title: Extraction and partition chromatography of tolbutamide as ion-pairs with quaternary ammonium cations.
abstract: The partition of tolbutamide (1-butyl-3-(p-tolylsulfonyl) urea) as ion-pairs with homologous tetraalkyl ammonium cations was studied. The determination of experimental extraction constants permitted quantitative calculation of distribution ratios, in agreement with theoretical relationships, over a continuous range of about one billion. The nature and the concentration of the counter-ion and solvent composition were the variables studied. Based on the theoretical results, a rapid partition chromatographic procedure was devised. A solution of tolbutamide sample in 10% aqueous tetraethyl ammonium hydroxide is incorporated in the system as the immobile phase in the partition column. A 1+1 mixture of chloroform and isooctane removes extraneous materials; then chloroform elutes the tolbutamide-tetraethyl ammonium ion-pair, which is converted to the free acid by passing the eluate through a phosphoric acid segment, and tolbutamide is determined spectrophotometrically without further treatment. Standard recoveries averaged 100.5+/-0.70%; commercial tablets assayed 100.5+/-0.85%.
mesh_terms: D001682:Biological Availability; D002852:Chromatography, Ion Exchange; D004304:Dosage Forms; D008722:Methods; D000644:Quaternary Ammonium Compounds; D012997:Solvents; D014044:Tolbutamide / Q000032:analysis*
chemical_list: D004304:Dosage Forms; D000644:Quaternary Ammonium Compounds; D012997:Solvents; D014044:Tolbutamide