Chromatography 1 Flashcards
What is Quality control?
Checking that the right ingredients are present at the right quantity
What is Quality Assurance?
Checking that the SOPs are such that the quality of the products can be assured
Define Chromatography?
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.
What is a 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
What is a 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.
State the general principles of Separation
- 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.
State the general principles of Separation
- 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.
If given the choice, a molecule made mainly of carbon and hydrogen is likely to dissolve best in?
A non-polar phase
Polarity is due to ……….
to an uneven distribution of electrons in a molecule
Methanol is relatively less polar than water . True or false?
True
Why is methanol relatively less polar than water?
Methanol (CH3OH) is also considered to be a polar solvent however it is relatively less polar than water. As you increase the ratio of carbon to electronegative atom compounds generally become less polar
OH, NH2 are very polar. true or false?
True
Which of the following solvents is most polar? Dichloromethane Hexane Methanol Ethanol Chloroform (CHCl3
Methanol
Facts about column chromatography
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.
Many different types of column chromatography differ according to ……..
the nature of the mobile phase, and stationary phase.
List the two types of column chromatography
- Liquid Chromatography
2. Gas Chromatography
State the type of mobile phase in liquid chromatography?
Liquid
List the 4 common types of liquid chromatography
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)
Facts about Adsorbent Chromatography
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.
What is the stationary phase in Partitioned Chromatography?
It is an inert solid, coated with a liquid e.g. SiO2/H2O.
What is the stationary phase in a normal phase chromatography?
The STATIONARY phase is POLAR
What is the mobile phase in a normal chromatography phase?
Mobile phase is relatively non-polar
In reverse-phase chromatography, the stationary phase is ……
Non-polar
In reverse phase chromatography, the mobile phase is…..
relatively polar
Separation occurs in a partitioned chromatography due to……..
the differences in solubility of the solute between the stationary and mobile phase liquids
In partitioned chromatography, The solute is partitioned between the two phases, the amount of time spent in each is dependant on solubility. True or false?
True
if the stationary phase is very polar, and the mobile phase is very non-polar, then polar compounds will spend more time on which of the phases?
the polar compounds will spend more time on the stationary phase than non-polar ones, and separation according to polarity may occur.
In normal phase chromatography, what type of bonds are most likely to account for the attraction of an analyte to the stationary phase?
Polar-polar interactions e.g. hydrogen bonding
In reverse phase chromatography, what kind of bonds are most likely to account for the attraction of an analyte to the stationary phase
Van der Waals
What is the stationary phase in an ion-exchange Chromatography?
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. SEE SLIDE 20
State what happens when the eluent containing ions is eluted through the column in an ion-exchange chromatography?
When the eluent-containing ions is eluted through the column, the electrostatically bound ions are released as others are preferentially bound.
Separation occurs in ion-exchange chromatography because of ……
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.
State why Gel Permeation Chromatography differs from others..
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.
State how separation occurs in a Gel Permeation Chromatography?
Separation thus occurs according to the size of the solutes
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.
Mobile phase is a liquid, stationary phase is usually a solid in a liquid chromatography. True or false?
True
Define a preparative column chromatography
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.
What is a High-Performance Liquid Chromatography?
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
