Mass spectrometry identifies organic compounds by which characteristics?

• A. Frequency of peaks and curve width patterns
• B. Position of peaks in time and area under curve(s) on a chromatograph chart
• C. Mass and fragmentation pattern
• D. Mass and area under curve(s) on a chromatograph chart

Answer: (C)

Mass spectrometry identifies organic compounds by their mass-to-charge ratios and the fragmentation pattern produced when the molecule is ionized. When a sample is ionized, it creates a molecular ion and smaller fragment ions; the mass spectrum shows peaks at specific m/z values corresponding to these ions, and the pattern of which fragments appear and their intensities is unique to the structure of the compound. This fragmentation fingerprint lets you identify the substance, often by comparing the spectrum to reference libraries. The amount of compound (quantity) is reflected by the peak intensities, not by identification. Retention time or the area under chromatographic peaks can aid in separating and quantifying components, but they do not by themselves define the compound.