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    Wonderful instrument

October 22, 2009

GAC instrument breaks down the past

Mass spectrometer versatile with earth

By Dan Linehan

ST PETER — It has a big price tag ($160,000) and a fancy-sounding name (Inductively Coupled Plasma Mass Spectrometer) but Gustavus Adolphus College’s newest laboratory tool does something simple.

It counts.

The mass spectrometer tallies any one of about 75 elements from the periodic table, mostly metals, in a given sample.

This analysis can be directed toward many ends: A peek into a 19th century Lake George using a 5-foot-tall cylinder of mud to billion-year-old limestone that carries a record of primordial oceans.

Professors and their students at the St. Peter liberal arts college hope to do this and more with the new instrument, which was purchased with a $250,000 grant from the National Science Foundation. In addition to $160,000 for the machine itself, the grant funds maintenance and three years of summer research by students.

The instrument arrived on campus Monday, was installed Tuesday and ran its first test Wednesday.

Four Gustavus professors, two in chemistry and two in geology, helped write the grant.

Here’s how they described its workings:

It needs a liquid sample to start. Solids like limestone and soil can be dissolved in acid to reach liquid form. A small amount of liquid mist is sent through a tube and into an argon torch. The plasma is 7,000 degrees Fahrenheit, about as hot as the sun. The heat separates the elements’ ions from whatever else they might have been bonded with. The ions then proceed through a tube and are sorted by mass. The ions’ electrical charge is then counted and displayed on a computer monitor. The whole process takes about five minutes.

Each professor has their own interest and potential use for the instrument.

Jeff Jeremiason, director of the college’s environmental studies program, wants to examine how mercury and lead get in the environment and how their concentrations change over time.

He plans to test a mud core from Lake George that he hopes will demonstrate the effects of the Industrial Revolution on environmental lead.

Julie Bartley in the geology department is interested in limestone, which contains a chemical record of the ancient oceans that helped form it. She has some limestone from this area that was formed from an ocean 400 million years ago. Other limestone reflects oceans more than a billion years ago. In the end, the presence of metals in modern limestone will help explain what life was like then.

Professors Dwight Stoll and Laura Triplett also helped write the grant.

Students like junior Ben Carlson, who helped collect the mud samples at Lake George, will help with research and gain experience with the instrument.

Other students will use the machine for class.

The college, like other institutions, has other mass spectrometers.

But the difference here is a specialized machine for metal analysis. That 7,000-degree plasma torch is a big part of it.

Jeremiason said the nearest such machine is owned by a private company in New Ulm and Mayo Clinic has 11. He said the University of Minnesota Duluth also has one.

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