Comparing ICP Results & Accuracy

[clifg]

It seems like this thread has run its course but I did say I would post the @AquaBiomics results when I got them in, so here we go! I mostly did it just for the fun and curiosity of knowing what's in my tank. I can say the company has great customer service & I got a personal e-mail with suggestions after I received the results. I'm not having any issues with my tank and so my recommendations reflect that. Obviously then, if you are having issues this would be a lot more beneficial than "just because." That being said, even without any issues I didn't feel pressured at all from this company to add anything more to purchases, which is a nice little bonus in this day and age. I found the eDNA fascinating and quite accurate. I'll probably do one of these every year or so as I add organisms and my tank changes and matures just to see!

Here are the results, keep in mind I started with half live rock half dead, I do not QT or dip.

 

[DeputyDog95]

For grins, I recently collected samples at the same time and sent them to two different ICP's to see how the results would marry up.

There seem to be some reasonably significant variances between the two. Not being critical of either company, but there are clearly differences in equipment, operators, and testing procedures. I had hoped they would be close to identical, but that wasn't the case.

It's hard to use these tests to shape your dosing and maintenance if you can't tell what is truly accurate and what isn't.

 

[DeputyDog95]

For grins, I recently collected samples at the same time and sent them to two different ICP's to see how the results would marry up.

There seem to be some reasonably significant variances between the two. Not being critical of either company, but there are clearly differences in equipment, operators, and testing procedures. I had hoped they would be close to identical, but that wasn't the case.

It's hard to use these tests to shape your dosing and maintenance if you can't tell what is truly accurate and what isn't.

I timed out on being able to edit my post.

But for what it's worth... I've used the top one many many times and it seems to align more with the things I can personally test.

 

[Rick Mathew]

For grins, I recently collected samples at the same time and sent them to two different ICP's to see how the results would marry up.

There seem to be some reasonably significant variances between the two. Not being critical of either company, but there are clearly differences in equipment, operators, and testing procedures. I had hoped they would be close to identical, but that wasn't the case.

It's hard to use these tests to shape your dosing and maintenance if you can't tell what is truly accurate and what isn't.

You are correct. Knowing what is a "Real" value and what is a reported value is difficult...Here is some work @taricha , @Dan_P and I did to look at this very question

How We Use ICP-OES Results Of Unknown Accuracy And Precision

A quantitative Method of Evaluating ICP-OES Results

www.reef2reef.com

 

[DeputyDog95]

You are correct. Knowing what is a "Real" value and what is a reported value is difficult...Here is some work @taricha , @Dan_P and I did to look at this very question

How We Use ICP-OES Results Of Unknown Accuracy And Precision

A quantitative Method of Evaluating ICP-OES Results

www.reef2reef.com

Interesting stuff. It's a lot to digest, but at a glance... Is it safe to say ICP-A didn't fare as well as the others?

 

[taricha]

Interesting stuff. It's a lot to digest, but at a glance... Is it safe to say ICP-A didn't fare as well as the others?

yeah. The point was to attempt to assess ICP overall as a protocol, individual vendors wasn't the main goal.
But it was clear that within vendors, ICP-A underperformed the others in multiple ways. The other three (Triton, FM, ATI) were similar enough that more data on different days might have flip-flop who looked the best.

 

[DeputyDog95]

Interesting...

One of the results I posted was from ICP-A and was wildly different from the other vendor I normally use (Reef Labs).

I found it odd that one would say I'm deficient in an element and the other would say I'm high. Very confusing... Reef labs is local to me and I know the owner personally. Great guy, big brain, and takes this very seriously, maintaining and operating his equipment to high standards from what i can tell.

As far as Phosphate and Salinity...

How accurate do you think ICP is for those since they're calculated values?

My Reef Labs ICP usually says I"m 33.8 ish, but yet my Milwaukee and refractometer (calibrated using BRS solution) say I'm 35ppt.

Also, my last Phosphate calculated reading from Reef Labs was .080ppm and my most recent was .151, which is really high. They were only done about two weeks apart and my routine has been the same.

I test my tank weekly using my ultra low range phosphorous Hanna checker and it always comes in at around .04 and .05ppm, and I also tested with a salifert phosphorous test which read the same.

I'm hardly a chemist and I know there are different forms of phosphate, but how much faith should I put in calculated phosphate and salinity with an ICP?

 

[Rick Mathew]

Interesting...

One of the results I posted was from ICP-A and was wildly different from the other vendor I normally use (Reef Labs).

I found it odd that one would say I'm deficient in an element and the other would say I'm high. Very confusing... Reef labs is local to me and I know the owner personally. Great guy, big brain, and takes this very seriously, maintaining and operating his equipment to high standards from what i can tell.

As far as Phosphate and Salinity...

How accurate do you think ICP is for those since they're calculated values?

My Reef Labs ICP usually says I"m 33.8 ish, but yet my Milwaukee and refractometer (calibrated using BRS solution) say I'm 35ppt.

Also, my last Phosphate calculated reading from Reef Labs was .080ppm and my most recent was .151, which is really high. They were only done about two weeks apart and my routine has been the same.

I test my tank weekly using my ultra low range phosphorous Hanna checker and it always comes in at around .04 and .05ppm, and I also tested with a salifert phosphorous test which read the same.

