Determination by Ion-exchange Chromatography of Trifluoroacetic Acid as a Biliary Metabolite of Isoflurane in the Rabbit

The optimal composition of eluant for trifluoroacetic acid (TFAA) analysis by ion-exchange chromatography was determined and a preliminary study to detect TFAA, a metabolite of isoflurane, in bile of rabbits during and after inhalation of isoflurane was made. The optimal composition of eluant for TFAA analysis by ion-exchange chromatography was determined to be a solution of 2rnM Na2C03 and 4mM NaHC03. Rabbits were divided into 4 groups; A group: 1 hr inhalation of 2% isoflurane, B group: 2 hr inhalation of 2% isoflurane, C group: 2 hr inhalation of 3% isoflurane, and D group: 2 hr inhalation of 4% isoflurane. The maximum biliary TFAA concentration in groups A, B, C and D averaged 17.5 ± 1.4 μM (mean ± S.D.) at 105 min, 37.1 ± 11.5 μM at 315 min, 54.5 ± 9.4 μM at 585 min and 34.4 ± 12.1 μM at 555 min after termination of inhalation. Cumulative excreted amounts of biliary TFAA for 20 hours were 746 nmols in A group (8 hours), 3,421 mnols in B group, 6,582 nmols in C group and 3,267 nmols in D group. Half-lives of biliary excreted TFAA were 63 min, 325 min, 478 min and 546 min, respectively. These results showed that ion-exchange chromatography is more convenient for detecting TFAA as a metabolite of isoflurane than isotachophoresis, gas chromatography, paper chromatography and thin layer chromatography and that TFAA was determined as a biliary metabolite of isoflurane in the rabbit.