Accuracy of Phosphate ICP analysis

[Mortie31]

You and me both! Hanna was "only" 7.5x higher than Triton this time, instead of 20x. So I guess I'm headed in the right direction lol

If they follow the usual pattern when asked previously, they will blame user error and testing differences

 

[Rick Mathew]

Wow, thanks for that! With the 736, I log the raw P data vs. doing the calculation to convert to PO4. I think Triton just does the math to convert P to PO4 as well.

Converting your values to P, Hanna is within the +/- 5 PPB error and the ICP results except your last test - like you said, something looks really off on the Hanna with that one.

In my case, my last comparison tests (this week) had the Hanna 736 reporting P at 22ppb and Triton reporting it at 6.984. That's one set of samples from one tank. Same timeframe, other set of samples from the other tank, Hanna reported P at 16ppb and Triton came in at 4.563.

Samples were all mailed in the same USPS express mail envelope, so presumably they were subjected to the same environmental conditions along the way. Could something affect them in transit, like temp? That might not help with your results though, since your last Hanna is so much higher than all your others.

Here are my results against known solutions of PO4 (HACH) using HI-732---Converted to PO4 ...

Standard Trial 1 Trial 2 Trial 3

.03ppm .02 .025 .028------- Relative Accuracy 81%------Precision .024 ± .008

.06ppm .046 .052 .058--------Relative Accuracy 87%------Precision .052 ± .012

.1ppm .089 .092 .101--------Relative Accuracy 94%------Precision .094 ± .012


rick

 

[foxt]

Here are my results against known solutions of PO4 (HACH) using HI-732---Converted to PO4 ...

Standard Trial 1 Trial 2 Trial 3

.03ppm .02 .025 .028------- Relative Accuracy 81%------Precision .024 ± .008

.06ppm .046 .052 .058--------Relative Accuracy 87%------Precision .052 ± .012

.1ppm .089 .092 .101--------Relative Accuracy 94%------Precision .094 ± .012


rick

Thanks for posting.

I am still waiting on latest ICP results. Triton did reply to me - they don't know why my results vary so widely between Triton and Hanna. No known environmental factors can affect the sample in transit. Suggest that my Hanna 736 is off, try calibrating it.

In the latest round of ICP submissions, I took Hanna numbers as well as ELOS hi resolution numbers. They were in line with each other, as much as the Elos can be given the wide range of values in the color chart. We'll see what the ICP results are this time.

 

[Rick Mathew]

Thanks for posting.

I am still waiting on latest ICP results. Triton did reply to me - they don't know why my results vary so widely between Triton and Hanna. No known environmental factors can affect the sample in transit. Suggest that my Hanna 736 is off, try calibrating it.

In the latest round of ICP submissions, I took Hanna numbers as well as ELOS hi resolution numbers. They were in line with each other, as much as the Elos can be given the wide range of values in the color chart. We'll see what the ICP results are this time.

Will be very interested in the results...Do you have a HI-736 Certified Standard Kit?---- https://www.bulkreefsupply.com/hi736-11-phosphorus-standards.html To test to see if the Checker is reading correctly? I have been using these ever since I discovered a "bad" Phosphate checker...I have one for all of my Hanna Checkers and check them once a month or if I suspect a problem?

 

[taricha]

Here are my results against known solutions of PO4 (HACH) using HI-732---Converted to PO4 ...

Doesn't this all point to trusting the test kit we can measure immediately over the ICP that looks at a sample after days or weeks?
(With the context that we are looking at reactive PO4, that loves adsorbing to surfaces, and gets taken up biotically as well.)

 

[Rick Mathew]

Doesn't this all point to trusting the test kit we can measure immediately over the ICP that looks at a sample after days or weeks?
(With the context that we are looking at reactive PO4, that loves adsorbing to surfaces, and gets taken up biotically as well.)

I would say this points in that direction....

 

[cjpitt80]

Doesn't this all point to trusting the test kit we can measure immediately over the ICP that looks at a sample after days or weeks?
(With the context that we are looking at reactive PO4, that loves adsorbing to surfaces, and gets taken up biotically as well.)

