INSTRUMENTAL ANALYSIS ACS FINAL
PREP EXAM.
what are the difference between calibration sensitivity and analytical
sensitivity - CorreCt Answers -calibration sensitivity is the slope of a
calibration curve at the concentration of interest while analytical sensitivity
is a response to the noise ratio
what are shims in NMR spectrometer, and what are their purposes -
CorreCt Answers -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 Answers -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 Answers -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 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 Answers -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 Answers -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
b)finite equilibrium time
c)multiple flow paths - CorreCt Answers -a) increase flow rate
b)decrease flow rate
c) no effect
PREP EXAM.
what are the difference between calibration sensitivity and analytical
sensitivity - CorreCt Answers -calibration sensitivity is the slope of a
calibration curve at the concentration of interest while analytical sensitivity
is a response to the noise ratio
what are shims in NMR spectrometer, and what are their purposes -
CorreCt Answers -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 Answers -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 Answers -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 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 Answers -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 Answers -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
b)finite equilibrium time
c)multiple flow paths - CorreCt Answers -a) increase flow rate
b)decrease flow rate
c) no effect
