Page 241 - Catalog Instruments and Supplies

SCP SCIENCE 241
AA Spectroscopy Supplies

Helpful Hints for
Graphite Tube Users

The lifetime of graphite components can vary for many reasons. Certain elements and solutions can be particularly damaging to them and will
cause reduced lifetimes. Nothing can be done to avoid this; however, by following these hints, you will extend the lifetimes as much as possible.
Always follow the manufacturer’s instructions for instrument use. The following hints are offered only as general information for most of the
common brands of instruments, and as such, cannot be as specific as the manufacturer’s directions.

1. Before installing a new tube, always check the condition of 5. Avoid overheating the tube. Overheating will dramatically
the contacts (electrodes). Contacts will wear out through the decrease lifetimes. Generally speaking, the “tube clean”
course of normal operation. Such wear causes the tube to function programmed into most instruments will overheat the
become loose during operation, resulting in reduced electrical tube, and should not be used.
contact area with subsequent erratic operation and results.
If a contact is chipped, pitted, burned, or worn, it should 6. If you have been running the instrument for a while at lower
be replaced immediately. Operating the instrument with a temperatures, and need to run at a higher temperature
damaged contact may give erroneous readings and greatly for elements such as Ni, Cr, V, or Ti, you may experience a
decreased tube lifetimes. “memory effect” from temporary contamination of the cooler
parts of the furnace. In such a case, it is recommended to run
2. Use a clean, plastic forcep (PTFE is best) to remove the tube a few blank cycles at the new temperature, with maximum
from its container, and to position the tube during installation. gas flow, to purge contaminants from the system.
Never touch a graphite tube with your hands! Touching the
tube, for only a moment, will contaminate it and likely cause 7. When nearing the end of the tube’s lifetime, offer it retirement
elevated readings for many elements including Ca, Na, and K. at the proper time. Pushing the tube until it finally fails will
greatly increase the likelihood of damaging the contacts.
3. Use the proper type of gas and flow rate. Using too little in
an effort to reduce costs can decrease tube lifetime and can 8. Use of Sulphuric Acid will greatly reduce the lifetime of your
increase the chance of contamination of the contacts and graphite tube.
shroud.

4. Once the tube is properly installed, you must condition
it before use according to instructions provided by the
instrument manufacturer.