New assay of 5-fluorouracil in serum by isotachophoresis.

Blood levels of 5-fluorouracil are quantitatively determined by isotachophoresis. Serum is deproteinized, purified on an ion-exchange column and concentrated to 20 microliter, and the drug is measured isotachophoretically. Down to 50 pmol (6.5 ng) of the drug can be determined in serum with a methodological error of +/- 6%. The method can be used for routine control of patients undergoing therapy with the drug.