SPECTROPHOTOMETRIC DETERMINATION OF NITROGEN-DIOXIDE (NITRITE)

A new spectrophotometric method is reported for the estimation of nitrogen dioxide and nitrite. Acidified p-rosaniline hydrochloride is diazotised in the presence of nitrite or nitrogen dioxide which is later coupled with bisphenol A in alkaline medium to yield a yellow colour dye with maximum absorption at 460nm. The method is applied to the determination of nitrogen dioxide in air employing alkaline sodium arsenite as well as bisphenol A solution as trapping agent. The nitrogen dioxide absorbed in bisphenol A is found to be very stable. The interference of copper(II), lead(II), Manganese (II), vanadium(V), Chromium (VI), sulphite and sulphide is investigated and results are reported. The method is simple, sensitive and nitrogen dioxide/nitrite content as low as 0.04 μg/ml can be estimated. © 1990.