Coaxial continuous-flow fast-atom bombardment vs electrospray ionization: a sensitivity comparison on a magnetic sector instrument.

The performance of an electrospray (ESI) source was evaluated and compared to that of a coaxial continuous-flow fast-atom bombardment source on a magnetic mass spectrometer using ten different peptides over the mass range of 400 to 3500 Da and using a variety of scanning modes. Results show that sensitivities using the two ionization techniques are similar, with limits-of-detection in the attomole to low femtomole range. In addition, proteins can be routinely detected using ESI at femtomole levels. The observance of the noncovalent complex of RNase A and cytidine 2'-monophosphate yields evidence that these complexes can be studied using instruments that operate at high accelerating voltages.