A grain of salt is so small it’s barely perceptible with the naked eye. Now try to imagine something a million times smaller than that grain of salt.
Just trying to picture something that tiny is enough to make most people’s head hurt; the thought of being able to identify something that size seems impossible.
But that’s exactly what chemists and biochemists at Oberlin College are now able to do with two new instruments .
In January, the college had a high-performance liquid chromatograph with photodiode array detector with a single quadrupole mass spectrometer and a gas chromatograph with a single quadrupole mass spectrometer installed.
Go ahead, try saying those names five times fast.
The equipment is often referred to as a liquid chromatograph-mass spectrometer, or simply LC-MS, and gas chromatograph-mass spectrometer, or GC-MS.
What both pieces of equipment can do is quite amazing.
“With the chromatograph part, you put a mixture in, such as river water or a biological sample,” said Rob Thompson, a professor in the Oberlin College department of chemistry and biochemistry. “Whatever it is, you put a mixture in with many, many different compounds. What the chromatograph does is separate those. It then spits them out one by one. Then, one by one, those compounds will go into the mass spectrometer, which essentially identifies the compound by its weight, mass, and to some extent its fragmentation.”
According to Thompson, both pieces of equipment can identify as little as a few picograms of a compound. A picogram is one trillionth of a gram.
The difference between the LC-MS and the GC-MS should be evident in their names. One looks at gas samples, and the other looks at liquid samples, which could be any from river water to a biological sample, such as blood.
“For a gas chromatograph, you need things that are volatile—things like gasoline that can evaporate quickly. That’s the only thing you’re going to be able to put through a gas chromatograph,” Thompson said. “For things that are aqueous-based, water-based, or with bigger molecules that you can’t evaporate so easily, you have to use a liquid chromatograph.”
Both machines have replaced instruments at the college that were around 15 years old. The new LC-MS and GC-MS are 100 to 500 times more sensitive than the previous equipment. Thompson compared it to the difference between a computer today and one 15 years ago.
No other primarily undergraduate college in the nation has a more capable LC-MS instrument, according to Thompson.
So what exactly can students and faculty at Oberlin College do with the new equipment?
They’re not exactly sure, just yet.
“We have to reorient,” he said. “We’re used to only being able to do certain things… We can do all these other things now.”
He did give a couple examples of what is being done with the LC-MS and the GC-MS.
“One thing is Rebecca Whelan, another analytical chemist here, along with Mary Garvin, who is in biology, have been looking at the exudates of birds onto their wings—so what a bird exudes onto its wings to make it waterproof, attract other birds, or whatever,” Thompson said. “Those are unknown compounds. They extract those compounds out of the feather, put it into the instrument, and separate those compounds. As they get spit out, the mass spectrometer identifies them.
“They’ve been using it to identify these compounds that nobody knew about before.”
In his work, Thompson sees the LC-MS being used to test the levels of toxins in fruit. For example, it might be used to measure pesticides in citrus fruit.
“We extract out those pesticides that are left over, not washed off, or go into the peel,” he said. “We put it into the instrument and now we’re looking for the quantification; we’re looking for how much. It can tell you if you’re over the maximum residue limits that the government has set up. We’re seeing, especially from China and other countries, products coming in that have more than they should.”
The two instruments have a combined list price of $430,000, and were purchased using donations from alumni and friends, gift funds, a discount by the manufacturer, Shimadzu Corporation, and funds from Oberlin College.
“We’re very lucky to get these instruments,” Thompson said. “We are very thankful to be able to provide this amazing technology to our students.”
Scott Mahoney can be reached at 440-775-1611 or @sm_mahoney on Twitter.
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