Tips for a reliable icp test

Lance M. · Jan 16, 2018

Theres also over saturation of the elements of interest when the concentration is too high, etc.

Randy Holmes-Farley · Jan 16, 2018

Lance M. said:
Because saltwater or high tds aqueous solutions will block up the flow into the ICP so a dilution is required, unless you are specifically set up to run those matrixes. But even then you will dirty up and require more pm on the parts (nebulizer, torch, etc.) leading in to injection.

You also typically want to match the solvent matrix between samples and standards. Typically you can choose the matrix or have custom made but 2% nitric is the most common, which I hope your tank (sample) is not close to.

There was a long discussion here between Triton and some others (e.g., Richard Ross and Craig Bingman) about the method details, and Triton does not use a standard method,and does not acidify the samples.

Lance M. · Jan 16, 2018

Randy Holmes-Farley said:
There was a long discussion here between Triton and some others (e.g., Richard Ross and Craig Bingman) about the method details, and Triton does not use a standard method,and does not acidify the samples.

Interesting. It is unfortunate that it seems to be a secret. I would like to see the paperwork on the development and qualification / verification.

Lance M. · Jan 16, 2018

Randy Holmes-Farley said:
There was a long discussion here between Triton and some others (e.g., Richard Ross and Craig Bingman) about the method details, and Triton does not use a standard method,and does not acidify the samples.

Interesting. It is unfortunate that it seems to be a secret. I would like to see the paperwork on the development and qualification / verification.

Randy Holmes-Farley · Jan 16, 2018

Lance M. said:
Interesting. It is unfortunate that it seems to be a secret. I would like to see the paperwork on the development and qualification / verification.

Ehsan said they spent a great deal of time optimizing the method for seawater before they commercialized it, so they don't want to just give it away to copycats that are already entering the market.

That said, they do show standard curves and the LOD for most elements:

https://www.triton-lab.de/fileadmin/user_upload/triton-lab/TRITON_LOD.pdf

Cory · Jan 16, 2018

Please tell me what speed of centrifuge is going to make a meaningful impact. I dont understand the graph in the link sent to me.

I can buy the 4000 rpm centrfuge for 20$ but im not sure if its good enough. Would be good to use it for alk tests too ro remove caco3 particles.

Lance M. · Jan 16, 2018

Randy Holmes-Farley said:
Ehsan said they spent a great deal of time optimizing the method for seawater before they commercialized it, so they don't want to just give it away to copycats that are already entering the market.

That said, they do show standard curves and the LOD for most elements:

https://www.triton-lab.de/fileadmin/user_upload/triton-lab/TRITON_LOD.pdf

5-6 pt curves with r >0.995? From what I see there, they did spend a great deal of time on it and seems to be well thought out. If I didn't have the ability to do it myself, I would try them out.

Cory · Jan 18, 2018

This is what marinlabs replied with:

"Hello,
maybe i expressed myself poorly. There is no need to centrifuge water samples, because most of the time customers send samples practically free from sediment, and possibly sediment will settle spontaneously. We take water to ICP by capillary form top of a vial. Very rarely customers send to us a suspension and that is the only case when we centrifuge samples."

Cory · Jan 22, 2018

Im curious what everyone thinks about the above post i made?

Randy Holmes-Farley · Jan 22, 2018

They only addressed macroscopic sediment, not bacteria. It's a nonanswer, IMO.

KimG · Apr 6, 2020

Sorry to unearth such an old post, but I'm curious about this.
In the lab I work, whenever we have to store samples for stuff like No2, No3 and others we always preserve them. Either by filtering through a 0.2 micron filter, by acidification or at least freezing them. The main point is to stop bacterial growth that would ruin the sample.
However icp test kits are just sent raw. How can this be precise? Anyone ever got a answer from any of the icp providers regarding this?
@Randy Holmes-Farley @Cory @Lance M.

Randy Holmes-Farley · Apr 6, 2020

KimG said:
Sorry to unearth such an old post, but I'm curious about this.
In the lab I work, whenever we have to store samples for stuff like No2, No3 and others we always preserve them. Either by filtering through a 0.2 micron filter, by acidification or at least freezing them. The main point is to stop bacterial growth that would ruin the sample.
However icp test kits are just sent raw. How can this be precise? Anyone ever got a answer from any of the icp providers regarding this?
@Randy Holmes-Farley @Cory @Lance M.

