A high-temperature catalytic oxidation technique for determining total dissolved nitrogen

A high-temperature catalytic oxidation method for determination of total dissolved N has been developed and tested on soil solution and throughfall. Unlike methods generally used for total dissolved N, this method is rapid, quantitative, and does not require use of strong acids or bases. The technique couples a commercially available chemiluminescent N detector with the combustion furnace of a commercially available C analyzer. An aqueous sample is combusted in an ultra pure oxygen environment at 680 degrees C, converting all forms of N to nitric oxide, which then reacts with ozone. The product, metastable NO2, is measured chemiluminescently by the N detector. The method is appropriate for samples collected in studies of forest soil solution and throughfall, having a method detection limit of 0.03 mg L(-1) total N, and a range from 0.03 to 10.0 mg L(-1). Tests of several organic and inorganic N-containing compounds showed recoveries >90% for concentrations up to 5.0 mg N L(-1). Urea was the only compound tested with recoveries <90%. Numerous field samples were analyzed and compared with results obtained using persulfate oxidation and high-temperature oxidation (uncatalyzed oxidation at 1100 degrees C). Results from this high-temperature catalytic oxidation method compare well with persulfate oxidation and high-temperature oxidation.