Sampling and Raman confocal microspectroscopic analysis of airborne particulate matter using poly(dimethylsiloxane) solid-phase microextraction fibers

Commercial poly(dimethylsiloxane) (PDMS) 7-microm solid-phase microextraction (SPME) fibers were used for sampling and Raman spectroscopic analysis of a tailpipe diesel exhaust, candle smoke, cigarette smoke, and asbestos dust. Samples were collected via direct exposure of the SPME fiber to contaminated air. The mass loading for SPME fibers was varied by changing the sampling time. Results indicate that PDMS-coated fibers provide a simple, fast, reusable, and cost-effective air sampling tool for airborne particulates. The PDMS coating was stable; Raman bands of the PDMS coating were observed exactly at the same wavenumber positions before and after air sampling. Raman spectroscopic analysis resulted in identification of several characteristic bands allowing chemical speciation of particulates. The advantage of the SPME fiber is the open bed geometry allowing for application of various spectroscopic methods of particulate analysis. This paper describes the first-ever combined application of SPME technology with Raman confocal microspectroscopy for sampling and analysis of airborne particulates. Advantages of the combination of solid-phase microextraction and Raman microspectroscopy for airborne particulate analysis are discussed. Challenges associated with combined SPME sampling and Raman analysis of single particles are also described.