Well, it depends a bit on how the samples are treated, but remember the chemical form doesn't matter for ICP, so bacterial conversion from one form to another makes no difference. Nitrogen is not sampled anyway since N2 from the air would interfere, but phosphate or certain trace elements might be taken up by bacteria and later centrifuged out as whole bacteria if that is how it is processed before testing. We aren't really privy to the processing techniques despite asking. I'm not sure how significant this is, but it is a possible issue.

KimG · Apr 6, 2020

Randy Holmes-Farley said:
Well, it depends a bit on how the samples are treated, but remember the chemical form doesn't matter for ICP, so bacterial conversion from one form to another makes no difference. Nitrogen is not sampled anyway since N2 from the air would interfere, but phosphate or certain trace elements might be taken up by bacteria and later centrifuged out as whole bacteria if that is how it is processed before testing. We aren't really privy to the processing techniques despite asking. I'm not sure how significant this is, but it is a possible issue.

Hi Randy.
Thanks for the answer.
While it makes very much sense, in a trial i'm currently running I have seen bacteria numbers and activiti doubling in about 3 hours in samples kept in the fridge after being collected from aquaculture system (much higher organic content). In the icp case there are at least two or three days for bacteria to grow, much more in some cases.
While I image a lot of chemical compounds will not change, I could imagine large changes to organic components, and in an extreme even dinitrification happening (depending on loading, oxygen conditions and transportation time).
Maybe I'm overthinking this, but I find it weird that samples can be kept unpreserved for so long and still deliver accurate results across so many parameters.

Miller535 · Apr 6, 2020

KimG said:
Hi Randy.
Thanks for the answer.
While it makes very much sense, in a trial i'm currently running I have seen bacteria numbers and activiti doubling in about 3 hours in samples kept in the fridge after being collected from aquaculture system (much higher organic content). In the icp case there are at least two or three days for bacteria to grow, much more in some cases.
While I image a lot of chemical compounds will not change, I could imagine large changes to organic components, and in an extreme even dinitrification happening (depending on loading, oxygen conditions and transportation time).
Maybe I'm overthinking this, but I find it weird that samples can be kept unpreserved for so long and still deliver accurate results across so many parameters.

I am no chemist, but I think most of us sending ICP in are looking for contaminants like heavy metals, and salt values (cal, mag, and so forth). I wouldn't think bacteria would impact that much if at all. I would wonder more if their N-doc was affected by bacteria then their standard ICP test.

KimG · Apr 7, 2020

Miller535 said:
I am no chemist, but I think most of us sending ICP in are looking for contaminants like heavy metals, and salt values (cal, mag, and so forth). I wouldn't think bacteria would impact that much if at all. I would wonder more if their N-doc was affected by bacteria then their standard ICP test.

I guess thats a fair point Miller professional stress I guess

Miller535 · Apr 7, 2020

KimG said:
I guess thats a fair point Miller professional stress I guess

Now as I said, from reading some of other people's post, I question both the accuracy and point to their N-DOC test. Their N-DOC test claims that it test's Nitrogen, dissolved organic carbon, and extended alkalinity. I am not sure I would believe this to be accurate, and really do not understand the point of it.

Christoph · Apr 7, 2020

Hello!

We also believe, that filtration is very useful for environmental and tank water samples:

Small particulates (such as a tiny flake of food or sediment) has the potential to alter several parameters in the ICP results (Fe, Zn, P,...). Also in biologically active (unfiltered) samples biofilms can form on the vial walls binding phosphates, thus lowering P within the sample "phase".

In our lab we also do IC-ECD/VWD with tank water samples, and especially for long term stability of nitrite and nitrate, biolgical activity in the sample must be avoided. Thats the reason we include a 0.2 µm syringe filter in the sampling kit.

We did not observe significant change in nitrate concentration in filtered tankwater samples stored for 360 days at room temperature.

All the best,
Christoph