Thermodynamic protonation constant values of meclizine and buclizine in acetonitrile-water binary mixtures

Abstract

In the study, the retention times (tR) values for meclizine (MCZ) and buclizine (BCZ) structurally related benzhydrylpiperazine were determined to modeling the dependence of retention on the acetonitrile concentration in the mobile phase. Reversed-phase liquid chromatography (RPLC) analysis of the MCZ and BCZ was realized with polar embedded amide (15x0.46 cm I.D, 5μm) column. The mobile phase pH range is selected from 5.0-9.0 to determine the structural changes due to protonation that result from a change in pH. The different retention time were attributed to their different hydrophobicities and ionization degree. The thermodynamic protonation constant () value for investigated compounds was calculated using the tR relationship to pH of the mobile phase and effect of the activity coefficients. Linear correlation between values and macroscopic parameters (XACN, 1/ε) was also determined.

Comparison of Classical and Green RPLC Methods in the Determination of pKa Values of Some Piperazine Group Antihistamines

“…Since cetirizine is difficult to elute from the HPLC column in the selected MeCN media and gives very high t R values, it was eluted from the column with lower t R values by working in MeOH‐water binary mixtures at higher concentrations. Since meclizine and buclizine are highly hydrophobic, they have only been studied in MeCN‐water binary mixtures [22] . Because of this, EtOH‐water binary mixtures were studied in this study.…”

“…There are a limited number of studies on the analysis of the antihistamine drugs selected in this study in a water‐organic solvent or water medium. Nane and Demiralay [22] performed the pK a determination of meclizine and buclizine in MeCN‐water binary mixtures containing 60 %, 62 %, 65 %, and 68 % (v/v) MeCN on a polar embedded amide column. Using the findings obtained, pK a values in the aquatic environment were calculated (Table 3).…”

“…Since meclizine and buclizine are highly hydrophobic, they have only been studied in MeCN-water binary mixtures. [22] Because of this, EtOH-water binary mixtures were studied in this study. For the study conducted in EtOH-water binary mixtures, the X Bridge C18 column was not chosen because the peak symmetries of the compounds were poor, and the compounds could not be eluted at some mobile phase pH values.…”

“…In this study, the retention behaviors of the compounds were determined depending on the mobile phase pH and the s s pK a Chemicalize [32] Literature values Cyclizine EtOH-water 8.326 8.402 8.510 2.16 � 0.02 [33] ; 8.05 � 0.03 [33] MeOH-water [34] MeCN-water 7.658 7.700 Cetirizine EtOH-water 8.479 8.574 7.790 2.90 [27] ; 7.98 [27] , 2.93 (� 0.03) [34] ; 8.0 (� 0.02) [34] MeOH-water [32] ; 7.938 [22] Buclizine EtOH-water 8.302 8.444 8.040 8.050 [22] amount of organic solvent used, and the s s pK a 2 values of the compounds were determined from the sigmoidal behaviors obtained. The results of the s s pK a 2 values obtained are compatible with each other.…”