bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of Near-Infrared Spectroscopy for Periodic Determination of Glucose in Cell Culture Media in Situ
Authors: Lewis Christopher B. , McNichols Roger J. , Gowda Ashok , Coté Gerard L.
Published: October 2003

Current techniques used to monitor glucose concentration of cell culture media (CCM) require invasive and tedious handling of the sample for sterile media removal and nutrient replacement. In order to optimize cell culture growth in bioreactors, biosensors must be developed that are capable of monitoring the cell culture processes noninvasively and continuously. In this study, on-line, noninvasive determinations of glucose in cell culture media were investigated via near-infrared spectroscopy (NIR) across the 2.0–2.5 μm combination region. A system was developed, using a unique fiberoptic coupling method and a commercial Fourier transform infrared (FT-IR) spectrometer, to characterize glucose single-beam spectra collected from cell culture media. This novel system is the first of its kind and integrates a completely noninvasive optical probe to measure glucose concentrations within cell culture media, in situ. Spectra recorded from a four-day fibroblast culture with this fiber coupled system and an FT-IR spectrometer have been analyzed and compared with standard clinical chemistry techniques. Partial least-squares (PLS) regression has been used to extract the analyte-dependent information and to build a successful multivariate calibration model. A combination of spectra from cell culture media and prepared media mixtures was used to eliminate unwanted correlations in the calibration data. The combined use of this unique fiberoptic system, PLS, and uncorrelated spectra resulted in a true glucose prediction error of 14.8 mg/dL in an independent validation set.
Two-Dimensional Correlation Spectroscopy Study of Visible and Near-Infrared Spectral Variations of Chicken Meats in Cold Storage
Authors: Liu Yongliang , Chen Yud-Ren
Published: October 2003

This paper reports the generalized two-dimensional (2D) visible/near-infrared (Vis/NIR) correlation spectroscopy study of chicken meats in cold storage. The 2D visible correlation analysis revealed that, besides the previously reported three absorption bands around 445, 485, and 560 nm ascribed to DeoxyMb, MetMb, and OxyMb, there is an additional band around 635 nm that could be assigned to SulfMb, a product from the reaction of myoglobin with H2S generated by bacteria. Unlike the spectral intensity reduction of the 440 and 560 nm bands, the intensities of the 490 and 635 nm bands increase with storage time. The asynchronous 2D visible correlation spectra indicated that OxyMb and MetMb produce SulfMb first; then complicated reactions such as the oxygenation and oxidization of DeoxyMb and the oxidization of OxyMb follow as storage is prolonged. In addition, several close and separated bands appearing around the 440, 490, and 560 coordinates could be a result of the changes in the molecular environment of the heme pigment portion. Hence, the decreasing intensity and the splitting of the 440 and 560 nm bands are responsible for the discoloration of meats. The 2D correlation spectra in the NIR region showed that the O-H/N-H bands change their spectral intensity before the C-H groups during the storage, suggesting a coordination process for hydrophilic O-H and N-H groups. It revealed two main possibilities: (1) water species interact with other meat components, and (2) the meat proteins undergo proteolysis and denaturation processes, which is associated with the development of tenderization during storage (aging). In addition, the asynchronous spectra correlating the spectral bands in both the visible and NIR regions suggested that the discoloration occurs earlier than other developments, such as tenderization process.
Development of a Hierarchical Classification System with Artificial Neural Networks and FT-IR Spectra for the Identification of Bacteria
Authors: Udelhoven Thomas , Naumann Dieter , Schmitt Jürgen
Published: October 2003

The practical value of elaborated vibrational spectroscopic techniques in medical and microbiological biodiagnostics depends strongly on the reliability, the speed, the ease of use, and the evaluation procedures of the acquired data. In the present study, artificial neural networks (ANNs) were used to establish a hierarchical classification system for microbial Fourier transform infrared (FT-IR) spectra suitable for identification purposes in a routine microbiological laboratory. A radial basis function network (RBF) proved to be superior for a top-level classification of the FT-IR spectra at the genus level. Species within these genera were sequentially further classified by using multilayer perceptrons (MLPs), which achieved a larger differentiation depth than RBF networks. The MLPs were trained with several learning algorithms. Best performance was achieved with the cascade correlation (CC) approach to determine the network topology combined with resilient propagation (Rprop) as the training algorithm. The final hierarchically organized model was able to discriminate between four genera of microorganisms comprising 42 different strains of Pseudomonacae, 33 strains of Bacillus, 46 strains of Staphylococcus, and 6 species and 24 strains of yeast genera Candida. Altogether, 145 strains from international microbial strain collections are comprised in 971 spectra. The species Candida albicans could be further classified with respect to susceptibility against the antibiotic drug fluconazole, which is of therapeutic relevance. Key factors for the classification results of the bacterial FT-IR spectra were the data pretreatment, the number of wavelengths selected by a feature extraction algorithm, the type of network, and the learning function used for the ANN training.
Measurement of Petroleum Fuel Contamination in Water by Solid-Phase Microextraction with Direct Raman Spectroscopic Detection
Authors: Jager Michael J. , McClintic Daniel P. , Tilotta David C.
Published: October 2003

