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Low-level atmospheric sulfur dioxide measurement using HPLC/fluorescence detection


An automated technique for measuring SO2 in ambient air has been developed. Air is passed through a gas/liquid exchange coil with an aqueous absorber solution containing 10 μM formaldehyde and 0.84 mM Na2EDTA. The SO2 rapidly equilibrates with bisulfite (HSO3-) and sulfite (SO32-) in the aqueous solution. The aqueous S(IV) is subsequently reacted with o-phthaladehyde in the presence of excess ethanolamine to form a fluorescent isoindole in a continuous flow stream. This derivative is then separated using reversed phase HPLC and detected via fluorescence with excitation and emission wavelengths at 330 and 380 nm, respectively. The lower limit of detection is 7 pptv (S/N=3), with a measurement period of eight minutes per sample. The instrument response is linear over several orders of magnitude. © 1993 Kluwer Academic Publishers.

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