Simon J. Prosser

A novel chromatographic method allows on-line reanalysis of the proteome.

Liquid chromatography combined with electrospray ionization is widely used for direct analysis of polar and labile molecules by LCMS. The on-line coupling in LCMS is a major strength but also causes a principal limitation that each eluting analyte has to be analyzed immediately and is not available for detailed interrogation after the LCMS run. Here we developed a new chromatographic strategy, which removes this limitation. After column separation the flow is split, one portion is analyzed directly, and the other is diverted to a capture capillary. After the direct LCMS run, the flow is switched, and the portion stored in the capillary is analyzed (“replay run”). We describe a setup consisting of an analytical column, a splitting valve, and a focusing column, which performs at full sensitivity and undiminished chromatographic resolution. We demonstrate three principal advantages of this system: nearly continuous MS utilization, duplicate analysis without requirement for additional sample, and targeting of important but undersampled features in the replay run.

Integrated microchip-based nanoelectrospray device for high-throughput mass spectrometry

The emerging field of microfluidics may provide for the rapid, automated analysis of samples. Here we describe the microfabrication and operation of a nanoelectrospray device formed from the planar surface of a monolithic silicon substrate for electrospray mass spectrometry sample analysis at low nanoliter per minute flow rates. To generate a useful electrospray from a microchip, a high aspect ratio nozzle structure of small dimensions is required. Deep reactive ion etching technologies allow these high aspect ratio structures to be fabricated in parallel and are widely available for the etching of silicon.