Biomedical subjects

A M Juppo

Publications and source records attributed to A M Juppo.

5 recordsLinked to original sources

PubMed2000

Mercury porosimetry of mannitol tablets: effect of scanning speed and moisture.

Purpose of the work was to study the effect of the scanning speed of mercury porosimetry and moisture content of the sample on the mercury porosimetry result for mannitol tablets. Tablets were compressed at three different compression pressures from nonhygroscopic mannitol powder and granules. Pore structure of tablets was determined with three different scanning speeds of a high-pressure mercury porosimeter after storage in three different moisture conditions. With low scanning speed, smallest pores of tablets were determined more accurately. Small amounts of moisture, even as low as 1%, before evacuation in nonhygroscopic mannitol tablets decrease the porosity. Decrease in porosity was observed at a pore diameter range of 50-1000 nm, not at the smallest determined pores. Thus, the role of water in pharmaceutical samples appears to be complicated. Reasonably slow scanning is recommended in high-pressure mercury porosimetry. If total pore volume is the only parameter of interest, fast scanning can be used. Pretreatment of the samples by proper drying before mercury porosimetry is important.

Humidity↗

PubMed1999

Rheological characterization of microcrystalline cellulose and silicified microcrystalline cellulose wet masses using a mixer torque rheometer.

The rheological properties of silicified microcrystalline cellulose (Prosolv 50) were compared with those of standard grades of microcrystalline cellulose (Emcocel 50 and Avicel PH 101). Cellulose samples were analyzed using nitrogen adsorption together with particle size, flowability, density and swelling volume studies. The rheological behaviour of the wet powder masses was studied as a function of mixing time using a mixer torque rheometer (MTR). Silicified microcrystalline cellulose exhibited improved flow characteristics and increased specific surface area compared to standard microcrystalline cellulose grades. Although the silicification process affected the swelling properties and, furthermore, the mixing kinetics of microcrystalline cellulose, the source of the microcrystalline cellulose had a stronger influence than silicification on the liquid requirement at peak torque.

Cellulose↗

PubMed1999

Microcrystalline cellulose and its microstructure in pharmaceutical processing.

Mercury porosimetry and nitrogen adsorption methods were used in pore structure and pore surface area characterisation of microcrystalline cellulose powder, granules and tablets. The effect of compression on pore structure and surface area of tablets compressed with three different compression pressures of powder and granules was determined. Densification of MCC in wet granulation led to decreased compactibility in tableting. Effects of granulation on the microstructure of microcrystalline cellulose and plastic deformation of powder during compression were detected with nitrogen adsorption, at the diameter range 3-200 nm. Structure of granules was destroyed during tableting when compression pressures of 196 MPa were used. Fragmentation and deformation of granules were observed from the results determined using both methods. Due to different measurement ranges, different theoretical basis of the methods and behaviour of the samples during analysis, results obtained with mercury porosimetry and nitrogen adsorption methods are not strictly comparable. Results obtained with mercury porosimetry give information on the behaviour of powder and granule particles in granulation or compression, whereas nitrogen adsorption brings out the changes in intraparticular structure of particles. The results obtained using these methods together can be used in the characterisation of behaviour of materials in granulation and tableting.

Adsorption↗

PubMed1998

Pore structure and surface area of mannitol powder, granules and tablets determined with mercury porosimetry and nitrogen adsorption.

Two methods used in pore structure characterisation, mercury porosimetry and nitrogen adsorption, were compared. Pore structure and surface area of mannitol powder, granules produced in wet granulation and tablets compressed with three compression pressures were studied. Greater surface area, more porous structure and greater number of small pores in granules, when compared with powder, increased the compactibility of mannitol granules in tableting. Plastic deformation and fragmentation of powder and granules in compression were observed in volume pore size distributions and surface areas measured with these methods. Pore volume and volume pore size distribution obtained with mercury porosimetry describe densification of mass better than those obtained with nitrogen adsorption. In spite of differences between the methods, the volume pore size distribution curves of samples in the overlapping pore size range had the same shape. The specific surface area of tablets, measured by the nitrogen gas adsorption method described well the deformation under compression. Fragmentation increased the surface area of powder, and plastic deformation decreased the surface area of granules in the pore size range determined. Surface area values measured with mercury porosimetry were larger than those determined with nitrogen adsorption.

Chemistry, Pharmaceutical↗

PubMed1995

Compression of lactose, glucose and mannitol granules.

The effect of the amount of granulation liquid, compression speed and maximum compression force on then compressibility and compactibility of lactose, glucose and mannitol granules was studied. The porosity based on the geometrical shape and the uniformity of weight of tablets was also studied. Lactose and mannitol granules showed a greater compressibility than glucose granules. Mannitol granules produced the hardest tablets and lactose and glucose the weakest. The change in the amount of granulation liquid caused changes both in the granule porosity and in the amount of binder; this was attributed to differences in tablet strength. All parameters studied were relatively insensitive to changing speeds of compression in the range used, except for the breaking force of mannitol tablets, which was greatest with the lowest speed of compression. All granule masses showed a relatively good continuous flow suitable for table production. Tablets compressed from lactose granules had the best uniformity of weight of the tablets studied.

Dosage Forms↗