Stability-indicating high-performance liquid chromatographic assay of busulfan in aqueous and plasma samples

A sensitive, specific and stability-indicating high-performance liquid chromatographic (HPLC) assay, involving pre-column derivatization and solid-phase extraction (SPE), was developed and validated for the quantitation of busulfan (BU) in aqueous and plasma samples. The linearity of the assay was in the concentration ranges of 0.15-10 microg/ml and 0.15-3 microg/ml for aqueous and plasma samples, respectively. The within-day and between-day variations were 2.90 and 3.31%, respectively, for the aqueous samples, and 9.24 and 14.56%, respectively, for the plasma samples. The overall recovery, derivatization yield and SPE efficiency of BU from plasma samples were 82.03, 108.01 and 86.69%, respectively. Forced degraded samples, either in highly acidic, neutral or basic medium, produced no interfering peaks in the chromatogram. The reported assay requires only 0.2 ml of plasma for the analysis, and its sensitivity is 150 ng/ml by monitoring samples at a wavelength of 254 nm, sufficient to study the plasma pharmacokinetics of BU in rats after a clinically relevant oral dose. Moreover, the sensitivity of the assay can be significantly increased to 30 ng/ml by monitoring samples at a wavelength of 278 nm. The applications of the assay were demonstrated with BU solubility measurements in two aqueous systems and with plasma samples from a Sprague-Dawley rat for an in vivo pharmacokinetic study. In addition, the assay has been employed in the development of a patented intravenous formulation, and in evaluations of stability, preclinical pharmacokinetics in rats and dogs, and clinical phase I trial of the formulation. The assay is readily adaptable to clinical therapeutic drug monitoring.