Micro- and Nanotechnologies
Novel sampling strategies and highly miniaturized systems for mass spectrometric analysis
Biochemical analysis needs are frequently addressed using liquid chromatography coupled to mass spectrometry (LCMS) in a centralized laboratory setting. While these systems can be quite versatile to address a broad range of biochemical measurement problems, they are correspondingly complex and require a trained operator to produce results. LCMS instrumentation also typically occupies a large footprint and requires utilities beyond a simple power outlet. Our laboratory has been pursuing miniaturized versions of liquid phase separation systems and mass spectrometers for over two decades. We are combining these two technologies to demonstrate a compact benchtop analyzer that can address measurement needs in areas such as cellular biology, clinical diagnostics, and biopharmaceutical research and development that would normally be accomplished using LCMS.
We have developed microfabricated capillary electrophoresis (microchip CE) devices with monolithically integrated nano-electrospray ionization (ESI) emitters that exceed the performance of conventional CE-ESI implementations. CE separations require ionic analytes, whereas LC can potentially separate either charged or neutral compounds. Biochemical species of interest are predominately ionic and CE systems outperform LC systems for separative performance, while the former can also be implemented more compactly with simpler components, e.g., voltage sources versus high pressure pumps. Microchip CE has been used to separate ions as small as elemental species to intact monoclonal antibodies. One million theoretical plates of separation can be generated in one to a few minutes. Moreover, the microchip CE cartridge is easy to use and does not require any plumbing to connect the ESI emitter.
We have also been involved in the development of a new form of mass spectrometry, HPMS, that can be implemented in a compact form as it operates at pressures several orders of magnitude higher than conventional MS, i.e. approximately 1 Torr. Operating at such pressures allows significant simplification of the vacuum system and the use of a vacuum pump that can rest in the palm of your hand. The mass analyzer in HPMS is a form of ion trap with sub-mm scale critical dimensions. We have theoretically and experimentally demonstrated that HPMS resolution can be increased by decreasing critical dimensions and correspondingly increasing the RF drive frequency.
In this presentation, we will describe microchip CE and HPMS and the coupling of the two technologies to create a compact and useful biochemical analysis tool. The instrument implemented with a 96 well plate autosampler is approximately the size of a tower computer. Example applications such as monitoring bioreactor broth constituents will be presented.