title: Quantitative solid-phase microextraction (SPME)-Raman spectroscopy for the detection of trace organics in water.
abstract: Solid-phase microextraction (SPME) was used along with Raman spectroscopy to quantify the partitioning of trace organics into polydimethylsiloxane (PDMS) matrices. PDMS has previously been utilized with SPME-Raman to pre-concentrate trace benzene, toluene, ethyl-benzene, and  xylene fuel components from contaminated water, thereby enhancing detected Raman signals. Here, we show that SPME can increase Raman signals more than two orders of magnitude for the compounds investigated. We also demonstrate the quantitative features of SPME-Raman by estimating PDMS-organic  partition coefficients for benzene [log(K) = 1.90 ± 10] and toluene [log(K) = 2.35 ± 20] by using linear regression fits in the dilute limit of concentrations. The K values obtained are within the range of values obtained with other quantitative SPME techniques.  The method was also used to characterize quinoline, a pyridine-based organic, which yielded reasonable K values [log(K) = 1.20 ± 20]. Combining PDMS-based SPME with a technique such as Raman spectroscopy potentially enhances optical detection methods used in microfluidic  systems, wherein PDMS is a common material of construction.
authors.affiliation: Department of Chemical Engineering, University of Washington, Seattle, WA 98195-1750, USA.
authors.forename: Ikechukwu C
authors.initials: IC
authors.lastname: Nwaneshiudu
authors.forename: Qiuming
authors.initials: Q
authors.lastname: Yu
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Schwartz