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Purnendu K. Dasgupta - One of the best experts on this subject based on the ideXlab platform.

  • cobinamide chemistries for photometric cyanide determination a merging zone liquid Core Waveguide cyanide analyzer using cyanoaquacobinamide
    Analytica Chimica Acta, 2012
    Co-Authors: Purnendu K. Dasgupta, Felix Zelder, Gerry R Boss
    Abstract:

    Diaquacobinamide (H(2)O)(2)Cbi(2+) or its conjugate base hydroxyaquacobinamide (OH(H(2)O)Cbi(+))) can bind up to two cyanide ions, making dicyanocobinamide. This transition is accompanied by a significant change in color, previously exploited for cyanide determination. The reagent OH(H(2)O)Cbi(+) is used in excess; when trace amounts of cyanide are added, CN(H(2)O)Cbi(+) should be formed. But the spectral absorption of CN(H(2)O)Cbi(+) is virtually the same as that of OH(H(2)O)Cbi(+). It has been inexplicable how trace amounts of cyanide are sensitively measured by this reaction. It is shown here that even with excess OH(H(2)O)Cbi(+), (CN)(2)Cbi is formed first due to kinetic reasons; this only slowly forms CN(H(2)O)Cbi(+). This understanding implies that CN(H(2)O)Cbi(+) will itself be a better reagent. We describe a single valve merging zone flow analyzer that allows both sample and reagent economy. With a 50 cm liquid Core Waveguide (LCW) flow cell and an inexpensive fiber optic-charge coupled device array spectrometer, a S/N=3 limit of detection of 8 nM, a linear dynamic range to 6 μM, and excellent precision (RSD 0.49% and 1.07% at 50 and 100 nM, respectively, n=5 each) are formed. At 1% carryover, sample throughput is 40 h(-1). The setup is readily used to measure thiocyanate with different reagents. We demonstrate applicability to real samples by analyzing human saliva samples and hydrolyzed extracts of apple seeds, peach pits, and almonds.

  • Cobinamide-Based Cyanide Analysis by Multiwavelength Spectrometry in a Liquid Core Waveguide
    Analytical chemistry, 2010
    Co-Authors: Purnendu K. Dasgupta, William Blackledge, Gerry R Boss
    Abstract:

    A novel cyanide analyzer based on sensitive cobinamide chemistry relies on simultaneous reagent and sample injection and detection in a 50 cm liquid Core Waveguide (LCW) flow cell illuminated by a white light emitting diode. The transmitted light is read by a fiber-optic charge coupled device (CCD) spectrometer. Alkaline cobinamide (orange, λmax = 510 nm) changes to violet (λmax = 583 nm) upon reaction with cyanide. Multiwavelength detection permits built-in correction for artifact responses intrinsic to a single-line flow injection system and corrects for drift. With optimum choice of the reaction medium, flow rate, and mixing coil length, the limit of detection (LOD, S/N = 3) is 30 nM and the linear dynamic range extends to 10 μM. The response base width for 1% carryover is

  • cobinamide based cyanide analysis by multiwavelength spectrometry in a liquid Core Waveguide
    Analytical Chemistry, 2010
    Co-Authors: Purnendu K. Dasgupta, William Blackledge, Gerry R Boss
    Abstract:

    A novel cyanide analyzer based on sensitive cobinamide chemistry relies on simultaneous reagent and sample injection and detection in a 50 cm liquid Core Waveguide (LCW) flow cell illuminated by a white light emitting diode. The transmitted light is read by a fiber-optic charge coupled device (CCD) spectrometer. Alkaline cobinamide (orange, λmax = 510 nm) changes to violet (λmax = 583 nm) upon reaction with cyanide. Multiwavelength detection permits built-in correction for artifact responses intrinsic to a single-line flow injection system and corrects for drift. With optimum choice of the reaction medium, flow rate, and mixing coil length, the limit of detection (LOD, S/N = 3) is 30 nM and the linear dynamic range extends to 10 μM. The response base width for 1% carryover is <95 s, permitting a throughput of 38 samples/h. The relative standard deviations (rsd) for repetitive determinations at 0.15, 0.5, and 1 μM were 7.6% (n = 5), 3.2% (n = 7), and 1.7% (n = 6), respectively. Common ions at 250−80 000× c...

