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If you use an API Ammonia test - test it!

Discussion in 'Water Chemistry' started by Josh Jacob, Aug 17, 2016.

  1. Josh Jacob

    Josh Jacob New Member

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    Short story - my API freshwater master test kit has a totally defective ammonia test. I have seen loads of people saying their always seems to read .25...I had thought maybe it was just a slight calibration issue and that .25 was really zero but in my case that is certainly not the issue. I highly recommend you test yours if you are using the API freshwater ammonia test.

    set up a few test tubes to test side by side. Have a control tube that is clean water - ideally use bottled or purified water, tap should still work though. Then start adding various dilutions of ammonia water to your following tests. In my case, I had to add enough ammonia that it should have been completely off the scale dark green before it budged from .25 to .5 ppm!


    If anyone wonders, the full background details on how this came up can be found in this thread http://aquaponics.net.au/forum/threads/calculating-ppm-of-ammonia.8210/
     
  2. Robert123

    Robert123 Active Member

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    Interesting. My well water reads 0. Just sharing a data point. Your tap water got chloro amines?
     
  3. Josh Jacob

    Josh Jacob New Member

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    Nope my tap is untreated well water with no chlorine, chloramine, flouride or other additives. It has low hardness, no sulfurous smell (a lot of wells around here are stinky), ph is just above 7. This API test shows purified, tap, and system water all as identical .25 ppm light green (which would only be possible if the light green was a mis-calibration of 0ppm, or the test is completely borked...I had assumed the former, turns out it's the latter). And to be clear for anyone wondering, yes I fill tube to line, add 8 drops from vertically held bottle 1, cap, shake, add 8 from bottle 2, cap, shake, wait 5m, check result - so I don't think it's user error unfortunately.
     
  4. Robert123

    Robert123 Active Member

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    If you are getting the green color, you must have some ammonia or chloroamine around. It is a simple reaction with salicylic acid. Salicylic acid is clear (or a bit yellowish when concentrated). The more ammonia you present to the reaction, the more color you form.

    ammonia-salicylate.png

    The final ring structure is a green-blue dye.
     
  5. Josh Jacob

    Josh Jacob New Member

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    Hi Robert, I think you are misunderstanding the issue. Regardless of what is or is not in my tap water there is no ammonia or chloramine in purified water. Purified water gives the same reading as my system water and tap water .25 ppm. This is a common "false positive" frequently experienced with the API ammonia test, a quick google search "API ammonia false positive" will show you many threads about it. However this is the not the critical issue I'm describing here.

    The critical issue is that I added varying amounts of ammonia out of a jug to the water and tested it and could not get over a .5 ppm reading. It should have been off the chart in my last test...the water reeked of ammonia. I posted this as a warning. I only have a sample size of one so its certainly not conclusive evidence of all false positive test kits having the same issues as mine. However, in my case once "something" happened to my test kit it quit reading zero as zero returning the same exact false positive other people were reporting AND it will also no longer register the upper range properly either which as far as I know no one else talking about false positives has tested upper ranges...or at least they didn't mention doing so..if this is an issue with all tests giving the false positive we absolutely need to know this and the only way to find out is for people to check their kits.

    Since I know some people's set gets the false positive reading and some don't, and since I know mine was fine when I got it, and no longer worked 6 months later, what I'm suggesting is that if you have a set that currently gives the false positive reading of .25 ppm I highly recommend you check the upper range just in case it's a symptom of whatever happened to mine. If you have a set that is experiencing the same false positive failure then it may also be experiencing the same upper range failure, and if it is then you really have NO IDEA WHAT LEVEL OF AMMONIA IS IN YOUR WATER. My fish died...if you use one of these sets and it gives a false positive reading of .25 on purified water don't let your fish die without checking your test for accuracy on the upper range!
     
  6. Robert123

    Robert123 Active Member

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    I've worked in chemicals for almost 40 years. One of my jobs over my career has been (and is) that of a color chemist. We make colorants for a living. Not this specific colorant, but I do know this reaction. The green chromophore that this test relies on simply can't happen without the presence of an amine of some sort.

    API test solution 1 is sodium salicylate in PEG (water white to pale yellow), and solution 2 is diluted sodium hydroxide and sodium hypochlorite in water (essentially chlorox bleach). You MUST have the amine to make the green chromophore.
    I cannot come up with any chemical explanation how the test kit used on distilled water could ever be incorrectly high, so when someone reports they get the green with "real" distilled water that tells me the only reasonable error can come from interpretation of the data. A couple possibilities:

    1) Are you reading your tubes against a white background in good broad spectrum lighting? The source of the lighting and/or it's wavelength may be affecting your ability to read the color accurately.

    2) About 10% of the world has some amount of green-red color blindness that could certainly affect one's ability to read the test to at least some degree. (Don't take this as an attack please, it's just simply a fact.)

