Determination of nitrite and nitrogen dioxide by spectrophotometry after solid phase extraction

A simple method for the determination of nitrogen dioxide using alkaline Ferron as an absorbing medium as well as coupling agent is proposed. Nitrite ion diazotizes p-aminoacetophenone in the absorbing solution and the diazotised p-aminoacetophenone is subsequently coupled with ferron. The orange-red dye was extracted in an amino cartridge, which shows a maximum absorbance at 485 nm, obeys Beer's law in the range of 0.04 to 0.36 mu g mL(-1) of nitrogen dioxide and has a molar absorptivity of 9.40 center dot 10(4) 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 method has been successfully applied for the analysis of nitrogen dioxide in cigarette smoke, scooter exhaust, and workroom air. The method has also been applied for the determination of nitrite in water, soil etc.