Diluted Testing, But Will The Reverse Also Work?

TwoTankAmin

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I know about diluted testing and the hows and whys of it. they make prefect sense and it works. But after replying to another thread about .25 ppm of ammonia no mater what a person did every day for 3 weeks, I got to wondering. especially since the thread in question had another poster comment about how hard it would be even to tell the difference between .05, .10, .15, ,20 and .25.
 
Well this got me to wondering. Would the reverse work as well to help delineate say between .125 and .25 ppm of ammonia if we did a concentrated test? Suppose one only filled the test vial with 1/2 the amount of tank water of alternatively added twice the number of drops of the reagent(s)? Could one then not divide the results by 2 and get the real level? If the concentrated test read .50, this would mean it was really .25. But if it read .25, we would know it was really .125.
 
In theory this makes sense, but who can tell me if it will work in practice. That much extra reagent may make things not work right for reasons of which I am not aware. Might the error potential may be so much greater that the results would be too inaccurate w/o using more sophisticated mixing and dispensing equipment?
 
if you have a background or knowledge that can help with an answer to this, please post it.
 
Well as you are well aware I don't have the background or knowledge, but I know a man who does and when I got my forst API test kit - the ammonia looked to be a very slight green all the time. I tried half the volume but the same number of drops for the full amount and it was bright yellow, a very resounding 0!
What that said to me at the time was that it was ok, but I asked Neonblueleon who I believe is/was a chemistry teacher and he said:
"Some chemical reactions are not affected by how much chemicals are mixed, and some chemical reactions are totally affected by how much is mixed"
Also that since API don't list what indicators they use it's virtually impossible to answer that question and best to use the suggested amount.
 
With my limited chemistry knowledge... If you put half the amount of water in then it will still have the same concentration of ammonia because that's what you are measuring ie parts per million. Mixing more of the indicator solution will only give a false reading, or if it shows the same as before this would be correct.
 
In theory if you reduced the volume of the water by reduction (boiling) then you would see a higher concentration of anything that didn't evaporate. However I suspect the ammonia etc would probably boil away too so this wouldn't be accurate either.
 
I see where you are coming from but don't think it works that way.
 
Well it works in the other direction. The resulting reading must be multiplied by the dilution factor in order to get a correct reading of the concentration. As far as I know one can do diluted testing both ways. One can double the sample volume or halve the reagent amount. So use twice the water and multiply the result by 2.
 
The concentration of ammonia obviously stays the same, however there is a reaction that occurs based on the amount of reagent added to the water. So in theory half the water or twice the reagents should give one a reading that needs to be divided to compensate. So use half the water and divide the result by 2.
 
 
In the ammonia test method that employs the Salicylate chemistry, free ammonia reacts with hypochlorite to form monochloramine. Monochloramine reacts with salicylate, in the presence of sodium nitro-ferricyanide, to form 5-aminosalicylate, a green-colored complex. This test method measures free ammonia and monochloramine. Results are expressed in ppm (mg/L) ammonia- nitrogen, NH3-N.
from http://www.chemetrics.com/ammonia
 
 
Ammonia compounds combine with chlorine to form monochloramine. Monochloramine reacts with salicylate to form 5-aminosalicylate. The 5-aminosalicylate is oxidized in the presence of a sodium nitroprusside catalyst to form a blue-colored compound. The blue color is masked by the yellow color from the excess reagent present to give a final green-colored solution.
from http://www.hach.com/asset-get.download.jsa?id=7639984373
 
 
Now for your nerds out there here is a link to the patent filing for salicylate ammonia testing. What all this will boil down to is that the the ultimate determination of how much ammonia is present is based on the wavelength of the the color that results. This is why accuarte ammonia testing does not rely on the tester's eyesight and the ability of it to differentiate color precise color difference. Instead the method was intended to be used with a color reading device rather than the human eye. http://www.google.com/patents/US3432395
 
My point in making this thread is to try to determine if the theory of concentrated testing might make reading very low levels of ammonia showing up on a hobby kit easier by shifting the results to the darker shades which are easier for the human eye to differentiate.
 
The results of diluted test, and potentially concentrated testing, are only "false" if they are not adjusted by the proper factor. What I see as the primary drawback for the concentrated method would be you can only reduce the water volume by so much before the sample size is too small to work with accurately or even to get a good reading from when holding it against the card. I can dilute a sample down to 10% but I doubt i can do the the opposite. 10% of 5 ml is only .5 ml and that surely is not big enough to get a reading held against a card as far as I can tell. The only way I can see this might work is to use a bigger sample and then use a lot more reagent. This is not economical past some point.
 
of course there is one way to get more accurate low level ammonia readings, one could simply use a much more expensive kit. But how many hobbyists can afford to be spending $90 or so to be able accurately to read very low level of ammonia?
 
