Analytical Sciences

Abstract − Analytical Sciences, 17(10), 1203 (2001).

Multiwavelength Spectrophotometric Resolution of the Micro-Equilibria of Cetirizine
Kin Y. TAM*  and Luc QUERE**
*Sirius Analytical Instruments Ltd., Riverside, Forest Row Business Park, Forest Row, East Sussex RH18 5DW, UK
**UCB Pharma, B-1420 Braine-l'Alleud, Belgium
The acid-base properties of the antihistamine (H1 receptor antagonist) cetirizine have been studied by using a previously developed multiwavelength spectrophotometric titration method. A new computational procedure called "Two-Step-Divide-and-Conquer" (TSDC), which applied evolving factor analysis (EFA) and target factor analysis (TFA), has been derived to unravel the micro-equilibria of the triprotic zwitterionic compound from the spectral data. We have demonstrated that a single spectrophotometric titration experiment is sufficient to determine the 12 unknown microconstants and the distribution of microspecies, which are in good agreement with literature values, where available.