DIY Mass Spectrometer

Okay - Not quite a real mass spectrometer, but an excellent learning tool for demonstrating the principals of mass spec. This can be very useful for teaching students who may not have a strong physics background. Plus it's a fun game - like pinball. 

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"Mass spectrometry has been described as the smallest scale in the world, not because of the mass spectrometer’s size but because of the size of what it weighs -- molecules. Over the past decade, mass spectrometry has undergone tremendous technological improvements allowing for its application to proteins, peptides, carbohydrates, DNA, drugs, and many other biologically relevant molecules.... mass spectrometry has become an irreplaceable tool in the biological sciences." CREDIT: https://masspec.scripps.edu/mshistory/whatisms_details.php#Basics

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The principle is quite simple. You have a sample you'd like to analyze - using a Mass Spec, this is performed by ionizing the sample into it's constituents, accelerating those particles down an electromagnet chamber, influencing their trajectory using a magnetic field, and observing the degree of deflection from known standards. If that sounds like an earful -- here, let's try this: 

"If something is moving and you subject it to a sideways force, instead of moving in a straight line, it will move in a curve - deflected out of its original path by the sideways force. Suppose you had a cannonball travelling past you and you wanted to deflect it as it went by you. All you've got is a jet of water from a hose-pipe that you can squirt at it. Frankly, its not going to make a lot of difference! Because the cannonball is so heavy, it will hardly be deflected at all from its original course.

But suppose instead, you tried to deflect a table tennis ball travelling at the same speed as the cannonball using the same jet of water. Because this ball is so light, you will get a huge deflection. The amount of deflection you will get for a given sideways force depends on the mass of the ball. If you knew the speed of the ball and the size of the force, you could calculate the mass of the ball if you knew what sort of curved path it was deflected through. The less the deflection, the heavier the ball." CREDIT: http://www.chemguide.co.uk/analysis/masspec/howitworks.html

This model is made of a 4' x 4' sheet of Whiteboard material ($13 at Lowes), 1" x 4" Poplar, wood screws, wood glue, rubber bands, ball bearings, and a very strong Neodymium Magnet. Source: http://www.magnet4less.com/
*** Warning: These magnets are no joke.  They will pinch and are very difficult to separate. Keep away from small children and only use under adult supervision!

The advantage here is the entire surface is whiteboard - which makes it very smooth for good results, but also a great opportunity to draw, trace, and write learning material directly on the surface. 

The neodymium magnet can be calibrated, or scaled, based on the size of your sample (ball bearings).  The ionization charge introduced to the sample can be modulated via rubber band.  The detector at the end is covered with dry-erase marker and is easily scuffed by even the smallest ball bearings - indicating the mass-to-charge ratio which you can plot above it.  Just like a real Mass Spec!  Samples are held in place by a smaller neodymium magnet counter-sunk in front of the rubber band.  Introduction to basic electromagnetic theory can be done with a simple wound coil and battery. 

For additional reading about Mass Spectrometry. See these links
Wikipedia
Scripps Center for Metabolomics and Mass Spectrometry
Chemguide
ThermoFisher

Image Credit: Thermofisher,