High Performance Liquid Chromato-Graphic Assay For 5-Fluorouracil and 5-Fluorocytosine

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Abstract
A high performance liquid chromatographic assay for separating 5-fluorouracil and 5-fluorocytosine in the presence of potential decomposition products urea, barbituric acid, uracil 6-hydroxycytosine, and cytosine was developed. It was found that ion-pair chromatography using a reversephase C18 column, 0.46 cm i.d. by 15 cm in length, employing gradient elution was satisfactory for separating the various compounds, however, isocratic elution was more appropriate for determining the concentration of the two drugs in the presence of their actual decomposition products. The mobile phase for isocratic elution was 85% aqueous phosphate buffer pH 2.1 and 15% methanol containing 0.0025 M pentane and heptane sulfonic acid sodium salts delivered at 1.0 mllmin. The eluent was monitored at 254 and 285 nm as all compounds do not absorb strongly at a single wavelength. A linear relationship was obtained for the peak height ratio for both 5-fluorouracil and 5-fluorocytosine against 5-methylcytosine, the internal standard over the range 0.125 to 1.000 × − 10−4 M 0