Mass Spectrometry: Determining Atomic Masses (2.2.1)

Question 1

• Mass spectrometry can be used to determine the molecular mass of a sample.

Answer 1

• Mass spectrometry can be used to determine the molecular mass of a sample.

Question 2

• Mass spectrometry data shows the number of particles detected versus the mass of the particle, with the highest mass being the molecular mass.

Answer 2

• Mass spectrometry data shows the number of particles detected versus the mass of the particle, with the highest mass being the molecular mass.

Question 3

The behavior of a charged particle in a magnetic or
electric field depends on its charge-to-mass ratio.
For example, J. J. Thomson was able to calculate
the charge-to-mass ratio of electrons by observing
their behavior when subjected to magnetic and
electric fields.

Mass spectrometry (MS) uses this concept to
determine the molecular mass of a sample. In mass
spectrometry, an ionized gaseous sample is
accelerated to a known kinetic energy. The
particles of the sample are then deflected in a
magnetic field.

Particles with a higher charge-to-mass ratio (in other
words, lighter particles) are deflected more easily.
Therefore, a lower magnetic field is required to
deflect a lighter particle. The magnetic field
required to deflect a particle into the detector is
proportional to the mass of the particle.

Answer 3

The behavior of a charged particle in a magnetic or
electric field depends on its charge-to-mass ratio.
For example, J. J. Thomson was able to calculate
the charge-to-mass ratio of electrons by observing
their behavior when subjected to magnetic and
electric fields.

Mass spectrometry (MS) uses this concept to
determine the molecular mass of a sample. In mass
spectrometry, an ionized gaseous sample is
accelerated to a known kinetic energy. The
particles of the sample are then deflected in a
magnetic field.

Particles with a higher charge-to-mass ratio (in other
words, lighter particles) are deflected more easily.
Therefore, a lower magnetic field is required to
deflect a lighter particle. The magnetic field
required to deflect a particle into the detector is
proportional to the mass of the particle.

Question 4

Mass spectrometry data shows the number of
particles detected versus the mass of the particle,
with the highest mass being the molecular mass.

For example, for butane (H3CCH2CH2CH3), the
heaviest particle gives a signal corresponding to a
mass of 58 g/mol—the molecular mass of butane.
However, several different masses will also be
detected, each corresponding to a different
fragment of butane. Analysis of these different
masses can yield information about the connectivity
of the molecule. For example, the sequence of a
protein can be determined from the fragmentation
pattern detected in a mass spectrometry spectrum.

Answer 4

Mass spectrometry data shows the number of
particles detected versus the mass of the particle,
with the highest mass being the molecular mass.

For example, for butane (H3CCH2CH2CH3), the
heaviest particle gives a signal corresponding to a
mass of 58 g/mol—the molecular mass of butane.
However, several different masses will also be
detected, each corresponding to a different
fragment of butane. Analysis of these different
masses can yield information about the connectivity
of the molecule. For example, the sequence of a
protein can be determined from the fragmentation
pattern detected in a mass spectrometry spectrum.

Question 5

Mass Spectrometry (MS)

Answer 5

An analytical technique in which atoms or molecules of a sample are ionized and then accelerated through a magnetic field to determine their masses

Question 6

Nucleon

Answer 6

A collective term for proton or neutron

Question 7

Isotopes

Answer 7

Two atoms that have the same number of protons but different numbers of neutrons