Tips for a reliable icp test

[Cory]

Anyone got any pointers before i send off the icp water sample?

Was thinking a few things:

1) use filter socks
2) dont send cloudy water or disturb sand bed
3) stop vinegar dosing so theres less bacteria in the sample.
4) take sample away from dosers and return pumps.

Are these reasonable things to do? Im not sure if marinlabs puts your sample in a centrifuge or not but id think particles would skew the results no?

 

[Randy Holmes-Farley Verified Community Expert]

One of the things that worries me and I've never gotten a good understanding of is how much particulate matter, and which sizes, are removed from ICP samples we send to the hobby analysis companies.

I'd want all particulates removed down to very small sizes, but I do not know what they accomplish in this regard in practice.

 

[Lasse]

I´m always de-cap my sample tube 10 cm below the surface and take my sample from there. This because of the risk to get the lipid rich (and rich in other compounds) surface film in the sample

Sincerely Lasse

 

[Cory]

One of the things that worries me and I've never gotten a good understanding of is how much particulate matter, and which sizes, are removed from ICP samples we send to the hobby analysis companies.

I'd want all particulates removed down to very small sizes, but I do not know what they accomplish in this regard in practice.

My concern too since they can really change the readings right? What would make you suspect particulate contamination, very high phosphourus? I emailed marinlabs to see if they uss centrifuge.

 

[Cory]

I´m always de-cap my sample tube 10 cm below the surface and take my sample from there. This because of the risk to get the lipid rich (and rich in other compounds) surface film in the sample

Sincerely Lasse

Thats actually pretty smart i never thought of that one!

 

[Cory]

So if they dont centrifuge, i guess thats another reef toy to buy?

I seen a diy centrifuge. It attaches to a drill. Maybe thats a good idea?heres one to attacth to a drill:

 

[Randy Holmes-Farley Verified Community Expert]

My concern too since they can really change the readings right? What would make you suspect particulate contamination, very high phosphourus? I emailed marinlabs to see if they uss centrifuge.

I’d be most concerned about trace metals since I think some of them have the highest inside to outside concentration ratios.

 

[Cory]

I’d be most concerned about trace metals since I think some of them have the highest inside to outside concentration ratios.

What do you mean inside to outside ratios?

 

[Randy Holmes-Farley Verified Community Expert]

What do you mean inside to outside ratios?

Organisms take up certain elements very strongly in relation to the outside concentration. Many trace elements such as iron, for example. So the concentration of such a trace element is much higher in a bacterium than in in the water around it. Thus, leaving that bacterium int eh test gives an answer for that trace element that is higher than if that bacterium is removed from the test.

 

[Randy Holmes-Farley Verified Community Expert]

According to Lillero in chemical oceanography:

Cl- is rejected from organisms,

Na, Mg, Br, F, and SO4 are similar in organisms and outside

Most other elements are strongly concentrated into organisms

The concentration factor of many of the trace metals is on the order of 100,000. So there is 100,000 times as much in a bacterium than in a similar volume of seawater.

 

[Cory]

According to marinlabs:

"We do not centrifuge samples before testing, because it may affect the final results."

I dont understand how a cebtrifuge would effect results in a bad way.

 

[Randy Holmes-Farley Verified Community Expert]

According to marinlabs:

"We do not centrifuge samples before testing, because it may affect the final results."

I dont understand how a cebtrifuge would effect results in a bad way.

I agree that the results of centrifuging would be positive only since you typically only care about water and not particulates in it.

 

[Lance M.]

I've only always ever heard of "dilute and shoot" with saltwater samples, at least here in the US.

I guess you could filter and digest the samples but that seems excessive and will greatly increase the cost of the tests. I like to think of these offers as much better than a test kit but still a guide and not an end all result, due to all of the other (particularly operator) possibilities for error in testing.

 

[Randy Holmes-Farley Verified Community Expert]

I've only always ever heard of "dilute and shoot" with saltwater samples, at least here in the US.

I guess you could filter and digest the samples but that seems excessive and will greatly increase the cost of the tests. I like to think of these offers as much better than a test kit but still a guide and not an end all result, due to all of the other (particularly operator) possibilities for error in testing.

Triton told me they centrifuge the samples (at least that is what I was told the translation was, it was something like cyclone). But that said, I do not know what size particulates they actually remove.

I would not want them digesting samples since I am not interested in adding particulates into a "water" test.

 

[Cory]

I seen a centrifuge that does 4000 rpm. Would that be sufficient for our purposes?

 

[Randy Holmes-Farley Verified Community Expert]

This article discusses what you can precipitate at different speeds:

https://www.sigmaaldrich.com/technical-documents/articles/biofiles/centrifugation-basics.html

 

[Lance M.]

Triton told me they centrifuge the samples (at least that is what I was told the translation was, it was something like cyclone). But that said, I do not know what size particulates they actually remove.

I would not want them digesting samples since I am not interested in adding particulates into a "water" test.

I just mentioned that as the epa methods I have seen require filtration and digestion depending on which method used.

But I have never seen a method listed for any of these testing services. A researcher, who exclusively runs seawater on ICP, I met at Perkin Elmer told me she only does dilute and shoot with good results. I dont see any issue personally running 1:100 but Im only looking at a couple things.

 

[Cory]

So 18-22000 rpm is decent?

Should have went with Triton! I wonder how the two compare anyway.

 

[Cory]

I just mentioned that as the epa methods I have seen require filtration and digestion depending on which method used.

But I have never seen a method listed for any of these testing services. A researcher, who exclusively runs seawater on ICP, I met at Perkin Elmer told me she only does dilute and shoot with good results. I dont see any issue personally running 1:100 but Im only looking at a couple things.

Why would.you dilute the sample, not sure i understand the purpose.

 

[Lance M.]

Why would.you dilute the sample, not sure i understand the purpose.

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.