So I am still not sure that concentrated testing will not work. I need a chemistry person or lab. technician or similar to answer this Q I think?
 
Why don't you just test it, TTA?
 
You have a theory and while it sounds sound (excuse the expression) the best way is surely to do the test. 
 
Perhaps you could make up a few solutions of known amounts/concentrations of NH3/4 and then see what happens when you double either the water or the reagents or both.
 
As for your problem with tiny amounts of test liquid, you can scale these back up to still have 10% dilution but with higher volumes so long as you keep the ratio of reagents correct. For example, you use 10% of 5ml = 0.5ml, however, 10% of 50ml = 5ml as long as you increase the reagents by the same factor, in this case, 10.
 
It isnt the ammonia kit in which I am really interested. It is Nitrate. I am not sure if one can get a known nitrate solution.
 
The methodology is easy, its the chemistry factors that may or may not interfere. Also, the bottles used for test kits are cheap and I am not convinced how uniform the drops are. It may not matter when doing a normal test, but doing a concentrated test it amplifies the potential problem. The other side of the coin is that doing a double water test means a bigger vial than we get with the kits.
 
If you have read the directions I wrote in the Fish-in cycle rescue part II article you will see that I tell folks to use dilute 4 ouncse of water to 8 ounces and then pour 5 ml of that into the tube. I use so much water because if one is a few ml over or under 4 ounces, it wont have a huge affect. Working in concentrated testing it is the exact opposite. measuring becomes very critical. And using twice the reagents but the same water quanity doubles the cost of each test. Something I hate to do to folks if it wont work.
 
I would suggest that the best people to ask are Mars Fishcare, if we are specifically talking about the API kit, as they have always been exceptionally helpful when I've asked them technical questions in the past.
 
I would instinctively agree with SimplyFish that doubling the indicator solution may not have the expected results and it may not be a linear relationship.
 
In any case, if it were possible to differentiate between 0.125 and 0.25 ppm would we really trust the results from an API kit to give such a reliably accurate answer?
 
daizeUK said:
 
In any case, if it were possible to differentiate between 0.125 and 0.25 ppm would we really trust the results from an API kit to give such a reliably accurate answer?
 
Good point. And my answer would be a resounding, no!
 
No, this is not specifically about API, it applies to all kits. On the diluted side even the expensive Hach kits suggest the diluted testing. As noted above, the concern is more for nitrate levels which give people fits.
 
Its application for ammonia is more of a situational need. Here is is brought on by a desire to find a method for illustrating when one of those persistent .25 ppm reports is posted. In this instance the idea would be that a false reading might be revealed as the result of a "concentrated" test. My thinking here is that it might be that if one does a double concentrated test of .25 ppm, the result might show it is actually false This would happen if the concentrated test did not come out to close to double the concentration. If you still got a .25 ppm result, that would indicate that reading has to be false. but a second benefit is concentrated testing might be a way we could better delineate between low level readings.
 
The shortcomings of the test kits tend to occur at the ends of the results scale. We have solved the high end with diluted testing. Can we also do something at the low end with concentrated testing or not is what I am wondering? I tend to mistrust asking the folks at API as I would expect them to respond that the test kits should be used exactly according to the directions.
 
However, I may ask them just to see what they say.
 
Incidentally, this probably doesn't help you but there is a small amount of reference solution included with the Seachem Ammonia Multitest kit which is 1ppm NH3, 10ppm NO3 (and something similar I forget for nitrite), unfortunately they only supply a few ml of the stuff, enough for one 5ml API test.  I used mine up testing the ammonia kit so I don't have enough left to test a nitrate kit.  Still that's one place I know you can get a very small amount of nitrate reference solution, if you were determined to have some.
 
Sounds like that's where doing a diluted test with R.O. or D.I water would have been useful, daize!
 
Ammonia is easy- I am just too lazy to do it. I can get anhydrous ammonia and use ro/di to make my own reference solutions. But I am more interested in the chemistry involved before spending time and money. If concentrated testing cant be done for chemistry reasons, I am wasting my time. And this was my initial question, is there a reason because of the chemistry involved that concentrated testing cannot work.
 
If we don't know what the specific indicators are, no-one can answer that. You'd need to find out which ones are being used and then get a chemist on the case - I'd suggest Neonblueleon might be the one to ask.
 

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