TY - JOUR
T1 - Solution thermodynamics and preferential solvation of meloxicam in propylene glycol +water mixtures
AU - Holguín, Andrés R.
AU - Delgado, Daniel R.
AU - Martínez, Fleming
AU - Marcus, Yizhak
PY - 2011/12
Y1 - 2011/12
N2 - The equilibrium solubilities of the analgesic drug meloxicam (MEL) in propylene glycol + water mixtures were determined at several temperatures from 293.15 to 313.15 K. The Gibbs energy, enthalpy, and entropy of solution and of mixing were obtained from these solubility data. The solubility was maximal in neat propylene glycol and very low in pure water at all temperatures studied. A nonlinear plot of Δ solnH° versus Δ solnG° gave a negative slope from pure water up to 0.80 mass fraction of propylene glycol and a positive slope above this composition up to neat propylene glycol, at the mean temperature 303.15 K. Accordingly, the driving mechanism for MEL solubility in the water-rich mixtures was the entropy, probably due to water-structure loss around nonpolar moieties of the drug, while for the propylene glycol-rich mixtures it was the enthalpy, probably due to better solvation of the drug. The preferential solvation of MEL by the components of the solvent was estimated by means of the inverse Kirkwood-Buff integral method, showing rather small preferential solvation of MEL by propylene glycol at all compositions.
AB - The equilibrium solubilities of the analgesic drug meloxicam (MEL) in propylene glycol + water mixtures were determined at several temperatures from 293.15 to 313.15 K. The Gibbs energy, enthalpy, and entropy of solution and of mixing were obtained from these solubility data. The solubility was maximal in neat propylene glycol and very low in pure water at all temperatures studied. A nonlinear plot of Δ solnH° versus Δ solnG° gave a negative slope from pure water up to 0.80 mass fraction of propylene glycol and a positive slope above this composition up to neat propylene glycol, at the mean temperature 303.15 K. Accordingly, the driving mechanism for MEL solubility in the water-rich mixtures was the entropy, probably due to water-structure loss around nonpolar moieties of the drug, while for the propylene glycol-rich mixtures it was the enthalpy, probably due to better solvation of the drug. The preferential solvation of MEL by the components of the solvent was estimated by means of the inverse Kirkwood-Buff integral method, showing rather small preferential solvation of MEL by propylene glycol at all compositions.
KW - Activity coefficients
KW - Meloxicam
KW - Preferential solvation
KW - Propylene glycol solubility
KW - Solution thermodynamics
UR - http://www.scopus.com/inward/record.url?scp=84855887263&partnerID=8YFLogxK
U2 - 10.1007/s10953-011-9769-0
DO - 10.1007/s10953-011-9769-0
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AN - SCOPUS:84855887263
SN - 0095-9782
VL - 40
SP - 1987
EP - 1999
JO - Journal of Solution Chemistry
JF - Journal of Solution Chemistry
IS - 12
ER -