For the determination of nitrite, a 5-g portion of
each sample was weighed out and transferred to a
Falcon tube. Thirty milliliters of deionized water at
80 °C was added and the mixture stirred for 2 min.
The homogenized sample was heated and the temperature
maintained at 80 °C for 2 h. After cooling to
room temperature, the sample was filtered (using
Whatman 41 filter paper) and the volume adjusted to
500 mL with deionized water. A 5-mL aliquot of the
filtered solution was transferred to a 50-mL volumetric
flask and 2.5 mL of the sulfanilamide reagent added
with mixing. The mixture was left to stand for 5 min at
room temperature and then 2.5 mL of NED reagent
was added with mixing, followed by dilution to
volume. After 15 min, the absorbance was measured
at 540 nm.