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ICP-OES Method Development - Peak Resolution, S/B Ratio & Structured Background

Question asked by agricult on Feb 3, 2019
Latest reply on Feb 7, 2019 by agricult

Currently I’m engaged in some ICP-OES (5100) method development work and have some basic questions from my experiences so far regarding the data interruption.

1. My first question is about the analyte peak readings I’ve performed so far using pure standards. As seen from the attached images for each of the single element standards I’ve run, i.e. Zn, Fe, Mg, the analyte peaks are not centring exactly at their specific analyte lines, i.e. Zn at 202.548 nm / Fe at 238.204 nm / Mg at 279.553 nm. No matter how I adjust the measurement conditions the analyte peaks don’t centre. My assumption is that this is related to the instrument Resolution range for the various elements as highlighted on page 12 of this Agilent guide (, that the analyte peak won’t exactly centre on the specific analytical line. Can anyone confirm if this is correct or the normal?


9. Fe Peak 238.204 nm.jpg15.jpg


2. My second question relates to Signal-to-Background ratio between the analyte signal and background signal. At this initial stage I only want to develop a basic understand of the S/B importance. I assume a high analyte signal and the lowest background signal is what I should be aiming for at this stage. Can you take a look at both images below for Fe at 238.204 nm under different measurement conditions and explain which may the best and why briefly?

11. Fe S.B 238.204 nm.jpg13. Fe S.B 238.204 nm C2.jpg

3. My last question relates to the blank reading. As seen from the image, a small Fe signal is still being detected but this is mainly due to contamination of the diluent. My question is regarding the small peaks either side of the Fe peak. I assume this is the appearance of the structured background, would that be correct?

12. Fe Blank 238.204 nm.jpg


I’d really appreciate input from experienced users. I’m learning loads as I go and this would give me a great boost to further my understanding.