Application of Guanidine Hcl to Improve Enantioseparation of a Model Basic Drug, Cetirizine, By Capillary Electrophoresis Using Sulfated Β-Cyclodextrin

A common approach in resolving enantiomers of chiral basic drugs by capillary electrophoresis (CE) is to use cyclodextrins (especially their anionic derivatives) as chiral selector in the acidic buffer (pH ≤ 3) in normal or reversed (carrier) mode. Then, some organic modifiers are added to the buffer solution if the resolution is not satisfactory. In case of cetirizine (CTN), applying the same approach, i.e. a reversed mode capillary zone electrophoresis (CZE) method with an acidic buffer and sulfated-b-cyclodextrine (S-bCD) as chiral selector, was failed and no complete enantioseparation was achieved. Different organic modifiers, like urea and triethylamine HCl, were used to improve chiral resolution which led to partial resolution of the two peaks. Then, guanidine HCl at a concnetration of 100 mM was added to the running buffer and an acceptable resolution of the enantiomers of the drug was obtained. The method was successfully applied to determine optical purity of a levo-cetirizine (l-CTN) sample.