title: Characterization and use of a Raman liquid-core waveguide sensor using preconcentration principles.
abstract: A novel Raman sensor using a liquid-core optical waveguide is reported, implementing a Teflon-AF 2400 tube filled with water. An aqueous analyte mixture of benzene, toluene and p-xylene was introduced using a 1000 microl sample loop to the liquid-core waveguide (LCW) sensor and the analytes were preconcentrated on the inside surface of the waveguide tubing. The analytes were then eluted from the waveguide using an acetonitrile-water solvent mixture injected via a 30 microl eluting solvent loop. The preconcentration factor was experimentally determined to be 14-fold, in reasonable agreement with the theoretical preconcentration factor of 33 based upon the sample volume to elution volume ratio. Raman spectra of benzene, toluene and p-xylene were obtained during elution. It was found that analytically useful Raman signals for benzene, toluene and p-xylene were obtained at 992, 1004 and 1206 cm(-1), respectively. The relative standard deviation of the method was 3% for three replicate measurements. The limit of detection (LOD) was determined to be 730 ppb (parts per billion by volume) for benzene, exceptional for a system that does not resort to surface enhancement or resonance Raman approaches. The Raman spectra of these test analytes were evaluated for qualitative and quantitative analysis utility.
authors.affiliation: Faculty of Science, Research and Development and Department of Chemistry, Institute of Science and Technology, Chiang Mai University, Chiang Mai, Thailand.
authors.forename: Sumalee
authors.initials: S
authors.lastname: Tanikkul
authors.forename: Jaroon
authors.initials: J
authors.lastname: Jakmunee
authors.forename: Mongkon
authors.initials: M
authors.lastname: Rayanakorn
authors.forename: Kate
authors.initials: K
authors.lastname: Grudpan
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Marquardt
authors.forename: Gwen M
authors.initials: GM
authors.lastname: Gross
authors.forename: Bryan J
authors.initials: BJ
authors.lastname: Prazen
authors.forename: Lloyd W
authors.initials: LW
authors.lastname: Burgess
authors.forename: Gary D
authors.initials: GD
authors.lastname: Christian
authors.forename: Robert E
authors.initials: RE
authors.lastname: Synovec