ÖNORM EN 25663

1.1 Substance determined This International Standard specifies a rnethod for the determination of nitrogen by a Kjeldahl-type method. Only trivalent negative nitrogen is determined. Organic nitrogen in the form of azide, azine, azo, hydrazone, nitrite, nitro, nitroso, oxime or semicarbazone is not determined quantitatively. Nitrogen may be incompletely recovered from heterocyclic nitrogen compounds. 1.2 Type of sample This method is applicable to the analysis of raw, potable and waste waters. 1.3 Range A Kjeldahl nitrogen content, rho N, of up to 10 mg, in the test portion may be determined. Using a 10 ml test portion, this corresponds to a sample concentration of up to rho N = 1 000 mg/L 1.4 Limit of detection A practically determined (4 degrees of freedom) limit of detection, using a 100 ml test portion, is rho N = 1 mg/l. 1.5 Sensitivity Using a 100 ml test portion, 1,0 ml of 0,02 mol/l hydrochloric acid is equivalent to rho N = 2,8 mg/l.