Experiments on Raman versus primary light scattering fluxes from pressed discs

Klosowski, J.; Steger, E.

doi:10.1002/jrs.1250080311

Cited by 5 publications

(5 citation statements)

References 6 publications

(2 reference statements)

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“…The transmitted laser intensity decreased with sample thickness, whereas a maximum was observed in a plot of transmitted Raman intensity against sample thickness. Transmitted laser and Raman intensities were also measured experimentally through urea and sodium nitrate disks of different thicknesses, with the trends observed comparable to those predicted by calculation . A maximum was also observed in a plot of transmitted Raman intensity against sample thickness for various powders , and propranolol-mannitol tablets .…”

supporting

confidence: 71%

“…While early theoretical and experimental studies of transmission Raman spectrometry considered the effect of the optical properties of a powder on the propagation of laser and Raman photons, − such factors have not been considered in recent research examining the contribution of layers at different depths to the overall transmission Raman spectrum. ,, This study addresses the issue and reports for the first time the effect that differences in the size and type of particles in a sample have on the transmitted Raman intensity of an interlayer positioned at different depths. In addition, through comparison of measurements obtained from different experimental configurations, it has been possible to calculate attenuation coefficients associated with the propagation of the incident laser and resultant Raman radiation through the powders.…”

mentioning

confidence: 99%

“…Although transmission Raman spectrometry has not been used extensively to date, the transmission mode is not a recent development in the field of Raman spectrometry. In a number of early studies, the fundamental propagation of laser and Raman photons through solid samples was investigated. − In one such study, the propagation of laser and Raman photons through samples with different scattering properties and of varying thickness was calculated . The transmitted laser intensity decreased with sample thickness, whereas a maximum was observed in a plot of transmitted Raman intensity against sample thickness.…”

mentioning

confidence: 99%

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Effect of Particle Properties of Powders on the Generation and Transmission of Raman Scattering

Townshend¹,

Nordon²,

Littlejohn³

et al. 2012

Anal. Chem.

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This version is available at https://strathprints.strath.ac.uk/40538/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the Strathprints administrator: strathprints@strath.ac.ukThe Strathprints institutional repository (https://strathprints.strath.ac.uk) is a digital archive of University of Strathclyde research outputs. It has been developed to disseminate open access research outputs, expose data about those outputs, and enable the management and persistent access to Strathclyde's intellectual output. AbstractTransmission Raman measurements of a 1 mm thick sulphur-containing disc were made at different positions as it was moved through 4 mm of aspirin (150 -212 µm) or microcrystalline cellulose (Avicel) of different size ranges (<38, 53 -106 and 150 -212 µm). The transmission Raman intensity of the sulphur inter-layer at 218 cm -1 was lower when the disc was placed at the top or bottom of the powder bed, compared to positions within the bed and the difference between the sulphur intensity at the outer and inner positions increased with Avicel particle size. Also, the positional intensity difference was smaller for needle-shaped aspirin than for granular Avicel of the same size. The attenuation coefficients for the propagation of the exciting laser and transmitted Raman photons through the individual powders were the same, but decreased as the particle size of Avicel increased; also, the attenuation coefficients for propagation through 150 -212 µm aspirin were almost half of those through similar sized Avicel particles. The study has demonstrated that particulate size and type affect transmitted Raman intensities and consequently, such factors need to be considered in the analysis of powders especially if particle properties vary between the samples.2

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supporting

confidence: 71%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Effect of Particle Properties of Powders on the Generation and Transmission of Raman Scattering

Townshend¹,

Nordon²,

Littlejohn³

et al. 2012

Anal. Chem.

