Control analysis of a pharmaceutical preparation by near-infrared reflectance spectroscopy: A comparative study of a spinning module and fibre optic probe

The potential of near-infrared diffuse reflectance spectroscopy for quality control of the manufacturing process for a solid pharmaceutical preparation was investigated. The analytical procedure used for this purpose included identification and qualification of the product, as well as quantitation of its active compound. Two spectral recording systems based on a spinning sample cell and fibre optics were used and the results obtained are compared. The identification and qualification of the samples was carried out by reference to a library containing the second derivative spectra for 163 pure components commonly used in the pharmaceutical industry. Both sample holding systems provided satisfactory results in this respect. The active compound in the pharmaceutical was quantified by partial least squares calibration by using two different strategies to select samples for inclusion in the calibration set, viz. flat calibration and sample selection. The accuracy and precision of the results obtained by applying both selection strategies to the spectra recorded with the two systems are compared. Based on the errors of prediction obtained, which were less than 1% in all instances, the fibre optic probe was found to perform comparably to the conventional spinning cuvette. Also, the flat calibration model appears to be more robust than the sample selection model for choosing samples to be included in the calibration set.