Five test solutions were chosen that were known to have total nitrite or nitrate levels in the range of aquarium nitrite and nitrate test kits. These were: 1) A sample of "typical" aquarium water of NO₂^1- or NO₃^1- < 0.05 ppm (as a blank), 2) a sodium nitrite (NaNO₂) solution with NO₂^1- = 1.0 ppm, or a sodium nitrate (NaNO₃) solution with NO₃^1- = 20.0 ppm, 3) a sodium nitrite (NaNO₂) solution with NO₂^1- = 2.0 ppm, or a sodium nitrate (NaNO₃) solution with NO₃^1- = 75.0 ppm, 4) a sodium nitrite (NaNO₂) solution with NO₂^1- = 3.0 ppm, or a sodium nitrate (NaNO₃) solution with NO₃^1- = 100.0 ppm, and 5) a sodium nitrite (NaNO₂) solution with NO₂^1- = 4.0 ppm, or a sodium nitrate (NaNO₃) solution with NO₃^1- = 125.0 ppm. The sodium nitrite and sodium nitrate solutions were prepared from anhydrous solid sodium nitrite or anhydrous solid sodium nitrate weighed on an analytical balance to the nearest milligram and dissolved in ultra-pure de-ionized water, respectively.

        An example preparation of a nitrite solution would be: 2.0 ppm NO₂^1- = 2.0 ^mg/_L NO₂^1- X 1.50 mg NaNO₂/mg NO₂^1- = 3.00 ^mg/_L NaNO₂ -- weigh 30.0 mg NaNO₂ and dilute to volume in a 100 ml volumetric flask (0.300 ^mg/_ml). Take 10 ml of this solution and dilute to volume in a 1 L volumetric flask (3.00 ^mg/_L NaNO₂).

        An example preparation of a nitrate solution would be: 20.0 ppm NO₃^1- = 20.0 ^mg/_L NO₃^1- X 1.37 mg NaNO₃/mg NO₃^1- = 27.40 ^mg/_L NaNO₃ -- weigh 274.0 mg NaNO₃ and dilute to volume in a 100 ml volumetric flask (2.74 ^mg/_ml). Take 10 ml of this solution and dilute to volume in a 1 L volumetric flask (27.40 ^mg/_L NaNO₃).