Development and validation of a high-throughput method for the quantitative analysis of d-amphetamine in rat blood using liquid chromatography/MS~3 on a hybrid triple quadrupole-linear ion trap mass spectrometer and its application to a pharmacokinetic study

摘要

Amphetamines are a group of sympathomimetic drugs that exhibit strong central nervous system stimulant effects. d-Amphetamine ((+)-alpha-methylphenetylamine) is the parent drug in this class to which all others are structurally related. In drug discovery, d-amphetamine is extensively used either for the exploration of novel mechanisms involving the catecholaminergic system, or for the validation of new behavioural animal models. Due to this extensive use of d-amphetamine in drug research and its interest in toxicologic–forensic investigation, a specific and high-throughput method, with minimal sample preparation, is necessary for routine analysis of d-amphetamine in biological samples. We propose here a sensitive, specific and high-throughput bioanalytical method for the quantitative determination of d-amphetamine in rat blood using MS~3 scan mode on a hybrid triple quadrupole-linear ion trap mass spectrometer (LC–MS/MS/MS). Blood samples, following dilution with water, were prepared by fully automated protein precipitation with acetonitrile containing an internal standard. The chromatographic separation was achieved on a Waters XTerra C18 column (2.1mm×30mm, 3.5μm) using gradient elution at a flow rate of 1.0 mL/min over a 2 min run time. An Applied Biosystems API4000 QTRAPTM mass spectrometer equipped with turbo ion-spray ionization source was operated simultaneously　in MS~3 scan mode for the d-amphetamine and in multiple reaction monitoring (MRM) for the internal standard. The MS/MS/MS ion transition monitored was m/z 136.1→119.1→91.1 for the quantitation of d-amphetamine and for the internal standard (rolipram) the MS/MS ion transition monitored was m/z 276.1→208.2. The linear dynamic range was established over the concentration range 0.5–1000 ng/mL (r2 = 0.9991). The method was rugged and sensitive with a lower limit of quantification (LLOQ) of 0.5 ng/mL. All the validation data, such as accuracy, precision, and inter-day repeatability, were within the required limits. This method was successfully applied to evaluate the pharmacokinetics of d-amphetamine in rat. On a more general extent, this work demonstrated that the selectivity of the fragmentation pathway (MS~3) can be used as alternative approach to significantly improve detection capability in complex situation (e.g., small molecules in complex matrices) rather than increasing time for sample preparation and chromatographic separation.