Correctness and repeatability of ICP-MS seawater measurements

[Rick Mathew]

Hello Rick,

almost. Its not a calibration standard, its a certified reference material (CRM). The CRM is provided from an outside source with clearly defined parameters of those trace elements. It is not used for calibration, but for internal quality control.

You can think of it as a sample that we are measuring every time we are turning on the ICP-MS to measure customer samples. The 18 points represent measured values of those elements at consecutive measurement-days from late May up until now (we are not measuring daily). I did not skip a single measurement-day.

I will get back to all other questions in this thread as soon as i am having a little more time. This one was quick to answer ;-)

All the best,
Christoph

Thank you Christopher for getting back so quickly. Would these be similar to the NIST traceable standards that are sold as either single element or multi-element standards?

So your procedure calls for you to measure the CRM so as to insure the instrument is measuring that same sample with the acceptable accuracy and precision for the selected elements and if it does not then you make the necessary adjustments (re-calibrate or something)...

 

[taricha]

Thanks for providing this data Christoph.

Its not a calibration standard, its a certified reference material (CRM). The CRM is provided from an outside source with clearly defined parameters of those trace elements. It is not used for calibration, but for internal quality control.

This is also a helpful clarification that you are using different materials for your calibration and this not circular re-measurement of the same material used to do the calibration.

This data is indeed the sort of performance that we hope for on the 10ppb and below trace elements when we send ICP samples out.

I want to point out one of the things I think is fascinating about how ICP works.
What looks at first glance like random variation is actually highly correlated behavior. Check this out.
This is the Nickel data and the Zinc data overlayed and scaled to show how variations in one clearly predict the variations on that day of the other element.

(Molybdenum was also well correlated to these two, but these two are so tight that the picture needs no statistics.)

Since certified reference materials are expensive, Christoph probably isn't opening a new one every day he does measurements, so this is not variation in the standard, but correlated variation in the daily ICP machine operation.

These sorts of tight cross-element correlations show up across lots of hobby data from ICP vendors - some that @Rick Mathew , @Dan_P and I have written about before. See this chart from when Fritz re-sent a single sample of their saltwater to 3 vendors 1 month apart [fritz pdf].

The variation in measurement of each major element was tightly correlated to how that ICP vendor thought all the other major elements changed too.

This is another way of saying that variation was not in the elements at all - just in how the machine was operating on a given day.

I'm painting with a broad brush here: In @Christoph data +-10 or 20% daily variation among single digit ppb trace elements is not just acceptable, it's quite desirable performance, and may (or may not) be better than what anyone else or any other method provides....
But in major seawater components, that sort of day to day variation in machine performance may underperform what hobby kits can do. Rick, Dan, and I have something in progress to say on this last point.

 

[Christoph]

Thank you Christopher for getting back so quickly. Would these be similar to the NIST traceable standards that are sold as either single element or multi-element standards?

So your procedure calls for you to measure the CRM so as to insure the instrument is measuring that same sample with the acceptable accuracy and precision for the selected elements and if it does not then you make the necessary adjustments (re-calibrate or something)...

Rick,
you can find more info on the CRM here:

xxIRMM - JRC Science Hub - European Commission

xx25850

crm.jrc.ec.europa.eu

And yes, im sure NIST is providing CRM material aswell

The CRM is measured after the calibration (which is done every measurement day - you can only operate ICPs in a freshly calibrated state). The CRM measurement is used to validate the calibration and ensure correct machine operation.

@taricha, interesting overlay! The main error in ICP comes from sample introduction, which is then affecting most/all analytes.

As you have already mentioned all data above is in the single digit ppb range or even in the sub 100 ng/l-range (cobalt, lead). The higher the concentration, the more signal you are having, the smaller also the error. Typical error for macroelements is this in the 2-3% range, if performed well. For us this is still too much - this is why we are measuring Na, K, Mg and Ca in addition with cation chromatography since several months, which is even more robust and brings error down to the 1% range. We are also having a control sample (SST, system suitability test) we are measuring there in every sequence. Will post that data graph when time permits...

