ATTOMOLE DETECTION OF PROTEINS BY MATRIX-ASSISTED LASER-DESORPTION IONIZATION MASS-SPECTROMETRY WITH THE USE OF PICOLITRE VIALS

Significant improvements in the absolute detection limits for proteins in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) are demonstrated by the application of so-called picolitre vials. By the reduction of the sample volume from a few muL down to 250 pL and simultaneous reduction of the sample spot area from a few mm2 down to 0.01 mm2, low attomole detection limits are obtained for bradykinin and cytochrome c. The detection limit in a single-shot mass spectrum of bradykinin is estimated to be as low as 250 zeptomol. These are currently the lowest amounts of protein and the smallest volumes analyzed by MALDI-MS.