Biomedical subjects

Anders Sparén

Publications and source records attributed to Anders Sparén.

3 recordsLinked to original sources

PubMed2006

Transfer of NIR calibrations for pharmaceutical formulations between different instruments.

In order to evaluate how well existing techniques for transferring NIR calibrations perform for solid pharmaceutical formulations, a study on four assays of active ingredients was undertaken. The study included two configurations of dispersive NIR instruments and one Fourier transform (FT) instrument. Three methods for calibration transfer: slope/bias correction, local centring and piecewise direct standardisation (PDS), were tested and evaluated. Our conclusions are that the calibration transfer methods tested can perform equally well. It was shown that it is possible to transfer calibrations between instruments of different configurations or even of different types, without loosing the prediction ability of the calibration. To achieve a good calibration transfer, a larger variation in the content of the active ingredient in the samples and more samples are needed for the slope and bias correction method compared to the local centring method. For PDS to be a successful calibration transfer method, an optimisation of the number of transfer samples and how they are selected together with various factors specific for this method is needed. Local centring is the preferred transfer method as its performance is excellent yet it is simple to perform, no optimisation is needed, only a few transfer samples are required and the transfer samples do not have to vary in their content of the active ingredient.

Calibration↗

PubMed2005

Evaluation of basic algorithms for transferring quantitative multivariate calibrations between scanning grating and FT NIR spectrometers.

A key issue in near infrared spectroscopy (NIR) is the possibility to use calibrations generated on one instrument for predictions on others. A number of methods for calibration transfer have been proposed, but which method to choose is typically not straightforward. An evaluation of a number of methods for transferring quantitative calibrations between different instruments was carried out on near infrared diffuse-reflectance data from a pharmaceutical formulation. Six instruments were included in the study, five of which were scanning grating instruments, both with and without fibre-optic probe configuration, and one of which was a Fourier-transform instrument, equipped with a fibre-optic probe. The results show that it is possible to transfer calibrations between different instruments, provided that a structured procedure is used. Simple techniques for calibration transfer, such as slope/bias correction on the predicted results, as well as standard normal variate transformation and local centring of the raw spectra, gave considerably lower prediction errors on transfer than did standardisation with a certified diffuse-reflectance standard, or direct transfer without any transfer function. Notably, including more than one instrument in the calibration also improved the prediction ability of the models on calibration transfer. No significant differences in wavelength scale were found when a certified diffuse-reflectance wavelength standard was measured on the instruments studied. Nor did simulated wavelength scale differences below +/-0.3 nm cause any significant change in the prediction errors.

Algorithms↗

PubMed2003

In-situ near-infrared spectroscopy monitoring of the lyophilization process.

PURPOSE: The purpose of this work was to demonstrate the feasibility of using near-infrared spectroscopy (NIRS) to monitor the freeze-drying process in-situ. METHODS: The experiment was performed in a pilot-scale freeze-dryer, in which the NIRS probe was interfaced using a lead-through to the lyophilizer. Special equipment for the sample presentation was developed. NIRS measurements were made using a FT (Fourier transform)-NIR spectrometer fitted with a single fiber reflectance probe. RESULTS: The physical changes, that is, freezing, sublimation, and desorption, generated significant spectral changes. There was good agreement between NIRS monitoring and product temperature monitoring about the freezing process and the transition from frozen solution to ice-free material. The NIRS monitoring also provided new information about the process that was not possible to detect with product temperature monitoring, such as the rate of the desorption process and the steady-state where the drying was complete. The NIRS monitoring yields significantly more information about the actual process and essentially explains the observed changes of the product temperature during the lyophilization process. CONCLUSIONS: NIRS monitoring is a viable tool for in-situ monitoring, both qualitatively and quantitatively. It can facilitate investigations of the drying process within a sample. The small volume monitored makes sample presentation very important.

Chemical Phenomena↗