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Pharmaceutical formulation and quality assurance > Chromatography > Flashcards

Chromatography Flashcards

1
Q

What is quality control

A

Checking that the right ingredient is present in the qaunity

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2
Q

What is QA

A

Checking SOP such that the quality of the product can be assured

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3
Q

What is the BP

A

a book that contains info of on the acceptable parameters for the quality of formulated drugs

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4
Q

What is Chromatography

A

It is a process which a chemical mixture is carried around by a liquid or gas over

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4
Q

What is Chromatography

A

It is a process which a chemical mixture is carried around by a liquid or gas over a stationary phase

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5
Q

What is the stationary phase and what is it comprised of

A

A solid or liquid material this is coated onto thin layer if inert material.

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6
Q

What is the mobile phase and what is it comprised of

A

A gas of liquid that is allowed to flow over and through the stationary phase

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7
Q

What is Colum chromatography

A

It is when the stationary phase is held in a tube and the mobile phase is forced through the column under pressure or gravity

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8
Q

What are the two types of column chromatography

A

Liquid

Gas

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9
Q

What are the 4 different types of liquid chromatography

A 
-Absorption: 
       > S phase is an adsorbent solid- charcoal or silica
-Partition
       > S phase is a liquid coated solid 
-Ion exchange
       > S phase has ionic bonded phase 
-Gel permeation 
       > S phase is porous
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10
Q

What is the S phase of Absorption chromatography made of?

A

Made of a polar groups
> SiO2, Al2O3
>Molecules are attracted by Dipole-dipole force, Hydrogen bonding or weak Van der waals forces.

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11
Q

What is the S -phase of partition chromatography made of

A

Made of an inert solid, coated with a liquid SiO/H2O

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12
Q

What is a reverse phase chromatography

A

This when the stationary phase is non-polar and the mobile phase phase is polar

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13
Q

Why does separation occur in partition chromatography

A

Due to the difference in solubility of the solutes

>The solute is partitioned between the two phases, the amount of time spent in each is dependant on solubility.

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14
Q

What is the S phase of ion exchange chromatography

A

coating of solid of resin ions (cations and anions) is covalently bonded to it.

> Ions of opposing charges bind electrostatically to it.

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15
Q

How dose Ion exchange chromatography work

A

When eluent containing ions is eluted through the column, the electrostatically bound ions are released as others are preferentially bound.
>the smaller and more highly charged an ion is, the stronger it will be retained in the column

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16
Q

How do Gel permeation chromatography work

A

-Works without equilibrium between the solutes and stationary phase

-The stationary phase is passed through a porous gel
> Depending on size the molecules will, the larger molecules elute first

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17
Q

Preparative of liquid column chromatography (driven by gravity)

A

This is when the column is packed with large stationary molecules such as Silica or alumina.

Sample mixture is coated unto the top and Eluent is flushed down by the liquid mobile phase

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18
Q

Describe HPLC

A

It is an extension of liquid column chromatography

> particles are Small and passed through column by an eluent pumped under pressure of by gravity

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19
Q

What type of stationary phase can be used in HPLC

A 
It can use all sorts
>Adsorption
>Partitions
> Ion exchange
> gel permeation
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20
Q

What are the options for the HPLC packing material

A
  1. Microspheres
    - Particulate with thin SA
  2. Porous microspheres
  3. Bonded phase: When silica has different groups bonded to it.
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21
Q

Which is the most common material used as packing material in reverse phase chromatography

A

ODS silica

22
Q

Which factors affect retention time

A

The nature of the mobile phase
> More polar phase means more quickly eluted in Silica
> More lipophilic = quicker elution in ODS

23
Q

What are the ideal factors of a detectors for HPLC

A
  • Rapid and reproducible response to solutes
  • A linear response
  • Stability of operation
24
Q

What are the 2 classes of detectors

A

Optical

Electrochemical

25
Q

Name the types of optical detectors and the Advantages vs disadvantages

A
  1. Refractivity index: Monitor difference between a reference stream and the eluent.

> Advantage: it is universal
Disadvantage: It is not very sensitive
-Sensitive to temperature change

  1. UV/VIS
    a) fixed wavelength: A fixed wavelength (at which you expect the solute to absorb) is selected
    >Advantages: Response is linear providing the concentration is not too high
    >Disadvantage: can only use for species that absorb at a set know wavelength in the UV/Vis region. You can’t really analyse unknown samples.
    b)Diode array spectrometer: measures absorbance of the sample coming from the column over all wavelengths simultaneously
    >How it works:
    >Results in a 3D graph
  2. Detects light fluorescing from natural fluorescent solutes (fluoresces in the current wavelength of light )
26
Q

What are the two types of electrochemical detectors

A

Conductivity: Used in ion exchange chromatography.
> Samples are ionic and mobile phase had low conductivity

Redox electrochemical: These detectors are useful for solutes than can be oxidised or reduced.

