Uncertainty of nitrogen determination by the Kjeldahl method

The uncertainty of the Kjeldahl method for determination of nitrogen in insulin was evaluated according the procedure described in the Guide to the Expression of Uncertainty in Measurement. The relative standard uncertainty of the method was found to be 0.19%, compared to the relative intermediate precision experimentally found to be 0.085%. The uncertainty components were organized in Tables, which allowed an easy overview and evaluation. The largest contribution to the uncertainty came from volumetric equipment. Systematic uncertainty budgets such as the design presented here facilitate the uncertainty evaluation process and makes it easier to compare uncertainty evaluations performed by different analysts.