bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficient Rejection of Fluorescence from Raman Spectra Using Picosecond Kerr Gating
Authors: Matousek P. , Towrie M. , Stanley A. , Parker A. W.
Published: October 2003

An efficient method for the rejection of fluorescence from picosecond time-resolved resonance Raman (ps-TR3) spectra, applicable also to ground-state Raman spectroscopy, has been demonstrated. The technique removes fluorescence from Raman light in the time domain using a Kerr gate driven by 110 μJ, 1 ps pulses at 800 nm and a repetition rate of 0.65 kHz, giving a response time of ∼ 3 ps, representing the highest time resolution achieved experimentally for rejecting fluorescence from Raman spectra. The effectiveness of the method is proven by measuring Raman solvent bands and ps-TR3 spectra of S1 p-quaterphenyl from solutions contaminated with the laser dye DCM using laser wavelengths which excite the dye and so produce intense fluorescence emission. The optical transmittances accounting for losses in the optical elements and losses due to incomplete polarization rotation in the Kerr medium in the open and closed states were 15% and 0.005%, respectively. The use of the gate in a time-resolved fluorescence measurement of DMABN is also demonstrated.
Real-Time ATR-IR Spectroscopy of Samples on Exchangeable Composite Reflection Elements
Authors: Müller G. , Riedel C.
Published: October 2003

A method is described that enables the alternated total reflectance infrared (ATR-IR) spectroscopy of thin-layer samples deposited onto one side of an exchangeable silicon wafer, the uncoated side of which is pressed against a small-area diamond single-reflection element. The pressing device is designed as a hollow spindle with a small ring-shaped opening at the end facing the wafer; thus, the sample spot involved in the measurement remains undisturbed. The sample can be UV-irradiated, and the atmosphere above it can be flushed with an inert gas introduced through the hollow spindle. The performance of the method is illustrated by the investigation of the influence of pressing force on background and on absorption band areas. With a commercial real-time Fourier transform infrared (FT-IR) spectrometer, the measurement of the UV-polymerization kinetics following the vanishing of the double bounds is demonstrated for a few thin-layer samples that were deposited on silicon wafers by spin-coating or by the Langmuir–Blodgett technique.
Effects of Bandwidth and Overlap on Multivariate Calibration Models Based on Simulated Fourier Transform Infrared Interferogram Data
Authors: Cingo Ndumiso A. , Small Gary W.
Published: October 2003

Simulated Fourier transform infrared (FT-IR) interferograms and spectra of mixture samples are used to investigate the effects of bandwidth and overlap on a quantitative analysis in which multivariate calibration models are constructed from short segments of digitally filtered interferogram data. By a comparison of calibration models constructed with interferogram data to similar models built with spectral data of varying instrumental resolution, the concepts of spectral resolution are explored in the context of an interferogram-based analysis. In this work, nominal spectral point spacings of 1, 2, 4, 8, and 16 cm−1 are explored. Five data sets are constructed in which the width and overlap of an analyte and interference band are varied. Calibration models based on partial least-squares (PLS) regression are optimized for both interferogram and spectral data. Even in cases of extreme spectral overlap between the analyte and interference bands, interferogram-based calibration models constructed from segments of 151 points or less are observed to perform as well as or better than all models computed with absorbance and single-beam spectral data, regardless of instrumental resolution. These results suggest that an interferogram-based analysis is a viable option for applications in which an FT-IR spectrometer is used in a dedicated monitoring application.
Use of PFG-NMR for Mixture Analysis: Measurement of Diffusion Coefficients of Cis and Trans Isomers of Proline-Containing Peptides
Authors: Derrick Tiffany S. , Larive Cynthia K.
Published: October 2003

The analysis of complex mixtures is a prominent area of research that spans many disciplines of science. Recently, diffusion-based nuclear magnetic resonance (NMR) has found wide applicability in the field of mixture analysis. Pulsed-field gradient NMR (PFG-NMR) is a well-established method for the determination of diffusion coefficients, which are indicative of molecular size and shape. Diffusion coefficients were measured with the bipolar pulse longitudinal eddy current delay pulse sequence for the cis and trans prolyl isomers of two simple peptides, phenylalanylproline and phenylalanylprolyalanine, and for arginine vasopressin, a more complex peptide hormone. This methodology was also applied to a dipeptide, glycylsarcosine, which exhibits cis/ trans isomerism, but lacks a proline residue. Obtaining quantitative diffusion coefficients from PFG-NMR spectra of proline-containing peptides can be challenging due to the low content of the cis isomer in most peptides as well as the limitations imposed by spectral overlap. However, for each of the proline-containing peptides studied, statistically different diffusion coefficients were measured for the cis and trans isomers, and these diffusion coefficients reflect the smaller hydrodynamic radii of the cis isomers. In contrast, no significant difference was detected in the diffusion coefficients measured for the cis and trans isomers of glycylsarcosine.
Interpolation and Extrapolation of Infrared Spectra of Binary Ionic Aqueous Solutions
Authors: Max Jean-Joseph , Chapados Camille
Published: October 2003