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“…For example, in 1967 Schrader and Bergmann 33 calculated the relative efficiencies of Raman and Rayleigh detection in transmission and backscattering measurements of powders, concluding that the transmission mode was preferred. This was confirmed experimentally by Klosowski and Steger, 34 who studied transmission through 1 to 3 mm thick pressed discs of urea and sodium nitrate. An optimum thickness for the absolute transmitted Raman signal was observed, as was an improved Raman/Rayleigh ratio compared with backscattering mode, in qualitative agreement with predictions.…”

Section: Introductionmentioning

confidence: 52%

Measurement of Spatial Resolution and Sensitivity in Transmission and Backscattering Raman Spectroscopy of Opaque Samples: Impact on Pharmaceutical Quality Control and Raman Tomography

et al. 2010

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A practical methodology is described that allows measurement of spatial resolution and sensitivity of Raman spectroscopy in backscatter and transmission modes under conditions where photon migration dominates, i.e., with turbid or opaque samples. For the first time under such conditions the width and intensity of the point spread function (PSF) has been accurately measured as a function of sample thickness and depth below the surface. In transmission mode, the lateral resolution for objects in the bulk degraded linearly with sample thickness, but the resolution was much better for objects near either surface, being determined by the diameter of the probe beam and collection aperture irrespective of sample thickness. In other words, buried objects appear to be larger than ones near either surface. The absolute transmitted signal decreased significantly with sample thickness, but objects in the bulk yielded higher signals than those at either surface. In transmission, materials are sampled preferentially in the bulk, which has ramifications for quantitative analysis. In backscattering mode, objects near the probed surface were detected much more effectively than in the bulk, and the resolution worsened linearly with depth below the surface. These results are highly relevant in circumstances in which one is trying to detect or image buried objects in opaque media, for example Raman tomography of biological tissues or compositional and structural analysis of pharmaceutical tablets. Finally, the observations were in good agreement with Monte Carlo simulations and, provided one is in the diffusion regime, were insensitive to the choice of transport length, which shows that a simple model can be used to predict instrument performance for a given excitation and collection geometry.

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“…The SKM model [14,22] was applied and the experimental data for single layer BMS-A and BMS-B tablets were fit using simple linear regression to Eq. 2.…”

Section: Experiments 5: Effect Of Api Layer Thickness (Configuration E)mentioning

confidence: 99%

Quantitative Analysis of Pharmaceutical Bilayer Tablets Using Transmission Raman Spectroscopy

Zhang

McGeorge

2015

J Pharm Innov

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Introduction Transmission Raman Spectroscopy (TRS) has become an increasingly applied technology in the analysis of pharmaceutical tablets for quality control purposes and developing formulation and process understanding. One area that has received only cursory attention to date is that of bilayered tablets that represents an unusually challenging situation. This study aims to provide an understanding of the relationship of the active pharmaceutical ingredient (API) content and the transmission Raman spectral response in bilayered pharmaceutical tablets to facilitate development of quantitative models for the prediction of API content in multilayer tablets. Methods and ResultsThe Raman intensity was considered as a function of the Raman photon generation and decay in a layer of interest (the API layer) and Raman photon decay from a second layer (the non-API layer). To separate and understand the various contributions, a variety of tablet configurations were studied and it was found that (1) with increasing the thickness of the non-API layer, the API Raman signal displayed an exponential decay as a function of the non-API layer thickness as well as the total tablet thickness; (2) when only changing API concentration, the Raman signal linearly responds to the API content; and (3) when increasing the weight/thickness of the API layer and keeping the non-API layer constant, the Raman signal reaches a maximum at a particular thickness and then decays as tablets become thicker. The complex spectral response was effectively modeled according to a modified Schrader, Kubelka-Munk model where both the Raman photon generation factor and photon losses were accounted for. Coupling the results of these studies together yields a comprehensive approach for modeling multi-component bilayer tablets. The addition of a beam enhancer on the bottom surface allowed for a selective overenhancement of the bottom layer, which helps in the analysis of thin layers or coatings.

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Experiments on Raman versus primary light scattering fluxes from pressed discs

Cited by 5 publications

References 6 publications

Effect of Particle Properties of Powders on the Generation and Transmission of Raman Scattering

Effect of Particle Properties of Powders on the Generation and Transmission of Raman Scattering

Measurement of Spatial Resolution and Sensitivity in Transmission and Backscattering Raman Spectroscopy of Opaque Samples: Impact on Pharmaceutical Quality Control and Raman Tomography

Quantitative Analysis of Pharmaceutical Bilayer Tablets Using Transmission Raman Spectroscopy

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