High detection sensitivity achieved with cryogenic detectors in combination with matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry.

Cryogenic detectors directly measure the impact energy of any impinging particle independent of its velocity. Thus a very high, mass-independent, detection efficiency is expected from their application in TOF-MS. The cryogenic detector applied here is based on a superconducting phase-transition thermometer and was implemented in a dual reflector time-of-flight mass spectrometer (N-geometry). A dilution series using standard sample preparation procedures shows that the detection limit for insulin (Mr: 5,734) can be decreased by several orders of magnitude, down to 0.5 amol on the MALDI target. Detection limits for rhM-CSF beta (Mr: 49,032) and for polyclonal IgG (Mr: ca 150,000) in the high femtomole and low picomole range, respectively, were established.