Sunday, January 8, 2017

Paul Particle Trap

Normally a Paul Trap is used to catch individual ions, single nuclei or charged molecules, and then sort them according to their m/z ratio (mass to charge). However it is possible to scale the whole idea up to a table top size in order to catch finely ground powders like flour or corn starch.

The trap works by alternately pulling and pushing the particles in 2 or 3 axis. For one half of the cycle they are pulled up and down while being pushed inward from the sides, when the polarity of the trap reverses the forces reverse as well. The particles move according to the forces they feel but never get far before the reversal, trapping them in a small volume of space. When the voltage on the trap is increased the particles with the most charge relative to their mass will pick up more speed and eventually be flung from the trap, when the voltage is decreased the particles with the most mass relative to their charge will be overcome by gravity and will fall from the trap, in this way ions are sorted for used in mass spectrometers.