Nitrite-Greiss

Reagents & Equipment

  • Colorimeter

  • Cuvettes with caps (preferably semi-macro cuvettes)

  • Sulfanilamide, Sigma Cat # S9251-100G

  • 3M HCl, Carolina Cat # 867861

  • NED (N-1-napthylethylene diamine dihydrochloride), Sigma Cat # 33461-5G

  • 1 mL and 100 uL variable pipettes

  • 2 x small amber storage bottles

  • Analytical balance

  • Distilled water

Colorimeter set-up

  • Wavelength: 528 nm. Green led (colorimeter RGB board)

  • Nitrite standard data: 0 - 2.0 ppm NO2 range. Download a data file or prepare your own nitrite standard data

  • Before measuring a sample, blank the colorimeter against water or a distilled water sample developed with Greiss reagents as described below

Method

Step 1: Prepare fresh reagents

1% Sulfanilamide solution

  • Weigh out 0.15g of sulfanilamide into a small amber bottle.

  • Add 15mL of 3M HCl.

  • Shake to mix.

0.02% NED solution

  • Weigh out 2 mg (0.02 g) of NED into an amber bottle.

  • Add 100 mL of distilled water.

  • Shake to mix.

Step 2: Colorimetric assay

  • Transfer 1 mL of each sample to be tested into a cuvette

  • Add 50 µL of 1% sulfanilamide reagent, cap cuvette and invert several times to mix

  • Add 50 µL of 0.02% NED, cap cuvette and invert several times to mix

  • Let tubes stand for 5-10 mins to develop color.

  • Place the cuvette in the colorimeter and click measure. The program will return the nitrite concentration in ppm.