Accuracy of Phosphate ICP analysis

madweazl · Apr 18, 2018

I've had three Triton samples done and all three were considerably lower than my Hanna ULR. With that said, I've had three or four Hanna reagent refills and there hasn't been any issues batch to batch for me. Regardless of delta between Triton and Hanna, nothing has ever shown a difference in appearance (the middle result was very brief and I dont recall why it was higher than it normal is).

Triton/Hanna
0/.049
.048/.15
.010/.058

BigJohnny · Apr 18, 2018

madweazl said:
I've had three Triton samples done and all three were considerably lower than my Hanna ULR. With that said, I've had three or four Hanna reagent refills and there hasn't been any issues batch to batch for me. Regardless of delta between Triton and Hanna, nothing has ever shown a difference in appearance (the middle result was very brief and I dont recall why it was higher than it normal is).

Triton/Hanna
0/.049
.048/.15
.010/.058

Wow so for you Hanna is 3x-6x higher. Based on the fact that ICP should pick up more, all other things being equal and both tests being formed correctly, it is very likely that something is occurring in transit OR hannas just read high for some reason, but I'm not sure why that would be the case. I like @Hans-Werner post that the plastic may be absorbing some phosphate. I wish I had an ICP machine so I could do the two simultaneously without having the sample stored in the vial for 2 weeks +. Anyone have 40k+ they want to donate to the cause.........?

Mortie31 · Apr 18, 2018

It seems in the US you have far longer transit times than I do in the UK, I take my samples on a Sunday or Monday, post them on the Monday and they will be in Germany on the thur/fri and I usually get my results on the mon/tues, so 7-8 days max

BigJohnny · Apr 18, 2018

Mortie31 said:
It seems in the US you have far longer transit times than I do in the UK, I take my samples on a Sunday or Monday, post them on the Monday and they will be in Germany on the thur/fri and I usually get my results on the mon/tues, so 7-8 days max

Yes ours have to ship to California, US then again to Germany. Usually 2 weeks once mailed.

chicago · Apr 18, 2018

doesnt hana have like a .05 error range?

BigJohnny · Apr 18, 2018

not .05, 5ppb or 5%.

So not enough to explain a double reading

rkpetersen · Apr 18, 2018

It is just a guess, but I suspect that many people get high readings on the Hanna phosphate checker because of incomplete dissolution of the powder. It really does take a good 90+ seconds of constantly inverting the cuvette to complete dissolve the powder. Before that, small particles persist, which you can only see against a bright backlight. The persistence of small undissolved particles could possibly result in falsely elevated values.

BigJohnny · Apr 18, 2018

rkpetersen said:
It is just a guess, but I suspect that many people get high readings on the Hanna phosphate checker because of incomplete dissolution of the powder. It really does take a good 90+ seconds of constantly inverting the cuvette to complete dissolve the powder. Before that, small particles persist, which you can only see against a bright backlight. The persistence of small undissolved particles could possibly result in falsely elevated values.

Definitely not what is happening in my situation, unless it is physically impossible to dissolve the powder before the timer runs out. I perform every part of the test besides the mixing like a nascar pit stop, as fast as humanly possible. I pre cut the satchel etc, I mix it for as long as i possibly can before the timer expires. Also, you may be having a much harder time if all you are doing is inverting the cuvette. You can shake it gently.

Mortie31 · Apr 19, 2018

I’m also assuming you all use a syringe to measure the 10ml, the 10ml line on the hanna vial is way out.

ReefBum · Apr 19, 2018

I too have had much lower phosphate readings via ICP tests versus the Hanna ULR Phosphorous Checker. My corals did exhibit definitive signs of stress when phosphate levels were very low according to the ICP tests and have now recovered after I elevated levels via phosphate dosing, taking my skimmer offline and adjusting the light cycle of my algae reactor.

Rick Mathew · Apr 19, 2018

I was able to improve my repeatability or the Haana Test by rinsing the vial 3 times with the Hanna DI water. Before performing the test I rinse the vile with the sample to be tested dump it out then refill for the test. My Hanna test compares very well with my Triton results

BigJohnny · Apr 19, 2018

ReefBum said:
I too have had much lower phosphate readings via ICP tests versus the Hanna ULR Phosphorous Checker. My corals did exhibit definitive signs of stress when phosphate levels were very low according to the ICP tests and have now recovered after I elevated levels via phosphate dosing, taking my skimmer offline and adjusting the light cycle of my algae reactor.

So when your corals exhibited stress the icp was low but was the Hanna low enough to cause stress typically? Any idea what the measurements of the two were? Thanks for posting.

rkpetersen · Apr 19, 2018

BigJohnny said:
Definitely not what is happening in my situation, unless it is physically impossible to dissolve the powder before the timer runs out. I perform every part of the test besides the mixing like a nascar pit stop, as fast as humanly possible. I pre cut the satchel etc, I mix it for as long as i possibly can before the timer expires. Also, you may be having a much harder time if all you are doing is inverting the cuvette. You can shake it gently.

Ok. Just trying to help figure out where the problem is. Because it seems like you and others are saying that the Hanna ULR phosphate checker is inherently inaccurate. This is just not the case. The value and accuracy of this unit has been confirmed by many hobbyists, especially in the low range, and is probably the best hobbyist phosphate test out there. Red Sea has been mentioned here as an alternative - Their phosphate test is a pain to perform and completely inaccurate in the low range. Salifert has also been mentioned - All of their color-matching tests are poor due to their awful choice of cuvettes and mediocre color-matching technique. Neither is as good as the Hanna checker.

