Velp Scientifica
– UDK139 Operating Manual
10004762/B5
91
21 - Kjeldahl method to determine the protein content on plants
(vegetable)
Procedure
1) Sample:
mince and homogenize the sample by suitable devices, then weigh 0.5-
1.5 g in the test tube.
2) Reagents for digestion:
for each sample add in the test tube:
2 catalyst tablets ST (code CT0006609)
13 ml concentrated sulphuric acid (96-98%)
shake gently the tube with the sample.
3) Digestion:
heat for 60 min at 420 °C.
4) Cooling:
let cool test tubes to 50-60 °C.
5) Distillation-titration:
place in position the test tube with digested sample in the
unit UDK 139.
factor: 6.25
Reagents addition:
dilution water=75ml
H
3
BO
3
=30ml
NaOH=50 ml
Titrant: HCl 0.2N
Distillation time= 4 min
Steam power= 100%
Press the button starting distillation cycle.
References:
AOAC, “Official methods of analysis”, method 978.04
278