Bates CD, Watson DG, Willmott N, Logan H, Goldberg J. The analysis of 5-fluorouracil in human plasma by gas chromatography-negative ion chemical ionization mass spectrometry (GC-NICIMS) with stable isotope dilution.
J Pharm Biomed Anal 1991;
9:19-21. [PMID:
2043717 DOI:
10.1016/0731-7085(91)80231-w]
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Abstract
5-Fluorouracil (5-FU) was extracted from plasma and converted to its di-N-ditrifluoromethylbenzyl (DTFMBz) derivative by treatment with DTFMBzBr. Under negative ion chemical ionization (NICI) conditions the derivative yielded a mass spectrum in which most of the ion current was carried by the M(-)-DTFMBz ion (m/z 355). Selected ion monitoring enabled detection of this derivative in amounts less than 1 pg, and the practical limit of detection for 5-FU extracted from plasma was ca 400 pg ml-1. 5-FU was quantified by adding a fixed amount of [15N2]5-FU to samples of plasma before extraction, and comparing the ratio of the ions of m/z 355 and 357 against a calibration curve constructed over the concentration range under investigation. The method was used to measure the variation in the concentration of 5-FU with time during continuous infusion of the drug via three, different protocols in patients with hepatic tumour.
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