where fragmentation is very important in understanding the power of mass spec.So in college, a typical question might be having to piece together a precise structure of something that has a m/e of 84, as the fragmentation will give you the answer without ambiguity.......
Essentially it's to do with the collected data making it impossible to distinguish the actual mass and actual charge. In simple mass specs, however, it is possible to deduce the compound's mass by guessing the most abundant peak is the ion of the molecule with a charge of one. This doesn't always work, so it is correct to write mass over charge. To do otherwise would be to claim a higher degree of accuracy than is actually true.
Mass/charge ratio is given the symbol m/z (or sometimes m/e).
For example, if an ion had a mass of 28 and a charge of 1+, its mass/charge ratio would be 28. An ion with a mass of 56 and a charge of 2+ would also have a mass/charge ratio of 28.
In a mass spectrometer, you are measuring the ions produced.
Most people wind up only looking at the highest m/e to get the molecular weight, since in industry, fragmentation techniques are rarely used. But in education, students spend a lot of time understanding how the molecular ion fragments, to piece together the complete structure.
In industry, chemical ionization is usually used, and it produces few fragments. But in college courses, electron impact is the first focus, where fragmentation is very important in understanding the power of mass spec.
So in college, a typical question might be having to piece together a precise structure of something that has a m/e of 84, as the fragmentation will give you the answer without ambiguity.
