Hanna Phosphate Reagent Issues

[gws3]

Anyone else experiencing consistency issues with their Hanna Low Range Phosphate recently?

 

Ordered a box of 100 packs recently, HI 93713-0 Lot H134.  Results are all over the place on samples from the same system.  Anywhere from 0.03 to 0.09.  I think I even got one at 0.13.  I know the tolerance on the kit is advertised at +/-.04, but I have used this for years and always got extremely consistent results... my system is almost always 0.02-0.03. 

 

Sent Hanna an email and they sent me a replacement box, Lot H143.  Results are consistently 0.01 on both systems with new reagent, which seems lower than normal.  At least they're consistent, but now I am having trouble trusting either. 

[s2nhle]

Thank for sharing. Have you compare it with other test kitsr (seifer, or red sea)?

[Origami]

I'd be willing to trust the replacement, Graham, within their tolerance specs. While I've not had the wide variation that you've experienced - I guess that I've not got a bad batch - I've found Hanna very responsive to inquiries and concerns. You could always cross-check against a commercial phosphate standard if you're concerned.

[gws3]

Have not compared to any other test kits, but I don't think any other hobby grade test kits will compare well.

 

This is the first time it has been inconsistent for me since I've had it, 5+ years.  A reference solution would be ideal... I'll have to look to see if I can find one. 

[BowieReefer84]

I have the hanna phosphate standard for the Low Range reader.  If you want it let me know and I'll ship it to you for the cost of postage.  I used it twice maybe.

 

It's this:

http://www.bulkreefsupply.com/hi736-11-phosphorus-standards.html?gclid=CIGdu-ajhMICFWUF7Aodh0EAlQ

 

I can also send a couple reagents from other batches for you to compare.

 

Edit- You can't go wrong getting a new triple A battery either.  Supposed to last 5,000 tests but maybe not?

http://shop.hannainst.com/downloads/dl/file/id/1069/ist736_13_05_10.pdf

Edited November 18, 2014 by BowieReefer84

[gws3]

I have the hanna phosphate standard for the Low Range reader.  If you want it let me know and I'll ship it to you for the cost of postage.  I used it twice maybe.

 

It's this:

http://www.bulkreefsupply.com/hi736-11-phosphorus-standards.html?gclid=CIGdu-ajhMICFWUF7Aodh0EAlQ

 

I can also send a couple reagents from other batches for you to compare.

 

Edit- You can't go wrong getting a new triple A battery either.  Supposed to last 5,000 tests but maybe not?

http://shop.hannainst.com/downloads/dl/file/id/1069/ist736_13_05_10.pdf

 

I appreciate the offer.  I was looking at that standard on their website, but I believe it tests the meter, not the reagent, correct?  I think I need a standard solution with a know concentration of phosphate to test the reagent. 

 

I did replace the battery.  I have the old style of the low range phosphate meter, it takes a 9v battery.  Specs are the same, although I believe it has a tungsten lamp as opposed to LCD, and of course the cost was 4x when I got it years ago. 

[BowieReefer84]

I appreciate the offer.  I was looking at that standard on their website, but I believe it tests the meter, not the reagent, correct?  YES, that is correct.  I think I need a standard solution with a know concentration of phosphate to test the reagent. 

 

I did replace the battery.  I have the old style of the low range phosphate meter, it takes a 9v battery.  Specs are the same, although I believe it has a tungsten lamp as opposed to LCD, and of course the cost was 4x when I got it years ago. 

 

Goodluck creating your own standard.  Post up if you find something to test against.

[gws3]

Will do.  Thanks again for the offer.  I'll email Hanna and see if they recommend anything.  Maybe if I find time I'll attempt my own reference solution... of course at these low concentrations I may be limited by my scale accuracy... or I'll just have to dilute heavily.  Not sure I understand the chemistry of what form of phosphate is being measured either. 

[Origami]

It's probably reading unbound inorganic phosphate - PO4. The thing with making your own standard is accuracy and resolution. But, if you're just trying to get in the ballpark to test the meter, you may be able to DIY something that gives you confidence. I'm not sure what you'd use, though, to make a standard. Maybe some phosphoric acid?

