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Quantifying crystalline form composition in binary powder mixtures using near-infrared reflectance spectroscopy
P E Luner1, S Majuru, J J Seyer
1Division of Pharmaceutics, College of Pharmacy, University of Iowa, Iowa City 52242, USA. paul-luner@uiowa.edu
Pharmaceutical Development and Technology
|May 16, 2000
Summary
Near-infrared reflectance spectroscopy (NIRS) effectively differentiates and quantifies crystalline forms in pharmaceutical solids. This technique accurately detects low levels of crystal forms, offering a reliable method for physical characterization.
Area of Science:
- Analytical Chemistry
- Pharmaceutical Sciences
- Spectroscopy
Background:
- Crystalline forms (polymorphs) of pharmaceutical materials significantly impact drug properties and efficacy.
- Accurate identification and quantification of these crystalline forms are crucial for drug development and quality control.
- Traditional methods for characterizing crystalline forms can be time-consuming and may require sample preparation.
Purpose of the Study:
- To evaluate the effectiveness of near-infrared reflectance spectroscopy (NIRS) for distinguishing between different crystalline forms of pharmaceutical substances.
- To determine the accuracy of NIRS in quantifying the proportions of crystalline forms within binary mixtures.
- To assess the sensitivity of NIRS for detecting low concentrations of specific crystal forms.
Main Methods:
- Qualitative and quantitative analysis of various crystalline forms of sulfamethoxazole, sulfathiazole, lactose, and ampicillin using NIRS.
- Acquisition of near-infrared (NIR) spectra from binary physical mixtures directly through glass vials (1100-2500 nm).
- Development of calibration models using inverted least-squares regression and analysis of spectral derivatives; comparison with X-ray powder diffraction.
Main Results:
- NIRS successfully differentiated crystalline forms based on spectral differences interpretable from structural features.
- Quantitative analysis yielded high correlation coefficients (>0.99) and low standard errors, comparable to X-ray powder diffraction.
- NIRS demonstrated the capability to predict crystal form composition down to the 1% level, particularly in ampicillin and sulfamethoxazole mixtures.
Conclusions:
- Near-infrared reflectance spectroscopy (NIRS) is a valuable and accurate quantitative method for the physical characterization of pharmaceutical crystalline forms.
- The technique offers high accuracy comparable to established methods like X-ray powder diffraction.
- NIRS is sensitive enough to detect and quantify low percentages of specific crystal forms, making it suitable for quality control applications.