Determination of total nitrogen in rock by automatic Kjeldahl nitrogen analyzer

This paper is the result of titration of total nitrogen content in rocks.Objective This article established an analytical method for determining total nitrogen content in rocks using a fully automatic Kjeldahl nitrogen analyzer by conducting research on optimizing digestion procedures, distillation time and other experimental conditions, as well as accuracy of methods. Methods This method added sulfuric acid during the digestion process, and the nitrogen-containing organic matter in the sample was transformed into inorganic ammonium nitrosulfate.Under the action of a catalytic plate that made of potassium sulfate and pentahydrate copper sulfate, the reaction was accelerated, and ammonia gas was released by reacting with sodium hydroxide which was collected in a boric acid solution and titrated with standard hydrochloric acid solution for total nitrogen. Results The results showed that the detection limit of the method was 23.90 μg/g and the method was validated using the national first-class standard material GBW 07729, with a relative standard deviation (RSD) of 1.07% (n=4), and the recovery rate of the experiment was between 95.40% and 103.8%. Conclusions This method used a fully automatic Kjeldahl nitrogen analyzer to determine the total nitrogen content in rocks which is simple and accurate, and could fully meet the testing requirements of the geological industry.