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PM2A: Molecules and medicines > Pharmaceutical Analysis > Flashcards

Pharmaceutical Analysis Flashcards

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Organic Chemistry 101 flashcards
1
Q

What are the 3 classic separation methods?

A
  1. Electrophoresis
  2. Chromatography
  3. Membrane Separation
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2
Q

What is chromatography?

A

When components of a mixture are separated based on differences in the rate at which they are carried through a stationary phase by a gaseous or liquid mobile phase

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3
Q

What is the stationary phase?

A

Fixed in a place either in a column or on a planar surface

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4
Q

What is the mobile phase?

A

Moves over or through the stationary phase, carrying with it the analyte mixture

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5
Q

What are the 4 different examples of chromatography?

A
  1. Thin Layer Chromatography
  2. Column Chromatography
  3. High Pressure Liquid Chromatography
  4. Gas Chromatography
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6
Q

How is chromatography used to separate?

A
  1. Mobile or stationary phase
  2. Both have two different compounds, two different sets of functional groups
  3. One will interact with it in a different way from the other with the stationary phase
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7
Q

What is elution? And what does it mean when it runs quicker down through the column?

A
  1. The process of washing samples components through the stationary phase by continuous flow of the mobile phase
  2. Less interaction with solvent
  3. When component A or B gets to the detector, it makes a reading so we can see a graph
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8
Q

What is a chromatogram?

A
  1. A peak that appears when the saturated component reaches the detector at the end of a column
  2. Components are then identified by unique retention time under a certain set of separation conditions
  3. Factors such as tR (retention time) include:
    - velocity (flow rate) of mobile phase
    - chromatographic retention
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9
Q

What does retention time normally depend on?

A
  1. Amount of time the component spends in the stationary or mobile phase
  2. More time in mobile means it passes through faster so the partition co-efficient is smaller
  3. More time in stationary phase then partition co-efficient is larger
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10
Q

What is the aim of resolution and where is it found?

A
  1. Found in the chromatograph

2. It’s aim is how well it can separate two peaks

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11
Q

What is baseline resolution?

A

When the detector goes to zero between the two peaks which is good resolution as you can clearly distinguish between the peaks after

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12
Q

What is column efficiency?

A

The plate height that are relative to the retention time and affect the band broadening

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13
Q

What is longitudinal diffusion?

A
  1. When it runs down the column and doesn’t stay in one tight band, it longitudinally diffuses to separate into a broad band
  2. The faster we run the column, the less our longitudinal diffusion, so it remains a tight band.
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14
Q

What is resistance to mass transfer?

A
  1. When the band broadens due to the resistance to diffusion of the molecule in the mobile and stationary phase
  2. DependIrs on diffusion co-efficient of compound in each phase, diameter and shape of stationary phase
  3. It’s parabolic flow profile: pressure driven flow
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15
Q

What is Eddy diffusion?

A
  1. When the mobile phase moves through the column which is packed with stationary phase
  2. The more the column is packed- the lower eddy diffusion
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16
Q

How do the parameters following increase or decrease column efficiency?

  1. Low flow rate
  2. Large particle size of stationary
  3. Irregularly shaped stationary phase
  4. Very fast flow rate
A
  1. Low flow rate- broadens peak due to longitudinal diffusion
  2. Large particle size of stationary phase- Increases eddy diffusion and mass transfer scales with particle size, this leads to peak broadening and decreases column efficiency
  3. Irregularly shaped stationary phase- Eddy diffusion decreases with increasing particle size and packing uniformity- irregular shaped will increase peak broadening- impacts on diffusion due to mass transfer
  4. Very fast flow rate- peak broadening due to resistance to mass transfer- diffusion in stationary phase
17
Q

What does having a more efficient column mean?

A

Narrower peaks and better resolution

18
Q

What does HPLC (high performance liquid chromatography) consist of?

A

Normal Phase:

  1. Polar stationary phase, non polar mobile phase
  2. Molecules elute in order of increasing polarity

Reverse Phase

  1. Non-polar stationary phase, polar mobile phase
  2. Molecules elute in order of decreasing polarity (most polar comes out first and least polar comes out last
  3. About 80% HPLC separations
19
Q

Describe the normal phase in HPLC?

A

Consists of:
Stationary phase: Silica Gel with polar groups that are absorbed and retained

Mobile phase: hexane, dicloromethane, isopropanol, methanol (more polar mobile phase will elute compound more quickly)

20
Q

What is elution?

A

The process of extracting one material from another by washing with a solvent

21
Q

Describe the Reverse phase in HPLC?

A

Consists of:
Stationary phase: Octadecylsilane coated (ODS) Silica gel lipid groups adsorbed and retained

Mobile phase: Water, methanol, acetonitrile, tetrahydrofuran (the more lipophilic the mobile phase the faster elution of organic compounds)

Increasing in strength means increase in polarity

22
Q

What do you have to consider when it comes to elution of neutral components?

A

Balance between polarity and lipophilicity of compound: H-bonding capacity
Example: Rapid elution of prednisoline and betamethasone
- Much longer elution of esters

23
Q

What can you change for elution of ionisable compounds?

A
  1. Altering pH of the mobile phase can control solvent strength
  2. Works for weak electrolytes where solubility can be altered at working pH values in region of pKa
24
Q

What are the two main types of HPLC detectors?

A
  1. One is responsive to physical and chemical properties of sample components- known as UV and fluorescence detectors
  2. Responsive to changes in properties of the mobile phase- known as refractive index detector
    - non-specific and not as sensitive
    - only used when other detectors like sugars cannot be used
25
Q

What are the four types of HPLC detectors?

A
  1. UV absorption detector (most popular)
    - fixed wavelength, variable wavelength with photo diode array
    - mobile phase must not absorb UV
  2. Fluorescence detector- selective and sensitive
  3. Refractive index detector
    - Universal
    - based on RI difference between solvent and solute
    - Moderately sensitive
    - very temperature sensitive
  4. Mass Spectrometer
    - structural information
26
Q

What is HPLC-MS?

A
  1. An industry standard technique for the identification of chemicals in mixtures
  2. Very high sensitivity and specificity

PM2A: Molecules and medicines (22 decks)

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