Calculate the volumes of stock solutions.
Prepare standard solutions of 0, 0.2, 0.4, 0.6 and 1.0 ppm nitrite
by pipetting the appropriate amount of stock nitrite solution (ca. 20 ppm) into 100 mL volumetric flasks. Measure with a disposable plastic pipette and add to each flask 2 mL dilute HCl and 2 mL sulfanilic acid. Add 2 mL N-(1-naphthyl)ethylenediamine dihydrochloride solution and 2 mL 2 M sodium acetate. Dilute to the mark with distilled water. Mix well by stoppering the flasks and inverting several times. Let the standard solutions stand for 5 minutes.