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Related Concept Videos

IR Spectrometers01:25

IR Spectrometers

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There are two main infrared (IR) spectrophotometers: dispersive IR spectrometers and Fourier transform infrared (FTIR) spectrometers. In a dispersive IR spectrometer, a beam of infrared radiation produced by a hot wire is divided into two parallel equal-intensity beams using mirrors. One beam passes through the sample, while another is a reference beam. The beams then move through the monochromator, which separates the radiations into a continuous spectrum of different frequencies. The...
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IR Frequency Region: Fingerprint Region01:03

IR Frequency Region: Fingerprint Region

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IR spectra are divided into two main regions: the diagnostic region and the fingerprint region. The diagnostic region of the spectrum lies above 1500 cm−1. The absorptions resulting from single-bond vibrations of the N–H, C–H, and O–H stretch at higher wavenumbers and appear on the left side of the spectrum. The stretching absorptions of the C≡C and C≡N occur between 2100–2300 cm−1. In contrast, those arising from stretching absorptions of the...
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IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations01:08

IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations

1.2K
Identical bonds within a polyatomic group can stretch symmetrically (in-phase) or asymmetrically (out-of-phase). Similar to hydrogen bonding, these vibrations also influence the shape of the IR peak. Generally, asymmetric stretching frequencies are higher than symmetric stretching frequencies. For example, primary amines exhibit two distinct IR peaks between 3300–3500 cm−1 corresponding to the symmetric and asymmetric N-H stretching, while secondary amines exhibit a single...
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High-Resolution Mass Spectrometry (HRMS)01:15

High-Resolution Mass Spectrometry (HRMS)

1.5K
The resolution of a mass spectrometer depends on the efficiency of separating ions with different ion masses. The mass of an atom is approximated to the sum of the masses of protons and neutrons inside, considering the masses of protons and neutrons as equal. However, the masses of the proton (1.6726 × 10−24 g) and neutron (1.6749 × 10−24 g) are not truly equal. There is a minor error in the expression of atomic masses relative to the simplest atom of hydrogen. For...
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IR Frequency Region: X–H Stretching01:24

IR Frequency Region: X–H Stretching

1.0K
In IR spectroscopy, signals produced by the X−H bonds (such as C−H, O−H, or N−H) can be observed in the frequency range of  2700–4000 cm–1. The C−H stretching vibration forms sharp bands in the region 2850–3000 cm–1. The presence of the O−H stretching vibration leads to the forming of an absorption band in the frequency range 3650–3200 cm−1. At the same time, N−H stretching can be confirmed by absorption bands in...
1.0K
¹H NMR: Complex Splitting01:13

¹H NMR: Complex Splitting

1.3K
A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied...
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Detecting different amorphous - Amorphous phase separation patterns in co-amorphous mixtures with high resolution

Tuomas Kilpeläinen1, Tuomas Ervasti1, Emilia Uurasjärvi2

  • 1School of Pharmacy, University of Eastern Finland, P.O. Box 1627, FI-70211 Kuopio, Finland.

European Journal of Pharmaceutics and Biopharmaceutics : Official Journal of Arbeitsgemeinschaft Fur Pharmazeutische Verfahrenstechnik E.V
|September 19, 2022
PubMed
Summary

Amorphous solid dispersions improve drug solubility but can phase separate. This study uses imaging FTIR spectroscopy to visualize and quantify amorphous-amorphous phase separation in drug mixtures, revealing distinct patterns of separation over time.

Keywords:
API co-amorphousAmorphousDrugIR spectroscopyPharmaceuticalPhase separation

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Area of Science:

  • Pharmaceutical Sciences
  • Materials Science
  • Spectroscopy

Background:

  • Many active pharmaceutical ingredients (APIs) exhibit poor aqueous solubility, limiting their therapeutic efficacy.
  • Amorphous forms of APIs offer enhanced solubility but are thermodynamically unstable, prone to crystallization.
  • Phase separation in co-amorphous systems precedes crystallization, making its study crucial for formulation stability.

Purpose of the Study:

  • To develop and validate a high-resolution imaging method for studying amorphous-amorphous phase separation.
  • To investigate the kinetics and patterns of phase separation in API-API binary mixtures.
  • To assess the reproducibility and reliability of imaging Fourier transform infrared (FTIR) spectroscopy for this application.

Main Methods:

  • Amorphization of seven API-API binary mixtures (1:1 M ratio) via melt-quenching.
  • Thermodynamic characterization using differential scanning calorimetry (DSC) to determine glass transition temperature (Tg) and melting point (Tm).
  • High-resolution imaging FTIR spectroscopy in transmission mode to monitor phase separation above Tg, analyzed with principal component analysis (PCA).

Main Results:

  • Imaging FTIR spectroscopy demonstrated reproducible detection of amorphous-amorphous phase separation.
  • Phase separation kinetics were visualized using scatter-plots of phase-separated pixels.
  • Separation patterns were observed as either sigmoidal or linear, dependent on the specific API mixture.

Conclusions:

  • Imaging FTIR spectroscopy is a viable technique for studying amorphous-amorphous phase separation in pharmaceutical systems.
  • The method provides insights into the stability and physical transformations of amorphous drug formulations.
  • Understanding phase separation is critical for designing stable and effective amorphous solid dispersions.