Laser Raman spectroscopy of the effect of solvent on the low-frequency oscillations of organic molecules

Polymorph detection, identification, and quantitation in crystalline materials are of great importance to the pharmaceutical industry. Vibrational spectroscopic techniques used for this purpose include Fourier transform mid-infrared (FT-MIR) spectroscopy, Fourier transform near-infrared (FT-NIR) spectroscopy, Raman spectroscopy, and terahertz (THz) and far-infrared (FIR) spectroscopy. Typically, the fundamental molecular vibrations accessed using high-frequency Raman and MIR spectroscopy or the overtone and combination of bands in the NIR spectra are used to monitor the solid-state forms of active pharmaceutical ingredients (APIs). The local environmental sensitivity of the fundamental molecular vibrations provides an indirect probe of the long-range order in molecular crystals. However, low-frequency vibrational spectroscopy provides access to the lattice vibrations of molecular crystals and, hence, has the potential to more directly probe intermolecular interactions in the solid state. Recent advances in filter technology enable high-quality, low-frequency Raman spectra to be acquired using a single-stage spectrograph. This innovation enables the cost-effective collection of high-quality Raman spectra in the 200-10 cm(-1) region. In this study, we demonstrate the potential of low-frequency Raman spectroscopy for the polymorphic characterization of APIs. This approach provides several benefits over existing techniques, including ease of sampling and more intense, information-rich band structures that can potentially discriminate among crystalline forms. An improved understanding of the relationship between the crystalline structure and the low-frequency vibrational spectrum is needed for the more widespread use of the technique.

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“…Experimental interference from solvent low-frequency Raman bands deriving from quasi-elastic light scattering and the Boson peak occur. 35…”

Section: Resultsmentioning

confidence: 99%

Polymorph Characterization of Active Pharmaceutical Ingredients (APIs) Using Low-Frequency Raman Spectroscopy

et al. 2014

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“…The accumulation time was 300 s per spectrum. To compare spectra with different backgrounds we employed an original method from [15].…”

Section: Methodsmentioning

confidence: 99%

Laser ablation microsampling of copper phthalocyanine blue by the second-harmonic radiation of Nd:YAG laser

Balakhnina,

Zagladin,

Yu Chikishev

et al. 2023

Laser Phys.

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An original nonlinear optical method employing laser ablation with single nanosecond laser pulses at a wavelength of λ = 532 nm is used to study organic paint layer (copper phthalocyanine blue (PB15)). Two processes (photochemical reaction and formation of craters), which appear to be nonlinear result from the pulsed radiation. It is shown that the nonlinear optical procedure (laser ablation microsampling (LAMS)) can be used to obtain microparticles of PB15 sufficient for the further analysis. The Raman spectra of the surface of the paint layer prior to and after LAMS and microparticles are obtained. Spectral data, including those in the low-frequency region, are discussed.

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“…The original method from [12] was used to compare the spectra. The method makes it possible to represent the spectrum of a mixture of several substances as a sum of the spectra of individual components and a polynomial that simulates the background signal.…”

Section: Methods For Comparison Of Spectramentioning

confidence: 99%

Laser ablation as a method for microsampling of paint layers

Балахнина¹,

Брандт²,

Dedova³

et al. 2022

Laser Phys.

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Laser Raman spectroscopy of the effect of solvent on the low-frequency oscillations of organic molecules

Cited by 5 publications

References 12 publications

Polymorph Characterization of Active Pharmaceutical Ingredients (APIs) Using Low-Frequency Raman Spectroscopy

Polymorph Characterization of Active Pharmaceutical Ingredients (APIs) Using Low-Frequency Raman Spectroscopy

Laser ablation microsampling of copper phthalocyanine blue by the second-harmonic radiation of Nd:YAG laser

Laser ablation as a method for microsampling of paint layers

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