Mass spectrometry Knowledge-Based Download PDF

Questions

1. 1.

   According to the nitrogen rule in organic mass spectrometry, what does an odd-numbered nominal molecular ion mass indicate for a stable neutral molecule containing only carbon, hydrogen, oxygen, and nitrogen?

   • A) The molecule contains an even number of nitrogen atoms.
   • B) The molecule contains an odd number of nitrogen atoms.
   • C) The molecule contains an odd number of oxygen atoms.
   • D) The molecule contains an unpaired electron in its intact neutral state.
2. 2.

   In the mass spectrum of a halogenated organic compound, the molecular ion cluster exhibits two distinct peaks separated by two mass units with an intensity ratio of approximately 3:1 ($M : M+2$). Which element is primarily responsible for this characteristic isotopic pattern?

   • A) Iodine
   • B) Fluorine
   • C) Bromine
   • D) Chlorine
3. 3.

   Which ionization method in mass spectrometry is classified as a soft ionization technique that enables the analysis of intact, high-molecular-weight biopolymers by generating multiply charged ions with minimal fragmentation?

   • A) Electron ionization (EI)
   • B) Electrospray ionization (ESI)
   • C) Inductively coupled plasma (ICP) ionization
   • D) Thermal ionization (TI)
4. 4.

   In an electron ionization mass spectrum of a pure organic compound, what does the term base peak specifically designate?

   • A) The signal corresponding to the intact, unfragmented radical cation of the molecule.
   • B) The signal possessing the highest mass-to-charge ratio recorded across the spectrum.
   • C) The signal produced exclusively by the presence of a heavier carbon-13 isotope.
   • D) The signal displaying the greatest relative abundance, arbitrarily set to an intensity of 100%.
5. 5.

   In mass spectrometry, which fundamental property of an ion governs the degree of its deflection when it travels through a constant magnetic field at a fixed accelerating voltage?

   • A) The first ionization energy of the parent neutral molecule
   • B) The overall molecular dipole moment and collision cross-section
   • C) The total number of covalent bonds fragmented during ionization
   • D) The mass-to-charge ratio ($m/z$) of the ion