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Current Time and Temperature at Palmer Station
Current time and temperature at Palmer Station


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Headline: Learning Activities

Head: Clean the XAD

Glossary words on this page (glossary words are shown in red):

apparatus: equipment designed for a specific use

solvents: liquids that will dissolve many substances

Background

The POP team will be looking for very small amounts of POPs in Antarctica. To do this, the team will collect air and water samples. The samples will be passed through foam plugs or columns filled with special material. The POPs will stick to this material. Then machines will analyze the material to find and measure the POPs.

Columns packed with XAD resin beads are used to filter water samples. These small resin beads are material that POPs will stick on.

Amy and XADAmy and XADAmy and XAD

In the image above left, Amy is holding an XAD column. The material inside it looks like dried coconut.

The XAD resin must be very clean at the beginning of the measurements. That way, scientists will know that if POPs are found, they came from the Antarctic samples, not the XAD itself. So, the XAD has to be washed with powerful chemicals, or solvents (see image above center).

All the cleaning is done in the laboratory before the expedition to Antarctica. To do this, the team uses a special lab process and apparatus called a Soxhlet Extraction process (see image above right).

There are three parts to the Soxhlet equipment:

  1. The flask at the bottom, which sits on a heater. This flask holds the solvent.

  2. The Soxhlet filtering thimble in the middle, which holds the white XAD material being cleaned

  3. The condenser at the top, which recovers the solvent and recycles it through the equipment

Hot solvent bubbles through the XAD in the filtering thimble, washing it. The hot solvent cycles through the Soxhlet many times. Any contaminants that come out of the XAD are discarded when the solvent in the flask is changed. The kind of solvent in the flask is changed every 24 hours. There are eight different changes of solvent in order to clean the XAD material in the thimble.

Try these math problems that Michele needed to solve in order to prepare the materials for the expedition.

"Recipe" for cleaning the XAD