Factor analysis of the attenuated total reflection (ATR) absorbance spectra of aqueous saline solutions has shown that these spectra are linear combinations of two eigenspectra: pure water and salt-solvated water. This paper outlines the general equations needed to formalize these experimental results. In the case of binary salts in aqueous solutions, the equations allow interpolation and extrapolation from one concentration to another. The accuracy of the calculation method was adequately verified on aqueous solutions of KCl. The equations made it possible to calculate the ATR absorbance spectrum of a “pure” KCl-solvated water. The latter, which contains no ordinary water, enabled us to determine that solvated water forms clusters made up of a pair of ions with five molecules of water. The same results were obtained with NaCl aqueous solutions.
Raman Spectroscopy of the Low-Frequency Region of Kaolinite at 298 and 77 K
Authors: Frost Ray L. , Kloprogge J. Theo
Published: October 2003

Both Raman microscopy and Fourier transform (FT)-Raman spectroscopy have been used to determine the low-frequency vibrations of kaolinite at both 298 and 77 K. The low-frequency region is characterized by bands attributed to the hydroxyl deformation, hydroxyl translation, silicon oxygen bending, and OHO vibrations. The inner hydroxyl stretching frequency shifts from 3620 to 3615 cm−1 upon cooling to liquid nitrogen temperature, and the inner surface hydroxyl bands show increased complexity with a number of overlapping bands in the 3685 to 3710 cm−1 region at 77 K, which are not observed in the 298 K spectrum. The hydroxyl deformation modes shift by 3 cm−1 to higher frequency upon cooling to liquid nitrogen temperature. The hydroxyl translation and other spectral regions show less sensitivity to the thermal treatment. Upon cooling to liquid nitrogen temperature, additional bands are observed in the low-frequency region: in the hydroxyl deformation region a new band is observed at 943 cm−1, in the OSiO bending region at 448 and 411 cm−1, and in the low-frequency region at 370 and 330 cm−1.
Raman Shift Calibration of a Compact Multichannel Spectrometer
Authors: Vickers Thomas J. , Mann Charles K.
Published: October 2003

Calibration of the Raman shift scale of a compact spectrometer with a charge-coupled device (CCD) array detector is examined. Argon and neon line spectra are used as wavelength standards, and a shift standard is used to track changes in the wavelength of the doubled Nd:YAG laser line. A method is described to introduce controlled shifts of spectra relative to the detector elements. Excellent precision, on the order of 0.05 cm−1, is achieved in measuring Raman shift values over a period of several weeks. The abscissa accuracy, examined with the use of both Raman lines of known shift and atomic line wavelengths, is considerably poorer than the precision. The likely origins of this discrepancy are discussed.
Pressure Dependence of Laser-Induced Fluorescence of Sm3+ in Al2O3—Y2O3 System Compounds
Authors: Iida Yasuo , Sakaguchi Shuji , Tsugoshi Takahisa , Ohashi Masayoshi
Published: October 2003

The piezospectroscopic (PS) coefficients relating frequency shift to pressure are evaluated for Sm3+ in the Al2O3–Y2O3 system compounds, which include Al2O3, Y3Al5O12, YAlO3, Y4Al2O9, and Y2O3. The fluorescence peaks are inherently narrow for all the synthesized compounds, on the basis of the f–f transition nature of Sm3+ ion. Furthermore, the PS coefficients are ranged from −2.2 to −8.2 cm−1/GPa, which are similar to the reported value for the R1 line of ruby and suitable for the PS stress evaluation. PS stress distribution measurements are demonstrated with sintered Y3Al5O12 ceramics as a sample, with 50 μm intervals, under a microscope.
Measurement of the Intensity of Long-Lifetime Luminophores in the Presence of Background Signals Using Phase-Modulation Fluorometry
Authors: Szmacinski Henryk , Lakowicz Joseph R.
Published: October 2003

We describe a method to correct for background fluorescence and to measure the intensity of long-lifetime probes using phase-modulation fluorometry. The theoretically predicted and simulated data were supported by two experiments. The fractional contribution of background fluorescence in the sample was determined by measurement of phase angle and/or modulation at single modulation frequency. In certain experimental situations, where the mean decay times of the background and the long lifetime probe are widely separated, determination of background signals in the sample does not require a blank sample or information about the nature of intensity decay of the background. Hence, phase-modulation fluorometry can be used to directly determine the intensity of the long-lifetime probe in the presence of an unknown short-lifetime background. We also discuss the effects of ambient light (indefinitely long lifetime) and scattered excitation light (zero lifetime) on phasemodulation measurements.
Peak Fitting and Deconvolution for Determination of the Impulse Response Function of the Sample Introduction System in Flow Injection Inductively Coupled Plasma Spectrometry
Authors: Rattray Robin , Burns David H. , Salin Eric D.
Published: October 2003

A technique for determining the impulse response function for an inductively coupled plasma atomic emission spectrometry sample introduction system is demonstrated. The input response function may then be useful for the determination of outputs, and consequently the performances, of flow injection or other sample treatment systems, which precede the sample introduction system. In a procedure to generate a known input response, a bolus of analyte was proceeded and followed by an air bubble, which reduced dispersion to a minimum. The impulse response function was determined and used to deconvolute other inputs of known concentration and dispersion. The deconvolution of the outputs using the impulse response function returned the expected result, indicating that the technique and impulse response function were correct. When used with an unsegmented traditional flow injection sample introduction valve, the system demonstrated clearly that significant dispersion takes place even in very compact introduction arrangements.
Fluorescence Imaging of Glutamate Release in Neurons
Authors: Wang Ziqiang , Yeung Edward S.
Published: October 2003

