title: A mid-infrared sensor for the determination of perfluorocarbon-based compounds in aquatic systems for geosequestration purposes.
abstract: Perfluorocarbon (PFC) compounds have been used as chemical tracer molecules to understand the movement of supercritical carbon dioxide for geosequestration monitoring and verification purposes. A commonly used method for detecting PFCs involves the collection of a sample from either soil-gas or the atmosphere via carbon-based sorbents which are then analyzed in a laboratory. However, PFC analysis in aquatic environments is neglected and this is an issue that needs to be considered since the PFC is likely to undergo permeation through the overlying water formations. This paper presents for the first time an innovative analytical method for the trace level in situ detection of PFCs in water. It reports on the development of a sensor based on mid-infrared attenuated total reflection (MIR-ATR) spectroscopy for determining the concentration of perfluoromethylcyclohexane (PMCH) and perfluoro-1,3-dimethylcyclohexane (PDCH) in aquatic systems. The sensor comprises a zinc selenide waveguide with the surface modified by a thin polymer film. The sensitivity of this device was investigated as a function of polymer type, coating thickness, and solution flow rates. The limit of detection (LOD) was determined to be 23 ppb and 79 ppb for PMCH and PDCH, respectively when using a 5 μm thick polyisobutylene (PIB) coated waveguide. This study has shown that the MIR-ATR sensor can be used to directly quantify PFC-based chemical tracer compounds in water over the 20-400 ppb concentration range.
authors.affiliation: CSIRO, Earth Science and Resource Engineering, PO Box 1130, Bentley, WA 6102, Australia; University of Ulm, Institute of Analytical and Bioanalytical Chemistry, Albert-Einstein-Allee 11, 89081 Ulm, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Rauh
authors.affiliation: CSIRO, Earth Science and Resource Engineering, PO Box 1130, Bentley, WA 6102, Australia; University of Ulm, Institute of Analytical and Bioanalytical Chemistry, Albert-Einstein-Allee 11, 89081 Ulm, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Schwenk
authors.affiliation: CSIRO, Earth Science and Resource Engineering, PO Box 1130, Bentley, WA 6102, Australia. Electronic address: Bobby.Pejcic@csiro.au.
authors.forename: Bobby
authors.initials: B
authors.lastname: Pejcic
authors.affiliation: CSIRO, Earth Science and Resource Engineering, PO Box 1130, Bentley, WA 6102, Australia.
authors.forename: Matthew
authors.initials: M
authors.lastname: Myers
authors.affiliation: National Measurement Institute, 26 Dick Perry Avenue, Kensington, WA 6151, Australia.
authors.forename: Koon-Bay
authors.initials: KB
authors.lastname: Ho
authors.affiliation: CSIRO, Earth Science and Resource Engineering, PO Box 1130, Bentley, WA 6102, Australia.
authors.forename: Linda
authors.initials: L
authors.lastname: Stalker
authors.affiliation: University of Ulm, Institute of Analytical and Bioanalytical Chemistry, Albert-Einstein-Allee 11, 89081 Ulm, Germany. Electronic address: Boris.mizaikoff@uni-ulm.de.
authors.forename: Boris
authors.initials: B
authors.lastname: Mizaikoff
mesh_terms: D015374:Biosensing Techniques; D057965:Carbon Sequestration; D005466:Fluorocarbons / Q000032:analysis*; D011108:Polymers / Q000737:chemistry; D018036:Selenium Compounds / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D014867:Water / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis*; D017967:Zinc Compounds / Q000737:chemistry
chemical_list: D005466:Fluorocarbons; D011108:Polymers; D018036:Selenium Compounds; D014874:Water Pollutants, Chemical; D017967:Zinc Compounds; C568227:perfluoro-1,3-dimethylcyclohexane; D014867:Water; C044696:zinc selenide; C003073:perfluoromethylcyclohexane
keywords: Attenuated total reflectance; Geosequestration; Groundwater monitoring; Mid-infrared spectroscopy; Optical sensor; Perfluorocarbon