Buchi KjelSampler K-377 Manual de usuario descargar pdf (Pagina 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 %

1 2 ... 119 120 121 122 123 124 125 126 127 128 129 ... 159 160

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Buchi KjelSampler K-377 Manual de usuario Pagina 124