A new method for the measurement of trace amounts of HONO in the atmosphere using an air-dragged aqua-membrane-type denuder and fluorescence detection

A new method for the measurement of trace amounts of HONO has been developed. Nitrous acid in the ambient air is absorbed in an aqueous solution by an air-dragged aqua-membrane-type denuder. The absorbed nitrite is reacted with 2,3-diaminonaphthalene, and the formed 1-naphthotriazol is measured using a fluorescence method. The calibration curve of HONO shows a straight line from 0 to 4000 ppt, and the detection limit is estimated to be 8.1 ppt calculated as being three times of the base line noise. The time resolution, which is defined as the time required to become a constant value by changing from 0 to ca. 1000 ppt was 2 min. The present method is not affected by NO2, NO, SO2, O3 NH3 or mixtures of these gases and organic nitrate, organic carboxylic acids, alcohols and aldehydes. The determination results of HONO concentrations in the ambient air by the present method are in good agreement with those by the annular denuder system and the differential optical absorption method.