitan, manually or by automated methods see EN 25663, EN ISO 11732. ISO 112611.
9.4 Performance check
Substances with known and unchangeable content of nitrogen are used to control the digestion and the apparatus. This may be ammonium sulfate. acetanilide, L•aspartic acid. sulfanilic acid or other amino acids with known nitrogen content.
9.5 Blank test
Carry out blank determinations in each series and use the average blank value for calculations,
10 Calculation
Calculate the content of nitrogen wq. in milligrams per kilogram, using Formula (1):
11 Expression of results
The result shall be expressed ri milligrams per kilogram (mg1g) dry matter or In pef cent (%) on the basis of
dry matter arid reported to two significant figures.
12 Precision
The performance characteristics of me method have been evaluated (see Annex A).
13 Test report
The test report shall contain at least the following information:
a) a reference to this European Standard (EN 16169):
b) corri4ete identification of the sample:
c) the method used for the determination of Kjeldahl nitrogen:
d) the results calculated according to Clause 10 and expressed according to Clause 11;
e) any details not specified in this European Standard or which are optional, as well as any factor which may have attected the results.
