Comparative effects of surfactants on the behavior of an anticancer drug potentiometric sensor

Surfactants may incorporate drug molecules in a micelle, allowing a great enhancement of a 5-fluorouracil electrode. The performance characteristics of electrodes comprising selected surfactants were investigated as well as the effect of their concentrations. These surfactants were benzalkonium chloride as a cationic surfactant, sodium dodecylsulfate as an anionic surfactant and Tween 20 and Tween 80 as non-ionic surfactants. In solutions of 5-fluorouracil in benzalkonium chloride the sensor showed the best response with a Nernstian slope of 29.5 mV per decade, a wide concentration range from 5.4 x 10(-6) to 1.0 x 10(-2) M, a notably low detection limit of 4.4 x 10(-6) M and a significantly short response time (5 s). The electrode response is independent of the pH of the test solution in the range 3.2-9.5. Selectivity toward the drug ion was calculated for different inorganic cations, amino acids and pharmaceutical amines. Direct potentiometry and potentiometric titration were applied for the determination of 5-fluorouracil in its pure form and as an ampoule formulation and in urine.