研究目的
To quantify polymorphs of active pharmaceutical ingredients in pharmaceutical tablets using a novel transmission low-frequency Raman spectroscopy method and compare its quantitative ability with backscattering mode.
研究成果
Transmission low-frequency Raman spectroscopy is effective for quantifying crystalline polymorphs in pharmaceutical tablets, showing higher accuracy than backscattering mode. It has potential for real-time release testing but requires optimization for shorter measurement times and better instrument stability.
研究不足
The study used a prototype geometry with low excitation laser power (50 mW), leading to longer measurement times and potential instability in laser power. Sample heterogeneity and tablet thickness variations could affect results. The method requires calibration within the same day due to instrument variability, and it may not be suitable for very thick tablets without higher power lasers or improved optics.
1：Experimental Design and Method Selection:
Developed a transmission geometry for low-frequency Raman spectroscopy and compared it with backscattering mode using chemometrics (PLS analysis).
2：Sample Selection and Data Sources:
Prepared tablets with varying contents of carbamazepine polymorphs (forms I and III) and excipients (mannitol, microcrystalline cellulose).
3：List of Experimental Equipment and Materials:
Used an 853 nm laser with 50 mW power, a spectrometer with holographic transmission grating (RXN2, Kaiser Optical Systems Inc.), and a THz-Raman Probe system (Ondax Inc.). Materials included carbamazepine, D-mannitol, and microcrystalline cellulose.
4：Experimental Procedures and Operational Workflow:
Tablets were compressed using a single-punch press, Raman spectra were measured in transmission and backscattering modes with an exposure time of 300 seconds, and spectra were normalized using SNV transformation.
5：Data Analysis Methods:
PLS regression was used for quantification, with leave-one-out cross-validation to assess model stability.
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