Nitrogen is one of the five major elements found in organic materials. This is also found in foodstuffs, fertilizer and other substances. Danish chemist, johan G.C.T. Kjeldahl invented this chemistry in 1883 and Kjeldahl method is widely used for estimating the nitrogen in substances.
Kjeldahl method involves transforming all nitrogen in a weighed sample into ammonium sulfate by digestion with supfuric acid. Further alkalizing the solution and distilling it into a measured volume of standard acid, Nitrogen is determined by titration.
Kjeldahl method involves three steps to determine the Nitrogen
1. Digestion : Sample is heated upto 420°C with conc. sulphuric acid. This decomposes the organic sample by oxidation to liberate the reduced nitrogen as ammonium sulfate. The digestion is enhanced with a catalyst like Sodium or Poattassium sulfate to increase the boiling point of sulphuric acid. Digestion is complete with the release of fumes.
2. Distillation : The digested solution is then distilled with sodium hydroxide. Sodium hydroxide converts ammonium to ammonia is then dipped into a known volume of standard acid or weak acid like boric acid.
3. Titration : The excess of ammonia is titrated with standardized acid. The mount of Nitrogen is measured by titration. If boric acid is used, direct acid base titration is done with a strong acid of known concentration of HCl.
Kjeldahl method’s precision and reproducibility has been widely accepted internationally as a recognised method for estimating the protein content in foods and it is the standard method against which all other methods are judged. It is also used to assay soils, waste waters, fertilizers and other materials.
Nitroplus-1006 is designed and developed with latest technology to perform the various steps of Kjeldahl chemistry. Digestion, removal of acid fumes during digestion and distillation are carried out in a single unit thereby saving space and ease of operation. Samples are taken in Digestion tube of 250ml capacity and heated in the aluminium block using high grade casted aluminium alloy heater. Fumes liberated during digestion are removed using a unique glass exhaust manifold system. Non corrosive magnetic pump along with a glass filter pump are used to eliminate acid fumes into the water placed in a stainless steel tank. The acidic water in the tank is drained out everytime automatically by the system at the end of digestion.
Digested sample is then placed in the distillation holder for distillation. Akali is added through a peristaltic pump to make the content alkaline. In the mean time, steam is kept ready in the steam generator and passed through the alkaline sample to liberate ammonia. The liberated ammonia is dissolved in an acidic solution and excess ammonia is estimated by titration.
The digested sample with the manifold is lifted, out of the block and placed just above the block in the same system for cooling of tubes. Exhaust manifold is separated from the rack and placed in the same system. Drip tray is placed below the exhaust manifold to avoid dripping of condensed fumes.
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