Heavy Metal / Richard Harker and Randy Holmes- Farley articles in Advanced Aquarist

[wingd]

I just finished readiing Richard Harkers article on heavy metals in reef tanks and his conclusion that the research that has been done so far may not be adequate. My question stems from his indictment of inductively couple plasma (ICP) as a test for heavy metals in seawater. Didn't Randy Holmes-Farely use this same technique in his article on magnesium and strontium in limewater? If so how valid is his research?

I am just asking the question having read both articles. Did I misunderstand

[justgettinstarted]

i dont understand what you are asking...

How do they detect heavy metals in water? or why was that protocol not used?

[Randy Holmes-Farley]

Didn't Randy Holmes-Farely use this same technique in his article on magnesium and strontium in limewater? If so how valid is his research?

I didn't do a scan, which is the method that Richard points out in his article. I looked at each metal individually and manually. In my aluminum article I discuss how the results that I get by ICP may well be different than what other folks have gotten using ICP scans covering large numbers of ions.

http://www.advancedaquarist.com/issues/july2003/chem.htm

from it:

"In a recent survey of 23 reef aquaria, Shimek claimed that aluminum levels ranged from 0.070 to 0.32 ppm, with a mean of 0.173 ppm. That same study claimed that Instant Ocean Contained 0.110 ppm aluminum. Other than values reported later in this article, I am not aware of any other published values for aluminum in reef aquaria.

These values were all generated by ICP (Inductively Coupled Plasma) where the sample is injected into a plasma and the light emissions of the various ions are quantified at one or more specific wavelengths unique to each element. I am skeptical that all of the values in the survey above represent real measurements of aluminum rather than noise in the ICP since they are all right around the limit of quantitation for aluminum in seawater. While this issue may seem esoteric, it is important to know how much aluminum is typically present in aquaria...."



So I haven't measured many things. It is a slower and more tedious process to do it manually, but what I have investigated (copper and aluminum in tank water; magnesium and strontium in limewater, for example) you can be assured exactly what I found and can in some cases see the actual emission spectra (I look at every emission spectrum to see that it is a real peak and not noise, whereas in a scan I doubt anyone ever looks at any of them). You can also read details about the standards and wavelengths used, and also see a discussion of what the limits of quantitation are in relation to the numbers reported.

FWIW, ICP via emission detection is a great technique for strontium as it is VERY sensitive to it. It is a poor technique for many other ions, since the detection limits are quite high. ICP-MS has lower detection limits for many ions, but it is not a technique that I have available.

[wingd]

Thanks Randy for the explination. I do appreciate it. That makes sense. I had just read the articles and did not understand.

Dustin

[Randy Holmes-Farley]

That's a perfectly reasonable question to be asking. I too have concerns about broad use of ICPand ICP-MS to analyze samples. I recently reviewed a salt analysis article that showed every salt mix and NSW sample had greatly elevated levels of a particular ion. I suspect that was an artifact of the test, just as I expressed concern that aluminum might be an artifact in some studies (as discussed in the article linked above).

I'm not sure that I'd be quite as wholesale in my criticism as Richard is in that article, and it will be interesting to see where he goes with it in the second part. OTOH, Richard and Ron have been antagonizing each other for years, so it isn't surprising that it is still happening. :D

[Statman]

Originally posted by Randy Holmes-Farley
FWIW, ICP via emission detection is a great technique for strontium as it is VERY sensitive to it. It is a poor technique for many other ions, since the detection limits are quite high. ICP-MS has lower detection limits for many ions, but it is not a technique that I have available.

Randy, two questions: Which ions have "quite high" detection limits, and which ions can ICP-MS do much better measuring?

[Habib]

Where can I find the article by Richard Harker?

TIA :)

[andrejka]

Originally posted by Randy Holmes-Farley
I recently reviewed a salt analysis article that showed every salt mix and NSW...

I'm wondering what article it is? Is it published yet?

[andrejka]

Habib,

Richard Harker's article (http://www.advancedaquarist.com/issues/dec2003/feature.htm)

[Habib]

Originally posted by andrejka
Habib,

Richard Harker's article (http://www.advancedaquarist.com/issues/dec2003/feature.htm)


Andrejka, many thanks! :)


BTW is it you in the avatar? If so the left or right one? :)

[andrejka]

I'm on the left and my "babybrother" is on the right. He is much taller then me now :)

[Randy Holmes-Farley]

I'm wondering what article it is? Is it published yet?

Not that I've seen.

Randy, two questions: Which ions have "quite high" detection limits, and which ions can ICP-MS do much better measuring?

I'll have to check when back with my resources at work, but many transition metals (iron, copper, etc) are marginal by emission ICP, and probably are better by ICP-MS. The halogens (F, Cl, Br, I) are bad by emission ICP and better by ICP MS. The series Ca, Mg, Sr, Ba is very good by emission ICP.

Of course, all of these questions have to be asked relative to the amount present in seawater.