Simultaneous measurements of formaldehyde and ozone in air by annular denuder-HPLC techniques
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A denuder sampling method combined with HPLC analysis for the simultaneous determination of formaldehyde and ozone in ambient air is described. It is based on the reactions of CH2O and O3 with 2,4-dinitrophenylhydrazine (DNPH) and 4-allyl-2-methoxyphenol (eugenol)_respectively, both acting as coatings of two annular denuders connected in series. Formaldehyde released from the ozonolysis of eugenol is quantitatively collected on a third downstream DNPH-coated denuder. The two DNPH denuders are then extracted and analyzed as hydrazone derivative by HPLC with UV absorbance detection.
The stoichiometric factor of the eugenol-ozone reaction was found to be 2.0±0.1 moles of O3 per mole of CH2O. The limits of detection are 0.8μgm−3 CH2O and 3μgm−3 O3 for 100l air sampled, corresponding to 1-h sampling at 1.7l min−1.
Key WordsColumn liquid chromatography Ozone Formaldehyde Annular denuder Air monitoring
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