M. Jouan

Simulation et optimisation des capteurs à fibres optiques adjacentes

The geometry of adjacent optical fiber sensors to transport the laser beam and Raman signal in Raman spectrometry is simulated and optimized. The theory of the adjacent optical fiber sensors is developed using various models and the interaction depth is calculated. The efficiency vs the interaxes distance, the diameters of the optical fibers, and the angle between the two optical fibers are also given.

Quantitative analysis of cholesterol and cholesteryl esters in human atherosclerotic plaques using near-infrared Raman spectroscopy

Raman spectroscopy is a non-destructive analytical technique and previous results have shown that qualitative analysis of the lipid component of human atheromatous arteries is feasible. In this paper, we describe a quantitative analytical method for cholesterol and cholesteryl esters in human atherosclerotic plaques, combined with Raman spectroscopic results, using partial least-squares (PLS) regression, a statistical multivariate method based on factorial analysis. Twenty-nine human atherosclerotic pooled samples were studied and the results of Raman spectroscopy coupled with the PLS method were compared to biochemical results. The standard error of prediction was 16.1, 13.6, 1.9, 3.3 and 3.4 mg/g for total cholesterol, free cholesterol, palmitate cholesteryl, oleate cholesteryl and linoleate cholesteryl, respectively. The repeatability of Raman spectroscopy was found to be excellent. Our results show that Raman spectroscopy is a promising technique to obtain a consistent and non-destructive quantitative analysis of cholesterol and cholesteryl esters in human atherosclerotic lesions. In situ and in vivo analysis is a possibility in the near future.

Methode d'analyse quantitative par spectrometrie Raman-laser associee aux fibres optiques pour le suivi d'une fermentation alcoolique

Abstract Laser Raman spectrometry with a fibre-optic system is used to monitor the concentrations of ethanol, glucose and fructose at various stages of an alcoholic fermentation process. For evaluation of the data, cross-correlation and multivariate least-squares procedures are compared; the latter gives the best results. Ethanol, glucose and fructose can be determined remotely with a precision of ca. 10 g l −1 (10–15%).

Quantitative Analysis of Cholesterol and Cholesterol Ester Mixtures Using Near-Infrared Fourier Transform Raman Spectroscopy

Near-infrared Fourier transform Raman spectroscopy is a rapid and nondestructive technique that can provide reliable qualitative in situ information about the chemistry of biological samples. We have combined this technique with partial least-squares (PLS) regression to perform a quantitative determination of free and esterified cholesterol in two synthetic sample series. In 66 ternary mixtures containing various proportions of cholesterol, cholesterol linoleate, and oleate, the standard errors of prediction were 1.27, 1.17, and 0.94%, respectively. For the second series of experiments concerning the sensitive problem of quantitative analysis of cholesterol palmitate and stearate mixtures, the standard error of prediction for 49 samples was 3.02%. It is also possible to extract quantitative information for a single component of the ternary mixtures independently. These results are of great importance when—as in the case of arterial samples—many chemical species are present. Comparison between Raman spectra of ternary mixtures and atherosclerotic rabbit aorta shows that many bands, assignable to free and esterified cholesterol, are easily observed in the aorta spectrum.

New Raman Spectrometer Using a Digital Micromirror Device and a Photomultiplier Tube Detector for Rapid On-Line Industrial Analysis. Part I: Description of the Prototype and Preliminary Results

In this paper, a prototype of a new generation of Raman spectrometers, based on the use of a monochromator, a digital micromirror device as light modulator, and a photomultiplier tube as detector of the Raman light, is described. This spectrometer, containing no moving parts, is inexpensive, robust, and very precise. New in concept, this spectrometer makes it possible to record, in addition to classical Raman spectra, the intensity at several selected points of the spectrum and/or the total intensity in several selected intervals at the same time with great accuracy, thus giving new possibilities for analytical applications. Also, the work presented demonstrates the possibilities of this very simple prototype for rapid on-line industrial analysis, with an example of quantitative analysis of binary and ternary mixtures of xylene isomers. The precision obtained is satisfactory (errors of prediction ∼3% in 5–6 seconds per sample).

Etude par spectroscopies vibrationnelles des complexes phenyle bistrans-halogenotetracarbonyl) metallocarbyniques et de leurs derives perdeuteries

Abstract Phenylbis(trans-halotetracarbonyl)carbynemetal complexes and their deuterated species [Br(CO)4WC]2C6H4(I), [Br(CO)4WC]2C6D4(II), [Br(CO)4CrC]2C6H4(III) and [Br(CO)4CrC]2C6D4(IV) have been synthesised and their IR and Raman spectra recorded. The ν±(MC) signals at 1372 cm−1 for I and 1352 cm−1 for III are in the same region as those for single carbyne complexes. Investigation of some of the vibrational modes of the phenyl ring shows that the carbyne fragment influences the π-electronic distribution of the ring by localising the π-electrons on the bonds parallel to the axis of the complex molecule.

The Raman laser fiber optics (RLFO) method and its applications

Abstract The Raman laser fiber optics (RLFO) method has been performed in this laboratory for several years. The method is based on Raman spectrometry as an analytical tool, associated with optical fibers to transport the excitation and the diffused light; it has proved to be very promising for remote on-line analytical control of the chemical composition of mixtures. Many studies have already been carried out and this paper presents a review of the results already obtained: measurements at distances of up to several hundred meters between the instrument and the industrial site can now be routinely obtained. Mathematical treatments using, for example, factor analysis markedly improve the quality of the analytical procedures, together with the conception of new optrodes specific for various applications: control of the chemical composition in chemical plants, possibly in the presence of dusty, corrosive or radioactive atmospheres; checking the effect of high temperature and pressure in analytical processes; designing and testing industrial RLFO devices and systems for pharmaceutical control, food science, and biomedical problems including in vivo situations. A prospective of new improvements, like CD array detection systems, also in the near-infrared region, or new sources as laser photodiodes, is also presented.

Use of a Mono-Fiber Optrode in Remote and in Situ Measurements by the Raman/Laser/Fiber Optics (RLFO) Method

A new versatile mono-fiber optrode based on the combined use of a dual-fiber optrode and a short mono-fiber is proposed. The quantitative analytical possibility of this optrode configuration is tested on benzene/heptane mixtures with the use of a PLS procedure, and good results are obtained. The new all-purpose mono-fiber optrode is extremely simple and user friendly and can be used for in situ and in vivo detection.

Coupling of high-performance liquid chromatography with Raman spectrometry

Abstract Raman spectrometry has been tested as a method for detection in HPLC. Using a laboratory-made cell similar to classical UV cells, toluene and naphthalene have been analyzed as solutions in acetonitrile-water (75:25 or 95:5 v/v) mixtures. Using a monochannel detection, a detection limit of about 480 mg/l (9.6 μg for the 20-μl injection loop) for toluene has been found and the possibility to distinguish between co-eluted toluene and naphthalene and to make a quantitative analysis has been proved.

Etude par spectroscopie raman de resonance du schema de coordination du fer de derives ferriporphyriniques a liaison σ metal-carbone

Abstract The coordination scheme of σ-alkyl- (or aryl-)iron(III) porphyrins is studied by Raman spectroscopy. The spectroscopic data obtained show that the iron atom is always pentacoordinated whatever the solvent, the temperature, and the nature of the axial or macrocyclic ligands. Also, these measurements prove the presence of complexes with different spin systems. There are high spin ( S = 1 2 ), low spin ( S = 1 2 ), and high-low spin systems. Moreover, at low temperature the spin system of the metal depends definitely on the solvent.