All the best,
Christoph

 

[Reefahholic]

Good points. Let me add one

As @Rick Mathew has pointed out, you cannot describe a test as good or bad until you decide how much accuracy and precision you need to make good decisions. If you are happy with a test result that is ”not too low and not too high” you have a different criteria for accuracy and precision than if you need x.xx ppm to make a decision. This is called “fit for purpose”. The problem is if you are missing information about accuracy and precision. You cannot decide if the test is fit for purpose. Trust is not a valid criteria to make that call. Imagine if a hospital only trusted not proved that blood test results were correct.

What elements do you currently target in your reef and which test kits are you using to test and maintain your reef.

 

[Reefahholic]

But in major seawater components, that sort of day to day variation in machine performance may underperform what hobby kits can do.

Which hobby kits are you using for which elements.

The variation in measurement of each major element was tightly correlated to how that ICP vendor thought all the other major elements changed too.

Meaning the vendor changed the results?

 

[Rick Mathew]

What elements do you currently target in your reef and which test kits are you using to test and maintain your reef.

MEASURE THESE​	DOSE THESE
CALCIUM	YES
COPPER	NO
IODINE	YES
IRON	YES
MAGNESIUM	YES
PHOSPHOROUS	NO
POTASSIUM	YES
SILICA	NO

 

[Acros]

Honestly, these types of questions do need to be asked. Nothing wrong with transparency. I just hope the cost doesn’t increase, because I can barely afford it now. We should be skeptical, but I’ve honestly seen enough to have a high amount of trust with OCEAMO’s analyses.

Yes there will be some uncertainties, but even in our Certified labs here in the hospital nothing is perfect.

I will add that I do work for one of the most prestigious hospitals in the state. So this is not some little hole in the wall facility. We have ANCC Magnet recognition, and hold many other awards. We have been voted best hospital in the state of Texas for 11 years in a row, and we’re ranked one of the top 15 hospitals in the Nation. So you better believe our machines are calibrated constantly and consistently. However, at some point you still have to exercise a little faith. Nothing is ever perfect.

That is a damning statement about the functioning of that hospital. Do you work in the labs? Are you an MD at the said hospital? I am curious how you could confidently state that the hospital still has to exercise a little faith with their lab equipment. In a different thread, you also mentioned that the said hospital’s lab could produce different results for the same blood test, with the same sample.

 

[Jposch]

Can you also provide the accurate and precision data for your current hobby grade test kits since Hanna Checkers are awful. I may need to switch after combing through your data. Thx.

Salifert claims 50ppm with magnesium. You have to dig deep on thier website to see it. I do respect Hanna's transparency, but the marign of error with checkers is about on PAR for the average visual color chart test, IMO. I do use the ULR ppb phosphorous checker, but I use salifert reagents. I did a several tests of a sample, and it was much more consistent. Divide result by 3.12.
I also used api no3 reagents with the HR nitrate checker. Using a Vortex Mixer on the bottles reduces the error with that a bit. I know, API, but the hanna sachets were so inconsistent with nitrate especially.

 

[areefer01]

I will add that I do work for one of the most prestigious hospitals in the state. So this is not some little hole in the wall facility. We have ANCC Magnet recognition, and hold many other awards. We have been voted best hospital in the state of Texas for 11 years in a row, and we’re ranked one of the top 15 hospitals in the Nation. So you better believe our machines are calibrated constantly and consistently. However, at some point you still have to exercise a little faith. Nothing is ever perfect.

What is best? What is top? Definition please. Is it affordability? Is it education and technology? Is it peds? Is it adult? Is it patient satisfaction? What year? I was curious what one of the top 15 hospitals in the Nation would be and the first couple of results didn't list anything in Texas. Go figure. I was sure to find one in the almost 170 million search results. I did...