A method is described for determining petroleum fuel contamination in water based on solid-phase microextraction and Raman spectroscopy (SPME/Raman). In this method, contaminants are extracted from aqueous solutions into a solid phase and then detected directly by using spontaneous Raman spectroscopy. The solid phase consists of a small volume (∼ 20 μL) of poly(dimethylsiloxane) that has an optical window in the 830–1600 cm−1 Raman shift region. This region is suitable for determining both aromatic and aliphatic fuel components. Four “real world” fuels—aviation gasoline, unleaded gasoline, jet fuel A, and #1 fuel oil—were used to test this new method. As shown, the SPME/Raman determinations performed in the visible spectral region were not adversely affected from the fluorescence of the marker dyes in these fuels. The linear dynamic ranges for the determinations exceeded the water solubility limits and spanned 1–3 orders of magnitude. The limits of detection with the use of the most sensitive Raman bands in each fuel were in the 8–12 ppm range with the exception of #1 fuel oil (25 ppm), and relative standard deviations typically were 2–10%. Finally, the SPME/Raman method was applied to the determination of total petroleum hydrocarbons in natural water matrices. With the use of hexane and undecane as standards, the results of the determinations compared favorably to the standard methods of purge-and-trap gas chromatography and liquid-liquid extraction followed by infrared detection.
Molecular Sensing via an Immobilized Organometalcarbonyl Probe Group
Authors: Creaser Colin S. , Hutchinson William E. , Stephenson Richard G.
Published: October 2003

Tricarbonyl(cyclohexadiene)iron(0) reporting groups have been derivatized by attachment of an aminopropylsilyl link and attached covalently to silica. The infrared (IR) properties of the organometalcarbonyl moiety have been investigated by Fourier transform infrared (FT-IR) spectroscopy and have been shown to retain their capacity to function as a key element of a molecular sensor assembly. The v(CO) vibrational frequencies of the immobilized complexes shift with changes in the solvent environment when exposed to binary and ternary solvent systems. Principal components regression (PCR) was used to correlate the v(CO) shifts of the probe group quantitatively with solvent composition with a root mean square error of prediction (RMSEP) of 0.9% for a binary solvent system.
Chemically Tapered Silver Halide Fibers: An Approach for Increasing the Sensitivity of Mid-Infrared Evanescent Wave Sensors
Authors: Karlowatz M. , Kraft M. , Eitenberger E. , Mizaikoff B. , Katzir A.
Published: October 2003

In this work an innovative etching technique for tapering silver halide fibers is introduced. As silver halides form soluble complexes with thiosulfate in aqueous solution, the fiber can be chemically tapered by an etching process, which also warrants a high quality of the fiber surface. The evanescent field sensitivity of thus obtained tapered fibers was raised by more than one order of magnitude, demonstrated by calibration curves of tetrachloroethylene in hexane recorded with a tapered sensor fiber coupled to a Fourier transform infrared (FT-IR) spectrometer.
Dual Polarization Modulation: A Real-Time, Spectral-Multiplex Separation of Circular Dichroism from Linear Birefringence Spectral Intensities
Authors: Nafie Laurence A.
Published: October 2003

A real-time, spectral-multiplex method for the complete separation of circular dichroism (CD) spectra from linear birefringence (LB) spectra is presented. The method, called dual polarization modulation (DPM), involves the introduction of a second source of polarization modulation after the CD sample. The first source of polarization modulation, as in conventional CD spectrometers, is located before the sample. Intensity signals at the detector in phase with each of the two polarization modulation frequencies are demodulated simultaneously in parallel and combined electronically in opposition to eliminate the LB spectrum by real-time cancellation. The accuracy of the cancellation can be adjusted electronically without the need to change the optical alignment of the instrument. The DPM method permits baseline-corrected CD spectra to be measured without the need for a subsequent CD background measurement.
Resolution Enhancement in IR Spectra of Carbohydrates by the Deconvolution Method and Comparison of the Results with Low-Temperature Spectra
Authors: Buslov Dmitrii K. , Nikonenko Nataliya A. , Sushko Nataliya I. , Zhbankov Rostislav G.
Published: October 2003

This paper presents infrared (IR) spectra of β-d-glucose, cellobiose, and cellulose in the 1500–850 cm−1 range as well as the results of their deconvolution. Comparison of the results of deconvolution with the IR spectra of the investigated compounds obtained at room and helium temperatures of the sample as well as with the theoretical data has been made. It is shown that the use of the deconvolution method provides a better—compared to the low-temperature spectra—resolution of individual absorption band components for all the compounds being analyzed, especially for the polysaccharide cellulose. The results of deconvolution of IR spectra of monosaccharide β-d-glucose and disaccharide cellobiose are in good agreement with the data of normal coordinate analysis. It has been found that the minimum values of band halfwidths in the room-temperature IR spectra of β-d-glucose and cellobiose approximately coincide, while for cellulose they increase by a factor of about 1.5.
Measurement of Formaldehyde in a Single Puff of Cigarette Smoke Using Tunable Diode Laser Infrared Spectroscopy
Authors: Parrish Milton E. , Harward Charles N.
Published: October 2003

