Page 62 - Feed Lab

Estimation of Crude Protein - Micro Kjeldhal Distillation Method Suguna Management System Ver 1.0 / SOP / FQL / P2 - 02 Page 2 of 2

This is reagent blank. The reagent blank and direct 6. Add about 10ml of 40% sodium hydroxide. Steam
blank should be identical. passed through this solution for 20 minutes (or

RECOVERY
FTake 0.1 gm of urea and add 5 gm activated
sodium sulphate + 0.5 gm of cupric sulphate and
25 ml of concentrated sulphuric acid to the Kjeldhal
flask and do digestion and distillation as per the
crude protein procedure.

Calculation:
A = (28/60.06) x100
B = % of Nitrogen after distillation
Then (A/B) x 100 =recovery should be 100 +/- 1%

PROCEDURE
1. Take accurately 2gm of ground sample on butter
paper. Fold the above sample and transfer to 500
ml Kjeldhal flask.

2. Add 5gm activated sodium sulphate + 0.5gm of
cupric sulphate and 25 ml of concentrated
sulphuric acid to the Kjeldhal flask.
3. Digest for 90 minutes to 105minutes, till the
solution turns green/straw yellow colour. Cool the
flask. Add 10ml to 20mlof water by wash bottle and
again cool.
4. Carefully transfer the content into a 100ml
volumetric flask. Wash the Kjeldhal flask repeatedly
with ammonia free distilled water and collect the
washing also into the volumetric flask. Make the
volume up to the mark, cool under tap.

5. Take 10mlof the sample aliquot, in a Micro Kjeldhal
distillation unit.

CALCULATION
(Blank - titre value) X1.401 X6.25 X (100/10) X N. of NaOH
Crude Protein % = ------------------------------------------------------------------------------------
Sample weight, g

REFERENCE
1.Bureau of Indian Standard IS 7874 1975

2.Association of Official Analytical Chemist 2000.

Prepared by : Approved by :
50 Director - Technical