Search

A system that combines dispersive infrared micro-spectroscopic imaging and thermography has been developed to study the effect of thermal radiation on the infrared absorption spectra of prostate biopsy samples. The system allows the distribution of thermal signal intensity as a function of emissivity to be interpreted from the integrated absorbance obtained by spectroscopic imaging. Biochemical differences between cancer and benign areas within the specimens are identified in the spectra. Side-by-side comparison of H&E stained adjacent tissue sections with infrared images constructed before and after the removal of thermal effect showed that the latter strongly support differentiation of regions within tissues. The use of spectral bands at discrete wavelengths significantly reduced spectral acquisition time, making this technique promising as a future clinical diagnostic tool. A systemic methodology was implemented to process the data, first by k-means clustering on the second derivative spectra without a priori knowledge, followed by principal component analysis (PCA). Four distinct regions within the tissue samples were successfully classified based on the antisymmetric stretching mode of the methylene functional group. Separation between data in clusters occurs when projecting spectra on a PCA score plot on a plane made by first 2 principal components. The significance of the disparity was verified with statistical test. Regulation of signal to chopper and detector enables simultaneous acquisition of infrared and thermal images of the prostate biopsy tissues.

Attenuated total reflection (ATR)-Fourier transform infrared (FTIR) spectroscopic imaging combined with a gelatine tape lift method was applied to fingermarks contaminated with various types of cosmetic residues and drugs. This approach allowed not only the imaging of partial fingermarks but also demonstrated the advantage of this chemical imaging methodology in being able to detect heterogeneously distributed localized compounds after surfaces contaminated with various types of cosmetics or drug residues had been handled. This is the first time that the detection of cosmetics in fingermarks deposited on nonporous and porous surfaces has been performed. These results show a potential extension of the applicability of ATR-FTIR imaging to forensic science. Copyright © 2009 John Wiley & Sons, Ltd.

Poly(ethylene terephthalate) films impregnated with Disperse Red 1 from a supercritical CO 2 solution were studied using confocal Raman microscopy. Depth profiles of films dyed for different periods of time were measured using the oil immersion approach and concentration-depth plots of the relative dye concentration were generated. A one-dimensional Fickian diffusion model was used to evaluate the diffusion coefficient of the dye from the Raman microscopy data using a non-linear least squares regression. The calculated diffusion coefficient at 200 bar and 80°C was 6.75 ± 1.01 × 10 -14 m 2 . s -1 .

Fourier transform infrared (FTIR) spectroscopic imaging using a focal plane array detector has been used to study atherosclerotic arteries with a spatial resolution of 3-4 microm, i.e., at a level that is comparable with cellular dimensions. Such high spatial resolution is made possible using a micro-attenuated total reflection (ATR) germanium objective with a high refractive index and therefore high numerical aperture. This micro-ATR approach has enabled small structures within the vessel wall to be imaged for the first time by FTIR. Structures observed include the elastic lamellae of the tunica media and a heterogeneous distribution of small clusters of cholesterol esters within an atherosclerotic lesion, which may correspond to foam cells. A macro-ATR imaging method was also applied, which involves the use of a diamond macro-ATR accessory. This study of atherosclerosis is presented as an illustrative example of the wider potential of these ATR imaging approaches for cardiovascular medicine and biomedical applications.

Supercritical fluids are used for enhanced processing of polymeric materials. Therefore, there is a need to understand how supercritical fluids interact with polymeric materials and how they may modify many facets of process operations. In situ spectroscopy provides a route for understanding and optimising polymer processing with supercritical fluids. In situ spectroscopy probes interactions between supercritical CO 2 and polymers at a molecular level and provides a fundamental understanding of the origin of the plasticising effect of supercritical carbon dioxide on glassy polymers. The changes in polymers subjected to supercritical fluids have been elucidated via in situ ATR(Attenuated Total Reflectance)-IR spectroscopy. The key feature of our new approach is the use of a modified diamond ATR accessory to measure spectra of polymers subjected to high-pressure gas, supercritical fluids or near-critical water. A variety of novel applications for the use of in situ ATR-IR spectroscopy to polymers are described.

