HIGH-PERFORMANCE DETECTION OF BIOMOLECULES USING A HIGH MAGNETIC-FIELD ELECTROSPRAY-IONIZATION SOURCE FOURIER-TRANSFORM ION-CYCLOTRON RESONANCE MASS-SPECTROMETER

An improved, high-performance version of the concentric vacuum chamber design is shown for forming ions at high pressure in a strong magneti c field and detecting them in an adjacent Fourier transform ion cyclot ron resonance mass spectrometry (FTICR) trapped ion cell. improvements in system design, including primarily the addition of a mechanical sh utter to halt the flow of neutrals to the trapped ion cell during FTIC R detection, allow a more than 100-fold improvement in pressure drop b etween the source and analyzer chamber to be realized. Within a 20 cm distance, ions formed in an electrospray ion source at atmosphere are transported across five concentric tube conductance limits to a frappe d ion cell at a shuttered pressure below 2x10(-9) Torr. High resolutio n detection of electrosprayed proteins is demonstrated and, for exampl e, mass resolutions of 1x10(5) for the +14 charge state of horse heart myoglobin (at m/z 1211) and 2x10(5) for +5 charge state of bovine ins ulin (at m/z 1147) are obtained. The original advantages of the concen tric tube vacuum chamber are retained. Forming the ions within the mag netic field permits a 40-fold enhancement in sensitivity to be obtaine d. Narrow kinetic energy distributions are achieved because magnetic f ield confinement eliminates the need for complex electric focusing ass emblies that exhibit mass discrimination and broaden the kinetic energ y distribution. Finally, the shutter is demonstrated to serve effectiv ely as an alternative to pulsed valve assemblies for the transient int roduction of a collision gas to the trapped ion cell. (C) 1995 America n Institute of Physics.