Raman Spectroscopy For Identification Research Articles

Evaluation of Shifted-Excitation Raman Difference Spectroscopy and Comparison to Ordinary Portable Raman Spectroscopy in Identification of Seized Drugs

Rapid and accurate identification and detection of illicit drugs are important for combating drug crimes. As a newly developed technology, shifted-excitation Raman difference spectroscopy (SERDS) can greatly reduce the interference caused by fluorescence and improve the potential of Raman for distinguishing drug compounds in seized samples with fluorescent additives. In this work, 43 random seized drugs were scanned and analyzed by both SERDS and ordinary portable Raman spectrometers for the first time. The detected results of two Raman technologies were confirmed with gas chromatographic mass spectrometry test results, and compared in detail in the aspects of detection rate and matching accuracy. SERDS had significant advantages in eliminating fluorescence interference with a very high detection rate of 93.0%, compared with 53.3% obtained by an ordinary Raman spectrometer, although the ordinary Raman spectrometer analyzed the composition of multi-component mixed samples with higher accuracy. To some extent, the two Raman spectrometers realized functional complementarity, and a rational use of the two types of Raman spectrometers may be of benefit in the rapid detection of seized drugs.

Characterization of Montmorillonites by Infrared and Raman Spectroscopy for Preparation of Polymer-Clay Nanocomposites.

The detailed structural chemistry of clay minerals is an important aspect of polymer-clay nanocomposite research. A variety of analytical methods are currently available for material characterization. Keep in mind, however, that each method has some limitations. The best results are usually achieved by a combination of several analytical methods. The contribution demonstrates the potential and applicability of infrared and Raman spectroscopy in identification and structural characterization of montmorillonites. The vibrational spectra of montmorillonites (SAz-2, STx-1, SWy-2 and Kunipia-F), obtained by Fourier Transform infrared spectroscopy in the near infrared region (8000-4000 cm-1) and in the middle infrared region (4000-400 cm-1) together with Fourier Transform Raman measurements in the region from 4000-50 cm-1, are presented. The aim of the experimental study was to compare the spectral data of both analytical techniques in terms of their sensitivity to chemical composition, isomorphic substitution of central atoms, and layer stacking order of the clay minerals. The results confirmed that Fourier Transform infrared spectroscopy through middle infrared and near infrared spectral regions provided the most comprehensive information about octahedral, tetrahedral and hydroxyl structure units of montmorillonites.

MCR-ALS with correlation constraint and Raman spectroscopy for identification and quantification of biofuels and adulterants in petroleum diesel

Raman spectroscopy and multivariate curve resolution with correlation constraint were used for the identification and quantification of biofuels and adulterants in petroleum diesel. Firstly, quantification of two biofuels present in petroleum diesel (biodiesel and hydrotreated esters and fatty acids (HEFA)) was performed. The developed models for biodiesel and HEFA presented RMSEPs equal to 0.70%, indicating the practical application of the proposed methodology. Additionally, the identification and quantification of six adulterants (ethanol, cyclohexane, gasoline, hexane, kerosene and an ethanol/gasoline blend) in petroleum diesel with 10% of biofuels (B-10) were performed. In this case, it was possible to identify the adulterant with high confidence based on the recovered spectra and to estimate its concentration with absolute errors below to 8%.

Analysis of Wilhelm Ostwald’s “Colour Organ” with Raman microspectroscopy

The “Scientific Colour Organ” is a collection of 680 pigment powders, created by the chemist Wilhelm Ostwald in 1925 as a means to represent his colour system. Today, it remains a leading part of colour theory. Analysis of these materials was undertaken to understand how the colour system was realised and to gain indications for preservation of the collection to which it belongs. Dispersive Raman microspectroscopy was applied directly to the powders, as well as using alternative techniques to suppress fluorescence. Barium sulphate was detected in all of the samples with one exception. Portable X-ray fluorescence revealed that this compound was a constituent of lithopone pigment. Raman spectroscopy furthermore revealed synthetic ultramarine (C.I. PB 29) as well as six different synthetic organic pigments and dyes (C.I. PY3; C.I. PO5; C.I. PR81:1; C.I. PV2 and two different triarylmethane dyes). Thin-layer chromatography was applied to determine the exact combination of dyes causing the gradual change in colour of each powder compared to the adjacent samples. With the exception of triarylmethane, the synthetic organic dyes could be identified with Raman spectroscopy directly on the chromatographic plate. The efficiency of thin-layer chromatography combined with Raman spectroscopy for identification of organic pigments could thus be shown. X-ray fluorescence indicated the presence of tungsten–molybdenum lakes in some samples. Comparison of the analytical results to information published by Oswald in 1917 showed that he switched to more light-stable synthetic organic pigments used for his “Scientific Colour Organ”.

