Kjeldahl Method

The Kjeldahl method is a method for determining the total nitrogen in a compound or mixture. That is, in the presence of a catalyst, the sample is digested with concentrated sulfuric acid to convert all organic nitrogen into inorganic ammonium salts, and then the ammonium salts are converted into ammonia under alkaline conditions, which are distilled out with water vapor and absorbed by excess boric acid liquid, and then By titrating with standard hydrochloric acid, the amount of nitrogen in the sample can be calculated. Since the nitrogen content of protein is relatively constant, the protein content can be calculated from its nitrogen content, so this method is a classic protein quantification method.