UV-Excited Resonance Raman Spectroscopy of Narcotics and Explosives

Sands, H. S.; Hayward, Ian; Kirkbride, Tracy; Bennett, Robert D.; Lacey, R. W.; Batchelder, D. N.

doi:10.1520/jfs16178j

Cited by 52 publications

(28 citation statements)

References 12 publications

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“…Indications of photodegradation were substantially eliminated when the sample was placed into a small circular groove on a metal disk and then spun about the axis of the circle at 1 revolution per second. 12 This ensured that the laser was focused onto a given particle for only a very short period of time and therefore reduced the risk of photodegradation. As shown in Table 2, long acquisition times were required, in spite of the resonance Raman enhancement, as much of the powder sample being scanned was out of focus owing to variations in height of the powder on the rotating disk.…”

Section: Methodsmentioning

confidence: 99%

Dependence of the Raman spectra of drug substances upon laser excitation wavelength

Thorley

Baldwin

Lee

et al. 2006

J Raman Spectroscopy

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The laser excitation wavelength is an important parameter in obtaining definitive Raman spectra from pharmaceutical drug substances. This paper investigates the effect of changing wavelength on the Raman spectra of four different drug substances: paracetamol, paroxetine and ranitidine (polymorphic forms I and II). Excitation wavelengths in the range 244 nm to 785 nm have been used. The fluorescence intensities in the Raman spectra were found to be negligible at the two extreme laser wavelengths but tended to interfere in the visible range. Resonance Raman enhancement was observed with 244 nm excitation but there was evidence for sample degradation. Furthermore, the site selective nature of the resonance enhancement reduced the differences between the Raman spectra of the two ranitidine polymorphs.

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Section: Methodsmentioning

confidence: 99%

Dependence of the Raman spectra of drug substances upon laser excitation wavelength

Thorley

Baldwin

Lee

et al. 2006

J Raman Spectroscopy

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“…Illegal drugs are generally mixed with a variety of materials that may contain contaminants, all of which may fluoresce under visible light excitation. The use of near-IR or UV excitation is required to eliminate or reduce this interference (20,21).…”

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confidence: 99%

Identifications and Quantitative Measurements of Narcotics in Solid Mixtures Using Near-IR Raman Spectroscopy and Multivariate Analysis

Ryder

O’Connor

Glynn

1999

Journal of Forensic Sciences

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Raman spectroscopy offers the potential for the identification of illegal narcotics in seconds by inelastic scattering of light from molecular vibrations. In this study cocaine, heroin, and MDMA were analyzed using near-IR (785 nm excitation) micro-Raman spectroscopy. Narcotics were dispersed in solid dilutants of different concentrations by weight. The dilutants investigated were foodstuffs (flour, baby milk formula), sugars (glucose, lactose, maltose, mannitol), and inorganic materials (Talc powder, NaHCO3, MgSO4·7H2O). In most cases it was possible to detect the presence of drugs at levels down to ∼10% by weight. The detection sensitivity of the Raman technique was found to be dependent on a number of factors such as the scattering cross-sections of drug and dilutant, fluorescence of matrix or drug, complexity of dilutant Raman spectrum, and spectrometer resolution. Raman spectra from a series of 20 mixtures of cocaine and glucose (0–100% by weight cocaine) were collected and analyzed using multivariate analysis methods. An accurate prediction model was generated using a Partial Least Squares (PLS) algorithm that can predict the concentration of cocaine in solid glucose from a single Raman spectrum with a root mean standard error of prediction of 2.3%.

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“…Demonstration of enhancement of the Raman signal as the wavelength of the incident light approaches the wavelength of an allowed transition (resonance Raman spectroscopy) and the elimination of fluorescence when using incident radiation near 244 nm were first reported for explosives in 1997-1998 (43,44 Dieringer et al (54) have reported advances in single molecule SERS (SMSERS). Excitation of the localized surface plasmon resonance (LSPR) of a nanostructured surface or nanoparticle determines signal strength and reproducibility.…”

Section: Laser Raman Spectroscopymentioning

confidence: 99%