[Bidagdha_TADIR]

From "introduction to spectroscopy" by Donald L. Pavia I understand is that a magnetic sector MS should be able to separate C₂H₄^+. ion (m=28.0313) and CO^+. ion because a resolution of 770 is enough (from the equation of resolution).

But I thought magnetic sector MS were LRMS which can only determine nominal mass. So is it that magnetic sector MS can measure accurate mass for these two ions but not bigger ions (like 2-octanone and napthalene which require resolution of 2230 for separation)?

[MOTOBALL]

From memory, a double-focusing (magnetic & electrostatic sector) mass spectrometer should routinely give 5,000-10,000 resolution; fine-tuning could give up to possibly 25,000.

Accurate mass measurements are possible at much higher mass than 2-octanone/naphthalene, but above about m/z 500 there are so many possible elemental compositions (which is why you measure an accurate mass) that acc. mass is not as helpful as you might think.