An automated procedure for the determination of total Kjeldahl nitrogen |
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Authors: | LJ Lennox MJ Flanagan |
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Affiliation: | An Foras Forbartha, Pottery Road, Deansgrange, County Dublin, Ireland |
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Abstract: | A procedure for the determination of total Kjeldahl nitrogen in surface fresh waters and organic wastes is described. Organic nitrogen compounds are converted to ammonium sulphate by a catalytic (red mercuric oxide) acid-sulphate digestion. The digest time is 3 h and allows for a maximum of 36 samples, 2 blanks and 2 standards to be processed simultaneously. There is no pH adjustment required following the digestion. Calibration curves covering the ranges (i) 0.5–100 μg NH3---Nl−1 and (ii) 10–1000 μg NH3---Nl−1 were linear within ±2%. The detection limit of the method is 0.5 μg TKNl−1. The concentration range of TKN for which the method is suitable is 0.5 μg Nl−1–40 mg Nl−1. The method displayed a high tolerance to interferences from copper, iron, mercury and hardness. Digest procedure gave a high recovery and reproductibility over a wide range of nitrogen compounds tested. |
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