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CHY1402 - Analytical methods and applications > Automated chromatography > Flashcards

Automated chromatography Flashcards

1
Q

What does HPLC stand for?

A

High performance liquid chromatography

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2
Q

What is the basic set up of HPLC?

A

One pump transports solvent mix

Manual injection of sample through injector port

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3
Q

Types of HPLC?

A

analytical method

Semi-preparative - collect fractions

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4
Q

What is sophisticated HPLC?

A

Automated and controlled by a PC and specialist software

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5
Q

What does the PC control in sophisticated HPLC?

A

Gradient elution

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6
Q

What are the HPLC columns like?

A

Stainless steel

The stationary phase (normal phase) is made of silica

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7
Q

What are the differences between analytical columns and semi-preparative columns?

A

Semi preparative are larger, have a larger flow rate and have a larger sample size

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8
Q

Can you reuse the HPLC columns?

A

Yes

They are washed after every time

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9
Q

How does the particle size of SiO2 affect the reaction?

A

The smaller the particle, the greater the surface area
If they are smaller there are increased interactions between stationary phase and analyte
There is better separation of the components of the mixture

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10
Q

in HPLC, is the eluent polar or non-polar?

A

Non-polar

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11
Q

How does the price of eluents for HPLC compare to other chromatography methods?

A

They are more expensive

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12
Q

Which type of compounds elute faster in HPLC?

A

Non-polar compounds

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13
Q

What is different in reversed phase HPLC?

A

There is a different stationary phase

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14
Q

What is the particle size like for SiO2 in HPLC?

A

2-10 μm

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15
Q

What is the particle size like for the stationary phase in the reversed phase HPLC?

A

2-8 μm

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16
Q

How is the stationary phase different in the reversed phase HPLC?

A

The silica is modified

It is given a non polar surface with hydrocarbon chains attached

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17
Q

What is the mobile phase like in reversed phase HPLC?

A

Polar

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18
Q

What are some examples of the polar mobile phases used?

A

Methanol

Acetonitrile

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19
Q

What eluent is used in reversed phase HPLC?

A

Water

20
Q

What eluent is used for gradient elution in reversed phase HPLC?

A

Acetonitrile / water

21
Q

Which compounds elute first in reversed phase HPLC?

A

Polar

22
Q

Where is there attraction between in reversed phase HPLC?

A

Attraction between polar solvent and polar molecules and flow quickly through the column

23
Q

What do the non-polar compounds interact with?

A

Hydrocarbon groups and elute slowly through the column

24
Q

What is retention time?

A

Time taken for a compound to travel through the column to the detector

25
Q

Where is retention time measured from?

A

Injection to detection

26
Q

What do different compounds have?

A

Different retention times

27
Q

What does retention time depend on?

A
  • Solvent flow rate
  • Stationary phase
  • composition of the solvent
  • Temperature of the column
28
Q

What do you do to a HPLC chromatogram?

A

Integrate to obtain concentrations of each component

29
Q

What is the detector usually in HPLC?

A

a UV spectrometer

30
Q

In detection, what does the absorption depend on?

A

The amount of compound detected

31
Q

Solvents also absorb light, what do you need to do to do this?

A

Select a suitable wavelength

Background noise set to zero

32
Q

What is the output from the detector in HPLC?

A

A series of peaks
Each represents a compounds
Use values to identify the components of the molecule

33
Q

When would you have to use a modified column instead of a normal HPLC column?

A

To separate mixtures of very polar compounds

To separate enantiomers

34
Q

In gas chromatography, what is the stationary phase?

A

The column

35
Q

In gas chromatography, what is the mobile phase?

A

Inert carrier gas

36
Q

What are the parts of gas chromatography?

A

Injection port
Oven
Detector
Signal processing software

37
Q

Why do you need high temperatures in gas chromatography?

A

Makes sure there is a vapour of the molecule travelling through

38
Q

What is the process of gas chromatography?

A

The sample is introduced and vaporised
Carrier gas transports vapours
Column separates vapour mixture

39
Q

What should the solvent do in gas chromatography?

A

Completely dissolve the sample

40
Q

What should the sample not do in gas chromatography?

A

It shouldnt react with the sample or stationary phase
it should not elute at the same time as the sample
It should not be used in excess

41
Q

What happens when the constant temperature is too low in gas chromatography?

A

All components are separated

Peak diffusion with time

42
Q

What happens when the constant temperature is too high in gas chromatography?

A

Mixture of components co-elute

43
Q

What happens when there is a programmed temperature increase in gas chromatography?

A

Separated signals and they are all sharp and clear

44
Q

What is LC-MS?

A

Liquid chromatography is coupled to mass spectrometry

45
Q

What are the features of LC-MS?

A

Reverse phase HPLC separates components
Eluent is vapourised using a high voltage
Ions are detected for each fraction separately

46
Q

What is the output for LC-MS?

A

HPLC trace and mass spectra

CHY1402 - Analytical methods and applications (14 decks)

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