I'm hardly a chemist and I know there are different forms of phosphate, but how much faith should I put in calculated phosphate and salinity with an ICP?

Yes for sure it is confusing...I can not speak directly to the salinity measurement because I actually pay very little attention to there measurements for salinity...I do know that the method used to do the measurement makes a difference...Here is a great read by Randy if you have not already read it ....https://reefkeeping.com/issues/2004-06/rhf/index.php

Phosphorous/Phosphate on the other hand I have some experience with. To comment on the absolute accuracy of any ICP test (or any test for that matter), one needs a point of reference related to the measurement. This is usually provided by the person providing the measurement and it takes the form of a stated expected error...+ - some value related to the error that might be expected in the measured value. (If you look at the end of f the article these are some references to this issue)...The ICP vendors we used in putting together this study did not provide this information. The only thing we could compare their results to were our measurements, other ICP vendor's measurements and the repeat measurements of the same sample. Therefore we can not make any definitive statement. What we can say is covered under INTRODUCTION AND ABCKGROUND section of the article under the question 4) What can we say about accuracy.

All that being said...based on the results of the study the measurement of phosphorous is problematic on a least a couple of levels. First phosphorous is subject to variability due to storage time (see here https://www.reef2reef.com/ams/sample-storage-and-its-impact-on-measurement-results-part-3.800/)
Second as the article shows the repeatability of a measurement by any of the vendors in measuring P is not great. If they are unable to measure the same sample and get results within reasonable limits I would guess the chances of getting an accurate reading with one sample measurement is pretty low. This is why at least for now I use my measurements using the Hanna Checker as my guide to the Phosphate level in my tank

Not sure this helps much

Rick

 

[Randy Holmes-Farley]

The validity of the salinity boils down to their accuracy in the major ions (sodium, chloride, magnesium, sulfate, calcium, potassium) or some subset of them if they do not measure all of them (which makes it less accurate).

.

 

[DeputyDog95]

The validity of the salinity boils down to their accuracy in the major ions (sodium, chloride, magnesium, sulfate, calcium, potassium) or some subset of them if they do not measure all of them (which makes it less accurate).

.

Makes sense. They measure all of those things, yet it still doesn't align with my equipment. Is what it is.... I suppose as long as it's not too far off and you keep it consistent, that's probably more important.

 

[DeputyDog95]

Yes for sure it is confusing...I can not speak directly to the salinity measurement because I actually pay very little attention to there measurements for salinity...I do know that the method used to do the measurement makes a difference...Here is a great read by Randy if you have not already read it ....https://reefkeeping.com/issues/2004-06/rhf/index.php

Phosphorous/Phosphate on the other hand I have some experience with. To comment on the absolute accuracy of any ICP test (or any test for that matter), one needs a point of reference related to the measurement. This is usually provided by the person providing the measurement and it takes the form of a stated expected error...+ - some value related to the error that might be expected in the measured value. (If you look at the end of f the article these are some references to this issue)...The ICP vendors we used in putting together this study did not provide this information. The only thing we could compare their results to were our measurements, other ICP vendor's measurements and the repeat measurements of the same sample. Therefore we can not make any definitive statement. What we can say is covered under INTRODUCTION AND ABCKGROUND section of the article under the question 4) What can we say about accuracy.

All that being said...based on the results of the study the measurement of phosphorous is problematic on a least a couple of levels. First phosphorous is subject to variability due to storage time (see here https://www.reef2reef.com/ams/sample-storage-and-its-impact-on-measurement-results-part-3.800/)
Second as the article shows the repeatability of a measurement by any of the vendors in measuring P is not great. If they are unable to measure the same sample and get results within reasonable limits I would guess the chances of getting an accurate reading with one sample measurement is pretty low. This is why at least for now I use my measurements using the Hanna Checker as my guide to the Phosphate level in my tank

Not sure this helps much

Rick

It helps, sort of LoL

Since I can't ICP on a weekly basis, I'm going to just keep working off my Hanna ULR phosphorous checker and hope for the best.

I would think if my P04 was really .151, the tank would be overrun with algae. Or maybe not. Who knows... I feel like I've gone down a rabbit hole with the ICP testing and I'm really starting to overthink this.

 

[rtparty]

It helps, sort of LoL

Since I can't ICP on a weekly basis, I'm going to just keep working off my Hanna ULR phosphorous checker and hope for the best.

I would think if my P04 was really .151, the tank would be overrun with algae. Or maybe not. Who knows... I feel like I've gone down a rabbit hole with the ICP testing and I'm really starting to overthink this.

You can 100% throw out the ICP Analysis results. It's been shown time and time again they are the worst of the bunch

 

[Rick Mathew]

It helps, sort of LoL

Since I can't ICP on a weekly basis, I'm going to just keep working off my Hanna ULR phosphorous checker and hope for the best.

I would think if my P04 was really .151, the tank would be overrun with algae. Or maybe not. Who knows... I feel like I've gone down a rabbit hole with the ICP testing and I'm really starting to overthink this.

If the tank is looking good and the livestock is happy...The "numbers" are only data...I have seen some absolutely beautiful tanks with PO4 >1.0...So I would not worry about it...