Although I cannot respond directly to your inquiry of interelemental interferences, I can tell you that from my line of work both of these elements can show up in fairly appreciable concentrations in river and surface waters (i.e., they are naturally occurring).
Fact of the day that I didn't know before: In naturally occurring form Ba is found only in combination with other elements.....
City of Elyria Wastewater Pollution Control Laboratory
1194 Gulf Road
Elyria, Ohio 44035
From: PLASMACHEM-L: Analytical Chem.(ICP's, DCP's, MIP's). [mailto:[log in to unmask]] On Behalf Of Michael Murphy
Sent: Tuesday, December 07, 2010 1:45 PM
To: [log in to unmask]
Subject: Back to school for me -- Ba and Sr interfernces
Once again the dunce cap is on and I return to the classroom (virtual in this case). While setting up a new ICPMS instrument a "random" sample of tap water (this is well water) was analyzed and showed strong values and nice peaks for barium and strontium. This holds for Ba at mass 137 and 138 and for Sr at mass 88 and 86 in no-gas mode, H2 mode, and He mode. "Apparent" concentration is ~ 2300 ppb Sr and ~90 ppb Ba (the concentration for each analyte is the same at both masses).
This was confirmed on a second ICPMS (no cell installed) but, fortunately, the ICPOES did not see Ba or Sr.
Relieved as I am that I am not working overtop a future Superfund site I admit that I cannot see what species are causing these rather consistent readings (e.g. Ba138 = 607596 counts = 89.9 ppb, Ba 138 = 3874062 counts = 90.2 ppb, Sr 88 = 94962677 counts = 2390 ppb and Sr 86 = 10714443 counts = 2320 ppb). If it is a polyatomic problem I cannot find a structure(s) that make sense.
I am assuming that some of you know these interferences by heart, so any insight would be much appreciated.
Intertek USA, Inc., d/b/a QTI
PO Box 470
291 rt. 22 East
Salem Industrial Park, Bldg. 5
Whitehouse, NJ 08888
Please note that all comments are my personal opinion and do not represent the position of my company.