Sample preparation strategies for low-volume determinations inIn vitro studies of proteins by use of MALDI-TOF MS

A flow-through microdispenser, manufactured from micromachined silicon and based on a piezoelectric element, has been used as an interface for high-density target sample deposition in matrix assisted laser-desorption ionization-time-of-flight mass spectrometry (MALDI-TOF). The dispenser has been used for sample preparation in MALDI-TOF MS analysis proteins. Single 110-picoliter sample droplets containing between 200 and 300 attomol proteins can be determined. The sensitivity of analysis of a dilute protein was increased by use of pre-concentration procedure in which the protein solution was dispensed as four sequences each of 200 droplets.