In comparing the mass spectrum of a laboratory-prepared carbon sample with that of naturally occurring carbon, a chemist observes that the relative intensity of the peak at m/z = 13 is substantially larger in the laboratory sample, while the peak at m/z = 12 is correspondingly smaller. Which statement best describes the isotopic composition of the laboratory sample?
a) The sample is depleted in 13C relative to natural carbon.
b) The sample contains an additional isotope of carbon that is not found in nature.
c) The sample is enriched in 13C relative to natural carbon.
d) The sample’s ions are doubly charged, which alters the observed peak intensities.