Resolving power of an Orbitrap mass spectrometer can be increased by allowing more time for acquisition. Two closely spaced peaks that are resolved in the lower spectrum overlap in the upper spectrum.

a. Measure the full width at half-height of the broad peak in the upper spectrum and the taller of the two peaks in the lower spectrum. Calculate the resolving power (m/z)/(m/z)1/2(m/z)/(m/z)_1/2. The selected instrument resolving power was 17 500 17 500 for the upper spectrum and 140 000140 000 for the lower spectrum.

b. The tall peak in the lower spectrum has the composition C¹⁵H₂₆NO₃+.C₁₅H₂₆NO⁺₃ The smaller peak has the composition C¹³C₁₃H₂₃N₂O₃+.¹³CC₁₃H₂₃N₂O⁺₃ Calculate the exact mass for each composition and compare them to m/z m/z in the spectrum.

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Lower resolution Higher resolution 268.16 m/z 268.18 268.20