Researchers use powder flow rheometer to accurately predict the end-point of a granulation step, resulting in an optimised final dosage form
Researchers at pharmaceutical giant Pharmacia have used a powder flow rheometer from Freeman Technology to accurately predict the end-point of a granulation step, resulting in an optimised final dosage form.
To make tablets, a granulation liquid (in this case, water) is added to a dry powder mix of active ingredients and excipients.
This wet mass is then dried, milled and lubricated before being tabletted at a range of compression forces.
The end-point of the granulation process is the point at which the correct amount of liquid has been added and the mass blended for an appropriate time in order to achieve the optimum rheological properties - being able to accurately predict the granulation end-point is crucial to final product quality.
Orla Cassidy and Iwan Thomas at Pharmacia's Northumberland site used the FT3 powder rheometer to assess the rheological properties of a commercial formulation with haloperidol as an active ingredient1. "We found that the FT3 was very sensitive and was able to discriminate between samples that differ by less than 1% water content by weight," said Dr Cassidy.
"This is important for us because small moisture variations such as this can sometimes have a significant impact on final product quality." For example, energy profiles indicated that at low water content, more energy is required when mixing for shorter times; and as water content increased to 12% by weight, the energy requirement increased with longer mixing times.
"The FT3 appears to be much more sensitive than other instruments. Being able to quantify the end-point means that an inexperienced operator can easily assess the granulation process," said Cassidy.
"The FT3 has helped us optimise our granulation process and therefore improve our end product." The patented FT3 powder rheometer from Freeman Technology is said to be the only instrument on the market that measures all the relevant forces needed to give a complete and accurate measurement of powder flowability.
Sensitive and reproducible data are obtained by measuring both axial forces (as the blade moves vertically through the sample) and rotational forces (or torque) to determine flow energies.
Dry and wet powders may be evaluated in terms of each of the key variables.
The FT3 works on a patented helical blade principle, where the blade displaces powder as it moves along a helical path through the sample.
Depending on the direction and speed of movement a broad range of flow patterns and rates can be achieved.
The axial and rotational forces acting on the blade are measured and these data form the basis of the flowability assessment.
Force measurements are converted into energy to determine the total energy consumed or work done during the traverse.