I can't remember WHERE, but I BELIEVE Tim @ Triton has commented on this and there's no adsorption (or absorption, more specifically) by the plastic vials. Also, I've gotten Triton results in 7 days. I can confirm there's no decrease with the HANNA test. I have some Hach standards in polyethylene vials for months. They still measure within the meter's range of accuracy. Right now, it seems as though this is somewhat of a mystery and leaves some people (me) kinda in a bind. 0.012ppm vs 0.048ppm isn't such a big deal, but when my Hanna says I'm at 0.14 and Triton reads only 0.0068 that's kinda disconcerting. In one case I want to LOWER phosphate, in the other possibly DOSE it.

 

[taricha]

I can't remember WHERE, but I BELIEVE Tim @ Triton has commented on this and there's no adsorption (or absorption, more specifically) by the plastic vials. Also, I've gotten Triton results in 7 days. I can confirm there's no decrease with the HANNA test. I have some Hach standards in polyethylene vials for months. They still measure within the meter's range of accuracy. Right now, it seems as though this is somewhat of a mystery and leaves some people (me) kinda in a bind. 0.012ppm vs 0.048ppm isn't such a big deal, but when my Hanna says I'm at 0.14 and Triton reads only 0.0068 that's kinda disconcerting. In one case I want to LOWER phosphate, in the other possibly DOSE it.

Great info. No adsorption to plastic vials and long term stability of PO4 standards seems a blow against abiotic explanations. But it may still leaves us with the possibility of biological uptake?
A PO4 standard might be stable long term, but in live seawater, that same PO4 might be taken up by bacteria/etc in the intervening days.

 

[cjpitt80]

Great info. No adsorption to plastic vials and long term stability of PO4 standards seems a blow against abiotic explanations. But it may still leaves us with the possibility of biological uptake?
A PO4 standard might be stable long term, but in live seawater, that same PO4 might be taken up by bacteria/etc in the intervening days.

Excellent point, my friend. I will test and have an answer on Halloween!
An answer for HANNA that is. As much as I'd like to, I don't have the budget to run multiple Triton challenge samples at $50 a pop!

 

[foxt]

Well, my latest Triton test are in, and the results are similar - Hanna is higher by 2x-3x. Tim from Triton suggests that my Hanna is off, so I'm going to order the standards and see how the Hanna measures up on those.

FYI, Tim also confirmed that there is nothing environmental that could affect the P levels while in transit.

 

[cjpitt80]

If your results follow others, you'll be just as confused as me. My Hanna meter checks within range of my Hach NIST traceable standards. That's what's so confusing and frustrating. I test a NIST sample and the meter is right on so I trust it. Test my water and send out a sample exactly the same time and Hanna reads 7.5x-20x higher!! I guess we need to test Triton ICP results with a known standard. Anyone want to donate $50 to get this done?

Seriously though, I really hope we can somehow get to the bottom of this

Well, my latest Triton test are in, and the results are similar - Hanna is higher by 2x-3x. Tim from Triton suggests that my Hanna is off, so I'm going to order the standards and see how the Hanna measures up on those.

FYI, Tim also confirmed that there is nothing environmental that could affect the P levels while in transit.

 

[Rick Mathew]

If your results follow others, you'll be just as confused as me. My Hanna meter checks within range of my Hach NIST traceable standards. That's what's so confusing and frustrating. I test a NIST sample and the meter is right on so I trust it. Test my water and send out a sample exactly the same time and Hanna reads 7.5x-20x higher!! I guess we need to test Triton ICP results with a known standard. Anyone want to donate $50 to get this done?

Seriously though, I really hope we can somehow get to the bottom of this

Actually some one has already done what you suggested and sent TRITON known certified Sea Water Standard for analysis....actually 3 separate samples...It is an interesting read...It was done back in 2015 I think...here is a link

Skeptical Reefkeeping 12: Triton Lab ICP-OES Testing of a Certified Artificial Saltwater Standard

From ReefsMagazine By Rich Ross and Dr. Chris Maupin At MACNA 25 in Denver, the potential for the new ICP-OES aquarium water testing by Triton Lab in Germany made many saltwater hobbyists swoon. Th…

packedhead.net

 

[Lasse]

The Triton test count P atoms in the water samples - i trust the the result from Triton. In my last test - the result from TRITON was 10 time lower than Hannas result. (Hanna Low Phosphate) All my experiences had indicate low levels of nutrient but the Hanna have reported high. In my case - I trust the ICP test

