In roller compaction, particle distribution is recognized as one of the most critical parameters affecting downstream process performance and product quality. The particle distribution affects the following unit operations.
A roller compaction process is designed to yield consistent downstream tablet compression resulting in uniform dissolution and content uniformity. A successful process produces a granule with consistent particle size distribution, density and porosity control. However, inconsistencies occur during granulation scale-up due to a in change raw materials or process dynamics. Collaboration with Patheon demonstrates FBRM® at-line to map design space and optimize a series of roller compaction runs whilst varying vertical/horizontal feed speed, roller compaction force, and mill speed. Characterizing particle distribution allows users to directly link process control parameters to product quality. By designing a robust process, consistent processing from dry granulation to tablet compression is achieved.
A 19 batch DoE was performed in order to understand processing parameters affecting downstream product quality. FBRM®technology was used to measure and control changes in particle count and dimension. FBRM®is typically inserted in-line3 in a collection funnel downstream of the Comil and powder flows over the probe tip providing a representative measurement due to measuring in-line4 or at-line5 within concentrated particle systems, increasing sample size and providing high sensitivity to fine particles. In this case, an at-line method was used6. 10g of powder was sampled downstream and dispersed in 100g of mineral oil. Due to concentrated sample size, a representative measurement was achieved. Sample repeatability was <1% on the median (50th percentile) statistic.
The pre-blend distribution had fewer coarse particles compared with the distributions after roller compaction and milling (Fig. 1). Trial 10, 12, 13 and19 had the highest number of fine particles, high porosity and density. They also corresponded to 4000lb/inch roller force and 1000 rpm mill speed. The fines population is an early indication of downstream flow properties and possible dissolution inconsistency. Trials 6 and 11 had the highest number of coarse particles, low porosity and density. They also corresponded to 8000lb/inch roller force and 2000 rpm mill speed.
Particle distribution mean, number of fine particles counted per second (0-50μm) and number of coarse particles (200-2000μm) are early predictors of high sensitivity to compact porosity and changes in upstream roller compaction force and mill speed parameters. The particle mean and number of fine and coarse particles counted per second may also be early indicators of downstream flow and dissolution rate or disintegration time. In general, roller compaction force significantly affected ribbon density, porosity compacts and milled compact particle size.
Mean vs. Porosity Correlation
By measuring granule dimensions in real time, roller compaction process conditions can be controlled to target specific mean dimensions. Since mean dimensions correlate to granule porosity, there is an opportunity for real time control ensuring consistency.
Roller compaction is a complex process with competing mechanisms of breakage and agglomeration. Using FBRM®, it is possible to quantify the effect of critical process parameters and correlate this to ribbon parameters. By characterizing these effects, tools (FBRM®)can be usedto reduce scale-up time, minimize upsets and troubleshoot issues. In this study, high roller compaction force and mill speed resulted in coarser particles with lower porosity and density, whereas low compaction force and mill speed corresponded to a higher level of fine particles, porosity, and density. Inline particle characterization is also used to identify screen breaks and hardware malfunctions reducing manufacturing costs.
1. Sheffield Products
2. Peter Greven
3. Arp, Z. et al. AAPS, Atlanta, GA, 10 November 2008
4. Wiesweg, S. et al. Tablet Tech Seminar, Brussels; Belgium; 25 October 2007
5. Hu, X. et al. International Journal of Pharmaceutics 347 (2008) 54–61
6. Michaels J. N. et al. Powder Technology Volume 189, Issue 2, 31 January 2009, 295-303
Arasu Kondappan, Patheon for testing the compacted ribbon physical properties.
Diane Lillibridge, Patheon for providing guidance on the statistical design and performing the statistical analysis.
Russ Neldham, METTLER TOLEDO for performing FBRM®measurements.