[gws3]

Found a few options:

 

Fauna Marin makes a reference solution for multiple parameters.  Kinda pricey at $25, and I saw a RC thread where a guy tested the Fauna Marin solution with a Fauna Marin phosphate test kit and got a result 10x off... or something along those lines.

 

http://www.faunamarin.de/en/technic/water-tests/multi-reference-100ml/a-167/

http://www.bulkreefsupply.com/fauna-marin-multi-reference-solution.html

 

Reef Builders compared three different level Hanna phosphate meters.  They created a reference solution with a Seachem phosphate additive for planted tanks.  They got very close results 1.31 measured vs 1.35 calcualted.  I think I'll try their method... gives me an excuse to satisfy my Amazon Prime shopping addiction for today.  $6 shipped.... feed the machine.

 

http://reefbuilders.com/2010/04/20/hanna-phosphate-checker-review-notable-compromises-still-worth-the-resolution-and-portability/

Edited November 18, 2014 by gws3

[Origami]

Found a few options:

 

...

 

Reef Builders compared three different level Hanna phosphate meters.  They created a reference solution with a Seachem phosphate additive for planted tanks.  They got very close results 1.31 measured vs 1.35 calcualted.  I think I'll try their method... gives me an excuse to satisfy my Amazon Prime shopping addiction for today.  $6 shipped.... feed the machine.

 

http://reefbuilders.com/2010/04/20/hanna-phosphate-checker-review-notable-compromises-still-worth-the-resolution-and-portability/

Sounds like a great (and easy option). Let us know how it works out. And, thanks for posting the link!

[Origami]

Graham, note the typo in the article. They added 0.3 ml (not 0.3 liters) of the Seachem to 999.7 ml of RO/DI to get to the 1.35 mg/liter (ppm) phosphate reference solution. Be sure to convert to Phosphorus if you're using the ULR Phosphorus checker and not the phosphate checker. 

[gws3]

Graham, note the typo in the article. They added 0.3 ml (not 0.3 liters) of the Seachem to 999.7 ml of RO/DI to get to the 1.35 mg/liter (ppm) phosphate reference solution. Be sure to convert to Phosphorus if you're using the ULR Phosphorus checker and not the phosphate checker. 

 

Good catch, thanks. I'm using the older 93713 meter, which according to the manual reads phosphate (PO4) in mg/L or ppm. 

 

What I don't fully understand is that on the seachem website it says the guaranteed analysis is .3% P2O5 and .2%K20.  I am guessing in solution PO4 bonds with oxygen so it is no longer an ion?  But the test kit reagent reacts with PO4 and that is what is measured?  Been a while since freshman chemistry.

 

Seachem has an online calculator which matched the reef builders numbers (except typo)... to get 1.35 mg/L in .997 liters (.264 gallon) add 0.3 mL.  So the 4500 mg/L PO4 concentration jives with the calculator. 

[Origami]

P2O5 is an oxide of phosphorus commonly used in plant fertilizers. It hydrolyzes in water to create phosphoric acid that ultimately yields the phosphate ion that plants use. The phosphoric acid ionizes in the water to yield the phosphate (PO4--- ion).

 

P2O5 (phosphorus pentoxide) + 3H2O (water) ==>> 2H3PO4 (phosphoric acid) ==>> 6H (a cation) + 2PO4 (an anion)

 

The potassium is there because plants  need it for growth along with nitrate and phosphorus. Remember, this is a fertilizer that you're using.

 

Let us know how good your results are with the test. It would be handy to have a halfway decent DIY reference, even if it's a little inaccurate (but possibly still within the accuracy of the Hanna checker).

 

Looking more closely at some resources, my guess is that Seachem is starting with Dipotassium Phosphate in solution.... a salt that leads to both phosphate and potassium, and a common fertilizer. Why they spec it as P205, I could only hazard a guess. Unless it's because P205 is commonly referenced for plant fertilizers.

[gws3]

Got it, that makes sense, thanks.  I'll post my results once I get the additive and find some time. 

 

For my purposes I anticipate it will be plenty accurate.  I'll test it at the 1.35 ppm concentration and then dilute down to something in the range of reef aquarium... perhaps 0.03 ppm.  Any deviation from that value at the meter resolution would require the solution to be off by 33% percent, which is highly unlikely if seachem has any QC with their additives.  At that point it would likely be accuracy/percision of the meter.

