chromatography 1

Question 1

what is the difference between Quality Control/Quality Assurance?

Answer 1

Quality Control –
Checking that the right ingredients are present at the right quantity

Quality Assurance –
Checking that the SOPs are such that the quality of the products can be assured

Question 2

what are Some Questions Pharmaceutical Analysis Methods Can Answer

Answer 2

What is the concentration of a drug in a particular tissue or body fluid?

At what rate is a drug released from its formulation so that it can be absorbed by the body?

Are there any impurities present? What concentration?

What is the stability of the drug in the formulation and hence its “Shelf life”

To identify the purity of a “pure” drug substance before formulation

Is the identity of the drug in the formulated product correct?

What is the percentage of the stated content of a drug present in a formulation?

Question 3

_____________ is one of the most common analytical techniques used in pharmaceutical analysis.

Answer 3

Chromatography

Question 4

what is chromatography?

Answer 4

Chromatography is a process in which a chemical mixture (e.g. a medicine) is carried (by a liquid or gas) around or over a stationary liquid or solid phase. Components of the mixture are separated as a result of differential distribution of the solutes between the carrier phase (mobile phase), and the stationary phase.

Question 5

explain the Stationary Phase?

Answer 5

Stationary Phase: The stationary phase is a solid or liquid material that is either coated onto a thin layer of inert material such as plastic (Thin Layer Chromatography), or packed or coated around the edge of a column (Column Chromatography).

Question 6

explain the Mobile phase?

Answer 6

Mobile phase: The mobile phase, is a gas or a liquid that is allowed to flow over or through the stationary phase carrying the analyte with it.

Question 7

explain the General principles of separation

Answer 7

When the mixture is introduced onto the stationary phase it has the choice of either staying with the stationary phase, or moving with the mobile phase.

Most components will partition between both phases.
The amount of time a component of a mixture spends in each phase is dependant on the differing affinities it has for each phase. This in turn is dependant on its individual physical and chemical properties.

As the mobile phase passes through the stationary phase, the components of the mixture travel at different rates over or through the stationary phase and become separated.

Question 8

what generally makes a compound less polar?

Answer 8

As you increase the ratio of carbon to electronegative atom compounds generally become less polar.

Question 9

what generally makes a compound more polar?

Answer 9

Groups able to hydrogen bond (one of the strongest types of intermolecular bonding possible) e.g. OH, NH2 are very polar.

Question 10

explain Column Chromatography

Answer 10

In column chromatography, the stationary phase is held in a tube (column) and the mobile phase is forced through the column under pressure or by gravity. There are many different types of column chromatography, which differ according to the nature of the mobile phase, and stationary phase.

Question 11

what are the two main types of column chromatography

Answer 11

Liquid Chromatography

Gas chromatography

Question 12

In liquid chromatography, the mobile phase is always a ____________________

Answer 12

liquid.

Question 13

what are the 4 common types of liquid chromatography?

Answer 13

Adsorption chromatography (stationary phase is an adsorbent solid e.g. charcoal, silica).

Partition chromatography (stationary phase is a liquid coated solid, partition occurs)

Ion exchange chromatography (stationary phase has ionic bonded phase)

Gel permeation chromatography (stationary phase is a porous solid)

Question 14

explain Adsorption Chromatography?

Answer 14

Adsorbent solid stationary phases have polar groups on their surface e.g. SiO2, Al2O3.

Molecules are attracted to the surface by dipole, dipole forces, hydrogen bonding, or week van der waals forces. All of these interactions are weak, since in chromatography you must be able to displace the molecules from the adsorbent.

Question 15

explain Partition chromatography

Answer 15

The stationary phase is an inert solid, coated with a liquid e.g. SiO2/H2O.

In normal phase chromatography the stationary phase is polar and the mobile phase is relatively non-polar.

In reverse phase chromatography the stationary phase is non-polar, and the mobile phase is relatively polar.

Separation occurs due to the differences in solubility of the solute between the stationary and mobile phase liquids. The solute is partitioned between the two phases, the amount of time spent in each is dependant on solubility.

Question 16

in Partition chromatography: if the stationary phase is very polar, and the mobile phase is very non-polar, what would happen?

Answer 16

then polar compounds will spend more time on the stationary phase than non-polar ones, and separation according to polarity may occur.

Question 17

explain Ion exchange chromatography

Answer 17

The stationary phase is a coated solid. The coating is a solid resin with ions (cations and anions) covalently bonded to it. Ions of opposite charge are bonded electrostatically (ionically) onto these ions e.g.

When the eluent containing ions is eluted through the column, the electrostatically bound ions are released as others are preferentially bound.

Separation occurs because, the smaller and more highly charged an ion is, the stronger it will be retained in the column, and therefore the longer it will take to elute.

Question 18

explain Gel permeation chromatography (GPC)

Answer 18

This differs from the others in that no equilibrium exists between the solute and the stationary phase. Instead the solute (in solution) passes through a porous gel.
Depending on the pour size, smaller molecules are allowed in the pours and therefore have to travel through the entire volume of the column. Larger molecules are excluded from the pours and therefore have less volume to travel through and elute more quickly. Separation thus occurs according to the size of the solutes.

Question 19

Mobile phase is a liquid, stationary phase is usually a solid.
which chromatography is this?

Answer 19

Liquid Chromatography

Question 20

explain Preparative column chromatography

Answer 20

This involves a column packed with quite large stationary phase molecules (e.g. silica or alumina). The sample mixture is coated onto the top and the eluent is flushed down by the liquid mobile phase, taking the sample witnot for analytical determinations.

Question 21

explain High performance liquid chromatography (HPLC)

Answer 21

High performance liquid chromatography (HPLC) is an extension of liquid column chromatography where particle size is smaller and the eluent is pumped around the column under pressure rather than relying on gravity.