Bioanalysis without Sample Cleanup or Chromatography: The Evaluation and Initial Implementation of Direct Analysis in Real Time Ionization Mass Spectrometry for the Quantification of Drugs in Biological Matrixes

Two key bottlenecks in pharmaceutical bioanalysis are sample cleanup and chromatographic separations. Although multiple approaches have been developed in the past decade to either shorten or multiplex these steps, they remain the rate limiting steps as ADME (Absorption, Distribution, Metabolism, and Excretion) property screening is being routinely incorporated into the drug discovery process. In this work, a novel system incorporating an automated Direct Analysis in Real Time (DART) ionization source coupled with a triple-quadrupole mass spectrometer has been developed and evaluated for quantitative bioanalysis. This system has the capability of directly analyzing samples from their biological matrixes and therefore potentially eliminating the need for sample cleanup and chromatographic separations. A LEAP Technologies autosampler was customized to perform the automated sample introduction into the DART beam with high precision, which significantly improved the reproducibility of the method. Additional pumping was applied to the atmospheric pressure inlet on the mass spectrometer to compensate for the increased vacuum load because of the use of high-flow helium by the DART. This resulted in an improvement of detection sensitivity by a factor of 10 to 100 times. Matrix effects for a diversified class of compounds were evaluated directly from untreated raw plasma and were found to range from approximately 0.05 to 0.7. Precision and accuracy were also tested for multiple test compounds over a dynamic range of four orders of magnitude. The system has been used to analyze biological samples from both in vivo pharmacokinetic studies and in vitro microsomal/S9 stability studies, and the results generated were similar to those obtained with conventional LC/MS/MS methods. Overall, this new automated DART-triple quadrupole mass spectrometer system has demonstrated significant potential for high-throughput bioanalysis.