Comparison of various methods for the determination of total N in liquid effluents

Abstract

A high temperature catalytic oxidation method (HTCO) was used to determine total dissolved nitrogen in different liquid effluents produced by agro-industry. This technique consists of catalysed combustion of the sample by direct injection in a furnace at 900 C. Results obtained by HTCO were then compared with those determined by the Kjeldahl digestion method (TKN) and the dry combustion method (DCM) for freeze-dried effluents. The results obtained by HTCO within a concentration range of 10 to 800 mg N L -1 , were in good agreement with those obtained by TKN. Comparison with DCM method revealed large discrepancies which were probably due to the poor precision of this method and to the ammoniac-N losses occurring during the freeze-drying of samples.