BUCHI SpeedDigester K-436 - Manual (Page 28)

6 Operation
28 K-425 / K-436 Operation Manual, Version A
! 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.