Nitrogen Determination in Tobacco according to the Kjeldahl Method

It is generally considered that flavour and taste of smoke is correlated with the nitrogenous constituents. Flue-cured tobacco containing 1.6 to 2.3% total nitrogen gives the most satisfying smoke. The acceptable limit of total nitrogen is 1.0 to 3%. Apart from curing difficulty, tobacco with a nitrogen content higher than 3% would result in deep brown coloured trashy leaf which shatters readily and has flat, insipid tasting smoke.
To determine the nitrogen content, the samples require digestion with sulfuric acid to convert nitrogen into ammonium sulphate. After conversion to ammonia through the alkalinization with sodium hydroxide, the samples distilled into a boric acid receiver by steam distillation, followed by a titration with sulfuric acid solution.