Raman spectral imaging technique for API detection in pharmaceutical microtablets

In pharmaceutical manufacturing, quality monitoring of end products is essential to gain regulatory approval. In particular, monitoring the quantity of an active pharmaceutical ingredient (API) in the administered dosage is key to ensuring the content uniformity of the product. Thus, we herein aim to demonstrate the ability of the newly developed line-scan Raman hyperspectral imaging (RHSI) technique for the quantitative analysis of APIs in microtablet samples. Microtablets containing the API of interest and appropriate excipients of varying concentrations (i.e., 60-130% (w/w) API) were prepared by direct compression. The microtablet RHSI spectra were obtained over a wavelength range of 400-1800 cm−1. High-performance liquid chromatography was also employed as a reference method for the API assay. Multivariate analysis methods, including partial least squares and least-squares support vector machines, were employed to predict the API concentrations using the spectral and reference values of the microtablets. The developed models exhibited excellent prediction abilities for the API concentration, with a coefficient of correlation (R2) >0.95, which was associated with an error of <5% (w/w) API. Furthermore, visualization of the API concentrations and distributions in the microtablets was achieved through chemical imaging. These results confirmed that line-scan RHSI is a powerful tool for the characterization of pharmaceutical products. In addition, this approach is suitable for application in the pharmaceutical production line for the online inspection of bulk products and would be expected to easily replace conventional measurement techniques.