  • Measurement of nitrophenols in rain and air by two-dimensional liquid chromatography-chemically active liquid Core Waveguide spectrometry.
    Analytical chemistry, 2010
    Co-Authors: Lucksagoon Ganranoo, Santosh K. Mishra, Abul K. Azad, Ado Shigihara, Purnendu K. Dasgupta, Zachary S. Breitbach, Daniel W. Armstrong, Kate Grudpan, B. Rappenglueck
    Abstract:

    We report a novel system to analyze atmospheric nitrophenols (NPs). Rain or air sample extracts (1 mL) are preconcentrated on a narrow bore (2 mm) aliphatic anion exchanger. In the absence of strong retention of NPs exhibited by aromatic ion exchangers, retained NPs are eluted as a plug by injection of 100 μL of 0.1 M Na2SO4 on to a short (2 × 50 mm) reverse phase C-18 column packed with 2.2 μm particles. The salt plug passes through the C-18 column unretained while the NPs are separated by an ammonium acetate buffered methanol−water eluent, compatible with mass spectrometry (MS). The eluted NPs are measured with a long path Teflon AF-based liquid Core Waveguide (0.15 × 1420 mm) illuminated by a 403 nm light emitting diode and detected by a monolithic photodiode-operational amplifier. The Waveguide is rendered chemically active by suspending it over concentrated ammonia that permeates into the lumen. The NPs ionize to the yellow anion form (λmax ∼ 400 nm). The separation of 4-nitrophenol, 2,4-dinitropheno...

  • portable flow injection analyzer with liquid Core Waveguide based fluorescence luminescence and long path length absorbance detector
    Analytica Chimica Acta, 2003
    Co-Authors: Qingyang Li, Purnendu K. Dasgupta, Kavin J Morris, Ivo M Raimundo, H Temkin
    Abstract:

    We describe a multifunctional flow analysis instrument that is portable (25 cm × 20 cm × 11 cm, 2.3 kg) for facile field deployment. Using a 50 cm long Teflon ® AF tubing as final reaction and optical measurement conduit, we combine a liquid-Core Waveguide (LCW) based fluorescence detector that is transversely illuminated by an addressable light emitting diode array, a chemiluminescence (CL) detector and an absorbance detector with a solid-state broadband (400–700 nm) source. Several illustrative experiments have been carried out to test the performance of the instrument in different detection modes. A S/N = 3 limit of detection (LOD) of 0.25 gl −1 for chromium(VI) was established using the diphenylcarbazide chemistry, and an LOD of 5 gl −1 was similarly established for Al(III), using Pyrocatechol Violet (PCV) as the chelating chromogenic dye, in both cases using long path absorption detection. The LOD for aqueous hydrogen peroxide was 16 nM using a fluorescence method based on the formation of thiochrome from thiamine and 4 nM by a luminol chemiluminescence method. With a Nafion membrane diffusion scrubber (DS), the LOD was 8.0 pptv for gaseous hydrogen peroxide by the fluorescence method. © 2002 Elsevier Science B.V. All rights reserved.

Holger Schmidt - One of the best experts on this subject based on the ideXlab platform.

  • Perforated hollow-Core Waveguide devices for atomic spectroscopy with alkali vapor
    2016 Conference on Lasers and Electro-Optics (CLEO), 2016
    Co-Authors: Matthieu Giraud-carrier, Aaron R. Hawkins, Trevor K. Decker, Jennifer A. Black, Holger Schmidt
    Abstract:

    A novel design for hollow-Core Waveguide devices suitable for atomic spectroscopy is presented. Distributed vapor delivery via etched holes overcomes alkali vapor transport challenges, resulting in strong light absorption in rubidium with excellent environmental stability.

  • Liquid-Core Waveguide based optofluidics
    IEEE Winter Topicals 2011, 2011
    Co-Authors: Philip Measor, Aaron R. Hawkins, M.i. Rudenko, Aiqing Chen, Evan J. Lunt, Brian S. Philips, Holger Schmidt
    Abstract:

    Recent progress in liquid-Core Waveguide based optofluidic devices for sensing applications will be reviewed.

  • Liquid-Core Waveguide Sensors
    Springer Series on Chemical Sensors and Biosensors, 2010
    Co-Authors: Holger Schmidt
    Abstract:

    Much of chemistry and biology involves liquid substances. It is, therefore, not surprising that a strong need for instruments that can sense the presence, absence, or properties of liquids and their constituents exists in both of these vast fields. The miniaturization paradigm that has driven many industrial developments, including the area of sensors, provides a strong push to use optical Waveguides for implementing sensing functions in compact, robust, and convenient form. The most direct approach is the use of liquid-Core Waveguides, in which both light and liquids are guided through the same physical space, thus providing the most efficient interaction between the two. Fueled by recent developments of novel types of liquid-Core Waveguides, these devices are rapidly moving to the forefront of research and development of biological and chemical sensors. Here, we take a closer look at liquid-Core Waveguides by discussing the physical principles underlying the most important Waveguide types, discussing the most popular optical sensing modalities, and reviewing representative examples for liquid-Core Waveguide-based chemical and biological sensors.