ICP data, test consistency, much like one talking about being ranked in the top 15 of the nations hospitals. /s

Newsweek doesn't list any hospital in the top 15 from Texas:

This one here we see Houston in the 16th position:

 

[jda]

Can I suggest that we just let Christoph respond to the questions in this thread and interact with the members? There are other threads for the fanboydom and also threads to come about the findings from the other ICP studies that are ongoing.

I would really like for the questions and interactions with Christoph not be impeded in any way. I am wary of most ICP tests, and for what I think are very good reasons... but if he can help with the concerns, or if this thread helps the tests get better, then I would really like to see the discussions happen.

 

[areefer01]

Can I suggest that we just let Christoph respond to the questions in this thread and interact with the members? There are other threads for the fanboydom and also threads to come about the findings from the other ICP studies that are ongoing.

I would really like for the questions and interactions with Christoph not be impeded in any way. I am wary of most ICP tests, and for what I think are very good reasons... but if he can help with the concerns, or if this thread helps the tests get better, then I would really like to see the discussions happen.

You are probably replying to me - fair point, noted. However my point sort of echo's yours. If you want a serious dialog then people asking questions or participating should provide their credentials. Just like Christoph did. Otherwise it will be opinions or antidotal or mind stories.

I know Christoph's back ground. I know RHF. Others or myself included not so much.

 

[jda]

Not replying to anybody specifically... yet. We all know how these can spiral, so just don't want this one to go that way.

I am OK with questions from anybody to Christoph - no need for credentials and the questions can stand for themselves. Don't need questions to Dan or Rick in this thread - that seems to be coming. There are other places to flame and/or fanboy too.

I am OK with letting questions stand on their merit without credentials just like I don't care of Oceamo has ISO certifications in order to save some money. Smart is as smart does, just as stupid is as stupid does.

It would be fine with me if people answering posted their credentials... but I guess that a pile of actual results would work too. I don't need any defenders... just answerers.

 

[taricha]

Which hobby kits are you using for which elements.

Titrations (Red Sea and Salifert) for major elements. Hanna or Red Sea for things close to Zero.

Meaning the vendor changed the results?

Meaning that day to day maintenance and recalibration changed the results.
Each vendor was compared to themselves on a repeat of the same stored water.
So if one vendor thinks all the major elements increased 5%, another thinks they all decreased 10% and a third that they all stayed pretty level - then the variation in how the vendor machines were operating on the different days was dominating over any actual change in the sample major elements themselves.
That doesn't make ICP useless or any other dismissive description, but it should temper hobbyist expectations.

 

[Reefahholic]

Titrations (Red Sea and Salifert) for major elements. Hanna or Red Sea for things close to Zero.


Meaning that day to day maintenance and recalibration changed the results.
Each vendor was compared to themselves on a repeat of the same stored water.
So if one vendor thinks all the major elements increased 5%, another thinks they all decreased 10% and a third that they all stayed pretty level - then the variation in how the vendor machines were operating on the different days was dominating over any actual change in the sample major elements themselves.
That doesn't make ICP useless or any other dismissive description, but it should temper hobbyist expectations.

Yes, it is very interesting. It’s hard for me to believe anything unless I know how the tests are performed, see changes in my own system, or see enough results to gain trust through repeatability. Just to understand more, how did you guys store the NSW during the 30 day period? Do you think there could have been more degradation or increased microbial activity going on since the duration was 3-4x longer than that of a normal sample. I don’t fear the OCEAMO’s results, because I’ve been using them, plus I know that Andre has sent 3 analysis (of same water more than one time) to “secretly” test OCEAMO’s tolerance and repeatability before we rode that train. From what I’ve seen I’ve been more impressed with them vs anybody else. Plus, I won’t even touch an OES anymore. It’s useless for my needs now, but it’s still good (for the price) for guys/gals that are just starting up a reef who aren’t yet looking for the precision on ultra trace, but need to correct the major elements. I can only speak for ATI, because I have the most experience with them. Anyway, beginners aren’t very good at nutrient management or dosing anything yet so the MS would be kinda a waste of time and money for them if they are unable to control basic parameters.

