Velp Scientifica
– UDK139 Operating Manual
10004762/B5
93
19.2 Pre-defined Methods for different samples
23 - Kjeldahl method to determine total nitrogen on crude oil and
fuels (ISO n. 333)
Procedure
1) Sample:
homogenize the sample by shaking before analysis. Weigh 1g of sample
with an accuracy of
0.1 mg.
2) Reagents for digestion:
for each sample add in the test tube:
2 catalyst tablets ST (code CT0006609)
20 ml concentrated sulphuric acid (96-98%)
add carefully 10ml of hydrogen peroxide to avoid foaming.
Shake gently the test tube with sample.
3) Digestion:
start from room temperature and use heating ramps up to 420 °C ;
overall time:4 hours.
Maintain at 420 °C for 30 min. Overall digestion time: 4 hours and 30 min.
4) Cooling:
let cool the test tubes to 50-60 °C.
5) Distillation-titration:
place in position the test tube with the digested sample in
the unit UDK 139.
factor: 0.00
Reagents addition:
dilution water= 70ml
H
3
BO
3
= 30ml
NaOH= 70 ml
Titrant: HCl 0.1N
Distillation time= 4 min
Steam power= 100%
Press the button starting distillation cycle.
References:
ISO norm n. 333
280
