A method for the measurement of atmospheric HONO based on DNPH derivatization and HPLC analysis

A simple measurement technique was developed for atmospheric HONO based on aqueous scrubbing using a coil sampler followed by 2,4-dinitrophenylhydrazi ne (DNPH) derivatization and high-performance liquid chromatographic (HPLC) analysis. Quantitative sampling efficiency was obtained using a 1 mM phosp hate buffer, pH 7.0, as the scrubbing solution at a gas sampling flow rate of 2 L min(-1) and a liquid flow rate of 0.24 mL min(-1). Derivatization of the scrubbed nitrous acid by DNPH was fast and was completed within 5 min in a derivatization medium containing 300 mu M DNPH and 8 mM HCl at 45 degr ees C. The azide derivative was separated from DNPH reagent and carbonyl de rivatives by reverse-phase HPLC and was detected with an UV detector at 309 nm. The detection limit is less than or equal to 5 pptv and may be lowered to 1 pptv with further DNPH purification. Interferences from NO, NO2, PAN, O-3, HNO3, and HCHO were studied and found to be negligible. Ambient HONO concentration was measured simultaneously in downtown Albany, NY, by this m ethod and by an ion chromatographic technique after sampling using a fritte d bubbler. The results, from 70 pptv during the day to 1.7 ppbv in the earl y morning, were in very good agreement from the two techniques, within +/- 20%.