Research Instrumentation

MASS SPECTROMETER – Cheap power source

A mass spectrometer (called “mass spec”) is an instrument used by chemists to analyze molecules when only a tiny sample is available. The sample is injected into a vacuum chamber, then a stream of high energy electrons slams into it and creates ions (charged particles) which are then controlled by electrical and magnetic fields to rush across the chamber and separate according to how much charge they hold and how much mass they have. Different ions go to different places on the sensors and by keeping track of which ions arrive where, the original sample can be determined.

At Georgia Tech, researchers Wing and Fernandez have developed a replacement for the high voltage generator. You can make it yourself from a piece of copper and a piece of plastic for as little as two dollars. Maybe it will last for the life of the mass spec or even longer.

They realized that when you rub your shoes on a carpet or a balloon on your hair, you produce a high voltage between the two parts, that can manifest itself as a spark, as the electrons return to their original atoms. So why not use this to ionize the sample?

The effect has a name – triboelectricity and has been known by electrical researchers for hundreds of years. In this case, a small square of copper is rubbed against a suitable plastic film. Then the currents produced are led by wires into the mass spec.

The small currents are controlled better than those from the previous high voltage source and do less damage to the sample, so that smaller amounts of chemicals can be analyzed. For example, they were able to find 0.6 zeptomoles of cocaine in a sample. For those of you who, like me, never heard of a zeptomole, it is 10**(-21) moles or 10E-21 moles, or a millionth of a picomole. A picomole is already too tiny to think about, a millionth of a nanomole, and now we have come to a tiny sample that many people have heard of (think nanoparticles).

The research is reported in C&E News, March 6, 2017, p. 5.

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