ICP-MS Problem: Low %R for calcium

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NickGlick's picture
ICP-MS Problem: Low %R for calcium

 For the past month or so we have been running a seperate ICV, which is simply a 500 ppb single stock for just calcium. The problem occurs that the ICV derived from a secondary source (100 ppb) has roughly a 100% recovery rate, but the 500 ppb single stock only has a 70% recovery rate. We have done several different tunings for calcium. Using calcium 42, 43, and 44, however none of them seem tro increase this recovery rate. 

Has anyone had any similar problems with calcium, I know it is well documented, but there doesn't seem to be a quick fix method to this. The cones have been cleaned and replaced twice in the month, but the problem still exists. Is there another step I should be taking besides re-calibrating the machine and tuning it?

Jeremy Ruckle
Jeremy Ruckle's picture
What instrument are you using

What instrument are you using?

What are the cps for each ICV?

If you are using an Elan with a dual detector the problem may be that the 500 ppb ICV is high enough to be in the analog stage (over about 1,500,000cps) and if your dual detector calibration is off that could be the problem.  Or even if your high calibration standard is in the analog range it may be throwing off your cal curve.