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.