2.5.1. Particle Size Distribution

Granulometric analysis of the various liquisolid systems was performed using a Mastersizer 3000 Laser Particle Size (LPS) analyzer (Malvern Instruments, Malvern, UK). The particle size distribution curves were obtained, and Dv10, Dv90, and Dv50 were evaluated, indicating, respectively, 10% or 90% of the cumulative percent distribution and the median of the powder distribution curve. The SPAN value, i.e., the curve distribution width around the median, was determined as an index of the powder particle size homogeneity, by the following equation [49]:

$$\text{SPAN} = (\text{Dv}\_{90} - \text{Dv}\_{10}) \text{/Dv}\_{50} \tag{2}$$

#### 2.5.2. Differential Scanning Calorimetry (DSC)

Exactly weighed samples (5–10 mg, M3 microbalance, Mettler Toledo, Greifensee, Switzerland) of pure drug and mesoporous silica or clay, and of the corresponding liquisolid systems were put in pierced Al pans and scanned under static air at 10 ◦C/min from 30 to 300 ◦C using a TA4000 Star<sup>e</sup> system (Mettler Toledo, Greifensee, Switzerland) equipped with a DSC 25 cell.
