**4. Conclusions**

In the present study, Si-PANI sorbent obtained by in situ polymerization of aniline directly on silica gel particles (Si-PANI) was applied for dispersive solid phase extraction (d-SPE) and matrix solid–phase extraction (MSPD) of plant samples before HPLC analysis of triterpenic acids. The conditions of procedures were optimized experimentally. The sorbent was protonated (+) and deprotonated to change the ionization of surface and thus, to obtain the different sorption mechanism. Both on Si-PANI (+) and Si-PANI, analytes were strongly retained; however different impregnation solutions were required (water and methanol, respectively). Due to easier elution of investigated compounds, protonated sorbent was favorable. The other established optimal conditions were as follows: 3 min of extraction time, 2 mL of methanol water mixture (1:1, *v*/*v*) as washing solution, 4 min of desorption time and methanolic solution of ammonia as elution solvent. The optimized procedure was successfully used for pretreatment of *Viscum album* L. and *Ocimum basilicum* L samples using MSPD and d-SPE. The significant reduction of the matrix was observed for both techniques; however, after MSPD, the amount of determined analytes were lower than after d-SPE and this technique may be considered only for preliminary screening studies.

**Author Contributions:** Magdalena Wójciak-Kosior and Ireneusz Sowa conceived and designed the experiments; Maciej Strzemski, Jan Sawicki, Michał Staniak and Wojciech Szwerc performed the experiments; Magdalena Wójciak-Kosior, Ireneusz Sowa and Sławomir Dresler analyzed the data; Jarosław Mołdoch and Michał Latalski contributed reagents and materials; Magdalena Wójciak-Kosior and Ireneusz Sowa wrote the paper. All authors participated in manuscript preparation and approved the final version.

**Conflicts of Interest:** The authors declare no conflict of interest.
