You might check your calibration curve. If your calibration is simple
linear it might well be that the curve crosses the y axis > 0 which
leads to negative values at low concentrations according to the
calibration function y = mx + b
Moreover, check blanks and your internal standard.
Univ. Prof. Dr. DI. Thomas PROHASKA
University of Natural Resources and Life Sciences (BOKU)
Department of Chemistry - Research Group of Analytical Chemistry - VIRIS
Konrad-Lorenz-Straße 24, 3430 Tulln, AUSTRIA
scientific director 'blue area' FFoQSI
Technopark 1C, 3430 Tulln, AUSTRIA
Currently visiting professor
University of Calgary, Departments of Physics and Astronomy
2500 University Drive NW
Calgary, AB T2N 1N4
email: [log in to unmask]; [log in to unmask];
Tel.: +43 1 47654 77131; Fax: +43 1 47654 77059
>>> "Bill Perkins [wwp]" <[log in to unmask]> 01.06.18 8.49 Uhr >>>
Can you tell us how the samples were prepared? What is the matrix? Are
you standards matched to your matrix. Are you using an internal
standard? Could it be that your samples have high dissolved solids and
you have an issue with your nebulizer? When you did the Ag analysis did
you also check Ag 107? It would be interesting to know if they agreed.
Clearly you have a problem but the community needs some more information
to be able to help.
Dr William Perkins
Reader in Geochemistry
Department of Geography and Earth Sciences
Email: [log in to unmask]
Alias: [log in to unmask]
From: PLASMACHEM-L: Analytical Chem.(ICP's, DCP's, MIP's).
<[log in to unmask]> On Behalf Of Azam Noori
Sent: 01 June 2018 15:12
To: [log in to unmask]
Subject: Negative Data- ICP-MS
My name is Azam Noori. I am an assistant professor at Merrimack College.
We have purchased an ICP-MS lately. It is NEXION 350X (Perkin Elmer). I
am working with plants. I analyzed some samples yesterday. The
calibration curve for most elements was good (Correlation factor:
The concentration of elements in the first 5 samples was reasonable.
Then I used the standard 10ppb as a sample to make sure the instrument
is reporting the correct concentration. The concentration of most
elements was much higher than 10 ppb in this sample. For example for
silver (109), it was 623 ppb while when same sample was used as a
standard the concentration was 9.88 ppb. I analyzed some samples after
this, and the concentration of most elements (Ag, Mo, Cd, Sn, As, Ni,
Fe, Cr, Pb, and V) in all samples were negative. It is not what I
expected. Do you have any suggestions for troubleshooting?
Azam Noori, Ph.D.
Department of Biology
315 Turnpike Street
North Andover, MA 01845
Prifysgol Aberystwyth www.aber.ac.uk
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