| Summary: | The current research work proposed the solubility data and solution thermodynamic properties of the cardiovascular agent 6-phenylpyridazin-3(2<i>H</i>)-one [PPD] in twelve pharmaceutical solvents at “<i>T</i> = 298.2 K to 318.2 K” and “<i>p</i> = 0.1 MPa”. The measured solubilities of PPD were regressed well with “van’t Hoff and Apelblat models”. The solid phases of pure and equilibrated PPD were characterized using differential scanning calorimetry and powder X-ray differactometry, and the results suggested no transformation of PPD into solvates/hydrates/polymorphs after equilibrium. The solubilities of PPD in a mole fraction at “<i>T</i> = 318.2 K” were noted at a maximum in dimethyl sulfoxide (DMSO, 4.73 × 10<sup>−1</sup>), followed by polyethylene glycol-400 (PEG-400, 4.12 × 10<sup>−1</sup>), Transcutol<sup>®</sup> (3.46 × 10<sup>−1</sup>), ethyl acetate (EA, 81 × 10<sup>−2</sup>), 2-butanol (2.18 × 10<sup>−2</sup>), 1-butanol (2.11 × 10<sup>−2</sup>), propylene glycol (PG, 1.50 × 10<sup>−2</sup>), isopropyl alcohol (IPA, 1.44 × 10<sup>−2</sup>), ethylene glycol (EG, 1.27 × 10<sup>−2</sup>), ethanol (8.22 × 10<sup>−3</sup>), methanol (5.18 × 10<sup>−3</sup>) and water (1.26 × 10<sup>−5</sup>). Similar tendencies were also noted at other studied temperatures. The results of the “apparent thermodynamic analysis” showed an endothermic and entropy-driven dissolution of PPD in all pharmaceutical solvents. The results of the activity coefficients suggested a maximum interaction at the molecular level in PPD-DMSO, PPD-PEG-400 and PPD-Transcutol, compared with other combination of the solute and solvents.
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