A method has been developed for measuring formaldehyde in single puffs of mainstream (MS) and per cigarette in sidestream (SS) smoke with the use of tunable diode laser (TDL) infrared spectroscopy. Thirty to fifty percent of the total MS formaldehyde delivery per cigarette is generated in the lighting puff. This phenomenon is unique to formaldehyde compared to most other gaseous smoke components. The effect of the lighting technique, packing density of the tobacco in the cigarette rod, flow rate of air (heating rate) through the cigarette coal (burning zone), and tobacco type on the formaldehyde levels were studied. Calibration was based on measuring the second-derivative spectral response of formaldehyde generated from certified paraformaldehyde permeation tubes. The accuracy of the measured value of this standard was determined to be within ±0.7% of the certified formaldehyde delivery by performing periodic gravimetric measurements. In addition, the formaldehyde standard was collected in a water trap and analyzed by using a colorimetric analytical technique, providing an agreement of ± 2% with the TDL measurement. The TDL method precision was ≤ 1% with the use of the permeation standard. The MS formaldehyde deliveries for a Philip Morris monitor and Kentucky Reference 1R4F cigarette were 37 ± 5 and 27 ± 5 μg/cigt., respectively. The 1R4F value was in close agreement with results found by using an HPLC method reported in the literature. The MS sampling system can be quickly modified to determine formaldehyde levels in sidestream smoke. The SS formaldehyde delivery for the Philip Morris monitor cigarette was 2.1 ± 0.1 mg/cigt. (i.e., 0.27 ± 0.01 mg/min). The range of SS deliveries for reference, experimental, and commercial brands was much less than that observed for the MS smoke deliveries of similar cigarettes.
Correlative Spectroscopic Imaging: XPS and FT-IR Studies of PVC/PMMA Polymer Blends
Authors: Artyushkova K. , Wall B. , Koenig J. , Fulghum J. E.
Published: October 2003

Correlative X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) studies of the complex heterogeneous structure of 50:50 poly(vinyl chloride)/poly(methyl methacrylate) (PVC/PMMA) polymer blends are presented. The comparable lateral resolution and parallel imaging capabilities of both techniques allow for a direct comparison of surface (XPS) and bulk (FT-IR) measurements of polymer blends. To eliminate substrate influence and film-to-film differences, the same areas on the polymer films are analyzed by both methods. The effect of PMMA molecular weight on surface separation and surface segregation is evaluated by using six blends with a constant PVC molecular weight and a PMMA molecular weight varying from 75 to 2132 kDa. Imaging capabilities of both methods were used for a qualitative comparison of the heterogeneous structure of the blends, while a quantitative comparison of the bulk and surface compositions of the same areas of the samples used small-area spectroscopy from XPS and FT-IR. On the basis of the quantitative analysis, it is concluded that surface segregation of PMMA increases with increasing molecular weight. The determination of both surface and bulk properties of complex heterogeneous samples is important for a more complete understanding of the structure of complex films.
Controlled Formation of Isolated Silver Islands for Surface-Enhanced Raman Scattering
Authors: Stöckle Raoul M. , Deckert Volker , Fokas Christian , Zenobi Renato
Published: October 2003

Rough silver surfaces enhance the Raman scattering of adsorbed molecules by many orders of magnitude. The size, shape, and surroundings of the metal particles greatly influence the resulting Raman intensities. With the controlled formation of well-separated silver islands, direct investigation of the local origin of the Raman enhancement is greatly facilitated. We summarize the effects of experimental parameters during and after vapor deposition of silver on the resulting surface morphology. With the selection of suitable experimental conditions, particle sizes and shapes, as well as the interparticle distances, can be controlled so that well-separated silver islands are formed that still show high Raman enhancement. The surfaces were characterized morphologically by means of atomic force microscopy (AFM) and scanning electron microscopy (SEM). Optical characterization was carried out by using ultraviolet-visible and Raman spectroscopy.
Implementation of Raman Spectroscopy as an Analytical Tool Throughout the Synthesis of Solid-Phase Scaffolds
Authors: Pivonka Don E. , Sparks Richard B.
Published: October 2003

Raman spectroscopy has been implemented as an extremely powerful tool for the vibrational analysis of solid-phase synthesis. In this report, the application of both on-line and batch-mode Raman analysis is presented for the comprehensive characterization of a multi-step small-molecule synthesis. Throughout this application, near-infrared Raman spectroscopy also provides unprecedented utility for on-bead qualitative and quantitative investigations. Finally, the on-line experimental procedure presents the first opportunity for open-loop feedback control of solid-phase synthetic parameters through the real-time presentation of reaction progression using Raman spectroscopy.
FT-Raman Spectroscopy: A Tool for Monitoring the Demineralization of Bones
Authors: Kontoyannis C. G. , Vagenas N. V.
Published: October 2003

