We are having problems with reproducibility of calcium on our P-E Optima 2100 ICP-OES. Most elements do well to within +/- 3-4 %, but we can't get calcium to closer than +/- 10%.
Do we need an internal standard? Do we need an ionization buffer? My understanding is that buffers are mostly for alkali metals in axial viewing mode. Calcium is an alkaline earth, of course, and we look at it in radial mode.
Any suggestions? Thanks.
2600 South 600 West, South Salt Lake, UT 84115
[log in to unmask]