Activites (Post-Midterm) Flashcards

1
Q

N is ____ of the compound

independent or dependent?

A

independent

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2
Q

what does N vary with?

A

column dimensions
particle dimensions
mobile phase flow characteristics
etc…

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3
Q

higher N = _____ back pressures

higher/lower?

A

higher

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4
Q

higher N = ____ analytical times

shorter/longer?

A

longer

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5
Q

retention factors ____ influenced by the column dimensions

are/are not

A

are not

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6
Q

separation of components depends on ____ of solvents

A

the appropriate selection

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7
Q

do flow rates affect the separation?

A

they have a small impact

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8
Q

faster flow rates = ____ analytical times and ____ back pressures

shorter/longer?

lower/higher?

A

shorter

higher

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9
Q

higher temperature = ____ k’

incr/decr

A

decr

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10
Q

why are high temperatures not frequently used?

A

may be incompatible with

  1. usage of solvents
  2. stability of the stationary phase
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11
Q

what temperature is best to work at?

A

constant temp above room temp to avoid impact of room temp fluctuations

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12
Q

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

A

b)

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13
Q

decreasing particle size of the LC column stat phase will _____ separation

improve/not improve?

A

improve

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14
Q

decr particle size = ____ column back pressure

incr/decr?

A

increase

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15
Q

what does RMS mean?

A

root mean square

taking the average of multiple peaks

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16
Q

what are 2 main ways to assess the noise?

A

peak-to-peak method

RMS method (Root mean square)

17
Q

what are two functions of mass analyzers?

A
  1. continuously scan all signals over a m/z range

2. monitor specific m/z

18
Q

define liquid-liquid extraction

A

separating compounds based on their solubilities in two immiscible liquids

19
Q

define partition coefficient

A

the ratio of concentrations of a compound in a mixture of two immiscible phases at equilibrium

20
Q

describe how absorbance changes in respect to concentration

A

as absorbance increases, concentration increases

Beer’s law

21
Q

what is the x and y axis on a mass spectrum?

A
y = absorbance
x= m/z
22
Q

what is the order of components in mass spectrometers?

A

inlet
ion source
mass analyzer
detector

23
Q

what is tandem mass spectrometry?

A

has multiple steps of mass spectrometry

fragmentation occurs between the stages

24
Q

in GC, as column temp increases, vapor pressure of the analyte ___ (decr/incr). Thus, analytes elute ____ (faster/slower)

A

increases

faster

25
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
26
in GC, as temp increases, compounds elute ___ (faster/slower) out of the column
faster
27
in GC, as temp increases, how does this affect separation of compounds?
no increase in separation
28
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
29
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
30
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
31
in GC, which has higher separation efficiency? a) capillary columns b) packed columns
capillary
32
in GC, which can accept larger samples? a) packed columns b) capillary columns
packed. capillary can get overloaded by too much sample
33
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