The method is suitable for samples which contents nitrate or protein. The sample is digested with sulfuric acid in the presence of a catalyst. This converts organically bound nitrogen to ammonium sulfate.

In a distillation apparatus the digestion solution is treated with NaOH and the released ammonia (NH3) is distilled into a solution of boric acid. This solution is then titrated with an acid titrant (HCl or H2SO4) to a pH endpoint of 4.65.