SPECTROPHOTOMETRIC DETERMINATION OF NITROGEN-DIOXIDE (NITRITE)

A highly sensitive spectrophotometric method has been developed for th e determination of nitrogen dioxide (nitrite as NO2-) by reacting mang anese dioxide in 1:20 perchloric acid. An amount of manganese dioxide (MnO2) equivalent to the concentration of nitrogen dioxide becomes sol uble due to the reduction of Mn (IV) to Mn (II) by nitrite in acidic m edium. The soluble Mn (II) ion is filtered to remove excess of MnO2 an d is oxidized to permanganate ion by periodic acid in presence of phos phoric acid. The violet colored solution shows maximum absorbance at 5 25 nm. The sensitivity of the method is 0.08 ppm based on 0.0044 absor bance, and Beer's law is obeyed in the concentration range of 0.2 to 1 0.0 mug/mL of NO2-. Molar absorbance is found to be 2442 at 525 nm.