I personally tested for nitrite with expired and new nitrite reagent and both results were exactly the same.
Bad API test kit?
- Thread starter dr exum
- Start date
I personally tested for nitrite with expired and new nitrite reagent and both results were exactly the same.
API test kits are extremely technique sensitive, especially the nitrate test. If the reagents and test vial is not shaken exactly as directed, there will be an inaccurate reading. I suspect the remaining solution in the bottle is not what it should be since reagent was removed without proper mixing first. My biggest problem with the API test is the color chart. I have a difficult time differentiating slight nuances in color, so my nitrate readings were always a guess. I got a HANNA Nitrate Tester, which is also technique sensitive, but I no longer have to guess.
Wow that's pretty neat! Just saw online that they're not exactly cheap but seems a good investment and likely more cost efficient over time. I saw some of their Handheld Colorimeters (for ammonia & nitrate) that are much cheaper and look interesting but need to research more how accurate/dependable they are:
Yeah I was gonna say that
Lol I have no idea what the Nessler method is, nor why it might be a drawback -- but I'm sure you've got a chart to help elucidate this Squint buddy, so c'mon let's see it 
Yup, shake it with much vigor and long, hit it on a table to break up the crystals, etc.
If stored in a cool dark place, the API tests expired by years, even 5 years give the same readings as newly bought. IME anyway.
On the nitrAte tests. They can easily be off by a factor of 5x-10x. As in you are reading 40 ppm while in reality it is 200-400 ppm. There is a lot of interference from other anions, such as the ubiquitous chloride, in the measurement and many others, that neither home tests, nor even many laboratory tests are accurate.
IIRC, an ion-selective electrode would be needed that costs thousands of dollars and even using that has its caveats.
In any case, our nitrAte home readings are very, very approximate and are relative (not absolute) at best.
The rest of the tests are thought to be accurate in absolute terms in average circumstance.
If stored in a cool dark place, the API tests expired by years, even 5 years give the same readings as newly bought. IME anyway.
On the nitrAte tests. They can easily be off by a factor of 5x-10x. As in you are reading 40 ppm while in reality it is 200-400 ppm. There is a lot of interference from other anions, such as the ubiquitous chloride, in the measurement and many others, that neither home tests, nor even many laboratory tests are accurate.
IIRC, an ion-selective electrode would be needed that costs thousands of dollars and even using that has its caveats.
In any case, our nitrAte home readings are very, very approximate and are relative (not absolute) at best.
The rest of the tests are thought to be accurate in absolute terms in average circumstance.
