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Tablets & Capsules March 2019 41 while mini-tablets made with the coarser, more brittle vitamin C demonstrated greater differences in binder compaction behavior. Of the excipients, the RetaLac performed better than the spray-dried FlowLac 100 and the CombiLac. This may be attributable to RetaLac's composition having the highest level of plastically deforming materials, dominated by hypromellose. Additionally, load-time profiles showed a shift to greater plas- ticity by maintaining an increased curve symmetry, especially when using RetaLac. The impact of flowability on tab- let weight variation was monitored, and material characteristics such as particle size and size distribution and API morphology were critical. The blends demonstrating the best flowability resulted in the lowest tablet mass relative standard devia- tion (RSD). Research by Rumondor et al. found a similar trend for α-lac- tose monohydrate-based mixtures [2]. Nevertheless, the results showed that ratio and absolute values for angle of repose versus tablet mass RSD were also material specific. At a 39-degree angle of repose, vitamin C blends showed higher tablet mass tons. The angle of repose for each p o w d e r b l e n d w a s d e t e r m i n e d according to compendial methods (Ph. Eur. 2.9.16), and the average tablet breaking force was evaluated using an Erweka TBH 425TD hard- ness tester with ten compacts. The mini-tablet manufacturing process followed a typical direct compression (DC) scheme: excipient and API blending followed by lubri- cation and compaction. Vitamin B 2 mini-tablet dissolution testing was performed according to Ph. Eur. 2.9.3 using an Agilent 1260 Infinity Quaternary LC spectrophotometer at 445 nanometers. Tests were per- formed in triplicate. Results and discussion T h e m i n i - t a b l e t s ' c o m p r e s - sion-breaking force profiles were assessed, as shown in Figure 1. Results showed that mini-tablets made using the finer, more plastically deforming vitamin B 2 withstood approximately twice the absolute breaking force as mini-tablets made using the coarser, more brittle vitamin C. At 10 kilo- newtons compaction force, the vita- min B 2 compensated for performance variations in the three excipients, Table 2 API particle size distribution (microns) Vitamin B 2 Vitamin C d 10 0.8 43 d 50 3.7 282 d 90 10.7 557 Figure 1 Tablet compression-hardness profiles for 10-percent vitamin B 2 and C formulations 70 60 50 40 30 20 10 0 Tablet hardness (newtons) 25 20 15 10 5 0 Tablet hardness (newtons) Compression force (kilonewtons) 0 5 10 15 20 25 Compression force (kilonewtons) 0 5 10 15 20 Vitamin B 2 Vitamin C RetaLac FlowLac 100 CombiLac Blends were prepared using an IMA CyLab bin blender, and mixing qual- ity was monitored by a VIAVI MicroNIR PAT-W probe. For each formulation, 90 revolutions were used to incorporate the API and 30 revolu- tions were used for final lubrication. This was believed to be sufficient as supported by moving block standard deviation. Compaction was performed using an 8-station IMA Prexima 80 rotary tablet press. The mini-tablet diameter was 2.5 millimeters, and the shape was round with a flat face. XIMA software was used for data acquisition. The tablet press oper- ated at a constant rotational speed of 20 rpm and applied compression forces between 5 and 20 kilonew-