 

Right now I'm getting 0.01 ppm with new reagent and ~0.05 ppm with the old reagent.  It should at least tell me if either is close to accurate.

[Origami]

My luck with other Seachem additives being on target concentration-wise has been pretty good. Hopefully, you'll have the same luck with this new one.

[gws3]

It’s certainly taken me long enough but I finally got around to doing some more testing with the Phosphate Meter.

 

With the 1.30 solution the older batch was pretty close ranging from 1.24-1.25, and the newer batch was a bit low at 1.16-1.18.  There were a few outliers, which could be due to error on my part.  I chose to negate them (strikethrough).

 

When I diluted the 1.30 solution to make a 0.03 solution the results got confusing.  The old batch ranged from 0.04-0.07 and the new batch consistently hit 0.01. 

 

Next I tested water from my existing reef system.  The old batch ranged 0.03-0.05 and the new batch 0.00-0.02.

 

Testing water from my 300DD which is its own system the old batch ranged from 0.04-0.07 and the new batch 0.02-0.03.

 

Surprisingly I am now not getting a wide range of results with the old batch.  I haven’t change my method, so I don’t have an explanation for that.

 

I haven’t really reached any conclusions, other than my systems appear to be reasonably low in phosphate and I think I am going to spend less time measuring and controlling phosphate as I believe my systems to be too low in nutrients if anything.

 

Edited January 15, 2015 by gws3

[AlanM]

That is a lot of dissolving of that white powder. You should be really good at it by now. Should give tips to people on how to run the test correctly since it is kind of a pain.

Edited January 15, 2015 by AlanM

[gws3]

That is a lot of dissolving of that white powder. You should be really good at it by now. Should give tips to people on how to run the test correctly since it is kind of a pain.

 

It's definitely not the most fun I've had.  Fortunately the new batch is a very fine powder and dissolves readily.  The older batch is what I'm used to, with the white granules that are very hard to dissolve.  Perhaps they have changed something slightly with how they make the powder and this is impacting the results.

 

This is what I do to try to get consistent results:

 

First I add 10ml of water to the cuvette.  Then I wipe the sides of the cuvette with a towel.  Next I turn it on it's side so an air bubble is against the side of the cuvette.  I rotate the cuvette so the air bubble removes any smaller air bubbles from the cuvette wall.  Now it is perfectly clear and I zero the meter.

 

I add powder by cutting open the packet, folding a crease in the side, and tapping to get as much out as possible.  Then I carefully tear the package around the edges to get the rest into the cuvette.

 

I cap it with the clear plastic piece that comes with the cuvette.  Then I shake it vigorously until the powder is not settling at the bottom of the cuvette.  I press the button for the timed read, 3:00 counts down.  I do a little more shaking, and then turn the cuvette on the side and use the air bubble to remove any remaining particles or air bubbles from the side of the cuvette.  I wipe it clean again and place it in the meter.

 

Once I get a reading I typically remove the cuvette, use the bubble trick to get anything off the side wall of the cuvette, wipe the outside, and take another reading.  Especially if the reading it different than what I expect.  Typically it is the same or drops by 0.01.

 

 

I'm not convinced the importance of low phosphate values and using GFO isn't partially the result of marketing and product sales.  I read a pretty good thread on RC the other day.  Some more experienced reefers were recollecting when no one even measure for phosphates and they still managed thriving sps tanks.  Personally I recall better growth and deeper colors when I had a downdraft skimmer that I never cleaned often enough and patches of nuisance algae.  I notice paler colors in my SPS and less growth than I used to achieve.  Sometimes I think this is due to stronger lighting (better reflectors) coupled with lower nutrients (better skimmers, better gfo/gac reactors, etc). 

 

This thread has me considering trying some very simple husbandry on my newer 300DD... no GFO, no GAC... just 5% weekly water changes, reduced skimming (8 hours a day).  I may try this for several months and see if it causes issues.  I can always run GFO if my phosphate numbers creep too high.

 

 

http://reefcentral.com/forums/showthread.php?t=2289842