A sensitive spectrophotometric determination of nitrogen dioxide in the working atmosphere

Abstract

In the present investigation, a simple and sensitive spectrophotometric method for the determination of nitrogen dioxide in various environmental samples is described. Nitrogen dioxide in air was fixed as nitrite ion in alkaline sodium arsenite absorbing solution. The nitrite formed was diazotized with paminoacetophenone in acidic medium which was subsequently coupled with phloroglucinol to give yellow-orange dye in alkaline medium having an absorption maximum at 420 nm. Beer’s law was obeyed in the range of 0.008 - 0.12 μg mL^-1 of nitrogen dioxide and has a molar absorptivity of 2.875 x 105 L mol^-1 cm^-1. Optimum reaction conditions for diazotization, full colour development and the effect of variables like temperature, time and pH have been studied. Detailed studies to check the collection efficiency and NO²:NO² - stoichiometric ratio has been
carried out. The reaction has been successfully applied for the detection of nitrogen dioxide in cigarette smoke, scooter exhaust, and workroom air.