X. Zhang, D.A. Narcisse, K.K. Murray, On-line single droplet deposition for MALDI mass spectrometry, J. Am. Soc. Mass Spectrom.15 (2004) 1471–1477. doi:10.1016/j.jasms.2004.06.016.
A single droplet generator was coupled with a rotating ball inlet matrix-assisted laser desorption/ionization (MALDI) time of flight (TOF) mass spectrometer. Single droplets with 100 picoliter volume were ejected by a piezoelectric-actuated droplet generator and deposited onto a matrix-coated rotating stainless steel ball at atmospheric pressure. The single droplet deposit was transported to the vacuum side of the instrument where ionization was accomplished using a UV pulsed laser. Using this on-line interface, it was possible to obtain protonated molecule signal from as little as 10 fmol analyte.