Raman spectroscopy for identification and quantification analysis of essential oil varieties: a multivariate approach applied to lavender and lavandin essential oils

Lavender (Lavandula angustifolia) is used for cosmetics, perfumes and medicine (antimicrobial activity and relaxant properties) while lavandin (sterile hybrid of L. angustifolia P. Mill. × Lavandula latifolia (L.f.) Medikus) is used for air fresheners, deodorants and soaps. These plants are widely cultivated for essential oil production. In this study, 104 samples were analyzed including 62 lavandin and 42 lavender oil samples from several varieties. The Raman spectra are similar but can be differentiated by chemometrics treatment. Data structure may be studied by PCA. A PLS regression model was used for quantitative analysis of the main compounds such as linalyl acetate, linalool and eucalyptol. The reference data were obtained by gas chromatography. The performance of the method was also tested to discriminate between the two species and the seven varieties (Abrial, Fine, Grosso, Maillette, Matherone, Sumian and Super) by PLS-DA regression. The examination of PLS and PLS-DA regression coefficients allowed for the identification of species and of the varieties' metabolomic markers. Copyright © 2015 John Wiley & Sons, Ltd.

Use of Raman spectroscopy for identification of compatible solutes in halophilic bacteria

We explored the use of Raman spectroscopy to detect organic osmotic solutes as biomarkers in the moderately halophilic heterotrophic bacterium Halomonas elongata grown in complex medium (accumulation of glycine betaine) and in defined medium with glucose as carbon source (biosynthesis of ectoine), and in the anoxygenic phototrophic Ectothiorhodospira marismortui known to synthesize glycine betaine in combination with minor amounts of trehalose and N-α-carbamoyl glutamineamide. We tested different methods of preparation of the material: lyophilization, two-phase extraction of water-soluble molecules, and perchlorate extraction. Raman signals of glycine betaine and ectoine were detected; perchlorate extraction followed by desalting the extract on an ion retardation column gave the best results. Lyophilized cells of E. marismortui showed strong signals of carotenoid pigments, and glycine betaine could be detected only after perchlorate extraction and desalting. The data presented show that Raman spectroscopy is a suitable tool to assess the mode of osmotic adaptation used by halophilic microorganisms.

Multiexcitation Raman Spectroscopy in Identification of Chinese Jade

ABSTRACT The high-fluorescence background of jade creates a great impact on the Raman spectra measurements that impedes their application in jade analysis and treatment, particularly with ancient jade. The five most important materials of Chinese ancient jade are amphibole, serpentine, turquoise, agate/chalcedony, and anorthite-zoisite (Dushan jade). This study comparatively analyzed the Raman spectra of different wavelengths' excitation light sources (514.5 nm, 632.8 nm, 785 nm) in identifying these Chinese jades, and this article discusses the most applicable ones to the analysis of different jade materials. The results show that although 632.8 nm He-Ne laser is appropriate for turquoise jades, generally speaking, Raman spectra produced by the 785 nm semiconductor laser and the 632.8 nm He-Ne laser are better for most kinds of jades than the spectra produced by the 514.5 nm argon ion laser, and both of them can be effectively used jointly in research by nondestructive phase analysis of Chinese ancient jade.

Fourier Transform Raman Spectroscopy for Identification and Differentiation between Dosage Strengths of an Active Drug in White Opaque Hard Gelatin Capsules

Fourier Transform Raman Spectroscopy for Identification and Differentiation between Dosage Strengths of an Active Drug in White Opaque Hard Gelatin Capsules