Buchi SpeedDigester K-436 Manuel d'utilisateur télécharger pdf (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.

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Buchi SpeedDigester K-436 Manuel d'utilisateur Page 28