ENHANCED MASS RESOLUTION IN A QUADRUPOLE ION TRAP

The versatility of the quadrupole ion trap as a mass spectrometer in which the mass resolution may be varied over a wide range has been demonstrated. Mass resolutions of 0.8 X 10(7) and 1.2 X 10(7) have been obtained for ions of m/z 414 and m/z 614, respectively, well in excess of the normal value of 3m, where m is the mass of the ion. At the highest mass resolution, peak-widths at half-maximum are but 52 X 10(-6) u. While it has been shown previously that enhanced mass resolution in the quadrupole ion trap can be achieved by reduction of the mass scanning rate, the range of mass resolutions reported here were achieved by reducing the mass scanning rate, in stages, by an overall factor of ca 5.5 X 10(4).