Macherey-Nagel test strips for nitrate and nitrite together, in one presentation.
91313
A semi-quantitative test strip for nitrate and nitrite together, on one strip with two pads. Dip it, wait the stated time, and compare the pad against the colour scale on the tube.
The pair is more informative than either alone: nitrite high with nitrate low says the biological filter is still maturing, while nitrate high with nitrite at zero says it is working and the water simply needs changing.
A strip gives a range, not a figure. That is enough for the great majority of decisions — dose or do not dose, discharge or hold, keep running or stop — and it gives the answer where the sample is, in about a minute, with no instrument to calibrate and nothing to carry back to a laboratory.
When a number has to be defensible — a regulatory report, a dispute, a limit you are close to — a photometer or a laboratory method is the right tool. The strip's job is to tell you whether you need one.
Read both pads at the time the instructions state; the two reactions do not develop at the same speed.
Supplied in one presentation.