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.