Amiloride photostability at different pH values was studied in depth by applying Multivariate CurveResolution Alternating Least Squares (MCR-ALS) to the UV spectrophotometric data from drugsolutions exposed to stressing irradiation. Resolution of all degradation photoproducts was possible bysimultaneous spectrophotometric analysis of kinetic photodegradation and acid–base titrationexperiments. Amiloride photodegradation showed to be strongly dependent on pH. Two hardmodelling constraints were sequentially used in MCR-ALS for the unambiguous resolution of all thespecies involved in the photodegradation process. An amiloride acid–base system was defined by usingthe equilibrium constraint, and the photodegradation pathway was modelled taking into account thekinetic constraint. The simultaneous analysis of photodegradation and titration experiments revealedthe presence of eight different species, which were differently distributed according to pH and time.Concentration profiles of all the species as well as their pure spectra were resolved and kinetic rateconstants were estimated. The values of rate constants changed with pH and under alkaline conditionsthe degradation pathway and photoproducts also changed. These results were compared to thoseobtained by LC-MS analysis from drug photodegradation experiments. MS analysis allowed theidentification of up to five species and showed the simultaneous presence of more than one acid–baseequilibrium.

A study of pH-dependent photodegradation of amiloride by a multivariate curve resolution approach to combined kinetic and acid-base titration UV data

De Luca M
;
IOELE, Giuseppina;RAGNO, Gaetano
2012

Abstract

Amiloride photostability at different pH values was studied in depth by applying Multivariate CurveResolution Alternating Least Squares (MCR-ALS) to the UV spectrophotometric data from drugsolutions exposed to stressing irradiation. Resolution of all degradation photoproducts was possible bysimultaneous spectrophotometric analysis of kinetic photodegradation and acid–base titrationexperiments. Amiloride photodegradation showed to be strongly dependent on pH. Two hardmodelling constraints were sequentially used in MCR-ALS for the unambiguous resolution of all thespecies involved in the photodegradation process. An amiloride acid–base system was defined by usingthe equilibrium constraint, and the photodegradation pathway was modelled taking into account thekinetic constraint. The simultaneous analysis of photodegradation and titration experiments revealedthe presence of eight different species, which were differently distributed according to pH and time.Concentration profiles of all the species as well as their pure spectra were resolved and kinetic rateconstants were estimated. The values of rate constants changed with pH and under alkaline conditionsthe degradation pathway and photoproducts also changed. These results were compared to thoseobtained by LC-MS analysis from drug photodegradation experiments. MS analysis allowed theidentification of up to five species and showed the simultaneous presence of more than one acid–baseequilibrium.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.11770/132762
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