A nondestructive analytical method based on the use of Fourier transform Raman spectroscopy (FT-RS) for identification and quantitative analysis of hydroxyapatite (HAP) and collagen (COL) in bones was developed. A calibration curve based on the Raman spectra of known powder mixtures of HAP–COL was constructed with the use of the Raman bands at 960 cm−1 for HAP and 2937 cm−1 for COL. It was found that I960 /I2937 = 0.46/ WC — 0.36, where I960 and I2937 are the relative intensities for the 960 and 2937 cm−1 Raman bands, respectively, and Wc represents the weight fraction of collagen. The detection limit for HAP and COL was found to be 2.8 and 0.6 wt %, respectively. The potential of using RS for an in vitro point-by-point analysis (“mapping”) of bones was demonstrated successfully on an artificially demineralized ox femur sample.
Experimental Study of Optical Scattering and Fiber Orientation Determination of Softwood and Hardwood with Different Surface Finishes
Authors: Shen Jun , Zhou Jianqin , Vazquez Orlando
Published: October 2003

Optical scattering from wood of different surface finishes has been experimentally investigated. It has been found that for planed-Hemlock samples the scattering intensity distribution in the direction across the wood fibers is very close to perfect diffuse reflection, while that in the direction along the fibers appears as the combination of diffuse and specular reflection. The increase of wood surface roughness reduces the difference between these two scattering intensity distributions. The difference provides the basis for determining wood fiber orientation by measuring the scattering intensity variation with fiber orientation. When the sample surface becomes very rough, such as a rough sawn or porous hardwood sample, the scattering from the uneven surface overwhelms the difference and creates a difficulty in fiber orientation measurement. To solve the problem, we have been employed optical polarization detection in the investigation. With this detection method, for the samples used in this work, the intensity variation of the scattering vs. fiber orientation appears periodic despite the different surface finishes. With the help of Fourier analysis, fiber orientations of the rough sawn softwood and porous hardwood samples under investigation can be precisely measured.
Fluorinated Phosphoric Ester-Based Protective Material for Limestone-Made Ancient Monuments, Buildings, and Artifacts: An X-ray Photoelectron Spectroscopy Study
Authors: Spoto Giuseppe , Rizzarelli Paola , Torrisi Alberto
Published: October 2003

In this study, fluorinated phosphoric esters are evaluated as protective material for limestone from water-driven alteration processes. Hypotheses as to their molecular arrangement are also provided. The surface composition of limestone after treatment with a commercially available fluorinated phosphoric ester material was evaluated by X-ray photoelectron spectroscopy (XPS). Results were then compared with those obtained for the treated limestone after accelerated aging tests. In the limestone that had not been subjected to aging processes an XPS determined thickness of the protective coating equivalent to 95 ± 18 Å was observed. This fell to 49 ± 10 Å in the limestone examined after intensive aging tests. However, low surface wettability (θ = 135° ± 4) was seen to be maintained.
Effect of Operating Frequency on Spatial Features of the Inductively Coupled Plasma
Authors: Horner Julie A. , Yang Pengyuan , Hieftje Gary M.
Published: October 2003

An unambiguous comparison has been made of the spatial features of a 27.12 and a 40.68 MHz inductively coupled plasma. Experiments were carried out with a switchable-frequency, solid-state radio-frequency generator from the Leco 2000 system. Several features of analytical significance have been evaluated in a spatially resolved fashion. Results from optimization of the magnesium ion-to-atom (Mg II/Mg I) line-intensity ratio have been compared. The volume of the two discharges was estimated from molecular nitrogen-ion emission, and a spatially resolved map of the Fe(I) excitation temperature was determined by means of a Boltzmann analysis at each spatial location. Calcium and magnesium ion-to-atom line-intensity ratios have been calculated throughout both plasmas. Finally, limits of detection are presented. The results indicate that the plasma operated at 40.68 MHz provides slightly better figures of merit, although fundamental parameters suggest a lower degree of analyte excitation. This difference is explained by examining the results of a simulation of plasmas operated at 27.12 and 40.68 MHz.
Acoustic Trap for Simplified Micro-Sample Handling in Laser Spectroscopy
Authors: Davies Antony N. , Jacob Peter , Stockhaus Antje , Kuckuk Rudiger , Hill Wieland , Hergenroder Roland , Zybin Alexander , Klockow Dieter
Published: October 2003

A tailor-designed acoustic trap has been built and tested as a sample handling device for use in laser spectroscopy. It is based on a piezoelectric vibrator that sets up a standing acoustic wave with several nodes into which liquid or solid samples may be placed and held in a levitated position. The usefulness of such a system to hold samples without the need for sample cells was demonstrated for various experiments involving direct spectroscopic measurements on the suspended sample. Changes in the UV spectrum of bromocresol green dye during a simple pH titration on a drop of the levitated solution were followed by dual dye laser spectrometry. A chemical actinometry spectrochemistry experiment was conducted on Aberchrome 540 fulgide dissolved in DMSO in the levitated state by following changes in the molecular structure of the fulgide by Raman spectroscopy. Finally, crystallization experiments were carried out on droplets and bubbles of tris-(hydroxymethyl)-amino-methane and l-cystein.
Efficient Elimination of Fluorescence Background from Raman Spectra Collected in a Liquid Core Optical Fiber
Authors: Pelletier M. J. , Altkorn Robert
Published: October 2003

