Chemistry Of Api Test Kits

[ldsdbomber]

What are the chemicals and reactions in the liquid API test kits?
What happens when they start to get past their expiry date?
What happens if you don't clean out your old test tubes properly and do other tests?

I ask because now and then I will get a 0.25 reading on ammonia or nitrite, each time it happened I double and triple checked after thoroughly recleaning test tubes and they were clearly 0. The tank is cycled, a few months old, and lightly stocked, and fairly well planted. I didn't believe the non zero results, and glad I checked

My test kits are past their expiry date, one is well past (bloody LFS!), and also on occasion I notice that I have left a bit of the old test in the plastic cap, can for example tank water & nitrite test solution cause a false positive in a following ammonia test and vice versa?

 

[tom130691]

i clean the tubes in tap water including the lid for a few minutes then before i use them i wash them in the tank water to get rid of and tap water left in them

 

[ldsdbomber]

i clean the tubes in tap water including the lid for a few minutes then before i use them i wash them in the tank water to get rid of and tap water left in them

yeah, but I am interested in the chemistry of these things, and hence, be able to understand what happens as the kits get old and/or if you get contamination between test solutions and old test water.

 

[OldMan47]

The answer to contamination is quite simple. If you don't have a clean sample, you really do not know what you are measuring. The answer to what the actual chemical reactions are that you are measuring is much more difficult. I will leave that to the real experts.

 

[ldsdbomber]

Thanks, it is the chemistry I am interested in, the contamination issue was just a side interest, I have a proper test tube brush now and clean them thoroughly!

 

[Bridie]

Some of the tests work with acids and pH-indicator (not only the pH-test, but also the test for hardness). So e.g if there is a trace of acid left in your tube, and you are going to measure pH next, the result will be wrong (too low).
Some ingredients mentionted on my testkit: NO3:Ethoxydiglycol, Aminobenzensulphoric acid, Hydroclorid acid, Acetic acid; NO2: Hydrocloric acid, Acetic Acid, Aminobenzisulfphoric acid; NH3: Mercuric Iodine, Sodium Hydroxide; , ....
maybe somebody else is more into chemistry?
The NO2 test is based on the GRIESS-reaction, try Wikipedia to find out more.

Hope that will help to answer your questions,
Bridie

 

[OohFeeshy]

Ammonia appears to be based on this

http/en.wikipedia.org/wiki/Nessler%27s_reagent

 

[vear]

Here is the MSDS for the API ammonia test kit: http/cms.marsfishcare.com/files/msds/ammonia_test_060507.pdf
It seems like their "solution #1" contains sodium salicylate and polyethylene glycol, while "solution #2" contains Sodium Hydroxide and Sodium Hypochlorite which is essentially bleach. Anyway, I've been trying to figure this out myself, since I have access to various chemicals and I figure I can save some money on test kits. yay.

Anyway, please don't quote me on this b/c I haven't done much research on it but, it seems like the ammonia reacts with salicylate ions and hypochlorite ions to form a complex called indophenol blue (this gives the color). The only thing I don't quite understand yet is that I thought it needs to be in the presence of some other ion (different papers quote different ions) in order for this reaction to take place. I have to ask my boss... I'm sure he'll come up with a super explanation. lol. By the way, if your test is expired, it's useless... unless it JUST expired. The sodium hypochlorite is diluted... and with time the Cl escapes... especially if it's been opened. I'm not sure about the sodium salicylate, I would think that would have a longer shelf life. Anyway... I'll try to figure things out and come back

 

[cybergibbons]

I know this is an old thread...

This pdf explains the salicylate ammonia test. As said above, sodium hypochlorite smells of chlorine because it is giving off chlorine slowly - so the concentration of the reagent is changing - I think this will be the expiry on this test.

I've not worked out what the other tests are exactly. I should imagine the pH ones are stable for a long while. The nitrate ones I can imagine do have a short expiry.

As I have often said, it really frustrating that we don't know the chemistry or mechanisms of most aquarium products, which means we need to rely on blind trust.

 

[Doc7]

Where can I find the expiration date on my API Freshwater Master kit?

 

[Essjay]

They don't have the expiry date as such on them. They have the date of manufacture, and each tester lasts a certain length of time after that.

I emailed the company a couple of years ago and this is what they told me.

The date of manufacture is hidden in the lot number. It will look something like Lot#28A0108; the 28A refers to the type of test (in this case a pH tester) and the 0108 is the month and year, so here Jan 2008.
They last for -
3 years - wide range pH; high range pH; ammonia; nitrate; phosphate; copper; calcium; GH
4 years - nitrite; KH
5 years - freshwater pH (low range)


However, I was also told that once the bottle has been opened, it only lasts for 1 year regardless of whether it has reached its unopened shelf life.

 

[Squidward]

They don't have the expiry date as such on them. They have the date of manufacture, and each tester lasts a certain length of time after that.

I emailed the company a couple of years ago and this is what they told me.

The date of manufacture is hidden in the lot number. It will look something like Lot#28A0108; the 28A refers to the type of test (in this case a pH tester) and the 0108 is the month and year, so here Jan 2008.
They last for -
3 years - wide range pH; high range pH; ammonia; nitrate; phosphate; copper; calcium; GH
4 years - nitrite; KH
5 years - freshwater pH (low range)


However, I was also told that once the bottle has been opened, it only lasts for 1 year regardless of whether it has reached its unopened shelf life.

According to my API test kit, you get hundreds of tests out of it. (Don't have it with me at work, so don't have the exact figures). It was £30, so not cheap.
Now if I test once a week, I am only going to use a fraction of the solutions in a year. And then have to bin the rest of the kit and get a new one after using only a small amuont of the solutions.

And most hobbyists with a tank or two will be in the same situation.

But why would the chemicals degrade after a year? Surely if they are fine up to a year in a closed bottle, they would be fine way beyond that?

 

[Essjay]

I posted the info about expiry dates on another site, and someone who works for the company posted to add the bit about only lasting a year after opening. So I thought they should know what they are talking about, and that I'd better include that bit about the year in future.
I can only assume it because as the contents are used, the space will be filled with air - specifically the oxygen in the air. I don't know how the bottles are manufactured, but it is possible that the space in the bottle is filled with an inert gas then sealed. Once they are opened, oxygen will get in and speed up the "going off" process. This is just sheer speculation.
Of course, it could be that the comapny want us to buy the kits more often than when they reach the expiry dates

 

[Squidward]

Just had a look at my kit.
can't see anywhere where it says must be used within a year of opening.

 

[Essjay]

It isn't anywhere on the pack, the bottle or the instruction leaflet. I'd never come across it before until I was told by someone who works for the company.

I've just checked the post on the other forum, and the person who works for the company said - API recommend that you don't keep the kit open for more than a year, even if it is still within the expiry date.
I would give a link to the post, but linking to other forums isn't allowed.