Selenium Dosing

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I'm curious if anyone doses Selenium here, as i've got it undetectable in all my ICP.

I've found two products here maybe @Randy Holmes-Farley would be able to help me determine which to use.

One is Sodium Selenite 100 microgram per drop/serving

Sodium Selenite Selenium Drops



, and the other is L-Selenomethionine which is 200 micrograms per serving

L-Selenomethionine Selenium Drops

From what I have been able to read between the two, the Selenomethionine is found in the human body and food whereas the Sodium Selenite is some kind of inorganic form that has to be converted by an organism? Very little information that pertains to Selenium that I can find.

I'd be aiming for a setpoint of 50 microgram/litre so having a dropper makes it relatively simple to do, just determining which product is the question.

Thanks for any advice anyone can provide.
 

Randy Holmes-Farley

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Selenium is only present in the ocean at 0.18 ug/L. Can your ICP company detect that low?

If I were to dose it, I'd use an organic form, and the selenomethionine seems reasonable.



"In seawater, the speciation of selenium is depth-dependent (Cutter & Bruland 1984). In surface waters, selenium is predominantly associated with organic matter. "
 

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Hi!
Selenium is not very sensitive on ICP-OES, so no way a deficiency could be detected with this technique.

With ICP-MS our detection limit is ~ 30-50 ng/l (0,03-0,05 µg/l), thus also allowing to diagnose (to) low levels.

Best regards, Christoph
 
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Hi!
Selenium is not very sensitive on ICP-OES, so no way a deficiency could be detected with this technique.

With ICP-MS our detection limit is ~ 30-50 ng/l (0,03-0,05 µg/l), thus also allowing to diagnose (to) low levels.

Best regards, Christoph
Im using ati, it has a setpoint of .51ug/l, every test ive ever ran over the years shows no selenium at all, nor do any of the trace elements or anything i dose contain it.

@Randy Holmes-Farley Fauna Marin recommends a set level of roughly 2ug/l and states that tissuebloss wasnt observed till roughly 20ug/l. I only say this because it seems there may be some room for error before an issue to were arise.

As per your quote on the article here stating depth dependant for selenoum and organic at surface waters, i get a bit confused.

"In seawater, the speciation of selenium is depth-dependent (Cutter & Bruland 1984). In surface waters, selenium is predominantly associated with organic matter. "

Using this Selenomethionine would end up being the correct selenium versus the selenite? There are so many kinds to buy its a bit crazy, and i cant find any powder forms to mix my own solution for either. Should i mix some of both, would it not matter? Sorry if this is a strange question, and thank you for the help
 

Randy Holmes-Farley

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When it says organic forms, it means things like selenomethionine, but there are others. I don't know if any selenium dosing is useful, or, as Christoph noted, you can even know that yours is low.

ATI says its lower limit of detection is more than 20x higher than the average ocean level of selenium, as Christoph noted. So there's no way you can tell that it is low (it may even be high).

Selenic3.95 – 6.51 µg/l240 µg/l0.99999
 
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When it says organic forms, it means things like selenomethionine, but there are others. I don't know if any selenium dosing is useful, or, as Christoph noted, you can even know that yours is low.

ATI says its lower limit of detection is more than 20x higher than the average ocean level of selenium, as Christoph noted. So there's no way you can tell that it is low (it may even be high).

Selenic3.95 – 6.51 µg/l240 µg/l0.99999
Thank you for the link.

What test is christoph refering to that he says can test those lower limits?

Offhand would you happen to have a link to triton detection limits? Im going to google this myself right now too.

Screenshot_20220125-152118.png


Edit: found triton detection llimit. Seems that at 7ppb that is nearly half as sensitive as ati at 3, but still not reassuring that its that high on detection
 
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Randy Holmes-Farley

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Christoph is referring to a different ICP technique: ICP-MS. It detects elements based on weight (or charge/weight), rather than specific wavelengths of light emission from the very hot ions in the plasma.

I do not know what he routinely uses, but while ICP-MS often has lower detection limits for some trace elements, it also has interferences that can make it more challenging since many heavy elements have lots of isotopes and partly overlap in weights.
 

Christoph

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Hi all!

Even a 3 ppb limit of detection with ICP-OES for selenium is fairly optimistic.

Also on ICP-MS selenium (mass 78) is in principle difficult due to the 40Ar38Ar+ - Interference, as Randy already stated. Also the other selenium isotopes are not better. However those interferences can be efficiently removed using a reaction cells with appropriate cell gases. Thus detection of Selenium (and most other trace elements relevant in seawater) thus works well down to the ng/l range after careful method optimization.

As it comes to selenium dosing: We encounter quite frequently low levels in reef tanks. Since the possibility to quantify selenium in the relevant concentration range is very recent, it was difficult to know beforehand how much to dose and how much is consumed by a typical reef. Also there is no solid data on what effect selenium deficiency has in a reef.

The following statement is still far from scientifically verified, but my experience so far is that dosing Selenium in Selenium-deficient systems causes visibly increased coral growth rates.

You can find some info about ICP-MS on our webpage.

Best regards,
Christoph

PS.: we use ICP-MS and ICP-OES both routinely
 

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Sry I’m open to new ideas and new methods but I’ve been Reefing 20 years and been using quality salts, water changes, 2 part esv w mg and kalk top offs during overnite hours. Dabbled minimally w some Kz products Booster and flatworm for sps development. I keep a mixed reef. ICP test. I think frequent water changes would help replace those minor and trace elements when they become depleted. Don’t see a need individually target specific elements. Also don’t see an abundance of articles/ papers on the hobby level. Not saying it’s not important to water chemistry but Mayb not necessary based on what’s available, consumed, and reliably tested.
 

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@Randy Holmes-Farley Hey Randy if I want to make a stock solution for selenium dosing with chemical do you recommend? Thanks
1 sodium selenite
Screenshot_20230321_231958_Chrome.jpg

2. Selenomethionine
Screenshot_20230321_232041_Amazon Shopping.jpg

Screenshot_20230321_232053_Amazon Shopping.jpg
 

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Randy Holmes-Farley

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I'd use the now foods version (selenomethionine), and I'd dissolve it in fresh water and let any undissolved solids (the rice flour) settle out, then dose the clear liquid.
 

MikeTheNewbie

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I'd use the now foods version (selenomethionine), and I'd dissolve it in fresh water and let any undissolved solids (the rice flour) settle out, then dose the clear liquid.
Hi @Randy Holmes-Farley could you share why you'd go with selenomethionine over sodium selenite. It sounds easier to use the earlier that only has sodium and water. Is there any bioavailability difference?
Thanks
 

Randy Holmes-Farley

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It may not matter critically which form you use (or even if you dose at all), but this is among the most recent comments on selenium in the ocean in a scientific publication, and it suggests organic forms predominate.

"dissolved organic selenides (DOSe)"

"On a global scale, DOSe is the dominant Se species in tropical oceans, while Se(IV) and Se(VI) are major fractions in high-latitude oceans, resulting from changes in predominated phytoplankton and related biological assimilation."

 
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