Protolytic equilibria in homogeneous and heterogeneous aqueous systems of methyl- and propylparaben and influence of β-cyclodextrin on pKa values
Protolitičke ravnoteže u homogenim i heterogenim vodenim sistemima metil- i propilparabena i uticaj β -ciklodekstrina na pKa vrednosti
Апстракт
Acidity constants (Ka) and intrinsic hydrosolubility (Ks0) of two parabens, methylparaben and propylparaben, were spectrophotometrically determined at 25oC and a constant ionic strength of I=0.1 M (NaCl). Based on the determined equilibrium constants Ks0 and Ka, equilibrium constant Ks1 in heterogeneous system of methyl-and propylparaben was calculated. Solubility of the two parabens as a function of solution acidity was calculated applying the equation: s1 s0 3 [ ] S [H O ] K K + = + In addition, the effects of varying β-cyclodextrin concentrations on pKa values of the two parabens were examined. The results showed that β-CD influenced absorption spectra of the parabens (a decreased absorptivity and a bathochromic shift of the absorption maxima), but their pKa values remained almost unchanged.
Spektrofotometrijski su određene kiselinske konstante (Ka) i osnovna rastvorljivost (Ks0) u vodi metilparabena i propilparabena. Određivanja su vršena na temperaturi od 25 oC i pri konstantnoj jonskoj sili I=0.1 M (NaCl). Na osnovu određenih ravnotežnih konstanti Ks0 i Ka izračunata je ravnotežna konstanta Ks1 u heterogenom sistemu parabena. Rastvorljivost parabena u funkciji kiselosti rastvora izračunata je primenom jednačine 1 0 3 [ ] [ ] s s K S K H O+ = + Pored toga, ispitan je uticaj različitih koncentracija β-ciklodekstrina na pKa vrednosti datih parabena.
Кључне речи:
methylparaben / propylparaben / solubility / acidity constant / metilparaben / propilparaben / rastvorljivost / kiselinska konstantaИзвор:
Arhiv za farmaciju, 2004, 54, 5, 601-611Издавач:
- Savez farmaceutskih udruženja Srbije, Beograd
Институција/група
PharmacyTY - JOUR AU - Popović, Gordana AU - Čakar, Mira PY - 2004 UR - https://farfar.pharmacy.bg.ac.rs/handle/123456789/512 AB - Acidity constants (Ka) and intrinsic hydrosolubility (Ks0) of two parabens, methylparaben and propylparaben, were spectrophotometrically determined at 25oC and a constant ionic strength of I=0.1 M (NaCl). Based on the determined equilibrium constants Ks0 and Ka, equilibrium constant Ks1 in heterogeneous system of methyl-and propylparaben was calculated. Solubility of the two parabens as a function of solution acidity was calculated applying the equation: s1 s0 3 [ ] S [H O ] K K + = + In addition, the effects of varying β-cyclodextrin concentrations on pKa values of the two parabens were examined. The results showed that β-CD influenced absorption spectra of the parabens (a decreased absorptivity and a bathochromic shift of the absorption maxima), but their pKa values remained almost unchanged. AB - Spektrofotometrijski su određene kiselinske konstante (Ka) i osnovna rastvorljivost (Ks0) u vodi metilparabena i propilparabena. Određivanja su vršena na temperaturi od 25 oC i pri konstantnoj jonskoj sili I=0.1 M (NaCl). Na osnovu određenih ravnotežnih konstanti Ks0 i Ka izračunata je ravnotežna konstanta Ks1 u heterogenom sistemu parabena. Rastvorljivost parabena u funkciji kiselosti rastvora izračunata je primenom jednačine 1 0 3 [ ] [ ] s s K S K H O+ = + Pored toga, ispitan je uticaj različitih koncentracija β-ciklodekstrina na pKa vrednosti datih parabena. PB - Savez farmaceutskih udruženja Srbije, Beograd T2 - Arhiv za farmaciju T1 - Protolytic equilibria in homogeneous and heterogeneous aqueous systems of methyl- and propylparaben and influence of β-cyclodextrin on pKa values T1 - Protolitičke ravnoteže u homogenim i heterogenim vodenim sistemima metil- i propilparabena i uticaj β -ciklodekstrina na pKa vrednosti VL - 54 IS - 5 SP - 601 EP - 611 UR - https://hdl.handle.net/21.15107/rcub_farfar_512 ER -
@article{ author = "Popović, Gordana and Čakar, Mira", year = "2004", abstract = "Acidity constants (Ka) and intrinsic hydrosolubility (Ks0) of two parabens, methylparaben and propylparaben, were spectrophotometrically determined at 25oC and a constant ionic strength of I=0.1 M (NaCl). Based on the determined equilibrium constants Ks0 and Ka, equilibrium constant Ks1 in heterogeneous system of methyl-and propylparaben was calculated. Solubility of the two parabens as a function of solution acidity was calculated applying the equation: s1 s0 3 [ ] S [H O ] K K + = + In addition, the effects of varying β-cyclodextrin concentrations on pKa values of the two parabens were examined. The results showed that β-CD influenced absorption spectra of the parabens (a decreased absorptivity and a bathochromic shift of the absorption maxima), but their pKa values remained almost unchanged., Spektrofotometrijski su određene kiselinske konstante (Ka) i osnovna rastvorljivost (Ks0) u vodi metilparabena i propilparabena. Određivanja su vršena na temperaturi od 25 oC i pri konstantnoj jonskoj sili I=0.1 M (NaCl). Na osnovu određenih ravnotežnih konstanti Ks0 i Ka izračunata je ravnotežna konstanta Ks1 u heterogenom sistemu parabena. Rastvorljivost parabena u funkciji kiselosti rastvora izračunata je primenom jednačine 1 0 3 [ ] [ ] s s K S K H O+ = + Pored toga, ispitan je uticaj različitih koncentracija β-ciklodekstrina na pKa vrednosti datih parabena.", publisher = "Savez farmaceutskih udruženja Srbije, Beograd", journal = "Arhiv za farmaciju", title = "Protolytic equilibria in homogeneous and heterogeneous aqueous systems of methyl- and propylparaben and influence of β-cyclodextrin on pKa values, Protolitičke ravnoteže u homogenim i heterogenim vodenim sistemima metil- i propilparabena i uticaj β -ciklodekstrina na pKa vrednosti", volume = "54", number = "5", pages = "601-611", url = "https://hdl.handle.net/21.15107/rcub_farfar_512" }
Popović, G.,& Čakar, M.. (2004). Protolytic equilibria in homogeneous and heterogeneous aqueous systems of methyl- and propylparaben and influence of β-cyclodextrin on pKa values. in Arhiv za farmaciju Savez farmaceutskih udruženja Srbije, Beograd., 54(5), 601-611. https://hdl.handle.net/21.15107/rcub_farfar_512
Popović G, Čakar M. Protolytic equilibria in homogeneous and heterogeneous aqueous systems of methyl- and propylparaben and influence of β-cyclodextrin on pKa values. in Arhiv za farmaciju. 2004;54(5):601-611. https://hdl.handle.net/21.15107/rcub_farfar_512 .
Popović, Gordana, Čakar, Mira, "Protolytic equilibria in homogeneous and heterogeneous aqueous systems of methyl- and propylparaben and influence of β-cyclodextrin on pKa values" in Arhiv za farmaciju, 54, no. 5 (2004):601-611, https://hdl.handle.net/21.15107/rcub_farfar_512 .