Normal-Phase Automated Mass-Directed HPLC Purification of a Pyrrolobenzodiazepine Library with Vasopressin Agonist Activity

Preparative two-dimensional liquid chromatography/mass spectrometry for the purification of complex pharmaceutical samples

A new preparative two-dimensional liquid chromatography/mass spectrometry system (2D LC-LC/MS) has been designed and implemented to enhance capability and resolving power for the separation and purification of pharmaceutical samples. The system was constructed by modifications of a conventional preparative LC/MS instrument with the addition of a set of switching valves and a sample loop, as well as interfacing a custom software program with MassLynx. The system integrates two chromatographic separations from the first and second dimensions into a single automated run to perform the purification of a target compound from a complex mixture without intermediate steps of sample preparation. The chromatography in the first dimension, operated in the heart-cutting mode, separates the target compound from the impurities by mass-triggered fractionation based on its molecular weight. This purified fraction from the first dimension is stored in the sample loop, and then gets transferred to the second column by using at-column dilution. A control software program, coined Prep 2D LCMS, was designed to integrate with MassLynx to retrieve data acquisition status. All of the chromatographic hardware components used in this preparative 2D LC-LC/MS system are from the original open access preparative LC/MS system, which has high level of robustness and affords easy and user-friendly operation. The new system is very versatile and capable of collecting multiple fractions with different masses under various purification modes as configured in the methods, such as conventional one-dimensional (1D) purification and/or 2D purification. This new preparative 2D LC-LC/MS system is therefore the ideal tool for medicinal chemistry lab in drug discovery environment.