A noninvasive detection scheme based on glutamate dehydrogenase (GDH) enzymatic assay combined with microscopy was developed to measure the glutamate release in cultured cells from the central nervous system (CNS). The enzyme reaction is very specific and sensitive. The detection limit with charge-coupled device (CCD) imaging is down to μM levels of glutamate with reasonable response time (∼ 30 s). The standard glutamate test shows a linear response over 3 orders of magnitude, from μM to 0.1 mM range. The in vitro monitoring of glutamate release from cultured neuron cells demonstrated excellent spatial and temporal resolution.
Stratification of Butyl Acrylate/Polyurethane (BA/PUR) Latexes: ATR and Step-Scan Photoacoustic Studies
Authors: Urban Marek W. , Allison Claudia L. , Johnson Gary L. , Di Stefano Frank
Published: October 2003

Although the primary objective of these studies was to investigate stratification processes in multicomponent coatings, such as butyl acrylate/polyurethane (BA/PUR) (© 1999 by Air Products and Chemicals, Inc.) latex, other objectives include investigation of stepscan photoacoustic (SS-PA) Fourier transform infrared (FT-IR) spectroscopy depth profiling capability for analysis of multicomponent systems. These studies show that a combination of step-scan photoacoustic and attenuated total reflectance (ATR) FT-IR spectroscopy can be successfully utilized to elucidate stratification processes in BA/PUR latex as well as in other multicomponent systems. ATR FT-IR experiments revealed the absence of PUR moieties within the first 0.28 μm from the film/air (F-A) interface, a decrease of the BA component, and the appearance of PUR from 0.39 to 2.52 μm. Coalescence of BA/PUR latex at 149 °C affects the distribution of these components by driving PUR deeper into the bulk and BA closer to the surface. SS-PA FT-IR experiments allowed us to monitor stratification processes at greater depths, and in conjunction with phase rotation analysis, show that the BA component stratifies closer to the F-A interface, whereas PUR migrates towards the film/substrate (F-S) interface.
Characterization of a Surface Coating Formed from Carboxylic Acid-Based Coolants
Authors: Verpoort F. , Haemers T. , Roose P. , Maes J.-P.
Published: October 2003

Carboxylic acids are found to adsorb weakly to the native oxide surface of aluminum. Under heat exchange conditions, synergistic carboxylate combinations provide superior high-temperature aluminum corrosion protection and show excellent heat-transfer characteristics. The surface films formed under these dynamic heat-transfer conditions are characterized with the use of X-ray photoelectron spectroscopy (XPS). Fourier transform infrared (FT-IR) is also used for the study and characterization of the surface films formed. The results are compared with the FT-IR data of the pure Al–carboxylate complexes. The combination of these results reveals that, under heat transfer conditions, carboxylates are chemically bonded to the aluminum surface. This molecular film shows excellent inhibition properties for aluminum.
Dynamic Infrared Spectroscopy Using the Rapid-Scan Technique
Authors: Ekgasit Sanong , Siesler Heinz W. , Steeman Paul A. M.
Published: October 2003

A technique using rapid-scan Fourier transform infrared (FT-IR) spectroscopy to observe reversible dynamic changes of systems under an externally applied perturbation is introduced. The technique does not require a lock-in amplifier or synchronization between the applied perturbation and the spectral acquisition. With the use of a carefully designed sampling rate with respect to the perturbation period and reconstruction of the observed spectral intensities, dynamic spectral intensities of the system are obtained. Due to the repeated behavior, the reconstructed spectral intensities can be used to represent the dynamic characteristic of the system. The experimentation time of the rapid-scan technique is significantly shorter than that of the step-scan technique. The influences of noise and experimental parameters on the observed spectral intensities are verified. Applications of the technique to systems with sinusoidal dynamic changes and exponentially decaying dynamic changes are demonstrated.
Dynamic Infrared Linear Dichroism Study of Poly(p-Phenylene Vinylene) and its Precursor
Authors: Shah Hiren V. , Manning Christopher J. , Arbuckle Georgia A.
Published: October 2003

Poly( p-phenylene vinylene) (PPV) has many interesting electrical properties, particularly anisotropic conductivity upon uniaxial stretching, because of its delocalized π-electron system. In this study we have investigated the mid-infrared response of PPV and PPV-precursor films subjected to modulated uniaxial strain in order to study the degree of molecular motions and their time dependence during deformation. These studies have used a step-scan infrared spectrometer in conjunction with a piezo-driven in situ Polymer Modulator™. The viscoelastic properties are monitored simultaneously with the dynamic infrared vibrational response to the applied perturbation. The major molecular vibrations associated with the stretching of the precursor and of PPV have been identified and their time-dependence studied by using both phase-spectral and two-dimensional infrared (2D-IR) approaches. It has also been shown that the precursor, at ambient temperatures, is elastic in nature. However, after the introduction of conjugation on the backbone via conversion to PPV, the material becomes more viscous; the change is evident at both the microscopic and macroscopic levels.
Fractal Characterization of SERS-Active Electrodes Using Extended Focus Reflectance Microscopy
Authors: Yamaguchi Yoshinori , Weldon Millicent K. , Morris Michael D.
Published: October 2003

