Lesson 4: Liquid Chromatography

Front 1

T/F: Traditional LC has poor system efficiency and large plate heights.

Back 1

T

Front 2

Decrease of column material particle size will ___________ column efficiency. (increase/decrease)

Back 2

increase

Front 3

In HPLC, ___________ is applied to have good system efficiency, small plate height, narrow peak, and shorter separation time.

Back 3

pressure

Front 4

for nonvolatile compounds (HPLC / GC)

Back 4

HPLC

Front 5

For thermally unstable compounds (HPLC / GC)

Back 5

HPLC

Front 6

Applicable to inorganic ions (HPLC / GC)

Back 6

HPLC

Front 7

T/F: GC has UNPARALLELED resolution with capillary columns

Back 7

T

Front 8

T/F: GC is difficult to interface with mass spectrometry

Back 8

F

Front 9

2 requirements for the solvent in mobile phase

Back 9

filtered and degassed

Front 10

microfiltration membrane for organic compounds

Back 10

teflon

Front 11

microfiltration membrane for aqueous

Back 11

cellulose

Front 12

microfiltration membrane for organic and aqueous

Back 12

nylon

Front 13

give atleast 2 out of 4 degassing techniques

Back 13

vacuum pumping

heating & stirring

ultrasonicating

sparging

Front 14

process wherein dissolved gases are swept out of solution by fine bubbles of an inert gas that is not soluble in the mobile phase

Back 14

sparging

Front 15

mode of delivery for single solvent

Back 15

isocratic elution

Front 16

mode of delivery for 2 or more solvents

Back 16

gradient elution

Front 17

which type of elution in solvent delivery has steeper peaks?

Back 17

gradient elution

Front 18

T/F: isocratic elution solvent delivery can be linear (continuous) and stepwise (discontinuous)

Back 18

F - Gradient elution

isocratic elution is only linear (straight horizontal)

Front 19

Mixture of 2 mobile phases is considered isocratic as long as _________________.

Back 19

the composition of the mobile phase stays constant.

Front 20

Another term for gradient elution

Back 20

solvent programming

Front 21

number of pumps in isocratic elution

Back 21

1

Front 22

number of pumps in gradient elution

Back 22

2-4

Front 23

T/F: Mobile phase is programmed to change in composition during elution.

Back 23

T

Front 24

Gradient elution uses 2 or more solvent systems that differ significantly in _____________.

Back 24

polarity

Front 25

T/F: You do not need to re-equilibrate column to original conditions after each run

Back 25

F

Front 26

Supplies the force necessary to move the MP with a constant flow rate; mixes the various mobile phase solvents

Back 26

Pump systems

Front 27

Three pump types

Back 27

Reciprocating/Piston Pump

Syringe Pump

Gradient/Pneumatic Pump

Front 28

T/F: Maintenance is frequent in syringe pump

Back 28

F - not frequent

Front 29

Pump type which uses a motorized syringe to get a constant solvent delivery

Back 29

Syringe pump

Front 30

T/F: Flow rate can be varied by changing the motor speed in syringe pump

Back 30

T

Front 31

t/f: syringe pump is inconvenient when solvents are to be changed

Back 31

t - because it has limited solvent capacity

Front 32

Consist of a small chamber in which the eluent is pumped by the movement of a motor-driven piston

Back 32

Single Piston Pump

Front 33

ensures that eluent is not forced back down the inlet line on compression

Back 33

inlet check valve

Front 34

ensures that eluent is not pulled back into the chamber during suction

Back 34

outlet check valve

Front 35

Which reciprocating pump is better for flow? Twin - parallel or twin - series?

Back 35

Twin - series, because its flow rate can be modified.

Front 36

Pump type that provides pulse free output; inexpensive

Back 36

Gradient pump

Front 37

T/F: Gradient pump is dependent on solvent viscosity and back pressure

Back 37

T

Front 38

gradient pump for high pressure mixing

Back 38

binary pump

Front 39

gradient pump for low pressure mixing

Back 39

quarternary pump

Front 40

introducing a small sample without depressurization; uses syringe

Back 40

Manual injection

Front 41

produces the sample into the high pressure mobile phase flow without an interruption to the flow.

Back 41

sample injection

Front 42

autosampler in automatic injection has two valves namely..?

