Further to Steve's comments - as long as there is no other effect in play, there is no reason why your calibration has to be linear. You can handle a curved calibration perfectly well as long as it does not actually curve too far or "reverse" (where a higher concentration signal is the same as that of a lower concentration one). The only impact is that you will need more calibration points to clearly define the curve. If your instrument software does not handle this well, dump your data to Excel.
Dr. Otto Herrmann, Ph.D.,
800 Kipling Ave., Unit 2, Building KJ
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From: PLASMACHEM-L: Analytical Chem.(ICP's, DCP's, MIP's). <[log in to unmask]> on behalf of Pappas, Richard Steve (CDC/ONDIEH/NCEH) <[log in to unmask]>
Sent: 19 June 2018 12:55
To: [log in to unmask]
Subject: Re: Calibration range
In, "Pappas, RS, Stanfill, SB, Watson, CH, Ashley, DL. Analysis of toxic metals in commercial moist snuff and Alaska iqmik, J. Anal. Toxicol., 2008;32(4):281-291," my highest calibration standard for Ba was 2000 ėg/L. The Ba calibration range on our Element 2 at the time was entirely in Analog mode, but we were using an APEX-HF desolvating introduction system that resulted in approximately 4 x greater signal intensity at a given concentration without nitrogen addition than with a standard double pass spray chamber. Our Ba calibrations were linear. You did not mention what instrument you are using. When you post a question, the more information you give, the more accurately people can answer. I cannot be sure about YOUR instrument but on the basis of our instrument, 3500 ėg/L Ba would still be in linear range if not using a desolvating introduction system.
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). <[log in to unmask]> On Behalf Of Kyle Milke
Sent: Tuesday, June 19, 2018 12:36 PM
To: [log in to unmask]
Subject: Calibration range
I have samples that contain numerous metals. The two metals that I want to run as my majors are Al and Ba. Normally the majors only go up to 2000 ppb. The problem is that I have Ba concentrations in my sample that go up to 3500 ppb. I am short on money and am trying to avoid making a separate dilution for Ba because that will add more time to my run.
Can I just double the amount of Ba standard I add to my major stock to make the Ba calibration go up to 4000 ppb? My main concern here is that at 4000 ppb my calibration would not be linear and that I might overload the detector.
University of Alaska Fairbanks
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Kinectrics Inc. 800 Kipling Avenue, Unit 2 Toronto, Ontario, Canada M8Z 5G5