Evaluation of the concentration of compounds in the distillation solution on the quantification of total nitrogen by the Kjeldahl method

Optimizing the reagents on distillation solution used in the Kjeldahl method could be an important strategy to decrease risk to environmental and human health and consequent reduction in analysis costs. Here, we tested four distillation solution combining two concentrations of boric acid (40 or 20 g/L) and two alcohol solutions of the indicators (methyl red and bromocresol green, 25 mL/L and 12 mL/L, or 12.5 mL/L and 6 mL/L) in fifteen samples of low- and high-N materials. We demonstrated that a reduction of concentrations of those reagents does not affect the total N quantification in the different materials.