Liquid core optical fiber (LCOF) waveguides have been used to enhance the Raman sensitivity of liquid sample measurements by more than two orders of magnitude. These waveguides can also enhance photobleaching of fluorescence in transparent liquids. We report the reduction of fluorescence intensity by more than two orders of magnitude by rapid photobleaching of solutions illuminated in an LCOF. The same solutions showed no detectable photobleaching when illuminated in a cuvette. The observed rates of photobleaching are in good quantitative agreement with theory.
In Situ Generated Photolytic Silver in a Gelatin Matrix: An Approach for High-Throughput SERS Spectroscopy Applying Microtiter Plates
Authors: Saegmueller Bernd , Brehm Georg , Schneider Siegfried
Published: October 2003

In order to develop a high-throughput analysis method based upon surface-enhanced Raman scattering (SERS) spectroscopy, we have successfully tested the possibility of generating SERS-active silver surfaces from home-made AgX dispersions deposited in the wells of commercially available microtiter plates. In an effort to reduce the number of preparation steps, the SERS-active silver metal surface is generated from the silver halides in situ after sample application by the tightly focused Raman probe laser. The intensity of the SERS signal increases initially with the conditions for a high-enhancement factor becoming optimal. Later on, it decreases as the solvent is evaporated completely. The signal can, however, be restored to a great extent by adding new refreshing solvent, preferably methanol. Pilot experiments using aromatic thiols and amines as test analytes proved that sample volumes as small as 1 mL with analyte concentrations down to 10−6 M are sufficient for recording of SERS spectra suitable to identify the analyte. A feasibility study was performed aimed at the identification of several analytes contained in the various fractions of the output of an analytical high-performance liquid chromatography (HPLC) instrument.
Design and Applications of Rapid-Scan Spectrally Resolved Fluorescence Microscopy
Authors: Haralampus-Grynaviski Nicole M. , Stimson Michael J. , Simon John D.
Published: October 2003

This paper addresses the design and applications of a spectrally resolved confocal fluorescence microscope that measures spectral information for each pixel in the image with a fast multi-point approach. The combined spatial and spectral resolution of the device is demonstrated by performing two-photon imaging of mixtures of fluorescently labeled microspheres. Overlapping emission spectra of dye solutions contained in microcapillaries are readily distinguished. Images of a human skin tissue section and a mouse kidney section are presented which demonstrate that the structure and spectra of biologic samples can be resolved.
Fiber-Optic Raman Spectroscopy for in Situ Monitoring of Metal-Ion Complexation by Ligands Immobilized onto Silica Gel
Authors: Uibel Rory H. , Harris Joel M.
Published: October 2003

Fiber-optic Raman spectroscopy was adapted to measurements of metal-ion complexation by silica-immobilized 8-hydroxyquinoline (8HQ) under conditions typical of metal-ion preconcentration or recovery applications. The extraction of metal ions from aqueous sources onto immobilized ligands is useful in environmental cleanup initiatives and in the preconcentration of metal ions for ultratrace detection. In situ vibrational spectroscopy of metal complexation by silica-immobilized ligands can assist in the development of these applications. In the present work, in situ Raman spectroscopy and flow methods allowed the reactivity of silica-immobilized 8HQ with Cu2+ to be investigated. The structure of the complexed and uncomplexed neutral and protonated forms of the ligand could be resolved and quantified in Raman spectra taken under different solution conditions. Spectra of the ligand bound to different metal ions could be distinguished as well. Raman spectra taken under batch sampling conditions were able to confirm a 1:1 metal/ligand stoichiometry of the silica-immobilized 8HQ complex, which was reasonable in light of the surface coverage by the ligand. In situ monitoring under flowing solution conditions allowed changes in the state of binding to be followed in real time.
Raman Spectroscopy for the in Situ Identification of Cocaine and Selected Adulterants
Authors: Carter J. Chance , Brewer William E. , Angel S. Michael
Published: October 2003

We demonstrate the in situ identification of crack cocaine and cocaine·HCl by using a fiber-optic Raman probe and a portable Raman spectrograph. The Raman spectrum of freebase cocaine (crack) is obtained in just seconds without any sample preparation, and differs significantly from that of cocaine·HCl. We also show that the Raman spectra of these drugs are easily distinguishable from common cutting agents and impurities such as benzocaine and lidocaine. Another advantage of using Raman spectroscopy is that the drugs can be identified while contained in transparent containers, such as clear plastic evidence containers that are used to store drug evidence and to maintain chain of custody. We also demonstrate the in situ Raman identification of drugs separated by thin-layer chromatography. We discuss the utility of surface-enhanced Raman spectroscopy (SERS) in toxicological drug screening and present preliminary SERS data for cocaine in solution using colloidal silver. We believe this to be the first published SERS spectrum of freebase cocaine.
Realization of the Hadamard Multiplex Advantage Using a Programmable Optical Mask in a Dispersive Flat-Field Near-Infrared Spectrometer
Authors: Deverse R. A. , Hammaker R. M. , Fateley W. G.
Published: October 2003

