Detailed analysis of the online near-infrared spectra of pharmaceutical blend in a rotary tablet press feed frame

• The concentration of API in the tablet press feed frame is monitored through the univariate analysis of NIR spectra.
• The univariate approach is focused on the isolated API band and is tested via multivariate analysis.
• Online NIR measurements qualitatively agree with the assay of the tablets downstream.

The present study is an in-depth analysis of the online near-infrared (NIR) spectra acquired with a spectrometer mounted on the rotary tablet press feed frame. A 3.5% active pharmaceutical ingredient (API) formulation is analyzed. An attempt is made to determine the API univariately via the 2nd derivative spectra due to favorable appearance of the API and placebo bands in the formulation. However, the signal at the univariate API peak is ambiguous and principal component analysis is hence applied to understand better the structure of the data. To eliminate effect of the bias along the wavelength axis which is found to dominate the data, the analysis is restricted only to the spectral region that covers the API band of interest. This leads to significantly better results in terms of the univariate profile of the API now heavily overlapping with the first principal component and the elimination of the bias. Having thus proven that the univariate analysis is a viable option, an attempt is made to calibrate the API response by using some previous runs that involved alternation of the placebo and the formulation. This analysis produces mixed results due to baseline differences in the two sets of spectra. The final univariate profile of the API is therefore compared with the assay of the tablets and the two are found to agree very well. It is, therefore, concluded that the NIR probe in the feed frame can rapidly detect moderate changes in API concentration in the blend and be a good predictor of tablet potency at the same time point.

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