title: 405 nm absorption detection in nanoliter volumes.
abstract: Analytical UV absorption detection for microfluidic devices, capillary electrophoresis, and even high-performance liquid chromatography is hampered by the small detection volumes, short absorption paths, and the need to sample at a high rate with a stable background and low noise. Fiber-loop ring-down spectroscopy (FLRDS) permits absorption detection of dilute liquid samples in volumes as small as a few nanoliters, while being insensitive to light source fluctuations and permitting a millisecond temporal resolution. We demonstrate a FLRDS based detection scheme that is compatible in dimensions (<200 microm absorption path, 6.0 nL detection volume) and optical design (405 nm detection wavelength, fiber coupled) with existing separation systems. An optical/fluidic interface has been built that allows injection of laser light into the loop while also permitting delivery of the sample. The detection limit of tartrazine was determined to be 5 microM (30 fmol) corresponding to an absorption of 0.11 cm(-1). Equivalent results were obtained when detecting myoglobin, a heterocyclic pharmaceutical ingredient, and 5.17 microm diameter polystyrene beads.
authors.affiliation: Department of Chemistry, Queen's University, Kingston, Ontario, K7L 3N6, Canada.
authors.forename: Helen
authors.initials: H
authors.lastname: Waechter
authors.forename: Klaus
authors.initials: K
authors.lastname: Bescherer
authors.forename: Christoph J
authors.initials: CJ
authors.lastname: Dürr
authors.forename: Richard D
authors.initials: RD
authors.lastname: Oleschuk
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Loock
mesh_terms: D000042:Absorption; D007834:Lasers; D009211:Myoglobin / Q000032:analysis; D036103:Nanotechnology / Q000379:methods*; D013056:Spectrophotometry, Ultraviolet / Q000379:methods*; D013645:Tartrazine / Q000032:analysis
chemical_list: D009211:Myoglobin; D013645:Tartrazine