Cleaning a Contaminated Cell

 

Baseline anomalies are often the sign of a contaminated cell. DSC and PDSC cells must be cleaned properly to maintain satisfactory operation. Scraping the contamination off is not recommended.

If your baseline appears to show sample contamination, try the following recommended cleaning procedure. The procedure varies slightly depending upon the type of cell (QDSC Standard Cell or QDSC Pressure Cell) and the type of cooler that is installed.

  1. Begin by removing any pans from the cell. See also:  Loading/Unloading a Sample

  2. Choose from one of the following procedures:

Cleaning a Contaminated QDSC Standard Cell

NOTE:  Cleaning of the cell is performed with the lids off to prevent the lid gas exit tube from becoming plugged by condensing off-gases.  If your instrument is equipped with an Autolid mechanism you will need to open the cell manually at the start of the method.  You can open the cell by selecting Lid on the Control Menu Touch Screen or by selecting Lids/Open from the Control menu.

Burning Off Contamination in a DSC Cell with the FACS Installed

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Burning Off Contamination in a DSC Cell with an RCS or LNCS Installed

WARNING:  Do not exceed 100C with the RCS cooling head installed and the RCS power off.  Serious damage and/or injury could occur.

CAUTION:  We recommend that you do not use the RCS when running isothermal experiments above 400C.  Damage to the unit can occur if used at high temperatures for extended periods.

NOTE:  When removing the RCS/LNCS heat exchanger from the cell, it is recommended that the RCS or LNCS be allowed to warm to room temperature after turning it "off" before removing the heat exchanger.  That will minimize the chance for moisture condensation/contamination and will avoid the possibility of damaging the connector hose by moving while cold (and brittle).

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Cleaning a Contaminated QDSC Pressure Cell

A poor baseline is often the sign of a contaminated cell. PDSC cells must be cleaned properly to maintain satisfactory operation. Scraping the contamination off the cell's constantan disc is not recommended because the disc is very thin (about 0.1 mm, or 0.004 inches), and if the disc deforms, the baseline may be affected.  

If your baseline appears to show sample contamination, try the following recommended cleaning procedure:

  1. Remove any pans from the cell.

  2. Connect the air purge.

  3. Lightly brush out the cell with a small fiberglass eraser (included in the DSC accessory kit).

  4. Clean the disk with air.

NOTE:  Be sure to wear safety glasses or goggles when cleaning the cell with air.

  1. Begin cleaning by heating the cell with an air purge to 50 C above the highest operating temperature or 600 C, whichever is lower. Use a heating rate of 20 C/min. Ramp to 600 C, then hold isothermally for 15 minutes.

  2. After the cell has cooled down, repeat steps 3 and 4.

  3. Run the experiment again and compare the baselines. If there is a marked improvement but the baseline is still unacceptable, the contaminant probably oxidized and reduced to an inert ash. Run the experiment again and check for further improvement.  

  4. Once the baseline is acceptable, return to normal operation.

If the constantan disc looks clean and is not bent or cracked, but the baseline problem remains, it is probably not due to contamination; the cell may need to be replaced (contact your TA Instruments service representative).

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