5663 International Standard (TSO Water quality - Determination of Kjeldahl nitrogen : Method after mineralization with selenium Qualite de I'eau - Dosage de I'azote Kjeldahl -- Méthode apres mineralisation au selenium First edition - 1984-05-15 5663-1984 (E) UDC 543.34 Ref. No. ISO 5663-1984 (E) Descriptors : water, quality, chemical analysis, determination of content, nitrogen, Kjeldahl method, water pollution. Price based on 4 pages Not for Resale Foreword IsO(theInternational OrganizationforStandardization)is aworldwidefederationof national standards bodies (IsO member bodies). The work of developing International Standards is carried out through Iso technical committees. Every member body interested in a subject for which a technical committee has been authorized has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with iso, also take part in the work. Draft International Standards adopted by the technical committees are circulated to the member bodies for approval before their acceptance as International Standards by theISoCouncil. International Standard ISO 5663 was developed by Technical Committee ISo/TC 147, Water quality, and was circulated to the member bodies in December 1982. It has been approved by the member bodies of the following countries: Australia Germany, F.R. Norway Austria Hungary Poland Belgium India Romania Brazil iran South Africa, Rep. of Canada Irad Spain China Italy Sweden Czechoslovakia Korea, Dem. P. Rep. of Switzerland Denmark Mexico Thailand Egypt, Arab Rep. of Netherlands USSR France New Zealand The member bodies of the foilowing countries expressed disapproval of the document on technical grounds: Japan UnitedKingdom @ International Organization for Standardization, 1984· Printed in Switzerland Not for Resale INTERNATIONALSTANDARD ISO5663-1984 (E) Water quality - Determination of Kjeldahl nitrogen Method after mineralization with selenium 1 Scope and field of application Kjeldahl nitrogen: The content of organic nitrogen and am- moniacal nitrogen in a sample determined after mineralization. 1.1 Substance determined It does not include nitrate and nitrite nitrogen, and does not This International Standard specifiesamethodforthedeter- necessarily include all organically bound nitrogen. minationofnitrogenbyaKjeldahl-typemethod.Onlytrivalent negative nitrogen is determined. Organic nitrogen in the form of azide, azine, azo, hydrazone, nitrite, nitro, nitroso, oxime or 4 Principle semicarbazoneisnotdeterminedquantitatively.Nitrogenmay be incompletely recovered from heterocyclic nitrogen com- Mineralization of the sample to form ammonium sulfate, from pounds. whichammoniais liberatedanddistilledforsubsequentdeter- mination by titration. 1.2Type of sample Conversion of the nitrogen compouinds responding to the test This method is applicable to the analysis of raw, potable and to ammonium sulfate by mineralization of the sample with waste waters. sulfuric acid, containing a high concentration of potassium sulfate in order to raise the boiling point of the mixture, in the presence of selenium which acts as a catalyst. 1) 1.3Range Liberation of ammonia from the ammonium sulfate by the addi- A Kjeldahl nitrogen content, @n, of up to 10 mg, in the test por- tion of alkali and distillation into boric acid/indicator solution. tion may be determined. Using a 10 mi test portion, this cor responds to a sample concentration of up to @n = 1 000 mg/l. Determination of ammonium ion in the distillate by titration with standard acid. 1.4 Limit of detection Alternatively, direct determination of ammonium ion in the A practically determined (4 degrees of freedom) limit of detec- mineralizatebyspectrometryat655nm.(Seeclause11.) tion, using a 100 ml test portion, is Qn = 1 mg/l. 1.5 Sensitivity 5 Reagents Using a 100 ml test portion, 1,0 ml of 0,02 mol/I hydrochloric During the analysis, use only reagents of recognized analytical acid is equivalent