3. Results and discussion
Fig. 3 presents the MDs of three 20-kg batches in a 68-L bin blender at
each step of mixing with 1.25%, 2.5% and 5% w/w of API X, respectively.
The MD between the two samples after the first bin mixing step was
substantial (24.3%–83.5%). However, it decreased dramatically after the
comilling step (9.5%–17.1%) and was further narrowed after the second
bin mixing step (3.2%–6.2%). Such drops in MDs clearly suggested that
regardless of the target concentration of API X in the batch, macro-mixing
in the first bin mixing step was ineffective, and macro-uniformity still
relied on subsequent steps, i.e., comilling and the second bin mixing step.