The fractal characteristics of roughened silver electrode surfaces are used for a light microscopy diagnostic for the surface-enhanced Raman activity of the surfaces. It is shown that the fractal dimension of an electrode as measured from scanning electron microscope images (resolution 0.08 μm) is the same as measured from extended focus (EF) light microscopy images (resolution <0.4 μm). There is a threshold fractal dimension for SERS activity. The threshold is independent of the adsorbed molecule.
Direct Insertion of Trace Metals Preconcentrated on Activated Charcoal into an Inductively Coupled Plasma
Authors: Skinner Cameron D. , Cazagou Murielle , Blaise Joanne , Salin Eric D.
Published: October 2003

Trace metals have been concentrated onto activated charcoal by using oxalic acid, iminodiacetic acid, and 8-hydroxyquinoline. The charcoal was directly analyzed in an ICP by placing several particles in a direct sample insertion (DSI) cup, or fabricating a DSI probe with an activated charcoal cap. Detection limits in the tens to hundreds of parts per trillion were found for Pb, Cd, Zn, and Cu. The recovery for Cu was 2–5% but may be improved by reactivation of the plasma-cleaned charcoal. Cleaning the charcoal, derived from wood, in the plasma prior to adsorption was necessary to remove trace metals.
Development and Characterization of an Automated Direct Sample Insertion/Inductively Coupled Plasma/Atomic Emission Spectrometry System
Authors: Karanassios Vassili , Wood Todd J.
Published: October 2003

A new direct sample insertion (DSI) device that can be used vertically with inductively coupled plasma atomic emission spectrometry (ICP-AES) or horizontally with ICP mass spectrometry (ICP-MS) has been designed, and an automated ICP-AES system has been developed around this DSI device. The automated DSI-ICP-AES system was characterized by using microliter volumes of liquids and milligram amounts of powders. Analysis of solids with minimum pretreatment was a key goal in developing this system, and several calibration methods for powders were investigated. Examples of these are liquid standards, a few milligrams of different reference material or a different weight of the same material and standard additions of liquids onto a powder in the cup. Sample handling, weighing, sampling, and homogeneity concerns were partially addressed by using slurries. In addition, slurry DSI-ICP-AES for botanical, geological, and biological powdered reference materials is briefly described. Carbide formation is a key chemical limitation of graphite-cup DSIs, and it was addressed by using in situ chemical modification by mixing SF6 with the plasma gases.
Study on the Interaction between the Laser-Ablated Aluminum Plume and the Nitrogen Discharge Plasma by Time- and Space-Resolved Spectroscopy
Authors: Wang Pei-Nan , Pan Qi , Cheung N. H. , Chen Shu-Chi
Published: October 2003

Pulsed discharge of nitrogen was shown to be a very effective means to generate atomic nitrogen whose reactivity favored the synthesis of nitrides. In order to form aluminum nitride, such a plasma was allowed to interact with the plume generated by pulsed-laser ablation of aluminum. The plasma reaction was studied by time- and space-resolved optical emission spectroscopy. Emissions from ionic species of nitrogen (N+ and N2+) in the reaction region were observed. They were believed to be excited by the shock front generated by the pulsed-laser ablation. The delay time between ablation and discharge could be tuned to maximize the N+ emission. That condition also produced the purest aluminum nitride powders.
Monitoring the Secondary Structure of Proteins by Near-Infrared Spectroscopy
Authors: Robert Paul , Devaux Marie Françoise , Mouhous Nadine , Dufour Eric
Published: October 2003

Despite the numerous applications of near-infrared spectroscopy in the agricultural and bio-industrial sectors, the relevance of this technique to the study of the secondary structure of proteins has received little attention. The present research investigated the near-infrared spectra of 12 model proteins in the solid state by taking the corresponding mid-infrared data into account. The second-derivative spectra of myoglobin, β-lactoglobulin, and β-casein in the near-infrared region revealed characteristic absorption bands. While myoglobin presented absorption bands at 2055, 2170, 2289, and 2350 nm, β-lactoglobulin exhibited specific peaks at 2203, 2267, and 2300 nm. The second-derivative spectrum of β-casein showed a particularly intense band at 2269 nm. The results derived from a generalized canonical correlation analysis confirmed the potential of near-infrared spectroscopy to characterize the secondary structure of proteins: 2172 and 2289 nm appeared to be representative of α-helix structure; 2205, 2264, and 2313 nm were observed for β-sheet; 2265 nm characterized the unordered structure.
Directional Characteristics Model and Light-Path Model for Biological Material Having Cellular Structure
Authors: Tsuchikawa Satoru , Tsutsumi Shigeaki
Published: October 2003

Nondestructive measurements, based on NIRS (near-infrared spectroscopy), on biological material having cellular structure, such as wood, require a nontraditional approach. In this respect, a truly nondestructive measurement system that can accurately monitor the physical condition and chemical components of materials is very desirable. Supported by a series of experiments, we constructed optical characteristic concepts that account for the cellular structure of a sample. The system was successfully modeled by following theoretically the sequential propagation of light in a sample (specifically, scattering, reflection, absorption, and transmission), which varies according to the angle of the fibers with respect to the direction of incident light, θ, and with its wavelength. A set of optical models, which consists of a directional characteristics model and a light-path model, has been developed to describe the various steps in the sequence. On the basis of these models, the leakage ratios of diffusely reflected light from the aggregate width of semi-infinite tracheids, S(θ), for various conditions of irradiation were calculated. These values were in good agreement with the actual values obtained from the measured values of absorbance through the judicious use of a semi-theoretical equation.
Resolution Enhancement of Raman Spectra of Solids Using True Linear Prediction and Deconvolution
Authors: Sievänen O.-P.
Published: October 2003