Back 42

sampling valve (parks sample) and switching valve (rotates as sample is introduced into high pressure system)

Front 43

Used to extend the life of the analytical column by removing particulate matter and contamination that might bind to the stationary phase

Back 43

Guard column

Front 44

Short column (1-2 cm) placed between injection system and analytical column

Back 44

Guard column

Front 45

t/f: guard column have similar packing as analytical column, but longer

Back 45

f - shorter

Front 46

t/f (column heater): Heating a chromatographic column in liquid chromatography can increase retention time and improve resolution

Back 46

F - "decrease" retention time.

Front 47

T/F: PEEK tubing has low resistance to thermal degradation

Back 47

F - highly resistant

Front 48

PEEK tubing stands for

Back 48

poly ether ether ketone

Front 49

analytical column that has high speed and minimum column consumption

Back 49

microcolumn

Front 50

Separation of components of a mixture and collection of isolated components; non-destructive

Back 50

preparative column

Front 51

T/F: Detector selectivity is more important in liquid chromatography than in gas chromatography.

Back 51

T

Front 52

T/F: Detector should have small internal volume to reduce zone broadening

Back 52

T

Front 53

measures property of mobile phase (bulk property)

Back 53

universal detector

Front 54

measures property of solute not present in mobile phase (solute property)

Back 54

selective detector

Front 55

two types in bulk property (universal detector)

Back 55

refractive index

evaporative light scattering

Front 56

five types in solute property (selective detector)

Back 56

UV-Vis absorbance

Electrochemical

Optical rotation detection

fluorescence or chemiluminescence

mass spectrometer

Front 57

Measures the difference in refractive index between column eluent and reference stream of pure solvent

Back 57

refractive index detector

Front 58

T/F: Refractive Index Detector responds to ALL analyte

Back 58

T, as long as its RI is measurably different from the eluent

Front 59

t/f: refractive index detector can't be used in gradient elution

Back 59

t, since gradient elution doesn't use reference

Front 60

Detection is based on the scattering of a beam of light by particles of compound remaining after evaporation of the mobile phase.

Back 60

Evaporative Light Scattering Detector

Front 61

T/F: Evaporative Light Scattering Detector detects all analyte

Back 61

T

Front 62

Used to detect sample components which contain a chromophore that will absorb UV or visible light

Back 62

UV-Vis Absorbance Detector

Front 63

T/F: In UV-Vis Absorbance Detector, eluent should itself be strongly absorbing in the given wavelength

Back 63

F - should "not" itself be strongly absorbing

Front 64

specific type of detector in UV-Vis Absorbance Detector

Back 64

photodiode array (UV-Vis PDA detector)

Front 65

detector for samples with fluorescing species

Back 65

fluorescence detector

Front 66

example of reagent in fluorescence detector

Back 66

dansylchloride

Front 67

T/F: Fluorescence detection is less selective than absorption detection

Back 67

F - more selective

Front 68

detector that is not compatible with gradient elution

Back 68

electrochemical detector

Front 69

electrochemical detection may be based on: (3)

Back 69

amperometry, polarography, coulometry

- used to detect electrochemically active species that are easily oxidized/reduced

Front 70

Generally used for ion chromatography for the detection of ionic compounds

Back 70

conductivity detector

Front 71

detector specific for optically active compounds

Back 71

Optical rotation detector

Front 72

optical rotation detection techniques: (3)

Back 72

polarimetry, optical rotary dispersion (ORD), circular dichroism (CD)

Front 73

Optical Rotation Detection based on the differences in refractive index

Back 73

optical rotary dispersion (ORD)

Front 74

Differentiates enantiomers by measuring differences between the absorption of light and left-handed circulatory polarized light due to existence of a chiral chromophore

Back 74

circular dichroism (CD)

Front 75

Operates by converting the analyte molecules to a charged (ionized) state, with subsequent analysis of the ions and any fragment ions that are produced during the ionization process, on the basis of their mass to charge ratio (m/z)

Back 75

Mass Spectrometry Detector

Front 76

Give atleast three out of five causes of problems in peak shapes

Back 76

Ø Column DeteriorationØ Inappropriate Sample Solvent or Injection Volume (overload)Ø Dead Volume in Flow Lines (irregular flow in mobile phase)Ø Temperature Gradients Within ColumnsØ Inappropriate Detector Response Setting

Front 77

Problems in peak shapes (3)

Back 77

broadening, shoulder peak, peak splitting

Front 78

Parts of Liquid Chrom

Back 78

Solvent Reservoir > pump > injector > column > detector > data recorder