Study of different sample preparation conditions in the determination of total nitrogen by Kjeldahl method

Abstract

The purpose of this work was to evaluate the influence of different conditions of the sample preparation to determination of total nitrogen (TN) in foliar tissue. During the study three sample preparation procedures were evaluated: The first one was used a catalytic mixture composed by selenium/sodium sulfate in acidic medium. In the second and third were used a mixture of copper sulfate/sodium sulfate in acid medium and in the method three a small amounts of reagents were used. According to the results NT values obtained by the three methods have a variation coefficient (VC) less than 15% and a standard deviation less than 0.7. Also the t test results showed that there is no significant difference between the mean of the variables. The third method using small amounts of reagents and the catalyst mixture based on copper sulfate/sodium sulfate is the most indicated according the study. Due to the smaller amount of reactants used, reducing the analysis cost, less waste generated, and the substitution of selenium in the catalyst mixture that is hazardous to the environment and carcinogenic potential.