OREGON STATE UNIVERSITY
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In the Lab

 


Retene structure


DDT structure

Robert tells you that the hazy air on Mary’s Peak could have come from either the east or the west. Air from these locations tends to contain unique kinds of pollutants.

East: The Willamette Valley and the Cascade Mountains are located to the east of Mary’s Peak. Early season forest fires can create large amounts of smoke in the air. The presence of the chemical retene (REE-teen) in the air is a good indication of burning vegetation.

West: Mary’s Peak is close to the Pacific Ocean. Sometimes, dust storms from Asia carry particles of dust and pollutants in the air across the Pacific Ocean and over to North America. The presence of the pesticide DDT in the air is a good indication that the air is from Asia. DDT was banned in the United States in 1972, however it is still used in India and parts of Asia.

Your job is to determine whether the hazy air on Mary’s Peak came from the east or from the west.

Sample Preparation

In order to analyze the chemicals in the air sampler, they must be removed from the filter and resin beads used to collect them. This is done by dissolving the pollutants in a liquid called a solvent, which is strong enough to remove pollutants from the filter and resin beads.

In this situation, we have sampled outdoor air, however you can use the same methods and instruments if you wanted to sample and measure contaminants in indoor air.

An accelerated solvent extractor is used to dissolve the chemicals in less than one hour using high temperature and pressure. After this process, the liquid solvent contains the pollutants originally collected on the filter and resin.

The next step involves evaporating most of the solvent, leaving a concentrated solution of pollutants in a small volume of solvent. The volume is reduced from 300 ml to 1 ml in order to accurately measure all the pollutants present in one sample.

Now, the sample is ready to be analyzed on the GCMS.

How Does the GCMS Work?