Preparative high-performance liquid chromatography and preparative thin-layer chromatography isolation of tocainide carbamoyl-O-β-D-glucuronide: Structural characterization by gas chromatography-mass spectrometry and fast atom bombardment-mass spectrometry

Tocainide carbamoyl‐O‐β‐D‐glucuronide, a major urinary metabolite of the antiarrhythmic drug tocainide [2‐amino‐N‐(2′, 6′‐xylyl)propanoxylidide], was isolated by preparative‐TLC and preparative‐HPLC. The isolated glucuronide was hydrolyzed in sodium hydroxide (pH > 12) to 3‐(2′, 6′‐xylyl)‐5‐methylhydantoin. This hydantoin product was also identified when tocainide was reacted with urea in urine. Structural characterization of the isolated tocainide glucuronide was carried out using GC‐MS of the permethylated derivative. The molecular ion of the permethylated glucuronide was not observed, but ion fragments at m/z 232(244), 277(288), and 334(349) were found to correspond to the postulated novel carbamoyl ester structure of the permethylated (perdeuteromethylated) glucuronide. Structural evidence for the underivatized tocainide glucuronide was obtained using fast atom bombardment‐MS. The [M+H]+ ion at m/z413 was observed. Characteristic sodium ion adducts [M+Na]+ and [M‐H+2Na]+ were also observed at m/z435 and 457, respectively.