Degradation of busulfan in aqueous solution.

The influence of pH, phosphate buffer components and temperature on the degradation rate of busulfan was studied. The analysis was performed using gas chromatography with electron capture detection and reversed-phase liquid chromatography with radioactivity monitoring. The degradation rate of busulfan showed no pH dependence in the range pH 1.5-11 and increased at higher pH values. The degradation rate constant was 0.034 +/- 0.001 h(-1) (S.E.M.) for the degradation of busulfan in pure water and 0.45 +/- 0.01 h(-1)M(-1) (S.E.M.) for the reaction of busulfan with the hydroxide ion at 37 degrees C. The reactivity of HPO(4)(-2) was six times higher than the reactivity of H(2)PO(4)(-1) towards busulfan. The hydrolysis products were identified as tetrahydrofuran and methanesulphonic acid by nuclear magnetic resonance spectroscopy.