Application of standardisation methods to correct the spectral differences induced by a fibre optic probe used for the near-infrared analysis of pharmaceutical tablets.

Near infrared spectroscopy has become very popular in the pharmaceutical industry because of many important practical advantages. With the help of powerful chemometric techniques, multivariate calibration models are developed, relating near-infrared spectra to the values to be modelled. However, because of small instrumental differences between near-infrared spectrometers, a calibration model can only be used with spectra collected on the same instrument, which represents a serious limitation for the use of near-infrared spectroscopy in the pharmaceutical industry. To deal with this important problem, a certain number of different standardisation approaches were proposed in the literature. In this article, an application of instrument standardisation methods is presented, where two different data measurement modules (internal measurement cell and external fibre optic module) of a near-infrared spectrometer must be standardised for the quantitative determination of an active compound in pharmaceutical tablets.

Determination of ascorbic acid in pharmaceutical preparations by near infrared reflectance spectroscopy.

We developed a method for determination of ascorbic acid in pharmaceutical preparations containing various excipients by using near infrared diffuse reflectance spectroscopy and two different calibration methods, viz. stepwise multiple linear regression (SMLR) and partial least-squares (PLS) regression, which provided comparable results and resulted in prediction errors of 1-2%. However, the PLS method provided somewhat better results with the more complex samples.