Hanna Phosphate and Phosphorus checker accuracy?

[CMO]

So I've had the Hanna phosphate checker for a few months now which has always read zero. Not convinced with the accuracy I just got the Hanna ULR phosphorus checker to compare, but it again reads zero. My last Trition ICP test showed P at 24 ug/l and PO4 at .07 mg/l.

I have a good amount of algea growing on glass that needs cleaned every 2-3 days so I'm thinking the Trition results make more sense. Anyone have any faith in the Hanna checker reading?

 

[Dr. Reef]

Hanna claims 0.05 +- on accuracy so your 0 reading can be 0.05 Which is very close to trition result and then their testing would also have a window of accuracy.

 

[CMO]

If I understand correctly the ULR phosphorus checker should provide PO4 readings as low as .015 ppm (after converting the P reading to PO4 in ppm). Precision factor of 5 ppb phosphorus = 5*3.066/1000 = 0.01533 ppm phosphate?

 

[Dr. Reef]

Formula is correct though ULR goes as low as 0 or 0.01

 

[CMO]

Oh i see. So then even with the +-5 ppb precision range I should be getting a reading on the ULR checker with PO4 at .07 ppm per ICP.

 

[Dr. Reef]

No because you're reading on ulr even if it shows 0 could mean 0.05 keeping the accuracy in mind.

 

[CMO]

But the accuracy is 5 ppb phosphorus on the ULR checker. I have .07 ppm phosphate which = 22.8 ppb phosphorus (.07*1000/3.066). Or am i still missing something?

 

[Marc88]

I also have a Hanna phosphorous checker and was curious about this. My teats have been hovering around .01 and .02 ppm lately. I haven't sent a water sample to Triton for testing yet, but will be soon. I remember reading a thread similar to this a few months ago where someone had the exact same problem and was questing the exact same thing. The question was posed weather or not phosphate was being leached by the plastic Triton container during shipping. I don't know if there was ever a resolution to the question but a few members went round and round about it. There are multiple people who have had similar results in the variance between Triton tests and Hanna results. I don't quiet remember if I found the thread on this forum or anther.

 

[Marc88]

Here is the link for the thread I was talking about. ( https://www.reef2reef.com/threads/accuracy-of-phosphate-icp-analysis.381738/ )

I have faith in my Hanna checker reading. I follow a procedure with each of my phosphate tests even using different reagent batches, I get similar results. I think the key is to dissolve the reagent completely for two minutes before placing the cuvette in the checker for the C2 function. I spin the cuvette several times to dissipate the micro bubbles from the cuvette walls. Then I wipe down the outside of the cuvette with a micro fiber cloth before placing it in the checker for the test.

 

[Tony Thompson]

Hi @Chadmowens , I use the ULR Phosphorus and Alk Hanna handhelds. I have a reference solution kit for both. They cost about £16 each in the UK should be cheaper in the states.

I find reference solutions invaluable in giving one confidence in ones readings. I regularly rely on my reference solutions from Accurasea, ATI Referren and Fauna Marin Reference solutions. Here is a picture of my Phosphorus reference kit. As you can see the sample is certified at 0.1ppm +/- 0.01 ppm .

 

[Randy Holmes-Farley]

I don’t know if the Hanna’s you are using are giving accurate values, but I will note the discrepancy with Triton is not proof of an issue for many reasons, including they measure different things.

 

[CMO]

Thank you @Marc88 and @Tony Thompson. Good info.

I don’t know if the Hanna’s you are using are giving accurate values, but I will note the discrepancy with Triton is not proof of an issue for many reasons, including they measure different things.

So what exactly is the difference in what the two test types measure? Since I'm getting a good amount of algae on my glass every few days I have a hard time believing my phosphates are really zero. Is there another potential cause of the powdery algae on glass like this with phosphates at zero?

 

[Randy Holmes-Farley]

Thank you @Marc88 and @Tony Thompson. Good info.

So what exactly is the difference in what the two test types measure? Since I'm getting a good amount of algae on my glass every few days I have a hard time believing my phosphates are really zero. Is there another potential cause of the powdery algae on glass like this with phosphates at zero?

The Hanna kit tests for inorganic phosphate only. Mostly H2PO4-, HPO4--,and PO4---, in our case.

Triton will detect anything with a P atom in it, which in our case is mostly going to be organic matter (proteins, DNA, RNA, phospholipids, whole bacteria, detritus chunks, etc.).

I don't know if that explains the difference you see, but it just points out that the values may not always match.

 

[Randy Holmes-Farley]

Is there another potential cause of the powdery algae on glass like this with phosphates at zero?

The cause is always "enough of lots of different things", including a source of phosphate. It is never caused by one thing. Can there be enough phosphate available when Hanna reads zero? Possibly.

 

[cracker]

There is a BRS video where they compare 2 Po4 kits. 2being the ULR& regular Po4 checker. check this out

 

[CMO]

@cracker great video. Thanks for sharing. That gives me a lot more confidence in the readings.

 

[Christoph]

Hi All,

in our ICP/OES-analyses we always encounter some phosphorus (usually at least 10 ppb P corresponding to 0.03 ppm phosphate) in reef tank samples. When we measure the amount of reactive (and bioavailable) orthophosphate by a sensitive photometric method, we often find phosphate undetectable, even in tanks that have a significant phosphorus signal in ICP.

The discrepancy between ICP and photometry is very small for high values of phosphorus, but is huge for low level measurements. The reason is that organophosphates and/or polyphosphates are almost always present in tank water. These forms of phosphorus are not readily available for metabolism, thus enabling phosphate deficiency, even when ICP-OES suggests a decent phosphate value.

For this reason we decided to always perform photometric phosphate detection on reef tank samples in addition to ICP.

Best,
Christoph

 

[CMO]

@Christoph thanks for sharing! That is very helpful.

 

[Randy Holmes-Farley]

in our ICP/OES-analyses we always encounter some phosphorus (usually at least 10 ppb P corresponding to 0.03 ppm phosphate) in reef tank samples. When we measure the amount of reactive (and bioavailable) orthophosphate by a sensitive photometric method, we often find phosphate undetectable, even in tanks that have a significant phosphorus signal in ICP.

Thanks for the info.

 

[Marc88]

Very good info. I'm sure many appreciate the insight. Solves that debate