The method developed earlier by the author for resolution enhancement of Raman spectra using true linear prediction and deconvolution has been applied to the problem of resolving some earlier detected or suspected cases of exciton splitting and Fermi resonance in solid naphthalene-h8. It is found that careful deconvolution combined with true linear prediction of the inverse Fourier transform of the recorded spectrum greatly aids in the interpretation of observed spectral structures. The results are compared to the ones obtained by applying the customary maximum entropy method (MEM) spectral estimator. It is seen that estimating the spectrum by using the MEM estimate may lead to erroneous results.
Depth Profiling of Photooxidized Styrene-Isoprene Copolymers by Photoacoustic and Micro-Fourier Transform Infrared Spectroscopy
Authors: Gonon Laurent , Vasseur Olivier J. , Gardette Jean-Luc
Published: October 2003

Transmission micro-FT-IR (Fourier transform infrared) and photoacoustic (PAS) FT-IR analysis have been combined to determine the oxidation profiles of various photooxidized polyisoprene-polystyrene copolymers. It is shown that only the polyisoprene phase is oxidized. The front photooxidized layers (0–22 μm) are analyzed by PAS, while the bulk (11–150 μm) is characterized by cross-sectional analysis of microtomed layers. A good agreement between the two methods is found in the region where the analyzed layers overlap (11–22 μm). The extent of the oxidation was determined by monitoring the ratio between the intensity of the carbonyl absorbance at 1718 cm−1 and the absorbance at 1600 cm−1. The results given in this article show that PAS FT-IR can be a rapid and nondestructive technique of quantitative characterization of the surface degradation of aged polymers.
Infrared and Dielectric Investigation of Curing in a Polymer-Stabilized Liquid Crystal System
Authors: Wall Bentley G. , Koenig Jack L. , Schuele Donald E.
Published: October 2003

The results of infrared and dielectric measurements of polymer stabilized liquid crystals (PSLCs) are correlated to each other. The novel experimental design allows these two different analytical techniques to be applied simultaneously on the sample. The dielectric data (capacitance, loss) follow closely the infrared absorbance data. Infrared data can be used to follow a chemical reaction, and because these data have now been correlated to dielectric data, dielectric measurements alone can be used to follow the course of a chemical curing reaction. This will allow for easier assessment of these types of systems, removing the challenging sample preparation steps required for infrared analysis.
Measurement of pH in Whole Blood by Near-Infrared Spectroscopy
Authors: Alam M. Kathleen , Rohrscheib Mark R. , Franke James E. , Niemczyk Thomas M. , Maynard John D. , Robinson M. Ries
Published: October 2003

Whole blood pH has been determined in vitro by using near-infrared spectroscopy over the wavelength range of 1500 to 1785 nm with multivariate calibration modeling of the spectral data obtained from two different sample sets. In the first sample set, the pH of whole blood was varied without controlling cell size and oxygen saturation (O2 Sat) variation. The result was that the red blood cell (RBC) size and O2 Sat correlated with pH. Although the partial least-squares (PLS) multivariate calibration of these data produced a good pH prediction cross-validation standard error of prediction (CVSEP) = 0.046, R2 = 0.982, the spectral data were dominated by scattering changes due to changing RBC size that correlated with the pH changes. A second experiment was carried out where the RBC size and O2 Sat were varied orthogonally to the pH variation. A PLS calibration of the spectral data obtained from these samples produced a pH prediction with an R2 of 0.954 and a cross-validated standard error of prediction of 0.064 pH units. The robustness of the PLS calibration models was tested by predicting the data obtained from the other sets. The predicted pH values obtained from both data sets yielded R2 values greater than 0.9 once the data were corrected for differences in hemoglobin concentration. For example, with the use of the calibration produced from the second sample set, the pH values from the first sample set were predicted with an R2 of 0.92 after the predictions were corrected for bias and slope. It is shown that spectral information specific to pH-induced chemical changes in the hemoglobin molecule is contained within the PLS loading vectors developed for both the first and second data sets. It is this pH specific information that allows the spectra dominated by pH-correlated scattering changes to provide robust pH predictive ability in the uncorrelated data, and visa versa.
Near-Infrared Spectroscopic Measurement of Myoglobin Oxygen Saturation in the Presence of Hemoglobin Using Partial Least-Squares Analysis
Authors: Schenkman Kenneth A. , Marble David R. , Feigl Eric O. , Burns David H.
Published: October 2003

Myoglobin is an important intracellular protein found in cardiac and skeletal muscle. It is involved in the intracellular transport of oxygen from the cell membrane to the mitochondria where oxidative phosphorylation takes place. The optical absorbance characteristics of myoglobin are similar to those of hemoglobin in the near-infrared spectral region. Distinguishing spectral information of myoglobin from hemoglobin should allow for determination of intracellular oxygen availability in muscle. Partial least-squares analysis is used in this report to determine the oxygen saturation of myoglobin, in the presence of hemoglobin, in vitro. Studies were performed with the use of both transmission and reflectance spectroscopic techniques. Transmission spectra of myoglobin solutions were determined with varying degrees of oxygen saturation achieved by deoxygenating the solution using E. coli. Calibration spectral data sets were developed with the use of varying concentrations of hemoglobin interference, and with varying degrees of myoglobin oxygen saturation. Reflectance spectra were obtained from myoglobin and hemoglobin solutions containing a scattering agent to mimic muscle tissue conditions. Predicted myoglobin saturation values were within 2% of the known saturation values from the use of this analysis. Partial least-squares analysis allows for accurate prediction of myoglobin oxygen saturation in the presence of hemoglobin from either transmission of reflectance near-infrared spectra.
Optical Spectroscopic Method for in vivo Measurement of Cardiac Myoglobin Oxygen Saturation
Authors: Schenkman Kenneth A. , Marble David R. , Burns David H. , Feigl Eric O.
Published: October 2003