Spectrometry and hyperspectral imaging are finding numerous applications for micro-optoelectromechanical systems (MOEMS). A type of MOEMS device in the form of a digital micromirror array (DMA) has been made commercially available by Texas Instruments USA for projector display applications. We use this device as a spatial light modulator (SLM) in a new type of flat-field, near-infrared dispersive spectrometer (NIRDMAS). Attributes of the DMA used in this manner are presented for discussion. Features that make a DMA attractive for spectrometry and imaging are described. A brief introduction to Hadamard transform (HT) techniques is presented to show that the DMA may be the best Hadamard encoding mask yet developed. A comparison of a conventional raster scanning (CRS) scan and a Hadamard transform spectrometry (HTS) scan with respect to the Hadamard multiplex advantage using a nonphoton noise-limited, single-element detector is presented. A signal-to-noise ratio comparison using four spectral lines from a mercury-argon calibration lamp demonstrates that the theoretical noise reduction is approached for the HTS scan compared to the CRS scan. Some future applications of MOEMS in spectrometry and hyperspectral imaging are suggested.
Two-Dimensional Correlation Analysis of the Second Overtone of the v(OH) Mode of Octan-1-ol in the Pure Liquid Phase
Authors: Czarnecki Mirosław A.
Published: October 2003

The temperature-induced variations in Fourier transform near-infrared (FT-NIR) spectra of pure liquid octan-1-ol were studied by two-dimensional correlation analysis. For the first time, the second overtone of the OH stretching band (3 v(OH)) due to the dimeric species and the splitting of the second overtone of the monomer band arising from the presence of two OH conformers have been observed. Fourier self-deconvoluted (FSD) and second-derivative spectra also confirmed the splitting of the monomer band into two components. It has been demonstrated that positions of the peaks appearing in the two-dimensional contour maps correlating the first- and second-overtone regions can be applied for determination of anharmonicity constants. The results presented in this paper suggest that the rule saying that the less associated species have the stronger overtones holds on going from the first to the second overtones as well.
Infrared Study on the Crystallization Behavior and Prestructural Change of Syndiotactic Polystyrene in its Blends with Small Amounts of Poly(2,6-dimethyl-1,4-phenylene Ether)
Authors: Ren Yanzhi , Murakami Tsuyoshi , Nishioka Toshikatsu , Tashiro Kohji , Ozaki Yukihiro
Published: October 2003

Fourier transform infrared spectra were measured for syndiotactic polystyrene (SPS) and its miscible blends with poly(2,6-dimethyl-1,4-phenylene ether) (PPE) of 3, 7, and 10 wt % over a temperature range of 303–493 K at an increment of 10 K. Crystallization of SPS from the glass state to the planar all -trans form occurred in the temperature range of 423–453 K and was delayed by about 10 K in the SPS/PPE blends, as evidenced by the temperature-dependent absorbance changes in bands at 2846.7, 1374.0, 1333.5, 1222.7, 1091.3, 964.1, 939.2, and 839.8 cm−1. A downward shift of the CH2 symmetric stretching band during the heat-induced crystallization was observed. A kind of “prestructural change” from 383 to 423 K was identified for pure SPS by the temperature-dependent changes in the combination modes of aryl CH out-of-plane deformation vibrations. It was diminished in the SPS/PPE blends with the increase in the PPE content, and disappeared in the blends of 10 wt % PPE. This phenomenon was explained by the favorable dispersive interaction between the phenyl rings of SPS and PPE, which was responsible for the blend compatibility.
High Spatial Resolution for IR Imaging Using an IR Diode Laser
Authors: Bailey James A. , Dyer R. Brian , Graff Darla K. , Schoonover Jon R.
Published: October 2003

By coupling an infrared diode laser to a conventional infrared microscope, one achieves resolution approaching the diffraction limit while enabling rapid data collection. This technique is demonstrated with the use of a layered polymer sample that has been contaminated by migration of a volatile additive from an exogenous source. The distribution of this additive in the layered structure is shown to correlate with specific layers and reveals a concentration gradient suggesting a diffusive mechanism of additive migration parallel to the layered structure.
Comparison of Near-Infrared, Infrared, and Raman Spectroscopy for the Analysis of Heavy Petroleum Products
Authors: Chung Hoeil , Ku Min-Sik
Published: October 2003

Near-infrared (NIR) spectroscopy has been successfully applied to the determination of API (American Petroleum Institute) gravity of atmospheric residue (AR), which is the heaviest fraction in crude oil. This fraction is completely dark and very viscous. Preliminary studies involving Raman and infrared (IR) spectroscopies were also evaluated along with NIR spectroscopy. The Raman spectrum of AR was completely dominated by strong fluorescence from polycyclic aromatic hydrocarbons, called asphaltenes. IR spectroscopy provided reasonable spectral features; however, its spectral reproducibility was poorer and noisier than that of NIR. Although absorption bands in the NIR region were broad and less characterized, NIR provided better spectral reproducibility with higher signal-to-noise ratio (which is one of the most important parameters in quantitative calibration in comparison to Raman and IR spectroscopies). Partial least-squares (PLS) regression was utilized to develop calibration models. NIR spectra of AR samples were broad, and baselines were varying due to the strong absorption in the visible range. However, the necessary information was successfully extracted and correlated to the reference API gravity with the use of PLS regression. API gravities in the prediction set were accurately predicted with an SEP (standard error of prediction) of 0.22. Additionally NIR showed approximately three times better repeatability compared to the ASTM reference method, which directly influences the process control performance.
Synthetic Multivariate Models to Accommodate Unmodeled Interfering Spectral Components during Quantitative Spectral Analyses
Authors: Haaland David M.
Published: October 2003

