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.
TY - 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 .
