Linear Dynamic Range

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Metalman 694
Metalman 694's picture
Linear Dynamic Range

I am in the process of developing an EPA 200.8 based method to run Ca, Mg, K, Fe, Na, and Zn on the Perkin Elmer Elan 9000 ICP-MS.  I wanted to see if anyone knew how concentrated I can make my standards before the linear range starts to degrade.  The other day I went up to 20 mg/l without any problems.  Any help is appreciated.  Thank you.

Metalman

Element
Element's picture
 You can run even up to 300

 You can run even up to 300 mg/l, however you have to change the resolution settings in your tune file.
A higher resolution will decrease your signal, but will extend your dynamic range. The pathfinder in the Elan software will guide you how to adjust the resolutions. Make sure that you also perform a dual detector calibration for these analytes after you changed the resolution settings. However, you should consider that higher total dissolved solids (TDS) will give more unwanted matrix effects.
Why did your company buy an standard ICP-MS i.s.o. a DRC?

Metalman 694
Metalman 694's picture
Thanks for the help.  I'll be

Thanks for the help.  I'll be sure to check/change my resolution settings.

We bought a standard ICP-MS (no DRC) because I am under the juristiction of the NJDEP (New Jersey Department of Environmental Protection) and they do not allow us to operate DRC instruments.  It doesn't make sense to me as to why they don't allow it, probably due to the fact that they are slow to implement technology changes.

Thanks again for your help!

ToxLabRat
ToxLabRat's picture
Hey Metalman,

Hey Metalman,

I just read this post (I know it is older), but at what point did you end up getting a saturated signal for Fe and Zn?  I am just curious to know how my older Elan 6000 is looking against a newer 9000.  So many people are running Fe in collision or reaction mode, so it is hard for me to find other people running 200.8 in standard mode to compare LDR's with.

Thanks

Tox

Metalman 694
Metalman 694's picture
Hi Tox,

Hi Tox,

We dropped Fe on the ICPMS.  Our lab manager felt that the samples were "too concentrated" to run on ICPMS so we kept our certification on Flame to run that.  Zn I run side-by-sides to compare data (management hasn't gotten around to telling me to drop Flame AA for Zinc yet) but I run up to 500 ug/l as my highest standard for Zn without any problems.  When I did my LDR check, I was able to run up to 1000 ug/l for Zn without any problems.  Sorry I couldn't help you with Fe (I'll try again in the future since the AA is getting old and we're going to start looking to replace it) but hopefully what I told you about Zn helps a bit. 

 

Greg Pronger
Greg Pronger's picture
your comment about management

your comment about management saying iron was "Too Concentrated" made me want to point out the obvious (myself being a "shirt" or the dreaded "management"), and that it is not uncommon for the guys at the bench to know which way will be more efficient. If you have access to a couple of months of data, it'd be pretty easy to sort out if the iron high enough in the typical sample to warrant running them all via flame, or if you'd be more efficient to handle all of the elements by ICPMS. Pull the data together and show that you'd be more efficient with them pulled together may earn you a few kudos.

Metalman 694
Metalman 694's picture
Greg,

Greg,

I agree with you.  It would be better to run everything together via ICPMS.  I did dilute our samples and the side-by-side results showed that both were similar.  I also think it sort of got lost in the shuffle of things since most of the resources are being pooled to get our Organics lab up and running.  I'll try again soon once that calms down.  We're a pretty small lab, so when our resources are focused on something, other things tend to get pushed to the back burner.  Thanks for the insight.

riverbrat
riverbrat's picture
I understand this is an old

I understand this is an old post, but I am curious, what was your mdl for iron on the elan 9000? Do you think a MDL of 2.5ppb is reliable with a low standard of 5ppb? We have a client that wants to go very low for Fe. We can now go from 25ppb to 5000ppb . I am thinking that if the range was narrowed, I could go down to 5ppb.

Thank you,
Riverbrat

Metalman 694
Metalman 694's picture
Riverbrat,

Riverbrat,

We spiked at 100 ppb, and got an MDL of 6.52 ppb.  This tells me that we could spike lower since the MDL came out to be about 15 times lower than our spike value.  Our curve was 100, 500, 1000, 5000, and 10000 ppb, so I'm thinking that we ran a curve of 2, 5, 10, 50, 100 ppb we would be good to go.  Let me know how it works for you.

ToxLabRat
ToxLabRat's picture
Riverbrat,

Riverbrat,

I am able to get an MDL of <0.5 ppb for iron running in standard mode.  The calibration curve I use to get this is 0.5, 10, 50, 100 ppb.  So yes, if you drop your calibration curve and tighten it up, then you shouldt have any issues getting much lower MDL for iron.

One thing I will tell you is that if you are not using Fe 57 then I would suggest using that isotope.  Also, if you are not really particular about your reagents, CRM's and acids, then you should go through them and check the CofA's for them and make sure they are going to provide you with low enough contaminant limits for Fe at lower levels.  I have found that not all manufacturers are created equal and there are no universal specifications for something being classified trace metal grade, ultra trace metal grade, plasma grade, etc.

Tox

riverbrat
riverbrat's picture
Thank you!

Thank you!

This makes me feel confident about the desired future Fe calibrations! I will keep you all posted about my outcome. We are currently using Omnipure Acids, but I have access to Fisher and SCP.

Thanks,
Riverbrat

riverbrat
riverbrat's picture
Tox,

Tox,

Thank you for suggesting Fe 57. I tried with a few different isotopes and 57 worked the best due to the Ar O interferences of the others. I don't think I would have tries 57 if you didn't recommend it!

Thanks again,
Joelle

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