Activites (Post-Midterm) Flashcards
N is ____ of the compound
independent or dependent?
independent
what does N vary with?
column dimensions
particle dimensions
mobile phase flow characteristics
etc…
higher N = _____ back pressures
higher/lower?
higher
higher N = ____ analytical times
shorter/longer?
longer
retention factors ____ influenced by the column dimensions
are/are not
are not
separation of components depends on ____ of solvents
the appropriate selection
do flow rates affect the separation?
they have a small impact
faster flow rates = ____ analytical times and ____ back pressures
shorter/longer?
lower/higher?
shorter
higher
higher temperature = ____ k’
incr/decr
decr
why are high temperatures not frequently used?
may be incompatible with
- usage of solvents
- stability of the stationary phase
what temperature is best to work at?
constant temp above room temp to avoid impact of room temp fluctuations
the number of theoretical plates of a LC column increases with
a) increasing particle size of the stat phase
b) decr particle size of the stat phase
b)
decreasing particle size of the LC column stat phase will _____ separation
improve/not improve?
improve
decr particle size = ____ column back pressure
incr/decr?
increase
what does RMS mean?
root mean square
taking the average of multiple peaks
what are 2 main ways to assess the noise?
peak-to-peak method
RMS method (Root mean square)
what are two functions of mass analyzers?
- continuously scan all signals over a m/z range
2. monitor specific m/z
define liquid-liquid extraction
separating compounds based on their solubilities in two immiscible liquids
define partition coefficient
the ratio of concentrations of a compound in a mixture of two immiscible phases at equilibrium
describe how absorbance changes in respect to concentration
as absorbance increases, concentration increases
Beer’s law
what is the x and y axis on a mass spectrum?
y = absorbance x= m/z
what is the order of components in mass spectrometers?
inlet
ion source
mass analyzer
detector
what is tandem mass spectrometry?
has multiple steps of mass spectrometry
fragmentation occurs between the stages
in GC, as column temp increases, vapor pressure of the analyte ___ (decr/incr). Thus, analytes elute ____ (faster/slower)
increases
faster
in GC, the order of elution depends only on the boiling point
true/false?
false.
it does depend on the boiling point but also depends on interaction with the stationary phase
in GC, as temp increases, compounds elute ___ (faster/slower) out of the column
faster
in GC, as temp increases, how does this affect separation of compounds?
no increase in separation
in GC, as temp increases, how does theis affect:
a) vapor pressure
b) analyte elution time
c) separation of compounds
vapor pressure of the analyte increases
analyte is eluted faster
separation of compounds doesn’t change
in the GC simulator, what happens to ___ in isothermal mode
a) width of peaks
b) time of analysis
width is narrower
time of analysis is longer
in GC, when length of column increases, how does N change? how does this affect separation and analytical times?
N (number of theoretical plates) increases
better separation
longer analytical times
in GC, which has higher separation efficiency?
a) capillary columns
b) packed columns
capillary
in GC, which can accept larger samples?
a) packed columns
b) capillary columns
packed.
capillary can get overloaded by too much sample
in GC, compare split vs splitless mode.
which has a larger signal?
splitless: injected sample is all transferred into the column
splitless: only some of injected sample has been transferred
thus, larger signal in splitless mode