For you, Randy, and some of the other researchers I think if you’ll keep an open mind and send a few ICP-MS and look at what the actual tolerances are within each individual element I believe you’ll find it’s acceptable, and also valuable for your team. I hope that Randy can have more dialogue with Christoph (Chemist to Chemist). When I first heard that we can target those Metallic’s I thought there is no way, but I went from rock bottom (almost depleted) coming off ATI when the tank was taking off to slowly coming up on each subsequent analysis little by little only adding 1x the daily recommended dosage on each element that was low (pretty much all of them). My Strawberry shortcake was getting very pale near the front glass, and it was only because my “consumption” was “increasing” and those elements were becoming “less and less available.” I literally watched the color shift with my own eyes. It was a beautiful transformation merely from those 6-9 elements. I tell you guys the truth, because I want you to also see and experience the color differences that I have because it made me quite happy to see that. The corals have become much more healthy and I’m enjoying the tank more and more. The difficult part is that when you increase the elements the tank starts to grow and the consumption increases. Lol. So the last 5 ICP-MS I’ve been increasing by 1X on almost all 6-9 elements to keep them from becoming to low, but they will likely hit a saturation point soon.

I’m glad to see you guys asking difficult questions because they need to be asked for people to gain trust, and also understand how everything is being done. I think the best thing to do is to send some tests out and keep an open mind. You know as well as I do that we are significantly limited with home test kits. I don’t want anybody to shoot themselves in the foot due to standards that are unable to be met for anything. It’s not always about perfect results. We must also weigh out our current regimen. Are we checking for pollutants? This is extremely important and the cause of many tank crashes? Are we looking at our source water? What elements are we leaving depleted?

If there’s a major tolerance, but the element is unimportant then it doesn’t matter much. Let’s say you get a 10-15 ppm difference with Calcium. That’s a lot considering we should be able to see more accurate results with that element, but still it’s not enough to cause much problems. Or let’s say we see a 10%-15% tolerance with something like Iodine, it’s not enough to crash the tank. Going from 75 ug/L to 63.75 ug/L isn’t that significant for me. Or from 75-86.25. Of course I’d like it to be perfect, but I don’t think we’ll ever see perfection.

Nevertheless, I’m always watching and listening to every opinion. The essence of education is to consider all viewpoints and seek for the truth.

 

[Christoph]

Hello everyone,

jda is right, we should try to stay on topic here or it will be difficult to follow the thread. As mentioned before im usually on a small time budget, so i cannot answer all questions promtly- sorry for that. I will try answering the chronologically. Please let me know if i have missed anyone.

Since I think that probably every ICP company would espouse their impressive consistency, can you speak towards any outside testing that you have done to verify that your results are accurate? Also, how do you know when to replace wearable items? Do you have stock solutions, or something, that you use to know when items need replaced?

IMO, just by engaging in dialogue and not defensive and argumentative gibberish makes you more credible. I appreciate you answering questions.

In my initial posting i have presented "hard data" towards consistency and correctness of our results, even in the low ppb (and sub ppb) range. Validation/checking of methodologies and calibrations using CRMs is something very established in the analytical community.

Regarding outside testing we have participated in such "ring testing rounds" regarding freshwater analyses. Unfortunately regarding seawater testing such modes of quality control are not offered (at least i am not aware of a provider). However we do have a mode of outside quality control currently under development, and will update the community once i am having news on this. For me it would also be much easier to have a certificate to show to all skeptics ;-)

This is mostly off topic, but do you see anything in the future that can determine what forms some of the elements are in? As you know, some forms are helpful, some are not and some are super dangerous. I would pay more for this.

