Testing a Hanna Phosphorus ULR Checker - Am I Missing Something?

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chipmunkofdoom2

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I have been emailing back and forth with Hanna over the last few days. After explaining my procedure and clarifying phosphorus vs phosphate a few times, the folks at Hanna confirmed that my math was correct. The only thing they could think of was some potential interference from copper, iron, silica, silicates, etc. These are generally not present in high enough quantities in reef aquaria to meet the interference levels that Hanna quoted, so I don't think this is likely.

I haven't decided if I want to order their calibration standard. I think I'm going to put this in a box on the shelf and forget about it for now. Maybe after a few weeks or months pass I'll be willing to waste some more time and money seeing if this thing actually works or not.
 

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I have been emailing back and forth with Hanna over the last few days. After explaining my procedure and clarifying phosphorus vs phosphate a few times, the folks at Hanna confirmed that my math was correct. The only thing they could think of was some potential interference from copper, iron, silica, silicates, etc. These are generally not present in high enough quantities in reef aquaria to meet the interference levels that Hanna quoted, so I don't think this is likely.

I haven't decided if I want to order their calibration standard. I think I'm going to put this in a box on the shelf and forget about it for now. Maybe after a few weeks or months pass I'll be willing to waste some more time and money seeing if this thing actually works or not.
Did you rule out the source material for your reference solution being a hydrate?
 

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The HI736 doesn't measure phosphates directly, it measures phosphorus. To convert the reading from the Hanna Phoshporus ULR Checker to phosphates, either use this chart or multiply by 3.066 and divide by 1000. A reading of 27 ppb means 0.083 ppm phosphate, not 0.027 ppm phosphate.
Your absolutely correct!
Bad news for me because now Hanna and Salifert Show two different readings.
 

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Yes, it is anhydrous. CAS# 7601-54-9, UNII SX01TZO3QZ.
Check the melting point if you can. I purchased the anhydrous form and received the hydrated form, 12 H2O! Your results might be closer if you assume your TSP is hydrated.
 
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Check the melting point if you can. I purchased the anhydrous form and received the hydrated form, 12 H2O! Your results might be closer if you assume your TSP is hydrated.

I'll ask the seller. The product was explicitly labeled as CAS# 7601-54-9, which is the anhydrous form. I doubt I have the dodecahydrate version.

Also, the math doesn't work for the dodecahydrate. After dosing 8.68 ml to my 5 gallon sample, the result would be around 0.0001 ppm phosphate (yes, 0.0001 ppm, or 0.1 ppb, or 100 parts per trillion). I have a really hard time believing the checker would read 0.15 ppm PO4 if the actual concentration was 0.0001 ppm.
 

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I'll ask the seller. The product was explicitly labeled as CAS# 7601-54-9, which is the anhydrous form. I doubt I have the dodecahydrate version.

Also, the math doesn't work for the dodecahydrate. After dosing 8.68 ml to my 5 gallon sample, the result would be around 0.0001 ppm phosphate (yes, 0.0001 ppm, or 0.1 ppb, or 100 parts per trillion). I have a really hard time believing the checker would read 0.15 ppm PO4 if the actual concentration was 0.0001 ppm.
Could be somewhere in between.
Can this be easily tested by weighing a sample, baking, then weighing again? Alternatively, can you add a known amount of water in a sealed container and make sure it’s still a solid?
 

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Could be somewhere in between.
Can this be easily tested by weighing a sample, baking, then weighing again? Alternatively, can you add a known amount of water in a sealed container and make sure it’s still a solid?
Luckily, the dodecahydrate decomposes at 100 C. It will melt and the water will boil . The other hydrates are 1, 6, and 8. I am not sure if they are available.

I placed some of my hydrated TSP in a small copper pipe cap used to close off copper tubing (hardware store) and heated that. Sure enough melting and bubbling. If you have a thermometer and have good manual dexterity, you can place some crystals on a thermometer bulb and carefully warm the thermometer bulb with a flame. If you are interested, I will give you more details how to pull this off. I used this method when I made chemicals on a very small scale.

I looked at your original table of numbers and 25% (hydrate) is much closer than 58%.
 
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homer1475

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I often times wonder about the hanna meter as well. I'm currently having an issue with 0 PO4, so I've been dosing brightwells neophos.

Unscientifically, 2 capfulls should give me about 0.1 PO4, but I often get 0 on the hanna. Yet I can see algae growing on the glass. I now just use the hanna to get a "rough" reading, but rely on how often I have to clean my glass to see if I have enough PO4 in the water.

On a side note....
When I first suspected issues I bought the standards. They do read within the stated accuracy, but still does not account for the often times low readings, or no readings it gives me
 

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Did you try checking back to back to see if any of your results change? For what its worth, I can test three different times and get three different results. Could be testing errors...could be acceptable range of the tester.....could be it isn't as accurate as we hope. Who knows.
 

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Did you try checking back to back to see if any of your results change? For what its worth, I can test three different times and get three different results. Could be testing errors...could be acceptable range of the tester.....could be it isn't as accurate as we hope. Who knows.
Same here...... I can run 5 tests back to back and get 5 different results, yet my testing procedure is exactly the same each time.
 

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I often times wonder about the hanna meter as well. I'm currently having an issue with 0 PO4, so I've been dosing brightwells neophos.

