DUAL TIME-OF-FLIGHT MASS SPECTROMETER: HIGH SPEED MS/MS

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We propose to develop a tandem time-of-flight (TOF) mass spectrometer which will have the capability to acquire MS/MS data at very high speed and sensitivity. The proposed instrument is expected to overcome many of the limitations of current MS/MS instrumentation; specifically the lengthy analysis time, the relatively large amount of sample required, and the problems associated with collisionally induced dissociation. The instrument is based on pulsed extraction of continuously formed ions, TOF separation of parent ions, photon fragmentation of selected parent ions, and TOF analysis of the daughter ions produced. The proposed instrument will produce up to one thousand daughter (or normal) spectra every second-about one hundred times more than current "fast" mass spectrometers. This instrument is unique in its highly efficient use of the sample. Time-of-flight instruments are widely known for their high on transmission and efficient extraction of ions from the source. The storage of ions formed between extractions makes very efficient use of a continuous-feed sample, and the ion packets produced have a signal-to-noise ratio that is up to one hundred times greater than the integration of an equivalent current for the same duration. The focusing of both the ions and the laser in the interaction region will lead to a very high fragmentation efficiency. Furthermore, the collection of all the daughter ions from each parent ion packet allows acquisition of daughter spectra with very little decrease in sensitivity over normal MS operation. The prototype instrument will be designed to obtain MS/MS spectra from samples introduced via a capillary gas chromatographic inlet. It will have at least unit mass resolution over a range of 0-1000 u for the daughter ions as well as for the parent ions, though the concept is extendable to much higher mass. Sample amounts required to produce complete MS/MS fragmentation maps should be comparable to or less than those needed for normal MS spectra on conventional gas chromatography/mass spectrometry instruments. These salient characteristics will be achieved by a novel combination of already-proven techniques. The proposed instrument should provide greatly enhanced capabilities in the many areas where MS/MS techniques are currently employed as well as opening up new areas of applications-particularly in high-performance chromatography MS/MS.