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Mansoura National University
Pharm D-Clinical Pharmacy Program Level 1 Pharm. Anal. Chem. 1 (PC 101)
Kjeldahl Method
▪ It was developed by a Danish chemist named Johan Kjeldahl
who first described it in 1883.
▪ This method is used for nitrogen analysis in a wide variety of
materials as calculating the protein content in
human and animal food, fertilizers, waste waters
and fossil fuels.
❖ The general procedure includes 3 steps:
1) Digestion of the ➢ Digestion of the sample with conc. H SO and a catalyst to
2
4
sample convert nitrogen in the sample into ammonium salt.
➢ By NaOH & Distillation of NH produced from boiling NaOH
3
2) Neutralization of with ammonium salt. NH is distilled in boric acid solution to
excess H SO 3
2 4 form ammonium borate (basic salt).
➢ Acid-Base Titration of ammonium borate against standard
3) Acid-Base Titration HCl.
of ammonium ➢ The E.P. is equivalent to the nitrogen content in the original
borate sample.
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