When we first started using the QQQ, there was no solid advice on internal standards. The assumption was to use unreacted internal standards. I chose to use standard internal standards but which underwent comparable reactions in the same mode, such as (all are positive ions: mentally add the + signs):
Te -> TeO as internal standard for As - > AsO and Se -> SeO
Rh -> RhO as internal standards for Ni -> NiO and Mn -> MnO
Ir -> Ir as internal standard for Cd -> Cd (neither appreciably reacts, but MoO interference is removed as MoOO)
Rh -> Rh(NH3)4 as internal standard for Cr -> Cr(NH3)2 and Co -> Co(NH3)2 (though Co forms Co(NH3)3 as well, the higher of the two forms is determined by He/NH3 gas flow)
No gas mode:
Ir -> Ir as internal standard for Be -> Be and Pb -> Pb
Tm -> Tm as internal standard for U -> U
Pappas RS, Martone N, Gonzalez-Jimenez N, Fresquez MR, Watson CH. Determination of toxic metals in little cigar tobacco with 'Triple Quad' ICP-MS. J. Anal. Toxicol. 2015;39:347-352.
In a similar smoke method, we made minor variation on the above theme, putting Pb in the oxygen mode as well, in order to make one fewer mode change, impart higher throughput:
Ir -> Ir as internal standard for Pb -> Pb (neither appreciably reacts).
Pappas RS, Gray N, Gonzalez-Jimenez N, Fresquez M, Watson CH. Triple Quad ICP-MS measurement of toxic metals in mainstream cigarette smoke from Spectrum research cigarettes. J. Anal. Toxicol. 2016;40:43-48.
R. Steven Pappas, Ph.D.
Team Lead, Tobacco Inorganics Group
Centers for Disease Control & Prevention
4770 Buford Highway, NE
M.S. F44, Building 110
Atlanta, GA 30341-3717, USA
From: PLASMACHEM-L: Analytical Chem.(ICP's, DCP's, MIP's). [mailto:[log in to unmask]] On Behalf Of Robert Dabeka
Sent: Friday, March 10, 2017 1:30 PM
To: [log in to unmask]
Subject: Triple Quad icpms
Related to the discussion on triple quads, I don't recall ever hearing how they deal with internal standards? (Can it be (my) age related). For example, would you have to use the oxide of the internal standard (which
element?) to monitor AsO+ and/or SeO+ sensitivity changes, and if you didn't, how would you cope with the large cell gas switchover time?
Robert Dabeka, Research Scientist
Food Research Division
Ottawa, Canada K1A 0L2
tel. 613 866-4395
email: [log in to unmask]