INSTRUMENTAL ANALYSIS ACS Exam 2026|2027 Advanced Practice
Questions and Answers with Complete A+ Solutions 100% Correct!!!
what are shims in NMR spectrometer, and what are their purposes - correct answer -In
NMR,it is critical to have a uniform magnetic field (the more uniform the magnetic field, the
higher probability that all proton spins will have the same Larmor frequency). Shims are
metal coils carrying electric current. This current can be adjusted to modify the magnetic
field
how are ions created in:
a) electron ionization
b)chemical ionization - correct answer -a) a 70 eV electron strikes the compound creating a
M+
b) the compound reacts with a proton donor to make M+
How are ions seperated in a:
a) single quadropole
b) triple quadrupole - correct answer -a) Two pairs of parallel rods make the quadrupole.
Ions are scanned by varying the direct current voltage (Vdc) and radio frequency voltage
(Vrf).Similar tothe ion trap, quadrupoles "trap"ions of a specific mass (only ions with the
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,appropriate mass will be able to travel along the rods). The main differenceis the shape of
the electrodes (rods vs ring for quadrupole vs ion trap)
b)three-quadrupole systemthat results in higher ion selectivity.Within the 2ndquadrupole,
analyte ions are fragmented via collisions with a neutral gas (collision induced dissociation
what is the detection range for:
a)ion trap
b) single quadrupole
c) triple quadrupole
d) TOF - correct answer -a) less than 20,000 g/mol
b)1500 to 3000 g/mol
c) 1500 to 3000 g/mol
d)50000 g/mol
describe how increasing the rod length would affect the ion separation for a quadrupole -
correct answer -increases the resolution. The longer the rod, the more time to allow ions
with a close but not exact target to get off track
if broadening is mainly due to ____, how should flow rate be changed to improve resolution?
a)longitudinal diffusion
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, b)finite equilibrium time
c)multiple flow paths - correct answer -a) increase flow rate
b)decrease flow rate
c) no effect
what are the relative advantages and disadvantages of packed and open tubular columns in
GC - correct answer -packed columns have a high sample capacity. Open tubular columns
have a better separation efficiency (smaller plate height), shorter analysis time and
increased sensitivity
why do open tubular columns provide greater resolution than packed columns in GC -
correct answer -there is no band broadening due to the multiple path (A) term in the van
Deemeter equation
When would you use ___ injection in GC?
a) split
b) splitless
c) on-column - correct answer -a) is good for high concentration samples, scans where you
want high resolution, or if you have a dirty sample
b) good for trace analysis
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Questions and Answers with Complete A+ Solutions 100% Correct!!!
what are shims in NMR spectrometer, and what are their purposes - correct answer -In
NMR,it is critical to have a uniform magnetic field (the more uniform the magnetic field, the
higher probability that all proton spins will have the same Larmor frequency). Shims are
metal coils carrying electric current. This current can be adjusted to modify the magnetic
field
how are ions created in:
a) electron ionization
b)chemical ionization - correct answer -a) a 70 eV electron strikes the compound creating a
M+
b) the compound reacts with a proton donor to make M+
How are ions seperated in a:
a) single quadropole
b) triple quadrupole - correct answer -a) Two pairs of parallel rods make the quadrupole.
Ions are scanned by varying the direct current voltage (Vdc) and radio frequency voltage
(Vrf).Similar tothe ion trap, quadrupoles "trap"ions of a specific mass (only ions with the
1|Page
,appropriate mass will be able to travel along the rods). The main differenceis the shape of
the electrodes (rods vs ring for quadrupole vs ion trap)
b)three-quadrupole systemthat results in higher ion selectivity.Within the 2ndquadrupole,
analyte ions are fragmented via collisions with a neutral gas (collision induced dissociation
what is the detection range for:
a)ion trap
b) single quadrupole
c) triple quadrupole
d) TOF - correct answer -a) less than 20,000 g/mol
b)1500 to 3000 g/mol
c) 1500 to 3000 g/mol
d)50000 g/mol
describe how increasing the rod length would affect the ion separation for a quadrupole -
correct answer -increases the resolution. The longer the rod, the more time to allow ions
with a close but not exact target to get off track
if broadening is mainly due to ____, how should flow rate be changed to improve resolution?
a)longitudinal diffusion
2|Page
, b)finite equilibrium time
c)multiple flow paths - correct answer -a) increase flow rate
b)decrease flow rate
c) no effect
what are the relative advantages and disadvantages of packed and open tubular columns in
GC - correct answer -packed columns have a high sample capacity. Open tubular columns
have a better separation efficiency (smaller plate height), shorter analysis time and
increased sensitivity
why do open tubular columns provide greater resolution than packed columns in GC -
correct answer -there is no band broadening due to the multiple path (A) term in the van
Deemeter equation
When would you use ___ injection in GC?
a) split
b) splitless
c) on-column - correct answer -a) is good for high concentration samples, scans where you
want high resolution, or if you have a dirty sample
b) good for trace analysis
3|Page
