Despite API reputation, the Chemicals in the test kits are actually good

[Dan_P]

I bought another API phosphate kit to use in the Hanna yesterday. I noticed 3 things.

1) the zero phos calibration on new salt water was a lot higher than the previous test kit. Old test kit read 0.51 on Hanna, new test kit reads 1.10. (There May be a little phos in the salt I suppose), but that’s a big jump.

2) the slope of colour change seems to have changed dramatically. Previously there was a 1:1 relationship between API increase and theoretical increase. For example, simply subtracting the 0.51 starting point from any reading with API gave a good reading throughout the entire range. This appears now not to be the case with the new API kit. it’s actually a much shallower slope, almost 1:2. For example, a theoretical increase of 0.3 is resulting in an API/Hanna increase of 0.16.

3) initially I was getting extremely wobbly results, with numbers wobbling around by 0.14. Strangely this happened with the original test kit to begin with, but settled down after a while. I shook the living daylights out of both API bottles in the new kit (not in the instructions as far as I can see), and it settled down.

Waiting for Hanna reagents to arrive to get my sanity back.

Had a similarly crappy experience with API phosphate and after that quit trying to make PO4 test an accurate and inexpensive test.

I hope recounting this helps with the re-sanity-tizing.

 

[taricha]

I bought another API phosphate kit to use in the Hanna yesterday. I noticed 3 things...

Had a similarly crappy experience with API phosphate and after that quit trying to make PO4 test an accurate and inexpensive test.

For me the API PO4 and NO3 have just too much lot to lot variation, so I came to the conclusion they weren't worth time and effort to tame when I have hanna and Red sea that myself and others have already run against standards.

 

[Garf]

Had a similarly crappy experience with API phosphate and after that quit trying to make PO4 test an accurate and inexpensive test.

I hope recounting this helps with the re-sanity-tizing.

For me the API PO4 and NO3 have just too much lot to lot variation, so I came to the conclusion they weren't worth time and effort to tame when I have hanna and Red sea that myself and others have already run against standards.

Well, Hanna arrived and have confirmed my old API phos test kit was giving me good numbers, so sanity restored I suppose the new test kit just needs a calibration curve re-done. Considering the amount of tests the API delivers for pennies, that’s probably what I’ll do (I’ve still got half a bottle of reagents left from the old API kit). I’m not one of those folks that strive for really low phosphate and to be honest I’ve seen no difference in the tank, no matter what phosphate levels are, ever. Perhaps that’s because I’ve always been over the threshold where the magic happens, lol.

 

[Red2143]

Since api ammonia can be used comparatively how would I go about making a "reference" for a warning level of ammonia using 10% ammonia hydroxide? I understand there may be a difference between nh3 and nh4 that would have to be accounted for to truly know danger to fish?

 

[Court_Appointed_Hypeman]

This topic is @Dan_P 's baby - I'm just running with it. Dan will even go further than I will and use some of the API kits that I won't mess with (NO3, PO4).

It's widely claimed that API tests can't be trusted and any values reported by API should be ignored until the hobbyist throws them in a trashcan and a more expensive test kit is purchased.
But when you measure the color response of these test kits to carefully made stock solutions of known concentration - you find that API kits perform exactly as they should in theory - forming color linearly proportional to the concentration.
I wanted to illustrate this by demonstrating the colorimetric performance of Total Ammonia, Nitrite, and High Range pH tests.

Here's API total ammonia test

Tightly linear over the range [0 - 2ppm]. The reagent amounts and ratios are tweaked a bit from the API box instructions for the range and the volume that I want to work with, but all the reagents are API. And whatever box of reagents I grab the performance is the same.


Next is the Nitrite - NO2 test.

With the recipe I'm working with, it stops being perfectly linear around 1ppm NO2 and above, so I use this when working with samples between [0 - 0.7ppm]. Above 1ppm, it still gets darker pink, just not in a clean linear way (at this reagent ratio).

And finally, here's API high range pH.
The pH test is a color indicator that's phenol red or very similar - it responds very well over the entire plausible range of saltwater pH. Here's the absorbance spectrum of the indicator in saltwater from pH of less than 7.0 to above 8.6.

The plot is showing the spectral data, but each of those colors is easily naked-eye distinguishable by comparison as well.

So if you do a ratio of the left peak and right peak absorbance and plot the log of that vs what a calibrated pH meter reads in the same solution you get this...

The log of the absorbance ratio is tightly linear to what my calibrated pH meter gives - within 0.05 pH units. (This means pH can be measured by recording color and no probe/calibration solution required, which is convenient sometimes.)

In all these examples, the technical details are unimportant, or at least the topic for another thread. What matters is that in all cases the API reagents are doing exactly what you want a chemical reagent to do. They have a repeatable, easily distinguished color response that is linear to the concentration of what you want to measure.

Here's an absurd example to drive the point home about the gap between how low the trust is of API vs how consistent the performance actually is.

I found this in a box in my garage: From the Lot numbers and the copyright info on the box and printed inserts - it was made in 2003.


So, how well does this 20yr old API ammonia kit work?
I used both API kits made 20 years apart to measure the same 0.0 and 1.0 ppm total ammonia saltwater solutions.

Pic taken at around 10 minutes - colorimetric measurements were made at around 30 minutes and I was a little shocked to see both kits gave completely identical results. ( I expected that the chlorine solution in reagent 2 would have lost its potency, but I guess the bottle was well sealed ... for 20 years. lol)


So when we say API results are "trash" etc (and there are some nonsensical results from API tests posted), we should probably talk about what we mean by that, and why they might be bad - because the chemistry is solid.

So telling somebody to go use a different set of chemicals to do the same thing seems unlikely to give a better result if the chemicals weren't the problem in the first place, right?

