# How does the “sample type” selection on the MassHunter software for Agilent 7900 ICP-MS affect the quantitative results?

I'm new to using the instrument, and recently I have tried to measure Cr in both the eluent(1% nitric acid) and a method blank (also 1% nitric acid, but after it has gone through the entire analytical procedure).

In the batch settings, I set the "sample type" for the eluent as "bkgd" (it stands for background), and my method blank as "samples". The result was that I obtained a negative CPS signal for my method blank. On the offline data analysis program, I was able to change the sample type of the the eluent to "samples" and told the program to reprocess the data, and lo and behold, the CPS signal goes back to positive.

What I think happened was that whenever I set something in my batch as the sample type bkgd, the instrument automatically references that cps count as zero, so that the subsequently analysed sample's signal will be referenced from that. However, I do not know exactly how the different sample types will affect my measurements. I have tried looking up the instrument manuals from Agilent, but none of them so far have given me any insight into this.

There are several sample types to choose from, such as blk (for blanks), sqstd(for tuning solution standards), calblk, etc. I don't want to risk selecting any of these until I'm confident I know what they do to my data.

Any response will be appreciated.

• Precisely because vendor software is often opaque, I tell it that every one of my samples, whether a blank, a standard, a spike-in, or whatever, is a Sample or an Unknown. Then I do all data processing, such as background subtraction, regression to find standard curves, etc., in an environment that I control and understand (e.g., R, Excel, or python). – Curt F. Mar 18 '19 at 23:49