Mixing effectiveness of a new pneumatic PTS-Batchmixer® with an in-line sampling device

The aim of this paper is to define the range of utilisation of a new pneumatic pilot plant mixer. We report the validation of the mixing performances and efficiency for a binary mixture of cohesive powders, lactose monohydrate as excipient and salicylic acid as tracer. We studied the effect of the fill levels (25%, 50% and 90%) and tracer concentrations (0.01%, 0.1%, 1% and 10% w/w) obtained without pre-blending on the blend homogeneity (relative standard deviation) and the mixing time. We also investigated the effect of the sampling size (30 g vs 1 g) on the stochastic homogeneity of 2% (w/w) salicylic acid blends with an automatic sampling device. The fill level has only a slight effect on the mixing performances of the mixer with 30 g samples. Moreover the different target concentrations were obtained in a single blending step in less than 6 min. Most of the related RSD were beneath 7%. A smaller sample size of 1 g showed a greater variation in the limits of ±10% of the target value. This mixer is a good alternative to most batch mixers used at the time in the pharmaceutical industry. Nevertheless, as assumed, we confirmed the crucial impact of the scale of scrutiny.