title: Highly sensitive determination of 5-fluorouracil in human plasma by capillary gas chromatography and negative ion chemical ionization mass spectrometry.
abstract: A sensitive method using gas chromatography and electron-capture negative ion mass spectrometry for the determination of 5-fluorouracil in plasma is described. 5-Chlorouracil was used as internal standard. Sample clean-up consisted of extraction of the 5-halogenated uracil derivatives with 2-propanol--diethyl ether (22:78, v/v) at pH 6, followed by a back-extraction into aqueous buffer at pH 10.5. Pentafluorobenzyl derivatives of 5-fluoro- and 5-chlorouracil were prepared by extractive alkylation with pentafluorobenzyl bromide with dichloromethane as solvent and tetrabutylammonium as counter-ion. The limit of sensitivity employing this technique was 50 fg on-column. Quantitation in human plasma was possible down to 3 X 10(-9) M (0.39 ng/ml). Mass fragmentographic analysis of 5-fluorouracil in plasma of patients after a bolus injection of 500 mg/m2 is presented. Plasma concentrations could be determined for at least 8 h after administration.
mesh_terms: D000478:Alkylation; D001976:Bromouracil / Q000097:blood; D003110:Colonic Neoplasms / Q000097:blood; D005472:Fluorouracil / Q000097:blood*; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D012004:Rectal Neoplasms / Q000097:blood; D013997:Time Factors; D014498:Uracil / Q000031:analogs & derivatives / Q000097:blood
chemical_list: D001976:Bromouracil; D014498:Uracil; C010889:5-chlorouracil; D005472:Fluorouracil