A high-sensitivity MCPP derivatization method for determination of aldehydes, ketones, and carboxylic acids in metro dust by nanoLC-MS and its application to health risk assessment.

Metro systems represent semi-enclosed environments in which limited ventilation promotes the accumulation of particulate matter, leading to the enrichment of carbonyl compounds in deposited dust and raising concerns regarding human exposure. However, the accurate determination of carbonyl compounds remains challenging owing to their high polarity, chemical reactivity, and limited compatibility of conventional derivatization strategies across different functional classes. To address these challenges, a unified pre-column derivatization strategy was developed for the parallel determination of aldehydes, ketones, and carboxylic acids. A novel acyl hydrazide-functionalized coumarin reagent, 3-(4-propanoylhydrazide)-7-methoxycoumarin (MCPP), was designed to integrate a reactive derivatization site with a signal-amplifying scaffold, enabling hydrazone formation for aldehydes/ketones and carbodiimide-mediated amidation for carboxylic acids. Coupling with nanoLC-MS significantly enhanced ionization efficiency, achieving a signal amplification of approximately 960-fold. Method validation results demonstrated that the proposed method enabled the qualitative and quantitative analysis of 29 aldehydes, 5 ketones, and 17 carboxylic acids, exhibited a wide linear range (10-5000 nmol/L), low limits of detection (<1 nmol/L), good reproducibility (RSD <5.34%), and satisfactory recoveries (80.39%-116.02%). Application to metro dust samples resulted in the identification of 43 carbonyl compounds, demonstrating the applicability of the method for trace analysis in complex environmental matrices. Preliminary non-carcinogenic health risk assessment indicated that certain α,β-unsaturated aldehydes, such as trans-2-hexenal and trans-2-heptenal, may pose potential non-carcinogenic health risks in dust from specific stations.