separation and chromatography

Question 1

pure substances

Answer 1

have fixed melting and boiling points

Question 2

purification

Answer 2

physical separation of a chemical substance of interest from foreign or contaminating substances

Question 3

why must drugs be pure in pharmacy

Answer 3

impurities could be harmful or cause additional effects
can alter the ability to formulate a drug correctly
can affect stability

Question 4

ways to purify

Answer 4

distillation
filtration
centrifugation
recrystallisation
chromatography

Question 5

what technique can be used for solubility

Answer 5

filtration
centrifugation
recrystallisation
liquid liquid separation

Question 6

Solubility of ionic compounds

Answer 6

More soluble in polar solvents than non polar solvents

Question 7

Solubility of covalent compounds

Answer 7

More soluble in non polar solvents

Question 8

Immiscible

Answer 8

Do not mix
Form separated layers or phases

Question 9

Partially miscible

Answer 9

Not too similar but not too different they may mix at determinate proportions

Question 10

Liquid liquid extractions

Answer 10

Two different molecules in one sample may be separated by giving them the choice between different immiscible solvents

Question 11

Criteria for organic solvent in a liquid liquid extraction

Answer 11

Should readily dissolve substance to be extracted
Should not react with the substance to be extracted
Should not react with or be miscible with water
Should ideally have a low bp so it can be easily removed from the product

Question 12

Partition

Answer 12

The distribution of a solute between two solvents
Compound present in both phases
The solute will distribute itself between the two liquids in accordance with its partition coefficient

Question 13

Partition coefficient

Answer 13

Ratio of the concentration of the solute in one liquid over the concentration in the other
Constant at constant temperature over a limited range of concentrations

Question 14

Partition coefficient equation

Answer 14

Concentration in organic/ concentration in aqueous

Question 15

Hydrophobic/ hydrophilic character measured using partition equation

Answer 15

P= concentration of drug in octanol/ concentration of drug in water

Question 16

High/low P in terms of hydrophobic and hydrophilic

Answer 16

Hydrophobic= high P
Hydrophilic = low P

Question 17

LogP

Answer 17

Measure of hydrophobicity if a drug

Question 18

Chromatography

Answer 18

Physical method of separation in which the components to be separated are distributed between two phases ( one stationary one in a definite direction)

Question 19

Distribution coefficient Kx equation

Answer 19

Kx= C(stationary) / C (mobile)

Question 20

Analyte

Answer 20

Substance to be separated/analysed

Question 21

Eluent

Answer 21

Fluid/ solvent entering the column

Question 22

Eluate

Answer 22

Fluid/ solvent leaving the column

Question 23

Elution

Answer 23

Process of passing liquid through a chromatography column

Question 24

Solid phase extraction

Answer 24

Used in sample preparation (pharmaceuticals, blood urine) to remove matrix interferences such as proteins

Question 25

Active substances for solid phase extraction

Answer 25

Unretained (matrix interferences adsorbed) Retained (matrix interferences washed through)

Question 26

Solid phase extraction vs chromatography

Answer 26

Column much smaller in SPE Specialised column in SPE typically analyses are strongly retained on the SPE column Impurities washed away in SPE

Question 27

Adsorption chromatography

Answer 27

Separation based on difference between the adsorption affinities of the sample analysts for the surface of a solid stationary phase Used for organic molecules

Question 28

Normal phase

Answer 28

More polar compounds more strongly retained More polar solvents increase elution

Question 29

Reverse phase

Answer 29

Less polar compounds more strongly retained Less polar solvents increase elution

Question 30

Exclusion chromatography

Answer 30

Separation based on exclusion effects (differences in size and shape) Small molecules are retained in the pores of the gel Used for proteins and nucleic acids

Question 31

Gel electrophoresis

Answer 31

Specialised example of size exclusion chromatography Separates based on size and charge

Question 32

Ion exchange chromatography

Answer 32

Separation based on differences in ion exchange affinities (differences in charges) Used for cations, anions, proteins, peptides, amino acids, nucleic acids

Question 33

Thin layer chromatography

Answer 33

Analytes move up the plate and are separated according to their Kx

Question 34

Retention factor (Rf)

Answer 34

Distance between the middle of the eluding spot and the baseline

Question 35

Column volumes

Answer 35

1/ Rf

Question 36

flash column chromotograph

Answer 36

gravity so the fastest moving solvent would come out/elute first

Question 37

solvent strength (Eo)

Answer 37

Ability of solvent to elute compounds more quickly from column more polar solvents elute analytes more rapidly

Question 38

instrumental chromatography

Answer 38

high performance liquid chromatography (HPLC) gas liquid chromatography (GC)

Question 39

HPLC

Answer 39

force the analyte through a column of stationary phase by pumping a liquid at high pressure compounds separated in terms of their ability to interact with the stationary phase

Question 40

advantages of HPLC

Answer 40

quantitative precision variety of columns and detector available easily automated no destruction or degradation of sample

Question 41

disadvantages of HLPC

Answer 41

creates large volumes of organic solvent waste drugs analysed must be soluble in the mobile phase needs maintenance

Question 42

Gas chromatography

Answer 42

force the analyte through a column of the stationary phase by the gas at high pressure and high temperatures through a column high volatility/ low molecular weight elutes first

Question 43

advantages of GC

Answer 43

quantitative precision easily automated cheap no mobile parts and low wear and tear low maintenance works with extremely low amounts of sample no solvent waste

Question 44

disadvantages of GC

Answer 44

only good for thermally stable and volatile compounds may require sample derivatisation

Question 45

single point calibration

Answer 45

solution with known concentration (standard solution) find out the relation concentration use the ratio when injecting unknown concentration of the compound

Question 46

internal standard

Answer 46

area under curve of the sample peak and the internal standard peak are compared to give a response factor