| Autor: |
Dasgupta PK; Department of Chemistry and Biochemistry , University of Texas at Arlington , Arlington , Texas 76019-0065 , United States., Qin C; Department of Chemistry and Biochemistry , University of Texas at Arlington , Arlington , Texas 76019-0065 , United States., Shelor CP; Department of Chemistry and Biochemistry , University of Texas at Arlington , Arlington , Texas 76019-0065 , United States., Kadjo AF; Department of Chemistry and Biochemistry , University of Texas at Arlington , Arlington , Texas 76019-0065 , United States., Su J; Department of Mathematics , University of Texas at Arlington , Arlington , Texas 76019-0408 , United States., Kraiczek KG; Agilent Technologies , Hewlett-Packard Strasse 8 , D 76337 Waldbronn , Germany., Marshall GD; Global FIA , 684 Sixth Avenue , Fox Island , Washington 98333 , United States. |
| Abstrakt: |
We trace the history of liquid core waveguides (LCWs, also called liquid core optical fibers) and the role Teflon AF (TAF) has played in their development. We show that, in any shot noise limited situation, the optimum signal-to-noise ratio (S/N) occurs at a path length of 1/α a {ln[1 + 2(α a /α b )]}, approximately 2/α b under most conditions, α a and α b being the light attenuation coefficient due to the analyte and the background, respectively. The analysis shows that LCW length should be selected depending on the applicable α b value. An overly long LCW may exhibit a lower signal-to-noise ratio. Water-filled TAF-clad fused-silica (FS) tubes show the lowest attenuation across the wavelength range. Nevertheless, except at λ ≥ 600 nm, the observed α b values far exceed those reported for pure water: it appears that both impurities in the water and waveguide losses are involved. In examining the attenuation in various water-filled tubes, we find that the transmission of air-surrounded FS tubes is second only to TAF-clad FS tubes and is better than that of TAF tubes or externally mirrored FS tubes. Surprisingly, except for a window centered at ∼250 nm, light transmission in a water-filled poly(tetrafluoroethylene) (PTFE) tube is worse than in poly(ether ether ketone) (PEEK) tubing. Light transmission in PTFE tubes improves with increasing wall thickness. |
