Abstract/Summary

High-speed analysis of large (prote)omics sample sets at the rate of thousands or millions of samples per day on a single platform has been a challenge since the beginning of proteomics. For many years, electrospray ionisation (ESI)-based mass spectrometry (MS) methods have dominated proteomics due to their high sensitivity and great depth in analysing complex proteomes. However, despite improvements in speed, ESI-based MS methods are fundamentally limited by their sample introduction, which excludes off-line sample preparation/fractionation due to the time required to switch between individual samples/sample fractions, and therefore being dependent on the speed of on-line sample preparation methods such as liquid chromatography. Laser-based ionisation methods have the advantage of moving from one sample to the next without these limitations, being mainly restricted by the speed of modern sample stages, i.e. 10 ms or less between samples. This speed matches the data acquisition speed of modern high-performing mass spectrometers while the pulse repetition rate of the lasers (>1 kHz) provides a sufficient number of desorption/ionisation events for successful ion signal detection from each sample at the above speed of the sample stages. Other advantages of laser-based ionisation methods include the generally higher tolerance to sample additives and contamination compared to ESI MS, and the contact-less and pulsed nature of the laser used for desorption, reducing the risk of cross-contamination. Furthermore, new developments in matrix-assisted laser desorption/ionisation (MALDI) have expanded its analytical capabilities, now being able to fully exploit high-performing hybrid mass analysers and their strengths in sensitivity and MS/MS analysis by generating an ESI-like stable yield of multiply charged analyte ions. Thus, these new developments and the intrinsically high speed of laser-based methods now provide a good basis for tackling extreme sample analysis speed in the omics.