A fiber-optic-based spectrophotometer was developed to acquire optical reflectance spectra from a living dog heart. A bullseye concentric optical probe with a 3 mm source-to-detector fiber separation was designed to obtain a 1.5 mm average tissue depth of light penetration. Spectra were analyzed in the near-infrared region from 660 to 840 nm. Myoglobin oxygen saturation was determined by partial least-squares analysis using a calibration spectral data set developed in vitro. Comparison of in vivo and in vitro spectra by Mahalanobis distance and residual ratio tests demonstrated good similarity, justifying use of partial least-squares analysis. Coronary perfusion with an oxygenated blood substitute, Fluosol®, was used to demonstrate that hemoglobin had little effect on the analysis. An increase in myoglobin saturation of 5% was noted when the animals were changed from inspired room air to 100% oxygen. Occlusion of the coronary artery resulted in prompt decrease in myoglobin saturation, and release of the occlusion was followed by rapid increase in saturation to a value above baseline. These experiments demonstrate that it is feasible to use partial least-squares analysis of near-infrared reflectance spectra to determine myoglobin saturation in the blood-perfused, beating heart.
Novel Instrumental Approach to the Measurement of Total Body Water: Optothermal Detection of Heavy Water in the Blood Serum
Authors: Annyas Jasper , Bicanic Dane , Schouten Frans
Published: October 2003

The optothermal window (OW) in conjunction with a low-power infrared source was used at 4 μm wavelength to measure the concentration of D2O needed to determine the total body water (TBW) in human subjects. The 30 ppmv D2O detection limit is comparable to that obtainable by infrared transmission (IRT) spectroscopy but can be further enhanced. Low cost and ease of sampling and operation are other advantages of the novel method.
Noise Probe Method for Band Detection in Raman Spectroscopy
Authors: Soneira M. J. , Yúfera J. M. , Ruiz-Moreno S.
Published: October 2003

In this work a noise probe method to detect Raman bands in spectra has been developed. The effectiveness of this approach is demonstrated with the use of silica and gypsum Raman spectra obtained under variable experimental conditions. The advantage of the proposed method stems from the fact that the location of the Raman bands is automated by using software based upon a signal processing algorithm with the use of a personal computer. This approach avoids subjective errors. The method is shown to be suitable to locate Raman bands and so to be an efficient tool to identify materials on the basis of their characteristic Raman spectrum.
Fluorescence Excitation Emission Matrices of Human Tissue: A System for in vivo Measurement and Method of Data Analysis
Authors: Zuluaga Andrés F. , Utzinger Urs , Durkin Anthony , Fuchs Holger , Gillenwater Ann , Jacob Rhonda , Kemp Bonnie , Fan James , Richards-Kortum Rebecca
Published: October 2003

We describe a system capable of measuring spatially resolved reflectance spectra from 380 to 950 nm and fluorescence excitation emission matrices from 330 to 500 nm excitation and 380 to 700 nm emission in vivo. System performance was compared to that of a standard scanning spectrofluorimeter. This “FastEEM” system was used to interrogate human normal and neoplastic oral cavity mucosa in vivo. Measurements were made through a fiber-optic probe and require 4 min total measurement time. We present a method based on autocorrelation vectors to identify excitation and emission wavelengths where the spectra of normal and pathologic tissues differ most. The FastEEM system provides a tool with which to study the relative diagnostic ability of changes in absorption, scattering, and fluorescence properties of tissue.
Fourier Transform Infrared Spectroscopic Characterization of Human Breast Tissue: Implications for Breast Cancer Diagnosis
Authors: Ci Yun Xiang , Gao Ti Yu , Feng Jun , Guo Zhen Quan
Published: October 2003

Some remarkable spectral differences are observed among normal, benign, and malignant breast tissue samples: (1) characteristic spectral patterns of fibroadenoma and carcinoma tissues appear in the frequency regions of 950–1150 cm−1 and 2800–3050 cm−1; (2) the peak at 970 cm−1 is sharper and stronger, and the prominent bands at 1204, 1280, and 1338 cm−1 are weaker and broader for carcinoma tissue, whereas the band near 970 cm−1 is weaker, and the prominent peaks of collagen are sharper and stronger for benign tissues; (3) the band near 1163 cm−1 in benign tissues shifts to 1171 cm−1 in carcinoma tissue; (4) A1032/ A1083 and A2958/ A2853 ratios in carcinoma tissue are the smallest, whereas they are the highest in fibroadenoma tissue among the corresponding ratios; and (5) A1459/ A1241 > 1.0 for normal tissue, A1453/ A1239 > 1.0 for fibroadenoma, and A1456/ A1239 < 1.0 for hyperplasia and carcinoma tissues. These significant differences reveal the differences in the relative contents of nucleic acids and collagen proteins in breast tissues. Furthermore, these differences have important implications not only for probing and analyzing the developing process of the breast lesion at the molecular level but also for evaluating the histological types and grades of breast diseases.
Analysis of Metal Salts by Combining Spectral Windows: Quantifying and Optimizing Cost-Effectiveness of Multispectral Analyses
Authors: Wu J. L. , Egan W. J. , Milanovich F. P. , Myrick M. L.
Published: October 2003