Sincerely Lasse

 

[cjpitt80]

The Triton test count P atoms in the water samples - i trust the the result from Triton. In my last test - the result from TRITON was 10 time lower than Hannas result. (Hanna Low Phosphate) All my experiences had indicate low levels of nutrient but the Hanna have reported high. In my case - I trust the ICP test

Sincerely Lasse

This seems to jive with most results (certainly mine). I've been dosing NOPX the last month for nitrates. My last HANNA reading was 0.04ppm (lowest EVER). I'll be very interested in what Triton reads. Again, the last 2 ICP tests have reported about 20X and 7.5X LOWER than Hanna, so we'll see. Perhaps Lathanum has very long lasting effects?

 

[Lasse]

From a post in my build thread when I answer a question from @Mortie31

Yes they can but the Triton test will be closest to the true concentration IMO. This is two different way of analyze the content with different methods.

The Hanna use a colorimetric method based named Ascorbic acid method. Together with molybdate it will form a bluish tint whose intensity is proportional to the concentration of the orthophosphate ion. As all colorimetric methods there is some compounds/ions that can interfere with the phosphate in the sample and give a false reading. In this case Silicia and silicate is known substances that will give a to high readings. the reading is also affected bu the turbidity of the sample.

In my case - high silica will probably interfere .

The ICP method have lesser interference´s but organic particles will give a higher reading - all P is not PO4 - however it must be calibrated often.

The interference of other compounds will also be more likely at very low levels of PO4 and 0.1 ppm PO4 is low from a analysts point of view. None of the analyzes gives you the true concentration - they give you a picture of it. In a complex water such as salt water, the disturbance effect of other substances can be considerable - therefore - I trust the ICP test more.

But thank you for being stubborn in this case - you force me to go back to the literature and check which interference's that is most important in this case

I found one that probably can explain the differences. At least in my case - my Si concentration is over 0.250 ppm and will probably interfere with the Hanna checker

Sincerely Lasse

Sincerely Lasse

 

[Lasse]

From a post in my thread that indicate some interference problems with Hanna´s UL meters compared with the low phosphate meter HI-713

I did a test yesterday with two different HI-713, my HI-774 and two different waters (from coral system 1 at the Maritime Museum and my home tank)

One of the HI-713 have been used as a reference tool to at least 50 different TRITON ICP tests and have normally nail the figures. The other HI-713 is a rather new meter and the HI-774 is mine that give 0.1 ppm when TRITON ICP report lower than 0.02

With the water from coral system 1 I read (with my way of doing the tests) 0.02 ppm for the older HI-713, 0.04 from the new HI-713 and 0.1 pmm from my HI-774.

The water from my home aquarium reads 0.02, 0.03 and 0.08 with respective meter.

@Sallstrom - who have done the most comparisons with the old HI-713 and TRITON ICP testz - read 0 with the old HI-713 and 0.07 with mine HI-774

This indicate that my gut feelings (that I had a low nutrition problem in spite of the fact that my HI-774 meter show around 0.1 ppm PO4) probably are right. at least - I´m going to act like a read of 0.1 can mean 0 with my HI-774. I have contacted Hanna in order to get information if I have a interference from the high Si concentrations in both water (around 0.12 and 0.24 ppm)

Sincerely Lasse

Sincerely Lasse

 

[Mortie31]

I’ve just bought a brand new ULR phosphate meter tested at the same time as I sent a Triton test off on Monday I got a reading of 0.05ppm so let’s see what my triton comes back as...

 

[Lasse]

I do not say that my experiences is valid for every ULR meter and for every water - only that all things indicate that my UKR meter and my water (and my jobs water) not are in direct compatible mode

Sincerely Lasse

 

[Mortie31]

I’ve just bought a brand new ULR phosphate meter tested at the same time as I sent a Triton test off on Monday I got a reading of 0.05ppm so let’s see what my triton comes back as...

Well got my Triton results back earlier and there identical to my readings, I do like the fast turnaround we get in the UK, these were posted Monday lunch, results friday lunch... maybe new and clean vials and a new device is the key to accuracy...

 

[Lasse]

What is your silicia (Si) levels ?

Sincerely Lasse