Unscientifically, 2 capfulls should give me about 0.1 PO4, but I often get 0 on the hanna. Yet I can see algae growing on the glass. I now just use the hanna to get a "rough" reading, but rely on how often I have to clean my glass to see if I have enough PO4 in the water.

On a side note....
When I first suspected issues I bought the standards. They do read within the stated accuracy, but still does not account for the often times low readings, or no readings it gives me

A “0” Hanna reading does not mean there are no phophates in the water
PO4 can be adsorbed to aragonite and organic carbon particle surfaces but will be available to living organisms
When PO4 is dosed, it can very quickly be adsorbed to aragonite surfaces
 

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Amazing how the life in our tanks use so much po4.
I also kept getting a 0 after checking at 24hrs after a dose of 5ml. Tank is only a 20 gallon tall. Dosed and checked 1 hr later. Got a reading. Checked again at 24hrs, back to 0.
I don’t have sand in my tank and minimal rock work. Corals look better. Dino’s are in retreat!!
The question I ponder is, when is 0 actually 0?!! When the Dino’s come I guess! Lol
 
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Also, the math doesn't work for the dodecahydrate. After dosing 8.68 ml to my 5 gallon sample, the result would be around 0.0001 ppm phosphate (yes, 0.0001 ppm, or 0.1 ppb, or 100 parts per trillion). I have a really hard time believing the checker would read 0.15 ppm PO4 if the actual concentration was 0.0001 ppm.

The math in this post is not correct. I made a decimal error when trying to do some quick calculations. For completeness, I'm sharing the correct numbers, but they're still pretty far off. Here's the full set of calculations:

Na3PO4.12H2O % PO4 = 30.97 / 380.12 = 8.147%
7.12g Na3PO4.12H2O * 8.147% PO4 = 0.58g PO4
0.58g PO4 / 3.785 gallons = 0.153 g/L = 153 mg/L = 153 ppm PO4

I used the following formula to solve for the final concentration after a given amount added:

1594209303660.png

Where:
Tv = Tank volume
Tc = Tank concentration
Sv = Solution volume
Sc = Solution concentration
C = final concentration
Tv+Sv > 0

The numbers are closer, but still off:

Na3PO4.12H2O

TestExpected Concentration (PO4)Expected Reading (PPB)Actual Reading (PPB)
1​
0​
0​
0​
2​
0.0069​
2​
2​
3​
0.0137​
4​
0​
4​
0.0343​
11​
25​
5​
0.0685​
22​
49​
 
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The numbers for hydrous Na3PO4, however, are a different story. These are much, much closer.

Na3PO4.H2O % PO4 = 30.97 / 137.99 = 22.44%
7.12g Na3PO4.H2O * 22.44% PO4 = 1.598g PO4
1.598g PO4 / 3.785 gallons = 0.42219 g/L = 422.19 mg/L = 422 ppm PO4

Na3PO4.H2O

TestExpected Concentration (PO4)Expected Reading (PPB)Actual Reading (PPB)
1​
0.000​
0​
0​
2​
0.019​
6​
2​
3​
0.038​
12​
0​
4​
0.095​
31​
25​
5​
0.189​
62​
49​

I will have to see what the vendor says. The supplement was sold by Loudwolf and was explicitly labeled as CAS 7601-54-9, which is anhydrous. I suppose it's possible it could be one of Na3PO4's various hydrates, although I'd be disappointed if it was and it wasn't labeled as such.
 
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Luckily, the dodecahydrate decomposes at 100 C. It will melt and the water will boil . The other hydrates are 1, 6, and 8. I am not sure if they are available.

I placed some of my hydrated TSP in a small copper pipe cap used to close off copper tubing (hardware store) and heated that. Sure enough melting and bubbling. If you have a thermometer and have good manual dexterity, you can place some crystals on a thermometer bulb and carefully warm the thermometer bulb with a flame. If you are interested, I will give you more details how to pull this off. I used this method when I made chemicals on a very small scale.

I looked at your original table of numbers and 25% (hydrate) is much closer than 58%.

This is possible, but I really don't want to have to go measuring the melting point to make sure the vendor sent me the right hydration. I'm checking with the vendor what the hydration is for the Na3PO4 I ordered. In general, the hydration of the Na3PO4 is normally not going to be a concern for me. If I have a tester that I can trust I'll just simply keep dosing until I get the desired result.
 
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Did you try checking back to back to see if any of your results change? For what its worth, I can test three different times and get three different results. Could be testing errors...could be acceptable range of the tester.....could be it isn't as accurate as we hope. Who knows.

No, I didn't. I was considering it if the numbers were close, but when they were way off, I decided to save the reagents. If I needed to retest later, I didn't want to have to buy another box.
 
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Amazing how the life in our tanks use so much po4.
I also kept getting a 0 after checking at 24hrs after a dose of 5ml. Tank is only a 20 gallon tall. Dosed and checked 1 hr later. Got a reading. Checked again at 24hrs, back to 0.
I don’t have sand in my tank and minimal rock work. Corals look better. Dino’s are in retreat!!
The question I ponder is, when is 0 actually 0?!! When the Dino’s come I guess! Lol

In general, this is going to be the rocks and sand, even if you only have a small amount of rock. Calcium carbonate has a very high capacity for binding phosphate relative to the concentrations we usually encounter in reef aquaria. Tests by a member here found that just one pound of aragonite rock was able to absorb 57 ppm of phosphate (yes, parts per million) from a 5 gallon test setup.
 

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