|Re: API Nitrite test - warning when cycling|
Subject: Re: API Nitrite test - warning when cycling
by Anna Robinson on 2012/11/13 18:28:07
When I saw this thread I mentioned it to the Head of Scientific Affairs at API. He wrote me a response, which I thought I'd post here for people to read.
Ranges for chemical measurements have limits. The lower limit is important because it determines whether a measurement is different from zero. The maximum Test Kit Detection Limit is important because this is the upper limit that any test kit can provide an answer for 99% level of confidence. All API Test Kits show the detection limits clearly on the packaging, instructions and colour charts.
API Test Kits are designed for use under normal conditions found within an aquatic environment (aquariums and ponds). The tests allow for, and are designed for, interferences and limited detection limits. When test results appear inaccurate, develop an unexpected colour or develop an unusual turbidity, repeating the test using a diluted sample with deionized water may be useful.(Dilution of samples is not appropriate for all tests, such as pH).
As an example the API Nitrite Kit is designed to provide accurate results from 0 to 5 ppm (mg/L). Under extreme conditions as high as 25 ppm (mg/L) the Nitrite Test Kit will still show a positive nitrite result but darker than the highest colour on the colour chart. A level of 25 ppm (mg/L) would be very unlikely in a home aquarium or pond and, of course, toxic to fish. Under even more extreme conditions, the API Nitrite Test Kit can be overwhelmed.
As an example I share the following to provide a better understanding of the API Nitrite Test Kit (liquid reagents):
At 0ppm Nitrite the test result reads as 0ppm Nitrite.
At 0.25ppm (mg/L) the test result reads as 0.25ppm (mg/L) Nitrite
At 1.0ppm (mg/L) the test result reads as 1.0ppm (mg/L) Nitrite
At 5.0ppm (mg/L) the test result reads as 5.0ppm (mg/L) Nitrite
At 25ppm (mg/L) Nitrite the test result stays deep purple for 5 minutes. (Note: purple colour is above the 5.0ppm top detection limit of the colour chart provided with the test kit)
At 50ppm (mg/L) Nitrite, the test result turns deep purple initially, but back to light blue after 5 minutes.
At 100ppm (mg/L) Nitrite, the test result turns deep purple initially, but back to light blue after 1.5 minutes.
At 1000ppm (mg/L) Nitrite, the test result turns light blue, never turning purple.