ATTOMOLE-SENSITIVITY ELECTROSPRAY SOURCE FOR LARGE-MOLECULE MASS-SPECTROMETRY

Full mass spectra of high resolving power are obtained from 0.2 nL sam ple volumes of large (>10 kDa) nucleotides and proteins using a new el ectrospray ionization (ESI) system combined with Fourier transform mas s spectrometry. The ESI needles are fabricated by laser-heated pulling of fused-silica tubing (5-20 mu m i.d.), followed by chemical etching and surface metalization. Total analyte loaded at the instrument of 8 .6 fmol and 216 amol produces signal-to-noise ratios of 400:1 and 60:1 , respectively, and resolving power of >10(5) for full mass spectra, w hile the total amount of material consumed is similar to 150 and 10 am ol, respectively.