Fast Atom Bombardment of Peptides Above 5000 Daltons
This paper summarizes analyses and investigations made through the last four years in a sector mass spectrometer with a 23 Kg magnet, transmitting ions up to about 3000 Daltons at full accelerating voltage. In order to work with ions above 5000 Daltons the accelerating voltage and often the resolution were lowered. Many of the considerations and much of the protocol we have developed to push this instrument to its limit will be applicable to higher mass magnets as these become available. The Kratos MS-50 used in this work was fitted with a saddle field gun for fast atom bombardment, an 8kV post accelerating detector, and the Kratos DS-55 data system with software written both in house and commercially. This instrument was routinely calibrated to assign masses in real time to about 4500 Daltons. Alternatively, the computer system could be calibrated through 3000 amu anywhere in the mass range up to at least 7500 Daltons for off-line mass assignment. Thus masses above 5000 were assigned either by peak matching or by computer supported off-line comparison to cesium iodide reference spectra.
KeywordsAverage Molecular Weight Fast Atom Bombardment Molecular Weight Determination Peak Match Perfl Uorohexane
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