J.P. SELECTA s.a.
Ctra. NII Km 585.1 Abrera 08630 (Barcelona) España
Tel (34) 93 770 08 77 Fax (34) 93 770 23 62
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GUIDE DE L’UTILISATEUR
CODE 80158.02
REV 0 02/10/09
(Sous réserve de modification)
Pag.: 24
1. Overview:
This methods consists on mineral-
izing the sample with concentrated
sulphuric acid and alkalinizing with
NaOH. The ammonium liberated is
carried by distillation and recovered
on boric acid. The subsequently ti-
tration with Cl H allows the calcu-
lation of the amount of the ammo-
nium on the sample.
2. Reagents:
• Sulphuric acid 96% (d=1.84).
• NaOH, dilution 35% (p/v).
• mixed of indicator, special for
ammonium titration.
• Kjeldahl Catalyst
• Boric Acid 4% (p/v).
• HCl 0.25N.
• Distilled water
• Pumice stone, granules
Note: It is very important that all
reagent will be free of nitrogen.
3. Material:
• Balance of resolution 0.1 mg.
• Digestion Unit (Bloc-Digest).
• Fume Removal.
• Distillation Unit Pro-Nitro I or II
• Titration Burette.
4. Digestion:
Weigh near 1 g. of sample perfectly
milled and homogenized into a pa-
per exempt of nitrogen and intro-
duced in a digestion tube.
Add to sample tube 10 g. of
Kjeldhal catalyst, 25 ml of sulphu-
ric acid at 96% (d=1.84), and some
granules purnice stone.
Put the digestion tubes with the
sample into the Bloc-digest with
the fume removal working.
Do the digestion at a temperature
between 350º and 420ºC and in a
period of time variable between 1
and 2 hours (see page 12 table).
At the end of the process, the ob-
tained liquid is of green colour or
transparent blue depending on the
used catalyst.
Let cool down the sample at ambi-
ent temperature.
It is important to avoid the precipi-
tation shaking from time to time.
Dosse slowly 50 ml of distillated
water in each tube of sample. (Pay
attention with the violence of the
reaction).
Let cool down the sample at ambi-
ent temperature.
If there is a precipitation, shake or
hot slightly.
5. Distillation.
Dosse 50 ml of Boric acid in an
Erlenmeyer flask and some drops
of mixed of indicator. Put the Er-
lenmeyer below the refrigerant pay-
ing attention to let the output tube
be immersed under the Boric acid.
The distillation has to be extended
the enough time in order to be dis-
tilled a minimum of 150 ml, approxi-
mately between 5 and 10 minutes.
6. Blank:
After the distillation of a sample,
make a blank test, applying the
described method, but using 5 ml
of distillated water instead of sam-
ple.
7. Titration:
Titrate with Hydrochloric acid 0.25N
the distilled obtained until the solu-
tion changes from green to violet
colour.
Calculate the quantity of nitrogen
detected by means of formulae:
Where:
P = Weigh g of sample.
V
1
= HCl consumption on tritation.
(ml)
N = Normality del HCl
V
0
= HCl Consumtion on blank
tritation. (ml)
F = Conversion factor to pass from
content in nytrogen to content in
proteines. For the proteine it is com-
monly used one value of of 6.25.
For more accuracy, in order to
distinguise the quality of the
proteine according to the nature of
the sample, there can be used other
factors of conversion.
KJ-02
KJELDAHL NITROGENUM DETERMINATION METHOD.
(Método DIRECT METHOD).
1.4 x (V
1
-V
0
) x N
% Nitrogen
=
P
% Protein
= % Nitrogen x F
CET ESSAI DEMANDE LA MANIPULATION DE SUBSTANCES DANGEREUSES
MANIPULATION OF CORROSIVE PRODUCTS IS REQUIRED
