ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 29, Number 1
JKCSEZ 29(1)
February 20, 1985 

Oxides of nitrogen (NOx) in exhaust gases was determined by absorbing the gas in alkaline peroxide solution containing 0.03% H2O2 and 0.1N NaOH. About 100 ppm of NOx was rapidly oxidized to NO2 or N2O5 by H2O2 and required a contact time of 2 minutes with the absorbing solution for complete absorption. With vigorous shaking including air or oxygen gas, high concentration of NOx (>200 ppm) can be absorbed within 30 minutes. The remaining H2O2 affect the absorbance of color solution strongly. However, the excess H2O2 was completely decomposed by zinc powder 0.5g and the sample solution should be adjusted to the pH range 6.1∼6.6 before the reduction so that conversion of nitrate to nitrite ion is possible. The absorbed NOx is determined colorimetrically by the diazotization-coupling method with sulfonilamide and NEDA as the coupling agent. The sensitivity of the new method was 4.48 × 104 as molar absorptivity which was high sensitive compared with that obtained for the usual zinc reduction NEDA method with O3. This method was far more rapid, brief and accurate than previously published O3-NEDA method in Korean industrial standard.