Accurate Quantification of Multifunctional C_2–3 Organosulfates in Atmospheric Aerosols Using Liquid Chromatography-Electrospray Ionization Mass Spectrometry: Overcoming Matrix Effects and Underestimation

Reversed-phase liquid chromatography (RPLC) coupled with electrospray ionization-mass spectrometry (ESI-MS) is widely used to analyze polar organic compounds in atmospheric particulate matter (PM). However, its efficacy for small, polar multifunctional C₂-C₃ organosulfates (C_2-3OSs)─conceivably key products of isoprene oxidation─is questionable. Notable matrix effects are anticipated to arise from poor retention and coelution with abundant salts in PM samples. Here, we systematically evaluated RPLC versus hydrophilic interaction liquid chromatography (HILIC) coupled with ESI-Orbitrap MS in quantifying PM-bound C_2-3OSs. We synthesized three C_2-3OSs, including glycolic acid sulfate, hydroxyacetone sulfate, and lactic acid sulfate. The availability of authentic standards enabled the first quantitative assessment of measurement bias for C_2-3OSs using the RPLC-ESI-Orbitrap MS method, revealing an underestimation of these compounds by 1-2 orders of magnitude. The measurement bias primarily stemmed from the matrix effects arising from the coexisting bisulfate in ambient PM. In contrast, HILIC notably outperformed RPLC in retentive capacities and peak resolving abilities, effectively avoiding matrix suppression effects. Additionally, the HILIC-ESI-MS method uncovered six previously unreported C_2-3OSs, expanding our knowledge of atmospheric OSs. This work enhances our capability of accurate quantification of aerosol components, thus helping to reduce constraints on studies of aerosols and their impacts.