Beyond Targeted Calibrations: Comprehensive Quantification of Oxygenated Organic Compounds in Urban Atmospheres.

Quantifying oxygenated volatile organic compounds (OVOCs) in the atmospheric gas phase remains a major challenge, particularly in urban environments where these compounds are important contributors to air quality and health impacts. Here, we present a collision-induced dissociation based voltage-scanning method to derive sensitivities for an ammonium-adduct chemical ionization mass spectrometer, enabling quantification of OVOCs beyond those available for direct calibration. The method was validated under laboratory conditions and applied during the 2023 AEROMMA airborne campaign and the 2024 SAPHIR-CHANEL chamber campaign. The approach extended quantification coverage to 98% of the total signal in chamber experiments and 78% in field measurements. Detected species spanned a wide volatility range, with chamber experiments allowing enhanced detection of more oxidized, higher-molecular-weight products compared to the more variable and diluted field observations. Although coverage decreased with increasing molecular size and oxidation state, the method consistently extended into these regimes, particularly under controlled chamber conditions. Sensitivity trends between chamber and field data showed strong agreement, supporting the use of chamber-derived calibrations for ambient quantification. Incorporating these additional quantified species increased estimates of OH reactivity and secondary organic aerosol formation potential by around 5% and around 62%, respectively, contributing to improved chemical closure in urban air.