Automated Separation and Conductimetric Determination of Inorganic Nitrogen

Experiments were conducted for the evaluation of a continuous flow conductimetric method that measures the inorganic nitrogen compounds ammonia (NH₃) and combined nitrite (${\mathrm{NO}}_{\mathit{2}}^{\mathit{-}}$) and nitrate (${\mathrm{NO}}_{\mathit{3}}^{\mathit{-}}$). Approximately 300 analyses were performed using the method during experiments to estimate the method detection level, to determine the bias and precision, and to determine the equivalency of the method to others found in Standard Methods. An estimated method detection level of 0.01 mg N/L (NH₃–N, ${\mathrm{NO}}_{\mathit{3}}^{\mathit{-}}$–N, or ${\mathrm{NO}}_{\mathit{2}}^{\mathit{-}}$–N) was measured. Precision values for ammonia and nitrate standards at concentrations ranging from 0.1 to 75 mg/L NH₃–N or ${\mathrm{NO}}_{\mathit{3}}^{\mathit{-}}$–N did not exceed 5.5 and 4%, respectively. Recovery values for ammonia and nitrate standards at the same concentration range did not exceed 104.8 and 103%, respectively. At concentrations of 0.05 mg/L NH₃–N or ${\mathrm{NO}}_{\mathit{3}}^{\mathit{-}}$–N, the precision values were 12.5 and 11%, respectively, which were high relative to others obtained in this study but are within the range of values reported in Standard Methods.