Membrane sensors for the selective determination of fluorouracil

The construction and electrochemical response characteristics of poly(vinyl chloride) matrix membrane sensors for fluorouracil are described. The membranes incorporate ion association complexes of fluorouracil anion with bathophenanthroline–nickel(II) [sensor 1], bathophenanthroline–iron(II) [sensor 2] and phenanthroline–iron(II) [sensor 3] as electroactive materials. These sensors show linear response for fluorouracil over the range 1.3–130 μg ml−1, with anionic slopes of 29.0, 27.9 and 34.3 mV per concentration decade with sensors 1, 2 and 3, respectively. These sensors exhibit fast response time (1.0–1.5 min), low determination limit (1×10−5 M), good stability (4–8 weeks) and reasonable selectivity. The sensors were used for direct potentiometry and potentiometric titration of fluorouracil in some pharmaceutical preparations. Results with mean accuracy of 98.6±0.9% of nominal were obtained which compare well with data obtained using the British Pharmacopoeial method. The sensors were also used to follow the stability of the drug in the presence of its degradates, namely formaldehyde, fluoroacetate and urea. In the presence of glycine, these products have no effect on the responses of the sensors.