Buchi KjelSampler K-377 Instrukcja Użytkownika Pobierz pdf (Strona 145)

8 Troubleshooting

145

K-375/376/377 Operation Manual, Version B

Problem Cause Corrective measure

Nitrogen content too low • Incomplete digestion

• Insufﬁcient H

2SO4

• Kjeldahl Tablets and H2SO4 in wrong

ratio

• Nitrogen content per sample tube is

too high

• Not enough NaOH or incorrect

concentration of NaOH used (required

is 32 %)

• Leakage during distillation

• Leakage during digestion

• Wrong titrant used

• Defective pH electrode

• Dirty glassware

Increase digestion time

Increase volume

Correct ratio

Not more than 200 mg Nitrogen per

sample tube

Correct volume until color change is

visible

Check and tighten, check connec-

tion between condenser and splash

protector, replace seal if required

Check sealing and scrubber suction

capacity

Check and correct

Calibrate electrode, replace if neces-

sary

Only use clean glassware

Poor repeatability • Air bubbles in titration system, buret,

tubes

• Aspiration not working properly

• Incorrect or no pH electrode calibra-

tion

• Sample inhomogeneous

• Sample weighing problems

• Incomplete digestion, digestion time

too short

• Suction capacity during digestion is

too strong

• Stirrer is not working

• Dip tube blocked, loose, too short or

defective

Fix tubing and reﬁll buret

Check for leaks and ﬁx

Calibrate electrode with fresh buffer

Homogenize sample

Use weighing boats to improve

procedure

Check color of samples during

digestion and choose digestion time

accordingly

Reduce suction power at the

Scrubber with the bypass valve

Clean the stirrer, replace if necessary

Check and correct

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