  • hollow Core Waveguide characterization by optically induced particle transport
    Optics Letters, 2008
    Co-Authors: Philip Measor, Aaron R. Hawkins, Evan J. Lunt, Sergei Kuhn, Brian S Phillips, Holger Schmidt
    Abstract:

    We introduce a method for optical characterization of hollow-Core optical Waveguides. Radiation pressure exerted by the Waveguide modes on dielectric microspheres is used to analyze salient properties such as propagation loss and Waveguide mode profiles. These quantities were measured for quasi-single-mode and multimode propagation in on-chip liquid-filled hollow-Core antiresonant reflecting optical Waveguides. Excellent agreement with analytical and numerical models is found, demonstrating that optically induced particle transport provides a simple, inexpensive, and nondestructive alternative to other characterization methods.

  • Planar hollow-Core Waveguide technology for atomic spectroscopy and quantum interference in alkali vapors
    Journal of Lightwave Technology, 2008
    Co-Authors: Bin Wu, John F. Hulbert, Aaron R. Hawkins, Holger Schmidt
    Abstract:

    Atomic vapors of alkali metals are widely used to slow and stop light in tabletop experiments. In order to take advantage of the underlying quantum interference effects in future commercial devices, highly reactive alkali atoms must be incorporated into small volumes with integrated optical access. With integration in mind, we describe the development of a hollow-Core Waveguide technology based on the combination of vapor-filled hollow Waveguides and conventional solid-Core Waveguides on a silicon chip. We discuss the underlying principles of the Waveguide design, the development of different approaches to building on-chip vapor cells, the demonstration of linear and nonlinear rubidium spectroscopy on a chip, and the prospects for quantum interference effects such as slow light and giant Kerr nonlinearities using this approach. Ultrasmall active vapor volumes on the order of 100 picoliters with simultaneously high optical density in excess of two illustrate the potential of planar hollow-Core Waveguides for linear and nonlinear optical spectroscopy of atoms confined on a chip.

Robert H Byrne - One of the best experts on this subject based on the ideXlab platform.

  • spectrophotometric measurement of total inorganic carbon in aqueous solutions using a liquid Core Waveguide
    Analytica Chimica Acta, 2002
    Co-Authors: Robert H Byrne, Eric Kaltenbacher, Xuewu Liu, Karen Sell
    Abstract:

    Abstract This work describes spectrophotometric procedures for direct measurements of total inorganic carbon in aqueous solutions. The procedures used for these measurements involve CO2 equilibration across the permeable wall of a Teflon AF-2400 liquid Core Waveguide. The Waveguide acts as both an equilibration membrane and an optical cell in which spectrophotometric pH measurements, obtained via measurements of absorbance ratios, are used to determine the CO2 fugacity and total carbon in acidified solutions surrounding the Waveguide. Total carbon concentrations (CT)a in the acidified external medium are calculated using the equation: log (C T ) a = log (K 0 ) a (K 0 ) i +B(t)− log R−e 1 1−Re 3 /e 2 where B(t) is an empirically derived constant, (K0)a and (K0)i are Henry’s law constants appropriate to the acidified external solution (a) and a solution inside the Waveguide (i) whose total alkalinity is known, R is an absorbance ratio of bromocresol purple (BCP) at 589 and 432 nm, and both e1 and e3/e2 are molar absorptivity ratios appropriate to bromocresol purple. Spectrophotometric (CT)a measurements of natural riverine samples obtained using the procedures described in this work are in good agreement with CT measurements obtained via coulometry.

  • construction of a compact spectrofluorometer spectrophotometer system using a flexible liquid Core Waveguide
    Talanta, 2000
    Co-Authors: Robert H Byrne, Wensheng Yao, Eric Kaltenbacher, Robert D. Waterbury
    Abstract:

    A liquid-Core Waveguide made of Teflon AF-2400 has been used to construct a simple, sensitive and robust instrument capable of performing fluorimetric and spectrophotometric analyses on aqueous solutions. The instrument, which uses a CCD array detection system, is unique in that high performance is achieved for both measurement techniques with minimal changes in instrument configuration. The fluorimetric detection limits for quinine sulfate and chlorophyll-a are 0.06 nanomolar and 0.03 nanomolar, respectively. Absorbance measurements using the same instrument demonstrate nanomolar detection capacities for hydrogen sulfide and subnanomolar detection limits for methylene blue.

