Synthesis of Reference Standards and Optimization of UPLC-ESI-MS/MS Method for Quantification of Organosulfates in...

Atmospheric PM_2.5 affects climate by altering radiative forcing and harms human health. Organosulfates (OSs) intensify these impacts, as cloud condensation nuclei modify the radiation balance and increase toxicological risks. We synthesized OSs reference standards and optimized a sensitive UPLC-MS/MS method, enabling precise quantification to mitigate PM_2.5 pollution on climate and health.

We synthesized five organosulfates (ethyl-, 3-methylbenzyl-, cyclohexyl-, benzyl-, and phenethyl sulfate) as reference standards. These, combined with four commercial standards (methyl-, phenyl-, octyl-, and 4-nitrophenyl sulfate), were quantified by ultra-high performance liquid chromatography coupled with electrospray ionization (ESI) tandem mass spectrometry (UPLC-ESI-MS/MS). Separation used a Waters HSS T3 column with a gradient mobile phase (0.1% formic acid in H₂O/CH₃OH). ESI in negative mode enabled sensitive MS/MS detection.

A nine-point calibration curve ranging from 0.08 to 20 ng mL^-1 of standards in solvent was used to establish instrument response. The method was validated by analysis of three replicate environmental samples fortified with 5 ng mL^-1 of mixed standard. The recoveries of various OSs were 44%-126%, and their method detection limits were 0.10 ng mL^-1 and the method limits of quantification were 0.50 ng mL^-1.

The optimized UPLC-ESI-MS/MS method was successfully applied for the determination of various OSs in PM_2.5 collected from Tianjin, China. It enables the precise measurement of OSs in aerosols that provide a critical tool to improve air quality monitoring and develop strategies to reduce pollution-related health impacts.