27
Q

What are the structural factors that effect the rate of elusion in HPLC in neutral compounds?

A

The balance between polarity and lipophilicity

Altering the pH of the mobile phase has no influence on this

28
Q

What are the structural factors that effect the rate of elusion in HPLC in ionisable compounds?

A

pH - Usually in reverse phase where the mobile phase is aqueous
>drugs are ionisable, and the degree of ionisation is dependant on the pH

29
Q

What is liquid chromatography-mass spec (LCMS)

A

It has 2 separate analytical techniques : chromatography and mass spec

30
Q

What is gas chromatography

A

mobile phase; Gas
stationary phase:
>Liquid adsorbed to a solid (GLC)
>organic species bonded to a solid surface

Separation is based on volatility

31
Q

What are the 2 factors that effect the desperation of GLS

A

> The volatility of the component at column temperature

>The polarity (solubility) of the component in the stationary phase

32
Q

What are the 2 different types of GC columns

A

Packed column:

Capillary column: Longer (up to 500m) and thinner
> Require small sample size so has very sharp peaks

33
Q

Types of stationary phases of GC and their properties

A

All based on silica polymers

> Methyl silicate: Non polar separation

> Cyanopropyl phenyl methyl silicate: food for moderate polarity eg Aromatic compounds

> Triflurosilicone: Good for polar separation eg Alcohol

34
Q

Good properties of a GC detectos

A

> Must respond rapidly

>Response must be linear (steep slope)

35
Q

How can the sensitivity of the detector be measured

A
  1. Measure the slope on a detector response versus amount of sample graph
  2. Look at the limit of detection, i.e. the smallest peak one can actually say with confidence is a peak and not just background noise

For a 95% confidence of a peak being an actual component the limit of detection (L.O.D) is equal to the mean background + 2 standard

36
Q

An ideal GC detector is:

A 
Sensitive
Linear response
temp ranges to at least 400 C
Quick response
High reliability 
Does not destroy the sample
Respond similarly to all solutes
37
Q

What is a flame ionisation detector and how does it work?

A

A detector used in GC

The column gas is mixed with air and H2(g) then burnt using a plasma to get to very high temperatures (>3000oC).

compounds are ionised (+ve) and detected by the cathode
Electrons flow to anode

38
Q

Advantages of Flame ionisation detector

A
  • Sensitive
  • Quick response time (<1 millisecond)
  • Peaks are proportional to amount of solute
39
Q

disadvantages of Flame ionisation detector

A
  • Can only detect combustible materials (mainly organic – carbon containing)
  • Destroys the sample
40
Q

What are chromatograms

A

A detector that responds to solute concentration which give different peaks which represent a separated component of mixtures

41
Q

What is retention time

A

The time it takes a solute to reach the detector after injection

42
Q

What determines a good chromatographic separation

A
  • Resolution

- Efficiency

43
Q

What is resolution

A

It is the measure of how well a peak separated and is needed for quantitative calculations.

R= 2(tR2-tR1)/ (wb1+wb2)

wb = with of base of each peak measured

The greater the value of R, the better the resolution of the two compounds

44
Q

What is an alternative calculation for the resolution if the base with is unclear

A

1.18 * (tR2 - tR1)/ wh1+ wh2

45
Q

What are the ways to improve resolution

A

Increase the column length but this affects efficacy

  • Alter mobile and stationary phase
  • Anything that increases efficacy and leads to narrow peaks
46
Q

How is efficacy calculates

A

n= 5.54*(tR)^2/ L x (Wh)^2

Wh = width at half height of the peak

47
Q

What are the factors that affect efficacy in a column

A

The length of the column
> The molecules of a single compound, despite having the same properties, take different lengths of time to travel through a column.

  1. The multiple pathway affect
  2. Non equilibrium mass transfer
  3. Sample size
  4. Diffusion
  5. Time on column
48
Q
  1. The multiple pathway affect
A

Packaging of column is not uniform so solutes can take different pathways and so travel at different speeds

49
Q
  1. Non equilibrium mass transfer
A

Some molecules may travel further into the stationary phase or be too far away for the surface

50
Q
  1. Sample size
A

if you increase the solute concentration too much, the stationary phase may become saturated

51
Q
  1. Diffusion
A

Diffusion occurs mostly in the mobile phase and is grater in gas chromatography, compare to liquid chromatography.

52
Q
  1. Time on column
A

longer a compound is on the column the more opportunity the molecules have had to diffuse

53
Q

Overall factors required for high efficiency (narrow bands)

A 
Small sample size 
Small particle size 
Thin layer of stationary phase 
Optimum mobile phase velocity 
Low dead volume

Pharmaceutical formulation and quality assurance (14 decks)

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