Question

A FT mass spectrometer has a resolution of 1.2 x 10⁶. (a) If the resolution is defined using the distance between neighboring peaks, can it distinguish two ions with m/z of 4825.1450 and 4825.1496? (b) If the resolution is defined using the peak width, can it distinguish two ions with m/z of 697.54120 and 697.54193?

Answer 1

In High resolution mass spectra (HRMS), the if the m/z calculated value and experimental value differ by less than 0.0005 (that is the fourth palce after the decimal point), then it is acceptable.

(a) 4825.1450 and 4825.1496 - have a difference of 0.0046 (much more greater than 0.005), obviously the two peaks can be distingushable.

(b) 697.54120 and 697.54193

upto 4th place of decimal point is (697.5412 and 697.5419), - both the values have a difference of 0.0007 (> 0.0005) and hence can be distinguished.