  • Construction of a compact spectrofluorometer/spectrophotometer system using a flexible liquid Core Waveguide
    Talanta, 2000
    Co-Authors: Robert H Byrne, Wensheng Yao, Eric Kaltenbacher, Robert D. Waterbury
    Abstract:

    A liquid-Core Waveguide made of Teflon AF-2400 has been used to construct a simple, sensitive and robust instrument capable of performing fluorimetric and spectrophotometric analyses on aqueous solutions. The instrument, which uses a CCD array detection system, is unique in that high performance is achieved for both measurement techniques with minimal changes in instrument configuration. The fluorimetric detection limits for quinine sulfate and chlorophyll-a are 0.06 nanomolar and 0.03 nanomolar, respectively. Absorbance measurements using the same instrument demonstrate nanomolar detection capacities for hydrogen sulfide and subnanomolar detection limits for methylene blue.

  • Long pathlength absorbance spectroscopy: trace analysis of Fe(II) using a 4.5m liquid Core Waveguide
    Analytica Chimica Acta, 1997
    Co-Authors: Robert D. Waterbury, Wensheng Yao, Robert H Byrne
    Abstract:

    Abstract A Liquid Core Waveguide (LCW) can be used to extend the sensitivity of conventional absorbance spectroscopy by two or more orders of magnitude. Analysis of dissolved iron concentrations with a 4.47 m pathlength LCW made of Teflon AF-2400 provides a 0.2 nmol dm−3 detection limit and a linear response between 0.5 and 10 nmol dm−3. No preconcentration is required in this analysis. The analytical procedures employed in long pathlength absorbance spectroscopy are amenable to miniaturization and autonomous operation.

Robert D. Waterbury - One of the best experts on this subject based on the ideXlab platform.

  • construction of a compact spectrofluorometer spectrophotometer system using a flexible liquid Core Waveguide
    Talanta, 2000
    Co-Authors: Robert H Byrne, Wensheng Yao, Eric Kaltenbacher, Robert D. Waterbury
    Abstract:

    A liquid-Core Waveguide made of Teflon AF-2400 has been used to construct a simple, sensitive and robust instrument capable of performing fluorimetric and spectrophotometric analyses on aqueous solutions. The instrument, which uses a CCD array detection system, is unique in that high performance is achieved for both measurement techniques with minimal changes in instrument configuration. The fluorimetric detection limits for quinine sulfate and chlorophyll-a are 0.06 nanomolar and 0.03 nanomolar, respectively. Absorbance measurements using the same instrument demonstrate nanomolar detection capacities for hydrogen sulfide and subnanomolar detection limits for methylene blue.

  • Construction of a compact spectrofluorometer/spectrophotometer system using a flexible liquid Core Waveguide
    Talanta, 2000
    Co-Authors: Robert H Byrne, Wensheng Yao, Eric Kaltenbacher, Robert D. Waterbury
    Abstract:

    A liquid-Core Waveguide made of Teflon AF-2400 has been used to construct a simple, sensitive and robust instrument capable of performing fluorimetric and spectrophotometric analyses on aqueous solutions. The instrument, which uses a CCD array detection system, is unique in that high performance is achieved for both measurement techniques with minimal changes in instrument configuration. The fluorimetric detection limits for quinine sulfate and chlorophyll-a are 0.06 nanomolar and 0.03 nanomolar, respectively. Absorbance measurements using the same instrument demonstrate nanomolar detection capacities for hydrogen sulfide and subnanomolar detection limits for methylene blue.

  • Long pathlength absorbance spectroscopy: trace analysis of Fe(II) using a 4.5m liquid Core Waveguide
    Analytica Chimica Acta, 1997
    Co-Authors: Robert D. Waterbury, Wensheng Yao, Robert H Byrne
    Abstract:

    Abstract A Liquid Core Waveguide (LCW) can be used to extend the sensitivity of conventional absorbance spectroscopy by two or more orders of magnitude. Analysis of dissolved iron concentrations with a 4.47 m pathlength LCW made of Teflon AF-2400 provides a 0.2 nmol dm−3 detection limit and a linear response between 0.5 and 10 nmol dm−3. No preconcentration is required in this analysis. The analytical procedures employed in long pathlength absorbance spectroscopy are amenable to miniaturization and autonomous operation.

