Activites (Post-Midterm)

Question 1

N is ____ of the compound

independent or dependent?

Answer 1

independent

Question 2

what does N vary with?

Answer 2

column dimensions
particle dimensions
mobile phase flow characteristics
etc…

Question 3

higher N = _____ back pressures

higher/lower?

Answer 3

higher

Question 4

higher N = ____ analytical times

shorter/longer?

Answer 4

longer

Question 5

retention factors ____ influenced by the column dimensions

are/are not

Answer 5

are not

Question 6

separation of components depends on ____ of solvents

Answer 6

the appropriate selection

Question 7

do flow rates affect the separation?

Answer 7

they have a small impact

Question 8

faster flow rates = ____ analytical times and ____ back pressures

shorter/longer?

lower/higher?

Answer 8

shorter

higher

Question 9

higher temperature = ____ k’

incr/decr

Answer 9

decr

Question 10

why are high temperatures not frequently used?

Answer 10

may be incompatible with

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

Question 11

what temperature is best to work at?

Answer 11

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

Question 12

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

Answer 12

b)

Question 13

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

improve/not improve?

Answer 13

improve

Question 14

decr particle size = ____ column back pressure

incr/decr?

Answer 14

increase

Question 15

what does RMS mean?

Answer 15

root mean square

taking the average of multiple peaks

Question 16

what are 2 main ways to assess the noise?

Answer 16

peak-to-peak method

RMS method (Root mean square)

Question 17

what are two functions of mass analyzers?

Answer 17

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

2. monitor specific m/z

Question 18

define liquid-liquid extraction

Answer 18

separating compounds based on their solubilities in two immiscible liquids

Question 19

define partition coefficient

Answer 19

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

Question 20

describe how absorbance changes in respect to concentration

Answer 20

as absorbance increases, concentration increases

Beer’s law

Question 21

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

Answer 21

y = absorbance
x= m/z

Question 22

what is the order of components in mass spectrometers?

Answer 22

inlet
ion source
mass analyzer
detector

Question 23

what is tandem mass spectrometry?

Answer 23

has multiple steps of mass spectrometry

fragmentation occurs between the stages

Question 24

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

Answer 24

increases

faster

Question 25

in GC, the order of elution depends only on the boiling point

true/false?

Answer 25

false.

it does depend on the boiling point but also depends on interaction with the stationary phase

Question 26

in GC, as temp increases, compounds elute ___ (faster/slower) out of the column

Answer 26

faster

Question 27

in GC, as temp increases, how does this affect separation of compounds?

Answer 27

no increase in separation

Question 28

in GC, as temp increases, how does theis affect:

a) vapor pressure
b) analyte elution time
c) separation of compounds

Answer 28

vapor pressure of the analyte increases

analyte is eluted faster

separation of compounds doesn’t change

Question 29

in the GC simulator, what happens to ___ in isothermal mode

a) width of peaks
b) time of analysis

Answer 29

width is narrower

time of analysis is longer

Question 30

in GC, when length of column increases, how does N change? how does this affect separation and analytical times?

Answer 30

N (number of theoretical plates) increases

better separation

longer analytical times

Question 31

in GC, which has higher separation efficiency?

a) capillary columns
b) packed columns

Answer 31

capillary

Question 32

in GC, which can accept larger samples?

a) packed columns
b) capillary columns

Answer 32

packed.

capillary can get overloaded by too much sample

Question 33

in GC, compare split vs splitless mode.

which has a larger signal?

Answer 33

splitless: injected sample is all transferred into the column
splitless: only some of injected sample has been transferred

thus, larger signal in splitless mode