Abstract: | Modification of the luminol solution by means of addition of various complexones and surfactants has been investigated to eliminate interferences from gaseous co-pollutants in the determination of ambient nitrogen dioxide using a chemiluminescence aerosol detector. The simultaneous presence of EDTA and triton X-100 or X-405 together with sulphite and iodide in the luminol solution suppressed interferences from ozone and peroxyacetyl nitrate to a negligible level and no scrubbers or corrections of the NO2 measurements were needed. In general, the best composition of the reagent solution included luminol, KOH, Na2SO3, KI, Na2EDTA and triton X-100. From the point of view of selectivity of NO2 determination, an optimum reagent solution consisted of luminol (0.002 M), KOH (0.5 M), Na2SO3 (0.2 M), KI (0.1 M), Na2EDTA (0.05 M) and triton X-100 (0.5 vol.%). Interferences from ozone (170 ppb (v/v)) and peroxyacetyl nitrate (81 ppb (v/v)) were 0.2 and 1.2%, respectively, for nitrogen dioxide at a concentration of 50 ppb (v/v) and 0.25 and 1.7%, respectively, for 0.5 ppb (v/v) NO2. The calibration graph was linear for NO2 concentrations ranging from 3 to 665 ppb (v/v). Below 3 ppb (v/v) NO2 the detector response to nitrogen dioxide can be fitted with a linear equation of the third order. |