Luminescence and Raman measurements of metal (Er3+, Tb3+, Sm3+, Eu3+, UO22+, and Na+) nitrates from multiple spectral windows are combined and analyzed to determine whether this multispectral approach provides any benefit over the best single-measurement, single-window technique by itself. The individual measurements we combined were obtained under the following conditions (1) excited at 488 nm and detected from 500 to 730 nm, (2) excited at 514.5 nm and detected from 530 to 700 nm, and (3) excited at 785 nm and detected from 800 nm to 920 nm. The first two conditions were excellent for producing fluorescence, while the latter was best for Raman spectroscopy because it avoided most fluorescence. Single-window measurements, particularly the near-infrared Raman spectroscopy of the nitrate counterions, were sufficiently similar to make visual identification of the metal salts from the spectra impossible. The combined data set provided easy visual differentiation between the metal salts. However, we found that hierarchical cluster analysis of the single-window measurements could also be used to identify the metal nitrates even when only the Raman spectral windows of the nitrates were studied. To select windows for a multispectral approach rationally, we define an efficacy parameter, πT, for each possible combination of measurement windows, plus a formula for cost estimation for the multispectral system. This parameter is evaluated for the data presented in the paper, with the conclusion that the least costly acceptable combination consists of only two windows with the same excitation source. In cases such as these, pooled multispectral analysis is proposed as an excellent means of selecting the appropriate technique and wavelength range for an optimal single measurement set, but subsets of the pooled data may function equally well or even better for specific monitoring tasks, especially when cost analysis is necessary. Means of optimizing costs are described briefly, as are means of performing the efficacy calculation when analyses are not of equal importance.
Quantification of Intramuscular Fat Content in Beef by Combining Autofluorescence Spectra and Autofluorescence Images
Authors: Wold Jens Petter , Kvaal Knut , Egelandsdal Bjorg
Published: October 2003

Autofluorescence spectra, autofluorescence images, and near-infrared (NIR) reflectance spectra were tested to determine intramuscular fat and connective tissue in meat slices (longissimus dorsi) from 45 Norwegian Red cattle. Excitation wavelength 332 nm was used to generate fluorescence that was spectroscopically measured and imaged over a total area of 33 and 21 cm2, respectively, for each sample. Five types of image features were extracted: the angle measurement technique, the autocovariance spectrum, measures derived from the gray-level co-occurrence matrix, singular value decomposition, and percentage of bright areas in the images. The fat content was 0.5–10.5% (w/wet w) and connective tissue 0.42–0.92% (w/wet w). Partial least-squares regression resulted in the following correlations ( R) and root mean square errors of cross-validation (RMSECV) for fat: autofluorescence spectroscopy (0.84, 1.10%), NIR (0.87, 1.01%), and the best image feature (0.78, 1.30%). The best result was obtained by combining autofluorescence spectra with image features (0.92, 0.80%). Connective tissue was poorly predicted ( R = 0.41) because of narrow range. The study demonstrates that the combination of spectral data and structural information from images can result in better and more robust prediction models.
Matrix Effect Studies in the Inductively Coupled Plasma with Monodisperse Droplets. Part I: The Influence of Matrix on the Vertical Analyte Emission Profile
Authors: Lazar Alexandru C. , Farnsworth Paul B.
Published: October 2003

The effects of different matrices on the analyte vertical emission profile in the inductively coupled plasma were evaluated with use of a monodisperse droplet sample introduction system in combination with a pneumatic nebulizer. The influence of matrix in the gas phase was separated from influences in the desolvation and volatilization steps. The results suggest that vertical shifts in the analyte emission profiles occur primarily during droplet desolvation and vaporization. The vertical shifts can be correlated to the size of the desolvated particles; larger particles produce emission profiles closer to the load coil. Possible effects of radiative heat transfer were also studied. Strongly absorbing species can increase the evaporation rate of the solvent and produce vertical shifts toward the load coil.
Matrix Effect Studies in the Inductively Coupled Plasma with Monodisperse Droplets. Part II: The Influence of Matrix on Spatially Integrated Ion Density
Authors: Lazar Alexandru C. , Farnsworth Paul B.
Published: October 2003

Monodisperse droplet sample introduction was used to study the ionization process in the inductively coupled plasma (ICP). The influence of the matrix on the analyte ion number density was evaluated by using laser-excited atomic fluorescence spectroscopy (LEAFS). The results suggest that the presence of 0.1 M NaCl enhances the ionization of the analyte species. With the addition of the NaCl, the spatially integrated Ba(II) signal decreases, apparently due to enhanced production of Ba2+. Added NaCl accelerates the appearance of Sc+, but does not affect the spatially integrated signal once ionization is complete. The possible effects on the fluorescence signal of quenching caused by the presence of the NaCl were evaluated by comparison of time-resolved and time-integrated detection. Quenching makes a small contribution to the fluorescence intensity change produced by the matrix but does not account for large loss in signal from singly ionized Ba.
Comparison of a Cross-Flow and Microconcentric Nebulizer for Chemical Speciation Measurements Using CZE-ICP-MS
Authors: Baker Scott A. , Miller-Ihli Nancy J.
Published: October 2003

