Determination of Total Kjeldhal Nitrogen


An experiment has been designed to determine the total Kjeldhal nitrogen in the given sample of organic compound. For the determination of total Kjeldhal nitrogen, two organic solutions samples having different total Kjeldhal nitrogen were selected for the determination of TKN. Each sample was first digested in a volumetric flask of Digesdhal Digestion Apparatus, separately, by using concentrated H2 SO4. After that, TKN was determined in each sample by means of distillation method. Actually there various methods for determination of TKN in the solution which is obtained after absorbing distilled ammonia in an acid absorbing solution. However approved methods include titration, colorimetric and specific ion electrode determination. Selection of a specific method depends upon the concentration level, the amount and types of interferences present. When the concentration of TKN is very small, sensitive methods (like ion chromatography and colorimetric) are used for the determination of ammonia nitrogen. We have selected the titration method for the determination of TKN because TKN in one of the provided sample is high while in the second provided sample it is very high. In the titration method this method, distillate of ammonia which is collected on the boric acid solution is titrated against the solution of a standard acid. The total Kjeldhal nitrogen is then calculated by using the following formula:

Total Kjeldhal nitrogen (in mg/litre) = (A-B) x N x F x 1000 /S


A = Milliliters of standard acid used to titrate the boric acid after collection of ammonia by distillation .

B = Milliliters of standard acid used to titrate the blank.

N = Normality of standard solution

F = Milliequivalent weight of nitrogen (14)

S = Milliliters of sample digested


Titration of blank was performed for both the samples in order to determined residual ammonia in the distilled water for accuracy of the results.

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