A rapid analytical method developed for the analysis of β-lapachone in in vitro samples could not be directly applied to the analysis of clinical samples because of interference from unknown substances. Here, we developed and validated a rapid interference-free analytical method to accurately determine β-lapachone levels in human plasma using liquid chromatography-tandem mass spectrometry. First, we achieved the baseline-separation of β-lapachone from any interfering substances within a total run time of 4 min by adjusting the eluent strength of the mobile phase. Second, precursor-ion scanning revealed the identity of the interfering substances. Sulfonate- or glucuronide-conjugated metabolites were converted to β-lapachone in an electrospray ion source, causing interference. In a method validation study, calibration curves for β-lapachone in human plasma were linear over a concentration range from 0.5 to 200 ng/mL (r > 0.999), and the lower limit of quantification was 0.5 ng/mL. The other validation parameters, including intra- and interday accuracy and precision, were acceptable with a coefficient of variation less than 10% (n = 5). The validated analytical method was successfully applied to a pharmacokinetic study of a single, oral dose of 100 mg MB12066 (a clinical form of β-lapachone) in healthy volunteers.
Keywords: Interference; LC-MS/MS; MB12066; pharmacokinetic study; β-lapachone.