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.
Summary of Contents for SpeedDigester K-425
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