    Again, I'm not saying you don't "see what you see", but rather that "what you see is not what is really there" for one reason or another.

    P.S. For those that have ever wondered, the test is designed such that the amine will always be the limiting reagent. If you add 12 drops each of the chemicals to the test tube versus 8 drops of each chemical, you will still get effectively the same result. The color development might occur more quickly with the 12 drops, but the same final amount of color will be formed eventually in both tests.
     
  7. Josh Jacob

    Josh Jacob New Member

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    1) Yes white paper in direct sunlight...unless of course the sun isn't shining (outdoor greenhouse system).
    2) Nope, no color blindness here

    I once assumed pretty much what you are assuming..that the "false positive" was simply a lighting issue, a poorly calibrated color card, fading of the card swatches from UV exposure or something of that nature and that the test was in fact still working. (It actually did read as 0 for the first few months that I used it, so I was leaning toward fading of the color swatches) HOWEVER 2 days ago when I actually tested it against water I had deliberately added ammonia to, and it completely failed to indicate the increased ammonia levels that assumption went out the window. While I'm not a chemist, I am qualified to teach high school science so I'm not completely ignorant of the issues at hand.

    Really you shouldn't be focusing on the false positive anyway. There are plenty of legitimate reasons for it to happen and I very clearly stated that is not the the problem just a probable symptom. The issue which you seem to have missed again is that the test is not reacting properly to high concentrations of ammonia. It sounds like you are more familiar with the reagents and reaction involved here so please answer this: If ammonia is added to water such that is has a concentration significantly higher than the testable range of 8ppm, should this reaction:
    1) show .5 ppm (this is what actually happens)
    2) show 8 ppm (the last color swatch on the chart)
    3) show a color that is even darker green than the last swatch (this is what your explanation of the amine color reaction above indicates is it not?)
    4) other ____________

    In laboratory conditions with reagents that you are sure have not been compromised your argument would make sense..but this is dropper bottle that has experienced extremes of hot and cold light and dark sitting in the greenhouse for a year. It has also been opened dripped into water containing various things numerous times so there's probably other possibilities such as some sort of cross contamination, or bacterial/fungal growth, some sort of oxidizing reaction to the frequent air exchange in the bottle, offgassing of some chemical in the plastic when it got hot, or any of the above environmenal factors somehow hastening it's expiration. API assured me that the heat/cold/light would not be an issue. But they were also very concerned what it's expiration date was. If these reagents can undergo a chemical change inside these bottles that makes them "expire" and no longer give accurate readings, then the question is what exactly causes them to expire and under what circumstances would that expiration be hastened?

    That said, if you Robert aren't getting a false positive from your test you don't need to worry about it. Other readers who may be seeing a false positive..it's your call...trust that it's ONLY a false positive and maybe risk the safety of your fish..or possibly waste a few drops checking against a high ammonia level to make sure the test still works. I know what I'll be doing as soon as my new bottles arrive, and I'll post a side by side picture of the two tests so you can see just how screwed up the old one is.
     
  8. Robert123

    Robert123 Active Member

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    Sodium salicylate solutions are extremely stable to temperature / storage conditions. Hypochlorite maybe not so much, but the loss of chlorine in the reaction won't cause green to form. The high pH conditions will fry most all bacteria, but even if it didn't the green again won't form. You clearly stated that in your case 0 ppm water read 0.25 ppm (i.e. You saw green). I have no idea how you formulated your standards but that is immaterial to your measurement of 0.25 on a 0 ppm NH3 solution.

    Sorry I could not help you. Hope the new test kit purchase resolves your issue or you find a more accurate way to measure NH3.
     
  9. Josh Jacob

    Josh Jacob New Member

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    Hey Robert, if you are still around do you know which reagent is in which bottle? I received the replacement set from API and there was an immediate and obvious difference I had failed to notice do to the gradual change. The contents of bottle #1 were no longer clear but are now an amber color. Any thoughts on what would cause that discoloration and lack of the above chemical reaction you described in the AP environment?

    Attaching an image of the test with the old and new bottles used on system water, and water with a tiny bit of ammonia added (though still well off the scale) Pretty clear difference in the results. Happy to say that the new test is reading 0 ammonia in system water as expected. The old test was just slightly greener on system water, and slightly greener again on the ammonia water.
     

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  10. Robert123

    Robert123 Active Member

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    Posted above.....

    Bottle 1 is the sodium salicylate.
    Bottle 2 is the hypochlorite.

    Of the two, the hypochlorite could deactivate due to age and heat causing low readings. Using your other bottle 2 or a couple drops of chlorox in its place could confirm that.
     
  11. Josh Jacob

    Josh Jacob New Member

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    Good idea, I'll check that. I'm only assuming bottle one had the issue due to it's color change but that's not necessarily the case.
     

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