Tegafur has been used as an internal standard for the analysis of 5′DFCR (5′deoxyfluorocytidine) and 5′DFUR (5′deoxyfluorouridine) using HPLC techniques
[1]. Tegafur has also been used as an internal standard for the chromatographic assay of azidothymidine (AZT)
[2].