Quantification of 5-fluorouridine in human urine by capillary gas-liquid chromatography with a nitrogen-selective detector

A method for the quantitative determination of 5-fluorouridine (I) in human urine is presented. The analysis involves the isolation of 5-fluorouridine and the internal standard, 5-chlorouridine (II), on immobilized phenylboronic acid; the extract is further purified by mini-column anion exchange chromatography. The resulting methanolic eluate is evaporated to dryness, the residue is dissolved in dimethyl sulfoxide and permethylated using potassium-t-butoxide and methyl iodide. The permethyl derivatives of the nucleosides are reextracted from the reaction mixture and analyzed by GLC on a glass capillary column coupled to a nitrogen-selective detector. Analytical recovery of 5-fluorouridine added to human urine in the 0--1 microgram/ml concentration range was 68 +/- 6% and a linear detector response was obtained up to 1 microgram/ml. The detection limit was found to be 10 ng/ml, using a 1-ml urine sample.