Measuring nitrite with the colorimeter

Greiss Assay

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Greiss Assay

_images/nitrite_greiss.JPG

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.

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