[jruckle]

I'm using a dual view ICP-OES to run drinking water samples and been having trouble getting K to pass.
So my questions are this:
1) What wavelength works best?
2) What calibration range works best?
and finally
3) should I use Axial or Radial viewing mode

[nilakkal]

You must use the radial mode to minimize the easily ionizable element effect from sodium and alkaline earth elements. If you happen to use a PerkinElmer Optima ICP, you have the option to reduce the viewing height in the radial mode. By deffault it will be 15 mm. You have to reduce it. hmm...10 may be ideal. But try it and optimize before you finalize the method. If you take care of these two factors you can work from ppb to more than 2000 ppm with out any dilution.