Instrumental Analysis Exam 2026
Questions and Answers
What is nominal molecular mass? - Correct answer-
What is a molecular ion? - Correct answer-a radical ion, formed by loss of one e⁻
after collision with a stream of other e⁻. The molecular ion has the same molecular
mass as the molecule
What is fragmentation? - Correct answer-Relaxation of newly formed excited state
molecular ions by breaking up to produce ions of lower masses.
What is rearrangement? - Correct answer-process that occurs when a fragment still
has a lot of energy and must lose that energy in some way
What ions are attracted through the slit of a mass spectrometer? - Correct answer-
positive ions
What are daughter ions? - Correct answer-the lower-mass ions formed by extensive
fragmentation of the molecular ion during its relaxation following its EI-induced
formation
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,What is a base peak? - Correct answer-The largest peak on a spectrum, which is
arbitrarily assigned a value of 100 This peak corresponds to the most abundant ion
in the sample, presumably formed by breaking the weakest bond in the structure
What is a peak's relative intensity? - Correct answer-a measure of that peak's height
(intensity) as a percentage of the base-peak height
What are collision product peaks? - Correct answer-∙peaks at higher mass numbers
than that of the molecular ion, resulting from ion-molecule collisions
What peak is produced by the protonated molecular ion collision product (transfer
of H atom to the molecular ion)? - Correct answer-∙an enhanced (M+1)⁺ peak
What determines the height of the (M+1)⁺ collision product peak formed by
protonation of the molecular ion? - Correct answer-This transfer is a second-order
reaction, and the amount of product depends strongly on the reactant concentration.
Consequently, the height of this (M + 1)⁺ peak increases much more rapidly with
increases in sample pressure than do the heights of other peaks, make it possible to
detect this atom-transfer reaction
What is a hard ionization source? - Correct answer-ionization sources that impart
enough energy to analyte molecules to leave them in a highly excited energy state.
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, Relaxation then involves rupture of bonds, producing fragment ions that have
mass-to- charge ratios less than that of the molecular ion.
What is a soft ionization source? - Correct answer-∙cause little fragmentation
∙usually produces the molecular ion and only a few, if any, other peaks
What are ionizing agents for MS? - Correct answer-the mechanisms used to ionize
the sample
What are gas-phase sources? - Correct answer-With a gas-phase source, the sample
is first vaporized and then ionized
What are the ionizing agents for the gas-phase sources? - Correct answer-
What is required in order to use gas-phase sources? - Correct answer-∙the sample
must be converted to the gas phase (vaporized) for the ionization process
∙restricted to thermally stable compounds with boiling points less than about 500°C
What are desorption sources? - Correct answer-with desorption sources, solid or
liquid samples are converted directly into gaseous ions
What are the ionizing agents for the desorption sources? - Correct answer-
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Questions and Answers
What is nominal molecular mass? - Correct answer-
What is a molecular ion? - Correct answer-a radical ion, formed by loss of one e⁻
after collision with a stream of other e⁻. The molecular ion has the same molecular
mass as the molecule
What is fragmentation? - Correct answer-Relaxation of newly formed excited state
molecular ions by breaking up to produce ions of lower masses.
What is rearrangement? - Correct answer-process that occurs when a fragment still
has a lot of energy and must lose that energy in some way
What ions are attracted through the slit of a mass spectrometer? - Correct answer-
positive ions
What are daughter ions? - Correct answer-the lower-mass ions formed by extensive
fragmentation of the molecular ion during its relaxation following its EI-induced
formation
©COPYRIGHT 2025, ALL RIGHTS RESERVED 1
,What is a base peak? - Correct answer-The largest peak on a spectrum, which is
arbitrarily assigned a value of 100 This peak corresponds to the most abundant ion
in the sample, presumably formed by breaking the weakest bond in the structure
What is a peak's relative intensity? - Correct answer-a measure of that peak's height
(intensity) as a percentage of the base-peak height
What are collision product peaks? - Correct answer-∙peaks at higher mass numbers
than that of the molecular ion, resulting from ion-molecule collisions
What peak is produced by the protonated molecular ion collision product (transfer
of H atom to the molecular ion)? - Correct answer-∙an enhanced (M+1)⁺ peak
What determines the height of the (M+1)⁺ collision product peak formed by
protonation of the molecular ion? - Correct answer-This transfer is a second-order
reaction, and the amount of product depends strongly on the reactant concentration.
Consequently, the height of this (M + 1)⁺ peak increases much more rapidly with
increases in sample pressure than do the heights of other peaks, make it possible to
detect this atom-transfer reaction
What is a hard ionization source? - Correct answer-ionization sources that impart
enough energy to analyte molecules to leave them in a highly excited energy state.
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, Relaxation then involves rupture of bonds, producing fragment ions that have
mass-to- charge ratios less than that of the molecular ion.
What is a soft ionization source? - Correct answer-∙cause little fragmentation
∙usually produces the molecular ion and only a few, if any, other peaks
What are ionizing agents for MS? - Correct answer-the mechanisms used to ionize
the sample
What are gas-phase sources? - Correct answer-With a gas-phase source, the sample
is first vaporized and then ionized
What are the ionizing agents for the gas-phase sources? - Correct answer-
What is required in order to use gas-phase sources? - Correct answer-∙the sample
must be converted to the gas phase (vaporized) for the ionization process
∙restricted to thermally stable compounds with boiling points less than about 500°C
What are desorption sources? - Correct answer-with desorption sources, solid or
liquid samples are converted directly into gaseous ions
What are the ionizing agents for the desorption sources? - Correct answer-
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