A standard cross-flow nebulizer and commercially available microconcentric nebulizer (MCN-100) have been compared for capillary zone electrophoresis (CZE) inductively coupled plasma mass spectrometry (ICP-MS) measurements. Metallothionein samples were separated and detected to characterize the performance of the two nebulizers for chemical speciation measurements. The MCN-100 offered improved sensitivity and lower detection limits compared to the cross-flow nebulizer, but provided slightly poorer resolution. The detection limit for 114Cd in metallothionein solutions was 90 ng/g with the cross-flow nebulizer and 10 ng/g with the MCN-100 for ∼ 4 nL injections. These values correspond to absolute detection limits of 360 fg Cd in the injected sample with the cross-flow nebulizer and 40 fg Cd for the MCN-100. Quantitation of Cd in metallothioneins (rabbit liver and horse kidney) with the use of a well-characterized rabbit liver metallothionein sample as the calibration standard is reported. Measured Cd concentrations agreed with results obtained by both graphite furnace atomic absorption spectroscopy (AAS) and solution nebulization ICP-MS.
XPS Characterization of Bi and Mn Collected on Atom-Trapping Silica for AAS
Authors: Süzer Ş. , Ertaş N. , Ataman O. Y.
Published: October 2003

The chemical state of analyte species collected on a water-cooled silica tube during atom-trapping atomic absorption spectrometric determination is investigated with the use of X-ray photoelectron spectroscopy (XPS) for Bi and Mn. Analysis of the Bi 4f7/2 peak reveals that the chemical state of Bi is +3 during initial trapping (before the atomization stage), but an additional 0-valence state of Bi is also observed after the atomization stage. With the use of the measured Mn 2p3/2 binding energy together with the observed 3s multiplet splitting, the chemical state of Mn is determined as +2 in all stages. Together with our previous determination of 0 valence for Au, it is now postulated that the stability of certain valence states of the three elements (Au, Bi, and Mn) on the silica matrix can be correlated to their electrochemical reduction potentials.
Raman Microspectroscopy with a Card-Based Spectrograph
Authors: Sommer André J. , Stewart Sarah A.
Published: October 2003

A Raman microprobe employing a card-based spectrograph and a HeNe excitation source was constructed and evaluated. Particular emphasis was placed on the low-cost room-temperature charge-coupled device (CCD) employed in the instrument. This detector exhibited a relatively high fixed pattern noise [198 e−/pixel/s, root mean squared (rms)] and read noise (35 e−, rms) compared to conventional charge-coupled detectors employed for Raman spectroscopy. However, by compensating for the fixed pattern noise and signal averaging, we obtained Raman spectra of a variety of common materials with reasonable signal-to-noise ratios at room temperature. Spectra having good signal-to-noise characteristics were collected on polystyrene spheres as small as 5 μm in diameter and a nylon fiber 23 μm in diameter. Although the sensitivity of the detector is limited for weak scatterers, the instrument can be used in specific industrial applications and for educational purposes. Suggestions are made for improving the system.
Use of CLS to Understand PLS IR Calibration for Trace Detection of Organic Molecules in Water
Authors: Haaland David M. , Han Ling , Niemczyk Thomas M.
Published: October 2003

Partial least-squares (PLS) and principal component regression (PCR) methods applied to spectral data can generally provide excellent quantitative analysis precision, but extraction of qualitative spectral interpretation from the models can be more difficult. For example, we have achieved sensitivity in the parts-per-million range for polar organic compounds in aqueous solutions using infrared (IR) spectroscopy and modified sol-gel-coated ATR sensors. The interpretation of PLS or PCR loading vectors obtained from calibrations involving orthogonally designed solutions of acetone and isopropanol in water yields a misleading understanding of the mechanism for the IR detection of isopropanol on these sensors. Examination of the loading vectors from PLS or PCR or the first weight-loading vector from the PLS model would suggest that the spectral calibration is based largely on the interaction of the isopropanol with the surface modifier of the sol-gel coating. However, a classical least-squares (CLS) analysis of the data shows clearly that this interaction is not a significant source of the spectral calibration, but rather the calibration is primarily due to the spectroscopic signal of the isopropanol analyte. In this case, the misleading qualitative interpretation of the PLS and PCR models is the result of the spectral variation being dominated by the effects of spectrometer drift. CLS can overcome this problem if a parameter is included in the CLS calibration that adequately represents the drift. In the example presented here, time of spectral data collection is an appropriate drift-related parameter that can be added to the CLS calibration concentration model in order to provide the qualitative information needed to correctly interpret the spectral data. Other methods to include the effects of spectrometer drift in the CLS model are also presented.
Accurate Concentration Measurements Using Infrared Absorption without Determination of the Baselines
Authors: Marteau P. , Tobaly P.
Published: October 2003

Infrared absorption spectra have become widely used for in situ determination of concentrations in complex mixtures. However, experimental accuracy is often limited by lack of knowledge of the baselines. The mathematical treatment described below allows the spectra to be superimposed on any background with a shape as complex as a parabolic one. The concentrations are thus accurately determined whatever the baseline of the mixture spectrum and even those of the calibration spectra. A mathematical proof of this property is given within the framework of the presently used method, and tests of the efficiency of the method are presented.