This goes a bit into detail. ICP is a destructive method. The sample enters the plasma, everything gets evaporated, dissociated, excitated and ionized. So if you want to know the chemical form a certain element is in, you need to seperate the different forms before ICP-MS. This is usually done by coupling ion chromatography or HPLC systems to the ICP-MS, using the ICP-MS as element-selective detector. Those combined techniques are abbreviated IC-ICP-MS or HPLC-ICP-MS.

This is called speciation analysis. Typical examples for speciation analyses are

Cr(III)/Cr(VI) - not relevant in the reef tank
Iodide/Iodate - not really relevant in the reef tank
Bromide/Bromate - only in certain cases relevant for the reef tank

We do have the technical capabilities and equipment to perform those speciation analyses. However those runs are far from standard procedure and take quite a lot of analysis time. Cost will be in the range of several hundred USD per speciated element. Also you need to know beforehand which chemical forms you are looking for.

What elements are you especially interested to get speciated? For which elements do you think speciation matters for the reef environment? Feel free to contact me when you are having specific tasks/questions where we could help with speciation.

Good post Christoph.

I have a quick question. What is preventing Oceamo from stating the accuracy and precision for each element in their ICP report?

Thank you Dan! Unfortunatel you will most likely not like my answer to your question:

Asking for accuracy and precision for every individual element in each individual run is very easy - but to deliver this data in a meaningful way is unfortunately almost impossible.

The CRM/QK data i provided in my first post give a good indication of accuracy and precision (accuracy: how close are we to the specified concentration, precision: how high is the variability between results).

I could now take this data and say (just as example) for arsenic we have a %RSD of 6,5% (calculated from the standard deveation and mean value of above 18 data points). This 6,5% RSD would however not be valid in general for arsenic. If the concentration of arsenic in the sample would be higher, the %RSD would be lower (better statistics) - if the arsenic concentration would be lower, it would be the other way round. Also factors such as salinity have an impact, if a sample would have very high salinity, %RSD would generally be higher.

To provide precision data for each individual analyses it would be rquired to run every sample several times to allow for statistics. This is however very time consuming, and would thus also increase cost very significantly. It is impossible to give data on accuracy for each individual result, because i do not know the actual ("true") concentration. - Accuracy can only be checked with CRMs or other control samples (data shown in my initial post).

Data that i can offer is the replicate %RSDs: In ICP measurements (OES and MS) we are not measuring a single data point, but 3-5 replicates within a short time span. This replicates also allow to calculate a %RSD and thus give a hint towards precision. However the only error range that arises from this data is machine error (sample uptake, plasma fluctuations,...), and does not show any potential error that is arising from sample preparation or calibration. The CRM data (initial posting) does indicate errors from the whole analysis procedure. If you are interested in specific replicate %RSDs for your oceamo measurement, just let me know - i can look them up. Having this data on every analysis report would imo be overwhelming and not very useful.

I hope now it makes more sense to use things such as CRMs with repeated testing to assure quality in general.

All the best, Christoph

 

[Christoph]

@Christoph this is awesome data to see. I can tell you take great care in what you do, and have confidence in your results. Thank you so much for providing this data!

I will definitely continue to use oceamo's ICP.

I was wondering if you might be able to do a couple things for us...

Could we see the test environment? It would be great to see that these tests are in fact being done in a lab.

I was also wondering if there are any elements that are more accurately tested on OES than MS tests?

Lastly, after using your test for the past seven months or so... I've seen my magnesium going all over the place. My trident (I hear you laughing!) is very stable, and I use it to adjust my magnesium. Is magnesium particularly inaccurate on ICP tests, or is my magnesium really that unstable (I have seen it anywhere from 1280-1450 on ICP, but keep it stable around 1350 on my trident)?

Time for another quick answer

Hello Hunter,

thank you!

to your questions:

1) sure. Find attached 3 pictures i just took quickly with my phone (dont mind the quality). Honestly, you could not just operate ICP-MS in a "garage" like setting, and produce good results. The surrounding is very important. For example we keep our lab at positive pressure of HEPA filtered air: Thus almost any dust is kept out of the lab environment. ICP-MS samples and standards are manipulated under a LFU (laminar flow unit), where it is possible to work almost particle free.

