Capillary microextraction of volatiles device for enhanced BTEX vapors sampling based on a phenyl modified PDMS sol-gel adsorption phase

Anal Chim Acta. 2018 Jul 19;1014:27-40. doi: 10.1016/j.aca.2018.01.043. Epub 2018 Feb 14.

Abstract

A novel phenyl modified PDMS (PhPDMS) sol-gel adsorption phase was developed for use with the capillary microextraction of volatiles (CMV) device, and determined to provide significant enhancement in BTEX recoveries when sampling trace (ng) amounts of these volatiles at ambient conditions. The previously reported reusable PDMS-CMV device has been demonstrated to rapidly and efficiently extract target compound's vapors in forensic and environmental applications. An improved recovery for VOCs was achieved with a cryofocusing system while extracting at -10 °C, but it was found to be impractical for field sampling. This report details a modification to the CMV's chemistry, by the successful introduction of phenyl groups to the PDMS sol-gel adsorption phase, allowing enhanced performance at ambient extraction conditions. Higher average recoveries, determined through a broad concentration range, were demonstrated for PhPDMS-CMV over its original PDMS-CMV, from cans simulating a closed space set-up. Within 7.8 (±10%) and 3.5 (±6%) folds higher for benzene and toluene, respectively and 2 (±2%) folds for ethylbenzene and xylenes. Significant higher retaining capabilities were demonstrated also at the more challenging set-up, simulating an open space environment. Whereas, benzene had completely breakthrough the PDMS-CMV, its reliable detection was still confirmed with PhPDMS-CMV pumping at 2 L or 6 L air, concentration dependent. At least 50 folds (±26%) more toluene was retained with PhPDMS-CMV at 6 L air than with PDMS-CMV. The enhanced overall performance lead to determination of trace LODs with the new CMV of 0.002, 0.00035 and 0.00015 ppm for benzene, toluene, ethyl benzene and xylenes, respectively. As proof of concept, for the first time solvent extraction is presented for the new CMV as an alternative to thermal desorption extraction. Extraction efficiencies of 60% for TEX, and lower concentration dependent for benzene, were demonstrated with the ease and rapid application of 100 μL acetone through the device. The improvements described in this study continues to build on the potential for the use of the reusable new CMV device by expanding its possible potential applications for fast and sensitive air sampling of VOCs. The solvent extraction step may offer compatibility with LC-based systems.

Keywords: Active air sampling; BTEX; Capillary microextraction of volatiles (CMV) device; GC-MS; Phenyl-PDMS (PhPDMS) coating; VOCs.