The variation of the indentation hardness of a high molecular weight poly(methyl methacrylate) (PMMA) subjected to CO 2 and Ar at high pressure was measured in situ. The samples were subjected to gas exposure for 3 h at 40 °C before a conical indenter of an included angle at 105 °, with a fixed load of 0.237 kg, was applied for a loading time of 60 s. The data show that both CO 2 and Ar reduce the hardness of PMMA to a comparable extent at low pressures. The hardness of PMMA subjected to Ar indicates a minimum at about 4 MPa and then increases. CO 2 produced a monotone decreasing trend in hardness in the pressure range studied, and the glass-transition temperature (T g ) was achieved at about 6.0 MPa. The change in hardness is attributed to plasticization of the polymer matrix that is more extensive for CO 2 . The relationship between the change in hardness for this PMMA subjected to high-pressure CO 2 , the corresponding change in the T g , and the associated swelling of the polymer is discussed.

Knowledge of the sorption rate and solubility of CO2 in polymers are of great importance for developing technologies utilizing high-pressure and supercritical CO2-assisted processes. Many conventional techniques for measuring gas sorption have inherent complications when used at elevated pressures. In this work, we demonstrate the use of near-IR spectroscopy as an accurate method to measure CO2 sorption kinetics and solubility in PET at elevated pressures. Sorption kinetics and solubility are measured at 0, 28, and 50°C between pressures of 57.1 and 175.2 atm. Both initially amorphous and initially partially crystalline samples of PET are studied, and the effects of the initial crystallinity are determined. In addition, the effects of CO2 processing on the final crystallinities of our samples are measured. Crystallization was induced in PET at 28 and 50°C over the range of pressures studied. However, at 0°C, no detectable crystallization occurred in PET, even in the presence of high pressures of CO2. The method demonstrated in this work could easily be extended to directly measure CO2 sorption in other polymers. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 764–775, 2000

In situ ultraviolet–visible spectroscopy has been used to study diffusion of two azo-dyes in a CO2-swollen matrix of poly(methyl methacrylate) (PMMA). The diffusivity of both dyes can be tuned simply be changing the system pressure. Higher pressure of CO2 enhances diffusion of a dye in PMMA. The diffusion of dyes in CO2-swollen PMMA can also be influenced by specific interactions. The partitioning of the dyes between the polymer phase and the fluid phase was measured, and the partition coefficients are large (104–105). Thus, supercritical fluid dyeing is possible, although the solubility of the dyes in the fluid phase is low. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 911–919, 1998

Opportunities exist to exploit the unique properties of carbon dioxide to process polymers for advanced applications. The diffusion of deuterated water in poly(methyl methacrylate) films swollen by carbon dioxide at 35°C over the pressure range 0 to 90 bar (corresponding density range: 0.0 to 0.66 g/cm3) was measured using in situ FTIR spectroscopy. The mechanism and time scale of the diffusion of deuterated water in PMMA are easily controlled by manipulation of the applied CO2 density. The enhancement of mass transport rate is consistent with the degree of plasticization of the polymer due to the absorption of carbon dioxide.

Cosolvents offer a sensitive tool to tailor equilibria, rates or yields of chemical reactions in supercritical fluid solvents. The tautomeric equilibrium of a Schiff base was chosen as a model system, and small amounts of protic cosolvents shift the position of tautomeric equilibria. The equilibrium was tuned from essentially one tautomer to another by modifying the solvent of pure SCF ethane with less than 2 mol % hexafluoroisopropanol cosolvent. The equilibrium constant was a function of cosolvent concentration and mixture density. A chemical-physical model of equilibrium constants deviates from the measured values in the near-critical region, which may have been caused by local composition enhancement of cosolvent around the Schiff base. Decrease in the degree of hydrogen bonding with pressure or density affects the keto-enol equilibria by decreasing the amount of the keto formation. Thus, solution density, as well as the degree of hydrogen bonding, is manipulated to tune the position of tautomeric equilibria.