2) Yes, sulfur and phosphorus work better on OES compared to MS for various reasons. That is however not an issue in our case, since we measure sulfate on the ion chromatography (which is also representing the sulfur concentration), and phosphate using a photometric method on the stabilized sample.

3) We do measure magnesium on the cation IC, which gives very good day to day reproduceability and usually errors <1% (this is better compared to ICP measurements). Please PM me the analysis numbers you are referring to and i will have a look at the raw data.

all the best, Christoph

 

[taricha]

The thing is, ICP can be really bad. And in some conditions, it can be really good - or at least look really good.
The data provided by ICP vendors justifies both the harshest critics and the strongest proponents of ICP measurement.
So both skepticism like JDA's, mine, and others and confidence like Christoph's and many Reef Moonshiner users can both be justified - It simply depends on what data you have in hand. Let me illustrate:

I'll take two presentations of the data just from Sanjay's article to make this point.
If you sent duplicate measurements to Oceamo and Fauna Marin like Sanjay did, and you compared the results and got something like this....

(Elements sorted from low to high Oceamo values, FM (red) and Oceamo (black) results plotted on log scale)

You'd say "wow, ICP has really gotten its act together and even vendors with different methodologies are reporting really consistent values from hundreds of ppb all the way down to <1ppb. These guys must know what they are doing."

(Or the skeptic would say at least those two labs had a lot of technique in common - or maybe @Christoph is running some samples for FM in his spare time, lol.)

On the other hand, If you sent duplicate water samples to ICP-Analysis and Reef-Labs like Sanjay also did, you'd come to a very different conclusion...

(Elements sorted from low to high ICP-A values, Reef-Labs (purple) and ICP-A (blue) results plotted on the same log scale as previous graph.)

This shows two vendors that report almost every single element here twice as much or more different than the other on everything from 1ppb to 500ppb. You'd say "All this talk of fancy labs and Ph.D's is nonsense. These are dart throwers or random number generators."

(to be fair, we have no standards in this water - one of these might be exactly right, and one very wrong and we can't know who.)

This - in large part - is why hobby opinion varies so much on "how good ICP is" - because frankly, the data that people get varies so much. And not everybody that talks a good game provides even plausibly decent data.

So we have skeptics and believers, and data to back both.

 

[Dan_P]

The thing is, ICP can be really bad. And in some conditions, it can be really good - or at least look really good.
The data provided by ICP vendors justifies both the harshest critics and the strongest proponents of ICP measurement.
So both skepticism like JDA's, mine, and others and confidence like Christoph's and many Reef Moonshiner users can both be justified - It simply depends on what data you have in hand. Let me illustrate:

I'll take two presentations of the data just from Sanjay's article to make this point.
If you sent duplicate measurements to Oceamo and Fauna Marin like Sanjay did, and you compared the results and got something like this....

(Elements sorted from low to high Oceamo values, FM (red) and Oceamo (black) results plotted on log scale)

You'd say "wow, ICP has really gotten its act together and even vendors with different methodologies are reporting really consistent values from hundreds of ppb all the way down to <1ppb. These guys must know what they are doing."

(Or the skeptic would say at least those two labs had a lot of technique in common - or maybe @Christoph is running some samples for FM in his spare time, lol.)

On the other hand, If you sent duplicate water samples to ICP-Analysis and Reef-Labs like Sanjay also did, you'd come to a very different conclusion...

(Elements sorted from low to high ICP-A values, Reef-Labs (purple) and ICP-A (blue) results plotted on the same log scale as previous graph.)

This shows two vendors that report almost every single element here twice as much or more different than the other on everything from 1ppb to 500ppb. You'd say "All this talk of fancy labs and Ph.D's is nonsense. These are dart throwers or random number generators."

(to be fair, we have no standards in this water - one of these might be exactly right, and one very wrong and we can't know who.)

