Granule size distribution of tablets.

The purpose of this study was to determine the variation in the granule size distribution in a die of an eccentric tableting machine. Theophylline anhydrate and alpha-lactose monohydrate were granulated with an aqueous solution of polyvinylpyrrolidone, using an instrumented fluid bed granulator. The granules were tabletted, using an instrumented eccentric tableting machine. Punch forces were recorded and tablets were collected in order during the tableting process. Powder samples, which had the same mass as the tablets, were also collected from the die for particle size determination. The particle size distribution was measured, using a spatial filtering technique. In addition, the segregation of microcrystalline cellulose pellets during tableting was analyzed. The particle size distribution changed dramatically during the tableting process, due to a segregation phenomenon.

Determination of the crushing strength of intact tablets using Raman spectroscopy.

In the present study, the Raman spectroscopy technique was used as a non-invasive, rapid analytical method for measuring the crushing strength of tablets. The compressed tablets were individually detected, using Raman spectroscopy, and the respective crushing strength values were measured, using a tablet hardness tester as a reference method. The tablets were compressed from a granule mass containing theophylline anhydrate as an active substance. For measuring the crushing strength of the tablets, Raman spectra were recorded from the tablets. Partial least squares (PLS) regression models were constructed to obtain information from the spectra. The correlation between measured and predicted crushing strength values for the tablets was shown to be very favorable. With Raman spectroscopy, shifting of the baseline was observed as the crushing strengths of tablets (and the smoothness of the tablet surface) were increased. Consequently, correlation between the crushing strength data on the present tablets and Raman spectra was observed. Multiple scanning electron (SEM) and non-contact laser profilometry (LP) micrographs from the surfaces of the tablets were taken to describe the surfaces and applied as supportive information for the proposed spectroscopy approach. In conclusion, Raman spectroscopy is a promising alternative for established off-line/at-line tablet-testing methods for some tablet formulations.

Uniformity of poorly miscible powders determined by near infrared spectroscopy.

The objective of this work was to study with near infrared spectrometry (NIRS) the degree of mixing of poorly miscible binary mixtures of carbamazepine (CBZ) and alpha-lactose monohydrate (LMH). CBZ was cohesive and the particle size difference between CBZ (0.3microm) and LMH (75microm) was substantial. Mixed batches were measured directly in the mixing container with a fiber-optic probe. The spectral data were filtered by applying a novel automated selection technique during the NIRS measurement. The data analyses were performed with partial least squares modeling. Reference measurements were carried out with ultraviolet spectrophotometry. The results describe the degree of homogeneity at various depths. Some of the mixtures densified when the mixing speed increased. The densification of the batches was a source of error because it caused changes in the measuring geometry. The automated selection technique for the spectra reduced this problem. NIRS detected differences in the mixing degrees of mixtures and the method is suitable for mixing studies. However, the difference in the particle size of the materials and the densification caused problems to the measuring geometry. NIRS can be used at line, but the method requires accurate operation and method developing before it is useable.