Light at the end of the tunnel: recent analytical applications of liquid-core waveguides

Dallas, Tim; Dasgupta, Purnendu Κ.

doi:10.1016/s0165-9936(04)00522-9

Cited by 116 publications

(76 citation statements)

References 66 publications

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“…Higher sensitivity absorption measurements have been recently achieved by increasing the path length of measurement through total internal reflection in liquid core waveguides (LCWs). 7,8 Typical path lengths of up to 5 m have been demonstrated. Liquid-phase measurements in the pico-to femto-molar range usually require the use of fluorescence-based techniques, which often are not applicable to many common analytes.…”

Section: Introductionmentioning

confidence: 97%

Liquid-phase broadband cavity enhanced absorption spectroscopy (BBCEAS) studies in a 20 cm cell

Seetohul

Ali

Islam

2009

Analyst

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Sensitive liquid-phase measurements have been made in a 20 cm cell using broadband cavity enhanced absorption spectroscopy (BBCEAS). The cavity was formed by two high reflectivity mirrors which were in direct contact with the liquid-phase analytes. Careful choice of solvent was required to minimise the effect of background solvent absorptions. Measurements were made on the broad absorber Sudan black, dissolved in acetonitrile, using a white LED light source and R $ 0.99 cavity mirrors, leading to a cavity enhancement factor (CEF) of 82 at 584 nm. The sensitivity as measured by the minimum detectable change in the absorption coefficient (a min ) was 3.4 Â 10 À7 cm À1 . Further measurements were made on the strong absorber methylene blue dissolved in acetonitrile at 655 nm. A white LED was used with the R $ 0.99 cavity mirrors, leading to a CEF of 78 and a min ¼ 4.4 Â 10 À7 cm À1 . The use of a more intense red LED also allowed measurements with higher reflectivity R $ 0.999 cavity mirrors, leading to a CEF of 429 and a min ¼ 2.8 Â 10 À7 cm À1 . The sensitivity was limited by dark noise from the detector but nevertheless appears to represent the most sensitive liquid-phase absorption measurement to date.

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Section: Introductionmentioning

confidence: 97%

Liquid-phase broadband cavity enhanced absorption spectroscopy (BBCEAS) studies in a 20 cm cell

Seetohul

Ali

Islam

2009

Analyst

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“…Researchers reported that light transmissivity through the capillaries was highly dependent on the glass capillary's surface conditions. 3.1.3 Teflon ® AF fibers-These are examples of fibers made with polymer sidewalls Dallas and Dasgupta 2004)-see Fig. 1c.…”

Section: Uncoated Fibersmentioning

confidence: 99%

Optofluidic waveguides: II. Fabrication and structures

Hawkins

Schmidt

2007

Microfluid Nanofluid

111

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We review fabrication methods and common structures for optofluidic waveguides, defined as structures capable of optical confinement and transmission through fluid filled cores. Cited structures include those based on total internal reflection, metallic coatings, and interference based confinement. Configurations include optical fibers and waveguides fabricated on flat substrates (integrated waveguides). Some examples of optofluidic waveguides that are included in this review are Photonic Crystal Fibers (PCFs) and two-dimensional photonic crystal arrays, Bragg fibers and waveguides, and Anti Resonant Reflecting Optical Waveguides (ARROWs). An emphasis is placed on integrated ARROWs fabricated using a thin-film deposition process, which illustrates how optofluidic waveguides can be combined with other microfluidic elements in the creation of lab-on-a-chip devices.

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“…One method of increasing spectroscopic sensitivity is to increase the sample cell pathlength via custom long-path cells (Bricaud et al 1981;Peacock et al 1994) or capillary optical waveguide cuvettes (D'Sa et al 1999;Belz et al 1999;Dallas and Dasgupta 2004). Long-pathlength liquid core waveguides (LCW), introduced commercially by World Precision Instruments in 1997, can be used for high-sensitivity UV-visible absorbance measurements of CDOM.…”

Section: Introductionmentioning

confidence: 99%

Untitled

2009

Limnology & Ocean Methods

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In the past decade, technological advances in optical sensors have facilitated an increased understanding of the relationship between optical characteristics and biogeochemistry of our oceans. In particular, long-pathlength liquid core waveguide cells (LCWs) are being used to "map" chromophoric dissolved organic matter (CDOM), as a biogeochemical tracer, in various coastal and open ocean regions. At present, two LCW cell types are used in the study of marine CDOM, and concerns about discrepancies in data collected with the different cell types and problems with baseline offsets have arisen. We conducted a direct comparison of absorption coefficient spectra of a dissolved spectrophotometric standard, molecular weight standard (MWS), and dilution series of natural seawater obtained in type I and type II LCWs to assess data agreement and potential colloidmediated biases. Although no statistical difference was observed for the dissolved standard, we found the type I to have a slight bias toward higher absorption coefficient values for MWS 14-150 kDa (within 95% confidence interval) and natural seawater. Seawater CDOM spectral slopes differed significantly between type I and type II LCWs, with a maximum difference in slope of 0.0006 nm -1 . Fastidious elimination of microbubbles from the capillary cells greatly reduced baseline offsets and markedly improved CDOM spectral slope precision.

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Light at the end of the tunnel: recent analytical applications of liquid-core waveguides

Cited by 116 publications

References 66 publications

Liquid-phase broadband cavity enhanced absorption spectroscopy (BBCEAS) studies in a 20 cm cell

Liquid-phase broadband cavity enhanced absorption spectroscopy (BBCEAS) studies in a 20 cm cell

Optofluidic waveguides: II. Fabrication and structures

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