Instrumental Analysis Final Exam questions with
verified answers
Ans✓✓✓
3D Quadrupole Trap Ans✓✓✓ Ions are sent through a slit, then
through an end cap electrode, between two parallel ring electrodes,
then through another end cap electrode, then to the detector; selected
ions should make it through to the detector while others don't make it
through
Absorption (of laser action) Ans✓✓✓ incident light is attenuated as
electrons are promoted to excited state
Absorption and Spin Transitions Ans✓✓✓ For an absorption to occur,
there must be an excess of the molecular population in the lowest
energy state (parallel state) relative to the higher (anti-parallel state)
*Increasing the external magnetic field strength increases the Larmor
frequency for a given nucleus, but also increases the population of the
lower energy state by increasing the energy of the spin transition,
change in E. This leads to an increase in sensitivity
Absorption spectroscopy Ans✓✓✓ absorption of photons by atomic or
molecular species causes promotion from their ground state to one or
,more excited states, measures the amount of light absorbed by the
sample as a function of wavelength, quantizes the transition
Accuracy Ans✓✓✓ Closeness to the correct answer
Adjusted retention time Ans✓✓✓ time required for solute to travel
through a column, beyond time required by solvent
Adsorption Chromatography Ans✓✓✓ -solid stationary phase, liquid or
gas mobile phase
Advantages of fluorescence in chemical analysis Ans✓✓✓ -Two
wavelengths are used in fluorimetry (as opposed to one in absorption
spec) which improves selectivity
-Fluorescence has greater signal to noise ratio because emitted light is
read at right angles to excitation source
-Fluorescence has a greater range of linearity
Affinity Chromatography Ans✓✓✓ -separation carried out using
specific interaction between solute and an immobilized molecule (ex.
protein and antibody to the protein)
Allowed Spin Orientations Ans✓✓✓ 2I + 1 orientations, I = spin
quantum number
,alpha emission Ans✓✓✓ loss of He atom (4/2)
Amplitude Ans✓✓✓ height of a wave
Analog Ans✓✓✓ encoded as a magnitude of an electrical quantity
(voltage, current, charge)
Analog filtering Ans✓✓✓ low pass filters remove high frequency
components of instrument response that may be due to thermal or
shot noise, high pass filters can be used to remove low-frequency
flicker and reduce drift
Analysis of Molecular Mass Spectra Ans✓✓✓ -Identify the molecular/
molecule ion
-odd or even electron ion for electron-impact ionization, protonated or
deprotonated molecule for chemical ionization, electrospray ionization
and MALDI
-Study the isotope distribution patterns of molecular/molecule and
fragment ions
-A, A+1, and A+2 patterns for stable isotopes
-Interpretation of isotope patterns can allow you to count the number
of certain atoms within a molecule
-Determine and interpret fragmentation patterns
-Functional groups tend to display or cause characteristic
fragmentation reactions/patterns in mass spectra
, Applications of X-ray Photoelectron Spectroscopy (XPS) Ans✓✓✓
Qualitative Analysis
-survey scans (low-resolution, wide-range scans of photoelectron
energy) allow determination of what elements are present at the
surface of the sample
-provides information about the top few nanometers of a material
surface
-work well for most of the periodic table (not H or He)
Chemical Shifts and Oxidation State
-when examined under high-resolution conditions, the position of the
photoelectron peak (an XPS chemical shift) is dependent on number of
valence electrons in the atom responsible for the peak
-a change in oxidation state therefore changes the binding energy of
the core level electrons
Chemical Shifts and Structure
-a chemical shift can also occur when valence electrons participate in
chemical bonding, and the degree to which neighboring atoms donate
or withdraw electron density and influence of effective nuclear charge
in the atom responsible for an XPS peak
Approaches for sampling surfaces Ans✓✓✓ - focusing a primary beam
on a single, small area of the surface and observing the secondary
beam (microprobe experiments)
verified answers
Ans✓✓✓
3D Quadrupole Trap Ans✓✓✓ Ions are sent through a slit, then
through an end cap electrode, between two parallel ring electrodes,
then through another end cap electrode, then to the detector; selected
ions should make it through to the detector while others don't make it
through
Absorption (of laser action) Ans✓✓✓ incident light is attenuated as
electrons are promoted to excited state
Absorption and Spin Transitions Ans✓✓✓ For an absorption to occur,
there must be an excess of the molecular population in the lowest
energy state (parallel state) relative to the higher (anti-parallel state)
*Increasing the external magnetic field strength increases the Larmor
frequency for a given nucleus, but also increases the population of the
lower energy state by increasing the energy of the spin transition,
change in E. This leads to an increase in sensitivity
Absorption spectroscopy Ans✓✓✓ absorption of photons by atomic or
molecular species causes promotion from their ground state to one or
,more excited states, measures the amount of light absorbed by the
sample as a function of wavelength, quantizes the transition
Accuracy Ans✓✓✓ Closeness to the correct answer
Adjusted retention time Ans✓✓✓ time required for solute to travel
through a column, beyond time required by solvent
Adsorption Chromatography Ans✓✓✓ -solid stationary phase, liquid or
gas mobile phase
Advantages of fluorescence in chemical analysis Ans✓✓✓ -Two
wavelengths are used in fluorimetry (as opposed to one in absorption
spec) which improves selectivity
-Fluorescence has greater signal to noise ratio because emitted light is
read at right angles to excitation source
-Fluorescence has a greater range of linearity
Affinity Chromatography Ans✓✓✓ -separation carried out using
specific interaction between solute and an immobilized molecule (ex.
protein and antibody to the protein)
Allowed Spin Orientations Ans✓✓✓ 2I + 1 orientations, I = spin
quantum number
,alpha emission Ans✓✓✓ loss of He atom (4/2)
Amplitude Ans✓✓✓ height of a wave
Analog Ans✓✓✓ encoded as a magnitude of an electrical quantity
(voltage, current, charge)
Analog filtering Ans✓✓✓ low pass filters remove high frequency
components of instrument response that may be due to thermal or
shot noise, high pass filters can be used to remove low-frequency
flicker and reduce drift
Analysis of Molecular Mass Spectra Ans✓✓✓ -Identify the molecular/
molecule ion
-odd or even electron ion for electron-impact ionization, protonated or
deprotonated molecule for chemical ionization, electrospray ionization
and MALDI
-Study the isotope distribution patterns of molecular/molecule and
fragment ions
-A, A+1, and A+2 patterns for stable isotopes
-Interpretation of isotope patterns can allow you to count the number
of certain atoms within a molecule
-Determine and interpret fragmentation patterns
-Functional groups tend to display or cause characteristic
fragmentation reactions/patterns in mass spectra
, Applications of X-ray Photoelectron Spectroscopy (XPS) Ans✓✓✓
Qualitative Analysis
-survey scans (low-resolution, wide-range scans of photoelectron
energy) allow determination of what elements are present at the
surface of the sample
-provides information about the top few nanometers of a material
surface
-work well for most of the periodic table (not H or He)
Chemical Shifts and Oxidation State
-when examined under high-resolution conditions, the position of the
photoelectron peak (an XPS chemical shift) is dependent on number of
valence electrons in the atom responsible for the peak
-a change in oxidation state therefore changes the binding energy of
the core level electrons
Chemical Shifts and Structure
-a chemical shift can also occur when valence electrons participate in
chemical bonding, and the degree to which neighboring atoms donate
or withdraw electron density and influence of effective nuclear charge
in the atom responsible for an XPS peak
Approaches for sampling surfaces Ans✓✓✓ - focusing a primary beam
on a single, small area of the surface and observing the secondary
beam (microprobe experiments)
