Rapid quantitative analysis of SVOCs in indoor surface film using Direct Analysis in Real Time mass spectrometry: A case study on phthalates

Abstract. Direct Analysis in Real Time Mass Spectrometry (DART-MS) is recently emerged as a promising approach for measuring semi-volatile organic compounds (SVOCs) in indoor surface films. However, its broader application in indoor environments is limited by low measurement repeatability and no separation of isomers. Herein we developed a sampling suite of indoor surface film for DART-MS analysis, optimized settings of DART to obtain higher analytical performance, and demonstrated the possibility of separating isomeric compounds using tandem mass spectrometry (MS/MS). Two pair of isomeric phthalate esters, including di(2-ethylhexyl) phthalate (DEHP) and di-n-octyl phthalate (DnOP), diisobutyl phthalate (DiBP) and di-n-butyl phthalate (DnBP), were used as examples for method optimization and validation. Under optimized conditions, the instrument responses for all four compounds exhibited good linearity (r > 0.992) and acceptable repeatability (intraday RSD < 11.0%). The limits of quantification for the four PAEs ranged from 0.042 to 0.24 ng/cm². The uncertainty in the separation of isomeric components using MS/MS was <11.4%, which is acceptable for real sample analysis. To further assess the developed method, we analyzed 10 film samples collected side by side in an occupied office. DnOP was not detected. The RSD among samples was 6.1% for DEHP, 4.6% for DnBP, and 10.4% for DiBP, indicating overall good repeatability of the collection and measurement method developed. With improved performance, the developed method increases the feasibility of the DART-MS technique for monitoring dynamics of chemical composition of indoor surface films.