If you're getting bad results with your Hanna checker, I suspect that your particular unit is defective, you got a hold of a bad reagent batch, or your technique is flawed in some way that hasn't been identified.

BigJohnny · Apr 19, 2018

rkpetersen said:
Ok. Just trying to help figure out where the problem is. Because it seems like you and others are saying that the Hanna ULR phosphate checker is inherently inaccurate. This is just not the case. The value and accuracy of this unit has been confirmed by many hobbyists, especially in the low range, and is probably the best hobbyist phosphate test out there.

I know you were trying to help, I was just explaining that was not the issue. I never said that it is inherently innaccurate, i said that it is always atleast 2x more than ICP test, which should be more accurate because it uses a $40,000+ sophisticated machine. I dont know that though, and thats why i created the thread. However, I am of the belief that something is happening in transit which is changing the concentration and explains the variation, which i stated clearly.

As far as the value (not relevant) and accuracy being confirmed by many hobbyists, I haven't seen anyone confirm the accuracy with standard solutions or anything like that. Even so, thats only one persons checker and the reagents they happen to have. maybe you are confusing consistency for accuracy. My hanna alk checker consistently measures very well, but is always .9 dKH higher than actual, confirmed a standard solution which measured correctly with salifert and my alkatronic alkalinity monitor. Also accuracy is a value representing the standard deviation from the actual result. The accuracy of something can be poor, so to say the accuracy has been confirmed means nothing, unless you are referring to the +/- 5ppb or +/- 5% stated by Hanna. I would also say that they have had many problems with reagents and inconsistency between tests so im not sure why you think its so accurate, as that is part of its accuracy.

rkpetersen said:
Red Sea has been mentioned here as an alternative - Their phosphate test is a pain to perform and completely inaccurate in the low range. Salifert has also been mentioned - All of their color-matching tests are poor due to their awful choice of cuvettes and mediocre color-matching technique. Neither is as good as the Hanna checker.

the only person that mentioned salifert was me and it was for the alkalinity test, not the phosphate test. It is a titration not a color matching. I dont like red sea tests either. The other one mentioned was the elos high res which based on my research is considered a very good test, but i have never used it.

rkpetersen said:
If you're getting bad results with your Hanna checker, I suspect that your particular unit is defective, you got a hold of a bad reagent batch, or your technique is flawed in some way that hasn't been identified.

I dont know if the results are bad, just different than ICP. That is the point of this thread, to try and determine which is more accurate and if anything in shipping could effect the results and by how much.

shred5 · Apr 19, 2018

There is a video on YouTube where a guy sent three different icp test from different companies. Results are interesting:

ReefBum · Apr 19, 2018

Here is a link to an article that explains more of what I observed.

https://reefbum.com/instructional/analysis-of-a-tank-crash/

BigJohnny said:
So when your corals exhibited stress the icp was low but was the Hanna low enough to cause stress typically? Any idea what the measurements of the two were? Thanks for posting.

sghera64 · Apr 19, 2018

BRS did a nice study on the Hanna ULR and Hanna phosphate Checkers.

https://www.bulkreefsupply.com/video/view/brstv-investigates-phosphate-or-phosphorus-which-is-best/

Save time and jump to 8:35 in the video. Seems like their ULR did quite well in terms of accuracy against a known standard in the range of 2PPB to 30PPB (0.002 - 0.030 ppm) PO4.

BigJohnny · Apr 19, 2018

sghera64 said:
BRS did a nice study on the Hanna ULR and Hanna phosphate Checkers.

https://www.bulkreefsupply.com/video/view/brstv-investigates-phosphate-or-phosphorus-which-is-best/

Save time and jump to 8:35 in the video. Seems like their ULR did quite well in terms of accuracy against a known standard in the range of 2PPB to 30PPB (0.002 - 0.030 ppm) PO4.

But did they test with all the bad reagent batches that have circulated lol......

I think the Hanna can be accurate for sure but icp should be more accurate. It's just odd that people are getting 2x-5x higher Hanna results. It must be occurring in transit since several people experience this, or there is something else we haven't thought of.

I guess I should just make myself a phosphate standard solution and check my hanna. I have some sodium phosphate, dibasic, anhydrous aka Na2HPO4.

@Randy Holmes-Farley

Most recent triton test said about .1ppm phosphate. How would I make a .1ppm phosphate standard solution? I have a gram scale that measures out to mg.

Would it matter that the checker is for saltwater but the solution would likely use rodi?

At least trying this will verify if my hanna/reagents are accurate before I look into why triton might be different.

BigJohnny · Apr 19, 2018

ReefBum said:
Here is a link to an article that explains more of what I observed.

https://reefbum.com/instructional/analysis-of-a-tank-crash/

This didn't say anything about what your hanna results said at the time though, just that your triton phosphate levels went down. Do you remember how much higher it was?

ReefBum · Apr 20, 2018

BigJohnny said:
This didn't say anything about what your hanna results said at the time though, just that your triton phosphate levels went down. Do you remember how much higher it was?

I would have to look back at my written records.....out of town right now.