Supercritical fluids are beginning to be used widely in chemistry. Applications range from extraction and chromatography in analytical chemistry to solvents for reaction chemistry and preparation of new materials. Spectroscopic monitoring is important in much of supercritical chemistry, and vibrational spectroscopy is particularly useful in this context because the vibrational spectrum of a given molecule is usually quite sensitive to the environment of that molecule. Thus, vibrational spectra are excellent probes of conditions within the fluid. In this review, we describe a variety of techniques and cells for IR and Raman spectroscopy in supercritical fluids and illustrate the breadth of applications in supercritical fluids. The examples include: the use of supercritical Xe as a spectroscopically transparent solvent for chemistry and for supercritical fluid chromatography with FTIR detection of analytes; Raman spectroscopy as a monitor for gases dissolved in supercritical CO2; the effect of solvent density on hydrogen bonding in supercritical fluids and the formation of reverse micelles; IR as a monitor for the supercritical impregnation/extraction of polymers and the reactions of organometallic compounds impreganated into polymers; reactions of organometallic compounds in supercritical fluids; and finally, the use of miniature flow reactors for laboratory-scale preparative chemistry. Overall, our aim is to provide a starting point from which individual readers can judge whether such measurements might usefully be applied to their own particular problems.

Uberkritische fluide Phasen werden in der Chemie in zunehmendem Mase eingesetzt. Ihr Anwendungsbereich reicht von der Extraktion und Chromatographie in der analytischen Chemie bis hin zu Losungsmitteln fur die praparative Chemie und zur Herstellung neuer Materialien. Das spektroskopische Verfolgen der Vorgange ist in der Chemie von uberkritischen Systemen wichtig, wobei die Schwingungsspektroskopie sich in diesem Zusammenhang als besonders nutzlich erweist, da das Schwingungsspektrum einer Verbindung fur gewohnlich recht empfindlich auf Veranderungen der Umgebung reagiert. Deshalb sind Schwingungsspektren ausgezeichnete Sonden fur die in der fluiden Phase herrschenden Bedingungen. In dieser Ubersicht wird eine Vielzahl von Techniken und Meszellen fur die IR- und Raman-Spektroskopie in uberkritischen fluiden Phasen beschrieben und versucht, die Bandbreite der Anwendungsmoglichkeiten in solchen Phasen deutlich zu machen. Die Beispiele umfassen die Verwendung uberkritischen Xenons als spektroskopisch durchlassiges Losungsmittel fur chemische Reaktionen und fur die Chromatographie mit uberkritischen fluiden Phasen sowie FT-IR-Detektion der Analyten, die Raman-Spektroskopie als Sonde fur in uberkritischem CO2 geloste Gase, dem Einflus der Losungsmitteldichte auf die Bildung von Wasserstoffbruckenbindungen in uberkritischen fluiden Phasen und die Bildung inverser Micellen, das IR-spektroskopische Verfolgen der Impragnierung oder Extraktion von Polymeren mit uberkritischen fluiden Phasen und der Reaktionen von in Polymeren eingebrachten metallorganischen Verbindungen, die Reaktionen metallorganischer Verbindungen in uberkritischen fluiden Phasen sowie schlieslich die Verwendung von Miniatur-Durchflusreaktoren fur die praparative Chemie im Labormasstab. Alles in allem ist es unser Ziel, dem Leser eine Grundlage zu verschaffen, die es ihm ermoglicht zu beurteilen, ob solche Messungen erfolgreich auf sein eigenes spezielles Problem angewendet werden konnten.

Supercritical fluids are beginning to be used widely in chemistry. Applications range from extraction and chromatography in analytical chemistry to solvents for reaction chemistry and preparation of new materials. Spectroscopic monitoring is important in much of supercritical chemistry, and vibrational spectroscopy is particularly useful in this context because the vibrational spectrum of a given molecule is usually quite sensitive to the environment of that molecule. Thus, vibrational spectra are excellent probes of conditions within the fluid. In this review, we describe a variety of techniques and cells for IR and Raman spectroscopy in supercritical fluids and illustrate the breadth of applications in supercritical fluids. The examples include: the use of supercritical Xe as a spectroscopically transparent solvent for chemistry and for supercritical fluid chromatography with FTIR detection of analytes; Raman spectroscopy as a monitor for gases dissolved in supercritical CO2; the effect of solvent density on hydrogen bonding in supercritical fluids and the formation of reverse micelles; IR as a monitor for the supercritical impregnation/extraction of polymers and the reactions of organometallic compounds impreganated into polymers; reactions of organometallic compounds in supercritical fluids; and finally, the use of miniature flow reactors for laboratory-scale preparative chemistry. Overall, our aim is to provide a starting point from which individual readers can judge whether such measurements might usefully be applied to their own particular problems.