Christopher J. Ledderhof - One of the best experts on this subject based on the ideXlab platform.

  • Integrated optical sensor using a liquid-Core Waveguide in a Mach-Zehnder interferometer.
    Optics express, 2008
    Co-Authors: Patrick Dumais, Claire L. Callender, Julian P. Noad, Christopher J. Ledderhof
    Abstract:

    We demonstrate experimentally an optical sensor based on a monolithically integrated Mach-Zehnder interferometer comprising a liquid-Core Waveguide in one of the optical paths. The device is fabricated with a technique for self-forming microchannels in silica-on-silicon using standard photolithography and deposition processes. Refractometry with a resolution of better than 4×10-6 is demonstrated using the thermo-optic effect of the liquid medium to vary its refractive index. The polarization dependence of the device response is analyzed.

  • Thermo-optic switching using liquid-Core Waveguides in integrated Mach-Zehnder interferometers in silica-on-silicon
    Photonics North 2008, 2008
    Co-Authors: Patrick Dumais, Claire L. Callender, Julian P. Noad, Christopher J. Ledderhof
    Abstract:

    The use of materials with a high thermo-optic coefficient would lead to significant improvements in energy consumption and thermal management in optical switching and sensing devices. Most liquids rank among materials having the highest thermo-optic coefficients, along with polymers and silicon. We have developed technology to directly incorporate liquids in integrated silica-on-silicon photonic device structures. Using this technology, we demonstrate experimentally integrated Mach-Zehnder interferometers (MZIs) comprising a liquid-Core Waveguide in one of the interferometer arms. Because of the large differential between the thermo-optic coefficients of silica and the liquid medium, the output of this device can be modulated through the thermal control of the device chip. A high contrast ratio (more than 20 dB) in the interferometer output modulation is obtained, demonstrating that the optical loss is well balanced between the two interferometer paths. The temperature variation required to fully cycle the output state is less than 0.5 degrees Celsius. Designs for low power thermo-optic switches based on these MZI structures with integrated heating electrodes are presented. The inclusion of a second liquid-Core Waveguide in the "passive" interferometer arm can enable athermal and polarization insensitive devices.

  • Temperature sensors and refractometers using liquid-Core Waveguide structures monolithically integrated in silica-on-silicon
    Photonics North 2008, 2008
    Co-Authors: Patrick Dumais, Claire L. Callender, Julian P. Noad, Christopher J. Ledderhof
    Abstract:

    Integrated optofluidic devices have many potential applications for on-chip analysis and sensing. The fabrication of single-mode liquid-Core Waveguides in an integrated format allows the implementation of robust and very sensitive interferometers that combine long optical paths (on the cm scale) with small volumes (less than a nanoliter). We have demonstrated the monolithic integration of microchannels and liquid-Core Waveguides with planar silica lightwave circuits, which allows a number of refractometer devices to be implemented. Of these, we demonstrate experimentally a monolithic Mach-Zehnder interferometer (MZI) comprising a 20 mm-long liquid-Core Waveguide. The liquid-Core Waveguide is quasi single mode at 1550 nm when filled with a liquid of nominal index of ~1.47 (such as toluene or an index matching fluid). In these conditions, the output of the MZI is a pure cosine function, as a function of a linear progression of the refractive index of the liquid medium. Furthermore, the high contrast ratio experimentally observed in the output function allows a precise monitoring of refractive index changes by tracking the position of the transmission minimum in the spectral domain. Refractive index variations can be measured to a precision on the order of 4x10 -6 . The large differential in thermo-optic coefficients between liquid media and silica allows the structure to function as a temperature sensor with a precision on the order of 10 -2 degrees Celsius. The measurement of the spectral fringe spacing of the interferometer response allows absolute-value measurements of temperature and refractive index.

  • Integrated liquid Core Waveguides for nonlinear optics
    Applied Physics Letters, 2007
    Co-Authors: Patrick Dumais, Claire L. Callender, Julian P. Noad, Christopher J. Ledderhof
    Abstract:

    A liquid Core Waveguide monolithically integrated with silica Waveguides is demonstrated as a nonlinear optical device. Continuum generation is achieved using toluene as a Core medium, with picosecond pulses at 1550nm wavelength. A 500nm wide spectrum is generated for an estimated peak input power of 60kW over a propagation length of 16mm.