Irregular Phosphate readings

[Ziggy17]

@randyholmes-farley

Hello Sir.

Any chance I can have a quick chat offline. Having some issues that I think you specifically can assist with.

If not, I’ll post the question here and open up the floor.

Cheers.

Zig.

 

[Dan_P]

@randyholmes-farley

Hello Sir.

Any chance I can have a quick chat offline. Having some issues that I think you specifically can assist with.

If not, I’ll post the question here and open up the floor.

Cheers.

Zig.

Randy typically requests discussions be public.

 

[Randy Holmes-Farley Verified Community Expert]

Yes, public is better for most topics so others can benefit from the discussion.

 

[Ziggy17]

Yes, public is better for most topics so others can benefit from the discussion.

Fair enough.

Is there anything in the tank aside from actual phosphate that could cause a reaction with the Hanna reagent causing the blue colour and a false high reading?

 

[Randy Holmes-Farley Verified Community Expert]

Fair enough.

Is there anything in the tank aside from actual phosphate that could cause a reaction with the Hanna reagent causing the blue colour and a false high reading?

There’s a small silicate impact.

 

[Lasse]

Fair enough.

Is there anything in the tank aside from actual phosphate that could cause a reaction with the Hanna reagent causing the blue colour and a false high reading?

I have wondered about this myself after completely inexplicable measurements. I have the impression that I will get better and more reliable results if I filter the sample water through a 0.22 µm syringe filter before testing.

Sincerely Lasse

 

[Ziggy17]

Could free flowing dinoflagellates that get captured in a water sample cause the Hanna reagent to react and create a false high reading? If it was shaken vigorously with the reagent in the cuvette?

 

[Ziggy17]

I have wondered about this myself after completely inexplicable measurements. I have the impression that I will get better and more reliable results if I filter the sample water through a 0.22 µm syringe filter before testing.

Sincerely Lasse

This was something that came up with another member regarding the issue. Based on my scenario, I’m not sure this could have been the culprit, but certainly not ruling it out.

 

[Lasse]

Could free flowing dinoflagellates that get captured in a water sample cause the Hanna reagent to react and create a false high reading? If it was shaken vigorously with the reagent in the cuvette?

IMO yes - the test use strong acid as I know it. Organic matter can be dissolved and release PO4 to the sample

Sincerely Lasse

 

[Randy Holmes-Farley Verified Community Expert]

I’m skeptical that microorganisms will release much in this context, but filtering the sample once as a test might clarify the question. If you have done an icp with a company that provides a syringe filter, you could reuse that.

 

[Ziggy17]

I’m skeptical that microorganisms will release much in this context, but filtering the sample once as a test might clarify the question. If you have done an icp with a company that provides a syringe filter, you could reuse that.

Something in the water caused a reaction with the reagent that couldn’t possibly be the phosphate. After a week of PO4 in the .1 range, yesterday morning In a 20 minute span with 3 tests, the readings went from 2.34, 1.6, .8 and an hour later to .12. It wasn’t a reading error as the blue colour of the sample clearly correlated to the reading. Dark blue on that first test, slightly lighter blue on the second, until the normal slight blue tint on the last one. So I can’t I fathom it was reading actual phosphate in the water.

I currently have dinos, hence my question about the possibility.

 

[Randy Holmes-Farley Verified Community Expert]

I would not be certain it is a water as opposed to a testing issue, but some folks have reported significant changes through a day which might possibly be real.

 

[Dan_P]

Something in the water caused a reaction with the reagent that couldn’t possibly be the phosphate. After a week of PO4 in the .1 range, yesterday morning In a 20 minute span with 3 tests, the readings went from 2.34, 1.6, .8 and an hour later to .12. It wasn’t a reading error as the blue colour of the sample clearly correlated to the reading. Dark blue on that first test, slightly lighter blue on the second, until the normal slight blue tint on the last one. So I can’t I fathom it was reading actual phosphate in the water.

I currently have dinos, hence my question about the possibility.

Try sampling the output of a reactor or filter sock to see if the current sampling point is nearer to the contamination. Do this sampling at the same time that you take a sample from your current location.

Are the dinoflagellates blooming or are they dying back? A die back might bump up phosphate, though not the numbers you are seeing.

 

[Ziggy17]

I would not be certain it is a water as opposed to a testing issue, but some folks have reported significant changes through a day which might possibly be real.

If the test sample colour didn’t match the reading, I would agree it’s a test issue. But the colour was a clear indicator that the reagents were reacting to the sample. And then the almost linear decrease was surprising. Half of the former test each time until it gave what I consider the final and correct reading.

 

[Ziggy17]

Try sampling the output of a reactor or filter sock to see if the current sampling point is nearer to the contamination. Do this sampling at the same time that you take a sample from your current location.

Are the dinoflagellates blooming or are they dying back? A die back might bump up phosphate, though not the numbers you are seeing.

Both blooming and dying. I used my UV sweeper on the sand bed 3 days ago to knock them back. But the next day I was still getting .1 readings. So unless they took two days to die after getting exposed to mortal UV, I’m not sure that’s a smoking gun. Definitely possible though. But I think it could be Dino related.

 

[Lasse]

I have been there too - in some of my cases 0.22 µm filtration solve the problem. In some (when it was a single high reading) - probably something wrong with the reagent powder FWIW - there is reports that many dinoflagellates does "luxury uptake" of phosphorus (P) by storing it as polyphosphate (polyP). It means that they can be rich in PO4 and - IMO - I can´t exclude that the acids in the test method and shaking to much excrete some PO4 into the sample.

Sincerely Lasse

 

[Ziggy17]

After school drop off I’ll see what’s going on with the PO4 today.

 

[Lasse]

After school drop off I’ll see what’s going on with the PO4 today.

That´s a good idea

Sincerely Lasse

 

[EnterName]

Something in the water caused a reaction with the reagent that couldn’t possibly be the phosphate. After a week of PO4 in the .1 range, yesterday morning In a 20 minute span with 3 tests, the readings went from 2.34, 1.6, .8 and an hour later to .12. It wasn’t a reading error as the blue colour of the sample clearly correlated to the reading. Dark blue on that first test, slightly lighter blue on the second, until the normal slight blue tint on the last one. So I can’t I fathom it was reading actual phosphate in the water.

I currently have dinos, hence my question about the possibility.

Just took a sample which I purposefully contaminated with diatoms (Licmophora sp., and some other genus I haven't identified properly yet), dinoflagellates (Ostreopsis), and even a poor ghost flatworm ended up in the sample. There were visible brown particles in the sample from the diatoms, etc.

The HannaChecker measured 23µg/L P, so roughly 0.07mg/L PO₄. This is the same result I have with an uncontaminated sample.

So even purposeful contamination with visible particles, diatoms, and dinoflagellates, does not necessarily increase the readings.

 

[Ziggy17]

After several attempts over two days, I’m unable to replicate the issue. PO4 holding steady in the .1 range again.

What I can rule out as an issue.

Hanna checker. The readings matched the sample colour. Dark blue for the really high reading and less blue as the tests read lower.

Collection method. Was done identical for all 4 tests. And as a former nurse, I’m well versed in obtaining collections with accuracy. Not that it’s needed here but I do have some expertise in the area. Again, I do it the same way every time.

Wage remaining culprits are the reagent or an unknown. The reagent could be the issue, but why just the 3 tests, and why was it so linear? Leaves us with an unknown, which I don’t like at all.