The analysis accuracy and precision of any multivariate calibration method will be severely degraded if unmodeled sources of spectral variation are present in the unknown sample spectra. A synthetic method for correcting errors generated by the presence of unmodeled components or other sources of unmodeled spectral variation has been developed. If the spectral shape of the unmodeled spectral component can be obtained and mathematically added in variable amounts to the original calibration spectra, then a new synthetic multivariate calibration model can be generated from the augmented data to accommodate the presence of the unmodeled source of spectral variation. The new method is demonstrated for a case where unmodeled temperature variations are present in the unknown sample spectra of dilute aqueous solutions of urea, creatinine, and NaCl. When constant-temperature partial least-squares (PLS) models are applied to spectra of variable-temperature samples, the standard errors of prediction (SEP) are approximately an order of magnitude higher than those of the original cross-validated SEPs of the constant-temperature PLS models. Synthetic models based upon constant-temperature data augmented with a classical least-squares (CLS) estimate of the spectral effect of temperature obtained from variable-temperature aqueous sample spectra are demonstrated to significantly reduce errors when predicting concentrations from spectra of solutions at variable-temperature. We demonstrate that the prediction precisions approach the original calibration precisions when the new synthetic PLS models are applied to variable-temperature solution spectra. Although spectrometer drift added bias errors to the analyte determinations, a method is demonstrated that can minimize the effect of long-term drift on prediction errors through the measurement and use of spectra obtained from a small subset of samples measured during both calibration and prediction. In addition, sample temperature can be predicted with high accuracy (±0.13 °C) with this new synthetic PLS modeling method without the need to recalibrate using actual variable-temperature sample data. Therefore, the synthetic method eliminates the need for expensive generation of new calibration samples and collection of their spectra. The method is quite general and can be applied by using any known source of spectral variation and used with any multivariate calibration method.
Effect of Sample Complexity on Quantification of Analytes in Aqueous Samples by Near-Infrared Spectroscopy
Authors: Riley Mark R. , Arnold Mark A. , Murhammer David W.
Published: October 2003

This study was undertaken to quantitate the impact of increasing sample complexity on near-infrared spectroscopic (NIRS) measurements of small molecules in aqueous solutions with varying numbers of components. Samples with 2, 6, or 10 varying components were investigated. Within the 10-component samples, three analytes were quantified with errors below 6% and seven of the analytes were quantified with errors below 10%. An increase in the number of varying components can substantially increase the error associated with measurement. A comparison of measurement errors across sample sets, as gauged by the standard error of prediction (SEP), reveals that an increase in the number of varying components from 2 to 6 increases the SEP by approximately 50%. An increase from 2 to 10 varying components increases the SEP by approximately 340%. While there appear to be no substantial correlations between the presence of a specific analyte and the errors associated with quantification of another analyte, several analytes do display a small degree of sensitivity to varying concentrations of certain background components. The analysis also demonstrates that calibrations containing an overestimation of the numbers of varying components can substantially increase measurement errors and so calibrations must be constructed with an accurate understanding of the number of varying components that are likely to be encountered.
Near-Infrared Turbidity of β-FeOOH Particle Suspensions
Authors: Berdahl P. , Espinoza L. H. , Littlejohn D. , Lucas D. , Perry D. L.
Published: October 2003

Near-infrared transmission spectroscopy can be complicated by the light scattering from heterogeneous materials. For the examination of an evolving system exhibiting such light scattering, transmission spectra near wavenumber v = 104 cm−1 were obtained during the hydrolysis of FeCl3 solutions. At first, the resulting turbid suspension of cigar-shaped β-FeOOH particles exhibits single-particle scattering, including a Rayleigh regime (attenuation ∞ v4). At later times, the scattering increases strongly as the particles aggregate, and becomes proportional to vα, with α ≈ 2, consistent with scattering models that interpret the structure of aggregates in terms of a fractal dimension df roughly equal to 2. In all cases investigated, the attenuation due to scattering is spectrally smooth and increases monotonically with wavenumber. It can be written in the simple form vα with 1 ≤ α ≤ 4. While over limited spectral ranges α may be taken independent of v, over wide ranges it decreases with increasing v. This behavior is consistent with the theoretical limits of α = 4 at v = 0, and α = 0 at v = ∞. Overall, the results suggest that a useful form for simulating scattering backgrounds in near-infrared spectroscopy is Avα, with A and α fitted constants.
Near-Infrared Spectroscopy for Monitoring Starch Hydrolysis
Authors: Chung Hoeil , Arnold Mark A.
Published: October 2003

