Determination of 1,2-bis (2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA free acid) in rat plasma, urine and feces by liquid chromatography with UV and tandem mass spectrometric detection

BAPTA free acid was identified as the main metabolic product of 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid tetra(actoxymethyl ester) (BAPTA-AM), a neuroprotective agent in cerebral ischemia, in rats. In this paper, liquid chromatography-ultraviolet (LC-UV) and mass spectrometry/mass spectrometry (LC–MS/MS) methods were employed for the determination of BAPTA free acid in rat urine and feces and rat plasma, respectively. By liquid–liquid extraction and LC-UV analysis, a limit of quantitation of 1000 ng/ml using 0.2 ml rat urine for extraction and 250 ng/ml using 1 ml rat fecal homogenate supernatant for extraction could be reached. The assay was linear in the range of 1000–50,000 ng/ml for rat urine and 250–10,000 ng/ml for rat fecal homogenate supernatant. Because the sensitivity of the LC-UV method was apparently insufficient for evaluating the pharmacokinetic profile of BAPTA in rat plasma, a LC–MS/MS method was subsequently developed for the analysis of BAPTA free acid. By protein precipitation and LC–MS/MS analysis, the limit of quantitation was 5 ng/ml using 0.1 ml rat plasma and the linear range was 5.0–500 ng/ml. Both methods were validated and can be used to support a thorough preclinical pharmacokinetic evaluation of BAPTA-AM liposome injection.