5 device monitoring – BUCHI KjelSampler K-377 User Manual
Page 124
7 Maintenance
124
K-375/376/377 Operation Manual, Version B
7 .2 .5
Device monitoring
In order to test/check the instrument, a nitrogen determination with a reference substance can be
carried out. We recommend the following parameters as standard application.
Parameters for checking the distillation and titration procedure with ammonium dihydrogen phos-
phate:
Check:
Distillation and titration
Reference substance:
Ammonium dihydrogen phosphate min 99.5 %
Nitrogen content:
w =0.1218 (12.18 %)
Original sample weight:
200 mg
Receiving solvent:
Boric acid 4 %, adjusted to pH 4.65 (with NaOH)
Titration solution:
Sulfuric acid 0.1 mol/L
Determination method:
Standard
Number of Blank Values:
≥ 3
Acceptable RSD Blanks:
≤ 5 %
Number of Samples:
≥ 3
Acceptable Recovery Rate
Standard:
98.0 ... 102 %
Acceptable RSD:
1 %
Parameters for checking the digestion, distillation and titration with glycine.
Check:
Digestion, distillation and titration
Reference substance:
Glycine (99.7 %)
Drying before analyzing:
8 h at 105 °C
Nitrogen content:
w = 0.1866 (18.66 %)
Original sample weight:
200 mg
Kjeldahl catalyst:
Titanium tablets
Catalyst amount:
2 tablets
Sulfuric acid conc. 98%:
15 mL
Digestion temperature:
Preheat to 320° C, digest at 420 ° C
Digestion time:
120 min
Receiving solvent:
Boric acid 4%, set to pH 4.65 (with NaOH)
Titration solution:
Sulfuric acid 0.1 mol/L
Determination method:
Standard
Number of Blank Values:
≥ 3
Acceptable RSD Blanks:
≤ 5 %
Number of Samples:
≥ 3
Acceptable Recovery Rate
Standard:
99.5 ... 102 %
Acceptable RSD:
1 %