This - in large part - is why hobby opinion varies so much on "how good ICP is" - because frankly, the data that people get varies so much. And not everybody that talks a good game provides even plausibly decent data.

So we have skeptics and believers, and data to back both.

Here is another look at Sanjay’s data. Since this thread is Oceamo’s party, I divided Oceamo results by each of the other four vendor’s results for all the elements in common in their reports. That means there are four other ways to compare the data. A ratio of one is perfect agreement. Zero is ambiguous because it can mean zero or divide by zero in Excel. Here is the picture. Except for ICP-Analysis, the vendors hang together from sodium until lithium. Most data I have seen shows a similar trend. At or below 100 pbb, results seem to be less trustworthy (I don’t have much experience with ICP-MS to determine whether this trend holds). I have just looked at more recent data and it showed somewhat better vendor agreement but the same breakup in agreement below 100 ppb.

Skeptic or not, how do you decide on the amount of trace elements to dose or whether you have an elevated pollutant when the data can be rather uncertain? Maybe the answer is that it could be good enough for managing a home aquarium, or, how Triton replied when challenged about the accuracy of their data, “it is fit for purpose”

 

[areefer01]

The thing is, ICP can be really bad. And in some conditions, it can be really good - or at least look really good.
The data provided by ICP vendors justifies both the harshest critics and the strongest proponents of ICP measurement.
So both skepticism like JDA's, mine, and others and confidence like Christoph's and many Reef Moonshiner users can both be justified - It simply depends on what data you have in hand. Let me illustrate:

I'll take two presentations of the data just from Sanjay's article to make this point.
If you sent duplicate measurements to Oceamo and Fauna Marin like Sanjay did, and you compared the results and got something like this....

(Elements sorted from low to high Oceamo values, FM (red) and Oceamo (black) results plotted on log scale)

You'd say "wow, ICP has really gotten its act together and even vendors with different methodologies are reporting really consistent values from hundreds of ppb all the way down to <1ppb. These guys must know what they are doing."

(Or the skeptic would say at least those two labs had a lot of technique in common - or maybe @Christoph is running some samples for FM in his spare time, lol.)

On the other hand, If you sent duplicate water samples to ICP-Analysis and Reef-Labs like Sanjay also did, you'd come to a very different conclusion...

(Elements sorted from low to high ICP-A values, Reef-Labs (purple) and ICP-A (blue) results plotted on the same log scale as previous graph.)

This shows two vendors that report almost every single element here twice as much or more different than the other on everything from 1ppb to 500ppb. You'd say "All this talk of fancy labs and Ph.D's is nonsense. These are dart throwers or random number generators."

(to be fair, we have no standards in this water - one of these might be exactly right, and one very wrong and we can't know who.)

This - in large part - is why hobby opinion varies so much on "how good ICP is" - because frankly, the data that people get varies so much. And not everybody that talks a good game provides even plausibly decent data.

So we have skeptics and believers, and data to back both.

But Oceamo (ICP MS) and Fauna Marin (ICP OES) are different types of test, correct? And can they be overlaid / compared if so? I don't know thus asking. Not suggesting you do this but grouping Oceamo and ICP-Analysis and then Fauna Marin, Triton, and Reef Labs may show something different.

With regards to skeptics there isn't anything wrong with that.

 

[taricha]

But Oceamo (ICP MS) and Fauna Marin (ICP OES) are different types of test, correct? And can they be overlaid / compared if so? I don't know thus asking. Not suggesting you do this but grouping Oceamo and ICP-Analysis and then Fauna Marin, Triton, and Reef Labs may show something different.

You noticed that fun nugget. ICP-A and Oceamo both are doing icp-ms test, so you would expect those two would hang together tighter than any other pair of vendors. This turns out not to be the case. FM was actually closer to Oceamo across these 100 ppb range and below than ICP-A was.
What does that suggest? I'm not sure. Maybe other technical things matter more across these elements than just having an ICP-MS machine?