In case you haven't checked this, can you check the concentrations of the internal standard entered in the file?  Open the file to see the number, rather than trusting the file name.  I had a similar problem that occurred because I had entered the concentrations for the internal standard but apparently hadn't hit "enter" but saved it.  When searching for the problem in the known sample analysis, the numbers for the internal standard were listed as the 1.0000ppb, the default starting value when you open a new standard file.  Good luck, Laurel

Laurel McEllistrem, Ph.D.
[log in to unmask]
University of Wisconsin-Eau Claire
Materials Science and Engineering Center
Eau Claire, WI 54701

-----Original Message-----
From: PLASMACHEM-L: Analytical Chem.(ICP's, DCP's, MIP's). <[log in to unmask]> On Behalf Of Azam Noori
Sent: Friday, June 1, 2018 9:12 AM
To: [log in to unmask]
Subject: Negative Data- ICP-MS

Good morning,

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: 0.998-0.999).
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.

Assistant Professor
Department of Biology
Merrimack College
315 Turnpike Street
North Andover, MA 01845
Mailstop: N8