Near-infrared (NIR) spectroscopy has been evaluated for monitoring the acid-catalyzed hydrolysis (thinning) of starch. In practice, the extent of starch hydrolysis is measured in fluidity units, which correspond to a physical property of the hydrolyzed starch material. NIR spectra of samples taken periodically during a series of starch-thinning reactions were used to predict fluidity. The standard error of prediction (SEP) was 1.06 mL with the use of partial least-squares (PLS) regression in conjunction with digital Fourier filtering. This SEP was significantly better than that reported before with a univariate calibration model based on the integrated area of the 4400 cm−1 (2272 nm) absorption band for carbohydrates. The improved SEP meets the industry demands for real-time monitoring. Although these calibration models were developed from samples prepared in the laboratory, no spectroscopic differences were apparent between spectra collected from these laboratory samples and spectra collected from samples taken directly from plant starch slurries during actual thinning reactions. This similarity in spectral features, and hence chemical matrix, supports the potential of NIR spectroscopy for on-line monitoring of industrial starch-thinning processes.
Binding of 2-Acetylnaphthalene to γ-Cyclodextrin: Stoichiometry of the Dimer Complex
Authors: Larose Ji Hyun , Werner T. C.
Published: October 2003

Naphthalene derivatives have the capability of forming higher order complexes than the typical 1:1 stoichiometry with all three of the common cyclodextrins (α, β, and γ). The 2-acetylnaphthalene (2-AN)/γ-cyclodextrin (γ-CD) system exhibits a long wavelength fluorescence emission at higher γ-CD concentrations, which has been assigned to an excimer band from bound 2-AN dimer. On the basis of the fact that only free 2-AN and the bound dimer fluoresce in this system, we have proposed mathematical models to decide whether the dimer formula is (2-AN)2/γ-CD or (2-AN)2/(γ-CD)2. Our analysis indicates that the latter formula is the correct one. This result is unanticipated, given the fact that a single γ-CD cavity could accommodate two naphthalene rings.
Influence of Gas Sampling on Analyte Transport within the ICP and Ion Sampling for ICP-MS Studied Using Individual, Isolated Sample Droplets
Authors: Stewart Ian I. , Hensman Carl E. , Olesik John W.
Published: October 2003

The effect of gas flow entrainment on the gas sampling, ion sampling, and ion detection processes in inductively coupled plasma mass spectrometry (ICP-MS) has been investigated. Isolated, single droplets of sample from a monodisperse dried microparticulate injector (MDMI) were used in conjunction with time-resolved ICP-MS, photographs of ion cloud movement, and time-gated imaging using a gateable, intensified charge-coupled device (ICCD) detector mounted on an imaging spectrometer. The results indicate that gas flow entrainment into the sampling orifice can have a significant effect on the plasma gas velocities as far as 7 mm from the sampling orifice. The effects are most pronounced within 3 mm of the sampling orifice. The trends in these results are consistent with theoretical calculations. Photographic images show that plasma gas initially as far as 3 mm off axis adopts a curved path into the sampling orifice. Time-resolved emission images of Sr+ ion clouds approaching the sampling orifice demonstrate the entrainment process and significant distortion of the ion cloud as it flows into the sampling orifice. Spatial maps of La+ ICP-MS signals were acquired as a function of distance from the vaporization point and distance from the plasma axis. The results suggest that gas entrainment has a significant effect on the spatial path of ions in the plasma and that accurate radially resolved spatial mapping of plasmas using mass spectrometry may not be possible. The widths of radially resolved La+ ICP-MS signal peaks do not change significantly when ions are sampled 2 mm from the vaporization point compared to 5 mm away. In contrast, ICP-MS signals measured on axis as a function of time clearly show broadening due to diffusion. These observations suggest that some detected ions may have originated from off-axis locations in the plasma.
Fluorescence of Tetrols, Tetrols Complexed with DNA, and Benzo[a]Pyrene-DNA Adducts in Methanol/Water Solutions
Authors: Steinbach Paul B. , Hurtubise Robert J.
Published: October 2003

Several solution fluorescence parameters were acquired for the four tetrol hydrolysis products of benzo[ a]pyrene-trans-7,8-dihydrodiol-9,10-epoxide (BPDE)-DNA adducts, tetrols complexed with DNA, and BPDE-DNA adducts in several methanol/water solvents. The relative polarity of the environment for the tetrols and BPDE-DNA adducts was determined by using a modified definition of the R value that is commonly employed for pyrene. The R values for the tetrols and BPDE-DNA adducts were calculated by obtaining the ratios of the intensities of the two major fluorescence emission bands at 380 and 400 nm ( I380/ I400). The positions of the hydroxyl groups on the hydroaromatic ring of the tetrols were compared in reference to the R values and the changes in the R values as a function of methanol/water composition. This approach resulted in a method for determining whether the hydroxyl groups in the 9 and 10 positions were on the same side or opposite sides of a hydroaromatic ring. The tetrols intercalated between the DNA bases showed quite different fluorescence spectra compared to tetrols not complexed with DNA. Also, the quasi-intercalated BPDE-DNA adducts gave significant changes in the R values with an increase in methanol in the solvent, and excitation spectra showed large shifts and changes in shape with an increase in methanol. The approaches developed provide unique structural and polarity information on tetrols and BPDE-DNA adducts.