THE ANALYTICAL PROCEDURE BY FRIT-FAB LC-M S AND DETECTABLE PERIOD OF SUXAMETHONIUM IN RATS TISSUES

The analytical procedure and detectable period of a muscular relaxant, suxamethonium, in postmortem rat tissues were studied. Rats were kill ed by intraperitoneal administration of suxamethonium at doses of 10 m g/kg body weight. The dead rats were stored at room temperature (25 de grees C) and in refrigerator (0 degrees C) until the time of the analy sis. Suxamethonium in the tissues was identified and quantitated using Frit-FAB LC-MS following the solid phase extraction with a Bond Elut CBA cartridge. The rat tissue was homogenized and deproteinized with p erchloric acid. The resulting supernatant was applied to the cartridge . Suxamethonium adsorbed on the cartridge was eluted with 1 ml of 0.1 hr hydrochloride-methanol (1:1, v/v). Hexamethonium solution was added to the eluate as an internal standard. An aliquot (1 mu l) of the elu ate was injected into the Frit-FAB LC-MS system. The LC column used wa s a capillary-type Develosil ODS-UG-5 (0.3 mm i.d. x 150 mm). The grad ient mobile phase system was composed of eluent A (0.1% trifluoroaceti c acid, including 0.4% glycerol) and eluent B (methanol, including 0.4 % glycerol), and the concentration of eluent B increased from 0% to 30 % over 20 min. The flow rate was 5 mu l/min. The mass spectrum of suxa methonium gave the adduct of a molecular ion with trifluor oacetic aci d (m/z 403) as a base peak. The detection limit of suxamethonium in th e tissue by selected ion monitoring (SIM) was 5 ng/g. Suxamethonium in rats stored at 25 degrees C and 0 degrees C after death were found to be detectable for 7 and 42 d in the liver, 7 and 42 d in the kidney, and 2 and 4 d in the heart, respectively.