Re: How can i measure the level of Potassium in something?

The best way to measure the level of most minerals, including potassium, is 
by a process called Inductively Coupled Plasma, or ICP for short.

Basically, ICP works by sending a fine spray of a mineral solution into a 
chamber filled with hot gas.  The gas "excites" the minerals, causing them 
to give off energy at a certain wavelength (each mineral gives off its 
energy at a specific wavelength).  The strength of the energy given off 
indicates how much of a mineral is contained in solution.

I have included the URL for a site which describes how this process works 
and includes pictures of the process. 
 http://www.chem.orst.edu/isp/high_school_students_setup_induc.htm