Dr. Wellfish says "Your garbage test results aren't my fault."

[Disclaimer, I don't love all API kits: NO3 and PO4 have too much lot to lot variation - so I'll always opt for hanna / red sea there.]

The PH one surprised me, because API always tests mine at 8.3, but probe I am usually 8 to 8.1. I have not tried another PH test, I might buy a new probe to see if thats the issue, but it reads calobration fluid dead on.

 

[Garf]

The PH one surprised me, because API always tests mine at 8.3, but probe I am usually 8 to 8.1. I have not tried another PH test, I might buy a new probe to see if thats the issue, but it reads calobration fluid dead on.

What are the values of the calibration fluid? PH7 & pH10?

 

[taricha]

Since api ammonia can be used comparatively how would I go about making a "reference" for a warning level of ammonia using 10% ammonia hydroxide? I understand there may be a difference between nh3 and nh4 that would have to be accounted for to truly know danger to fish?

Aim for 0.50ppm total ammonia. Run the API test on your water, and your water +0.50ppm do it at the same time. Photograph both next to the color card. Use this photo as the reference for concern. Unless color equals or exceeds that, I would not worry about it.

 

[taricha]

The PH one surprised me, because API always tests mine at 8.3, but probe I am usually 8 to 8.1. I have not tried another PH test, I might buy a new probe to see if thats the issue, but it reads calobration fluid dead on.

Ha, I should point out here. I am defending the quantifiable response of the API chemicals. I am absolutely not defending their color cards, which are sometimes confusing and often useless. For me to provide information that you could use regarding the API pH test, I would need to give you a picture of the pH indicator color versus the color card for each pH and you could use that information with more confidence. But I didn't think to take pictures along the way during this process!

 

[brandon429]

edit

 

[brandon429]

@taricha I think I posted this in the wrong thread ugg. Ill move data to the other thread

 

[Reefahholic]

No Red Sea, Salifert, or Hanna checker data?

 

[taricha]

No Red Sea, Salifert, or Hanna checker data?

Yes, lots! But those are in different threads

 

[Reefahholic]

Yes, lots! But those are in different threads

I find that Hanna Checkers to be pretty accurate, but my Red Sea Cal and Mag seem to keep coming back high on the ICP. I mentioned in another thread that what seems to be happening is that if you stop at first color change (less titration solution used) the value is lower so of course it would make anybody want to correct back to the target range. If Mag appears to be 1200 and I keep it at 1350 I’m fixing to dose it up. Same with Cal.

So lately I’ve been trying to get a complete color change, which of course is using more titration solution and the value is higher on the card. I think it’s more accurate this way. My ICP was coming back 50-100 ppm too high which is not even close, and those major elements have excellent sensitivity so I don’t believe it’s the ICP. It’s me! Lol.

The other possibility is that I use BRS Pharma for CAL/ MAG corrections, and maybe their calculator is off. Again, I still don’t wanna blame them, I’d rather blame myself.

Thought about switching to Salifert, but which are you finding more accurate?

 

[BeanAnimal]

Well it started off interesting for a few posts until it was taken over with cycling and seneye rambling. It’s a shame that happens so often.

Anyway, I now see why this brand and chemistry is often used in numerous hobby and other testing automation projects.

 

[Reefahholic]

Well it started off interesting for a few posts until it was taken over with cycling and seneye rambling. It’s a shame that happens so often.

Anyway, I now see why this brand and chemistry is often used in numerous hobby and other testing automation projects.

I guess it’s ok to say how much I’ve enjoyed your overflow then for the last 12-14 years I’ve been running it. Lost count.

 

[Randy Holmes-Farley]

Ha, I should point out here. I am defending the quantifiable response of the API chemicals. I am absolutely not defending their color cards, which are sometimes confusing and often useless.

I think the title is misleading folks. Maybe it should have read "the chemistry behind the kits is potentially good"

 

[Court_Appointed_Hypeman]

I find that Hanna Checkers to be pretty accurate, but my Red Sea Cal and Mag seem to keep coming back high on the ICP. I mentioned in another thread that what seems to be happening is that if you stop at first color change (less titration solution used) the value is lower so of course it would make anybody want to correct back to the target range. If Mag appears to be 1200 and I keep it at 1350 I’m fixing to dose it up. Same with Cal.

So lately I’ve been trying to get a complete color change, which of course is using more titration solution and the value is higher on the card. I think it’s more accurate this way. My ICP was coming back 50-100 ppm too high which is not even close, and those major elements have excellent sensitivity so I don’t believe it’s the ICP. It’s me! Lol.

The other possibility is that I use BRS Pharma for CAL/ MAG corrections, and maybe their calculator is off. Again, I still don’t wanna blame them, I’d rather blame myself.

Thought about switching to Salifert, but which are you finding more accurate?

I use the aquaforest standard to figure out the variance on my mag and calc kits, they are always off, but consistently for the life if the reagents. So usually its a +or -40 on mag and +30 on calc. When adjusting these values for the life of the kit it seems accurate when going from old to new kit.

 

[taricha]

I think the title is misleading folks. Maybe it should have read "the chemistry behind the kits is potentially good"

True.
Please change Title to "Despite API reputation, the Chemicals in the test kits are actually good." - or something similar.
That's really what I'm arguing.

 

[taricha]

Anyway, I now see why this brand and chemistry is often used in numerous hobby and other testing automation projects

yep. It's ideal for those purposes. Cheap, Liquids, scalable to small or large volumes, reliable linear color response to the things measured.

 

[Randy Holmes-Farley]

True.
Please change Title to "Despite API reputation, the Chemicals in the test kits are actually good." - or something similar.
That's really what I'm arguing.

Done.