9. Drug Detection and Analysis

Question 1

Gas Chromotography

Answer 1

Used to separate volatile compounds

• Sample injected, where it is vaporized and carried through the column by a carrier/inert gas
• Vapourized sample carried over to the stationary phase
• Components of vaporized sample pass through the column at different rates
• Library of known fragment patterns can be used to compare results

carrier gas is the mobile phase

Question 2

Gas Chromotography (Athletes)

Answer 2

Gas chromatography can be combined with mass spectroscopy (GC-MS) to detect the presence of steroids in urine samples of athletes

Molecular peaks of opioids/steroids

Question 3

Raoult’s Law

Answer 3

it states that the vapour pressure of an ideal solution is directly proportional to the mole fraction of the solvent.

The law applies to ideal solutions, where the components are chemically identical and the interactions between the molecules approach zero.

used to predict boiling points and freezing points of a solution

Question 4

Separating Aspirin for the mixture

Answer 4

• Dissolve compounds in an organic solvent
• Add NaOH(aq)/ OH-(aq) to convert aspirin to soluble salt
• Seperate the two immiscible layers
• Convert salt in aqueous layer back to aspirin by reacting with acid / H+
• Evaporate solvents and dry

cummy

Question 5

Fuel cells electrochemical process

Answer 5

Ethanol will oxidize into ethanoic acid. Electrons are released and current is compared to a reference [2]

Anode :
CH3CH2OH + H2O → CH3COOH + 4H+ + 4e-

Cathode :
O2 + 4H+ + 4e- → H2O

Question 6

Breathalyser

Answer 6

Uses the reaction between ethanol and acidified potassium dichromate(VI). Ethanol is first oxidized to ethanal.

3CH3CH2OH + 2Cr2O72− + 8H+ → 3CH3COOH + 2Cr3+ + 7H2O

Orange dichromate ion / Cr6+/ Cr2O72- is reduced, and converted into green chromium ion / Cr3+

Question 7

Fractional Distillation

Answer 7

Separated by
- Different Molar masses
- Different strengths of intermolecular forces
- Different boiling points

The temperature in the fractionating column decreases upwards. Different components condense at different temperatures, lower boiling points leaves the column first

Question 8

Chemical Shifts and Integration

Answer 8

Chemical Shifts :
Chemical shift is the measure of the magnetic environment of a nucleus in a molecule, particularly in NMR spectroscopy

Integration :
Integration in NMR spectroscopy refers to the area under each signal in an NMR spectrum,

• Corresponds to the number of protons contributing to that signal.
• It provides information about the relative number of protons in different environments within a molecule

Question 9

Solubility of Functional groups

Answer 9

Soluble in Polar solvents
- hydroxyl
- carboxyl

Soluble in non-polar solvents (E.g. Lipids)
- phenyl

The greater the solubility of a solute, the greater the boiling point