A simple measurement technique was developed for
atmospheric HONO based on aqueous scrubbing using a
coil sampler followed by 2,4-dinitrophenylhydrazine (DNPH)
derivatization and high-performance liquid chromatographic
(HPLC) analysis. Quantitative sampling efficiency was
obtained using a 1 mM phosphate 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 μM DNPH and 8 mM HCl at 45 °C. The azide derivative
was separated from DNPH reagent and carbonyl
derivatives by reverse-phase HPLC and was detected
with an UV detector at 309 nm. The detection limit is ≤5
pptv and may be lowered to 1 pptv with further DNPH
purification. Interferences from NO, NO2, PAN, O3, HNO3,
and HCHO were studied and found to be negligible. Ambient
HONO concentration was measured simultaneously in
downtown Albany, NY, by this method and by an ion
chromatographic technique after sampling using a fritted
bubbler. The results, from 70 pptv during the day to 1.7 ppbv
in the early morning, were in very good agreement from
the two techniques, within ± 20%.
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