Anticancer Drug 5-Fluorouracil in Aqueous Solution by Differential Pulse Polarography: An Assessment of Optimum Conditions

The potassium phosphate buffer as a supporting electrolyte of anticancer drug (5-fluorouracil (5-FU)) was the best among solutions of sodium phosphate buffer and Britton Robinson buffer in differential pulse polarography (DPP) at pH = 7.0 and T = 37 ℃. The changes of temperature did not effect on inactivity of the supporting electrolyte (potassium phosphate buffer at T = 10-50 ℃), and pH of the solution did not exceed 2% of each 5 ℃ (at pH = 7.0, by modified thermostat cell). However, the frequency measurements showed clear effect of temperature on diffusion current (IP /μA) of the chemotherapy compound in the range of 20-50 ℃ and under primary conditions. Then, the polarography measurements of 5-FU drug (at 10 μM, pH = 7 and T = 37 ℃) gradually led to the optimum conditions: deposition potential =–0.9 V; drop size = 9.0 mm³; deposition time = 15.0 s; equilibration time = 5.0 s; pulse amplitude = 100 mV; pulse time = 7.0 ms; voltage step = 6 mV; voltage step time = 0.3 s; and sweep rate = 20.0 mV/s. The thermal assessment of 5-FU drug (after achievement of the optimum conditions) in a new thermostat vessel at HMDE by DPP showed that the reaction of 5-FU molecules represented pseudo first order reaction, instead of first order); the secondary waves of 5-FU drug may be due to formation of molecular complexes in aqueous solution and the reduction of 5-FU molecules at mercury surface electrode appeared as physisorption, instead of chemisorption.