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Abstract

Intact, nonvolatile, biological macromolecules can be transferred directly from the solid state into the gas phase, in ambient air, for subsequent mass spectral analysis using non-resonant femtosecond (fs) laser desorption combined with electrospray ionization (ESI). Mass spectral measurements for neat samples, including a dipeptide, protoporphyrin IX and vitamin B12 adsorbed on a glass insulating surface, were obtained using an 800 nm, 70 fs laser with an intensity of 1013 W cm−2. No appreciable signal was detected when atmospheric matrix-assisted or neat (matrix-free) fs laser desorption was performed without ESI, indicating neutral desorption. Copyright © 2009 John Wiley & Sons, Ltd.