Using Raman spectroscopy in tablet moisture surface analysis: tablet surface markers

Method development and validation of a near-infrared spectroscopic method for in-line API quantification during fluidized bed granulation

Near-infrared spectroscopy (NIRS) is an excellent process analytical technology (PAT) tool for active pharmaceutical ingredient (API) quantification during fluidized granulation. Therefore, a portable near-infrared spectrometer combined with a new innovative method of extended iterative optimization technique (EIOT) was used to in-line monitor the API content uniformity during fluidized bed granulation. The principal component analysis (PCA) and partial least squares regression (PLSR) were also used to characterize and predict API concentration with changes from 75% to 125% of the label claim to prove the superiority of EIOT. The API content prediction accuracy of the EIOT method was verified through offline High Performance Liquid Chromatography (HPLC) measurement. Also, the spatial distribution of API in granules was visualized by Raman imaging technology. The results showed that the established NIRS method was suitable for the prediction of API content in fluidized bed granulation, which provides a new idea for the determination of API content during granulation.

A Comparative Study of Applying Backscattering and Transmission Raman Spectroscopy to Quantify Solid-State Form Conversion in Pharmaceutical Tablets

Selecting appropriate Raman measurement and data processing method are of importance to enable effective quantification of solid form conversions upon processing or storage. Therefore, a comparative evaluation is presented herein on using backscattering and transmission Raman spectroscopy to quantify salt disproportionation in tablet matrices. The second part focuses on different spectra processing approaches and calibration models for quantifications. Finally, samples under different mechanical stresses were comprehensively analyzed using different Raman measurements. Much as transmission Raman spectrometry may provide accuracy on bulk measurements by having large sampling volume, it has the drawback of signal attenuation and may overlook process-induced phase transitions occurring on local regions of tablet surface. To overcome this limitation, backscattering Raman with deliberate subsampling can be used as an orthogonal method to probe the existence of low-level form conversion distributed over a tablet's surface. In the present case, different levels of the form conversions were found at the edge and the center of tablets due to the uneven shear stress distribution invoked during tablet compression. In such a scenario, it would be beneficial to apply deliberate-focused backscattering and transmission Raman spectrometry together as complementary techniques to capture chemical information both locally and within the bulk of the tablet.

Quantifying Solid-State Mixtures of Crystalline Indomethacin by Raman Spectroscopy Comparison with Thermal Analysis

This paper investigates Raman spectroscopy as a quick and reliable method to quantify the alpha (α) and gamma (γ) polymorphic forms of indomethacin compared to differential scanning calorimetry (DSC). Binary mixtures with different ratios of α and γ indomethacin were prepared and analyzed by Raman and DSC. The Raman method was found to be more reliable and superior compared to DSC. The partial conversion of the alpha to gamma polymorphic form during the DSC measurement was the major limitation for the use of full DSC as a quantitative method and resulted in difference between the calculated and measured enthalpy of both polymorphic forms.