Buchi SpeedDigester K-425, Руководство по эксплуатации

Страница: 28 / 58

6 Operation
28
K-425 / K-436
Operation Manual, Version B
!
WARNING
Death or serious poisoning by contact or incorporation of harmful substances at use.
• Before operation, check the instrument for correct assembling
• Close unused suction module positions with glass caps
• Rinse suction modules, hoses and connectors before use
• Before operation inspect sealings and tubes for good condition and tightness
• Exchange worn out or defective parts immediately
• Only operate the instrument in a fume hood
• Directly withdraw released gases and gaseous substances by a Scrubber or a water jet pump
• Dispose of condensate in tubings and glassware safely after use
!
CAUTION
Risk of minor or moderate cuts when handling damaged glass parts.
• Handle glass parts with care
• Do not heat up empty sample tubes in the device
• Visually inspect every glass part before mounting
• Exchange damaged glass parts immediately
• Do not touch cracks or bits of broken glass with bare hands
6 .2 .1 Kjeldahl digestion —preparing sample tubes
During the preparation process, handling with strong acid and other dangerous substances is inevi-
table. Thus, all steps must be performed under safe laboratory conditions!
Prerequisites
• All sample tubes must be clean and free of damages.
• To achieve a reliable and reproducible digestion result the quality of sample material and additives
(e.g. acid and catalyst) must be free of impurities and of adequate amount.
Filling of a sample tube
• Take the sample tubes sequentially and weigh in sample material.
Add calatyst to the samples (e.g. Kjeldahl tablets, order no. 028765).
• Carefully(!) add sulfuric acid (
≈ 98 %)
of sufficient amount to the samples.
➡
The sample tubes can now be installed in a rack.
Note
• Note down the sample weight and position to keep the probe processing and its analysis repro-
ducible. All racks are marked on top with a "1" for the first sample position.
• The rack(s) can be used as a temporary storage for empty tubes during the preparation process.
• When adding the sulfuric acid, rotate the tube to wash down any sticky sample material to the
bottom and to coat the inside of the tube.