MC test: Drug detection & analysis

Multiple choice test on D.9 Drug detection & analysis

Use the following 'quiz' to test your knowledge and understanding of this sub-topic. As this relates to a sub-topic on the options you may need access to the IB data booklet.

If you get an answer wrong, read through the explanation carefully to learn from your mistakes.

Which drugs will give a strong broad peak between 3200 and 3600 cm−1 in their infrared spectrum?

The broad peak between 3200 and 3600 cm−1 is due to the O−H vibration and heroin does not contain an O−H bond. (Primary amines also absorb between 3300 and 3500  cm−1 but all three of these opiates possess a tertiary (not primary) amine which does not contain a N−H bond).

 

Which techniques are used to identify the possible presence of illicit anabolic steroids in a sample of an athlete's urine?

I. GC-MS

II. TLC-MS

III. LC-MS

Gas-liquid chromatography and high performance liquid chromatography can both be directly linked to a mass spectrometer (GC-MS and LC-MS) so that once the components have been separated by chromatography they can be passed directly into the mass spectrometer and the components identified. Thin layer chromatography (TLC) cannot be directly linked to a mass spectrometer.

 

3,4-methylenedioxy-N-methylamphetamine is a recreational drug commonly known as MDMA or ecstasy.

How many signals will be present in the 1H NMR spectrum of ecstasy? (Ignore the signal due to TMS and assume the phenyl protons  give just one signal).

In total there are 15 protons in a molecule of ecstasy in seven different chemical environments.

 

When a motorist blows into a simple breathalyser bag the crystals will turn green if the motorist's alcohol concentration is over the legal limit. What causes the crystals to turn green?

The acidified orange crystals of dichromate(VI), Cr2O72−, are reduced by the alcohol to form green Cr3+.

 

Amphetamine and methamphetamine ('speed') are two stimulant drugs.

Which are correct statements about amphetamine and methamphetamine?

I. The molecular ion peak in the mass spectrum of amphetamine will have an m/z value 14 units lower than that of methamphetamine.

II. A mixture of the two drugs can be separated into its individual components by high performance liquid chromatography (HPLC).

III. There will be one extra signal in the 1H NMR spectrum of methamphetamine compared to the 1H NMR spectrum of amphetamine.

The molar mass of methamphetamine, C10H15N, is 14 g mol−1 higher than that of amphetamine, C9H13N. Both can be separated from a mixture by either gas-liquid chromatography or high performance liquid chromatography. Methamphetamine will have one extra signal in its 1H NMR spectrum due to the extra methyl group.

 

The vapour pressures of propan-1-ol and ethanol are 13.3 and 29.3 kPa respectively at 50 oC. What will be the vapour pressure of the resulting solution at 50 oC  when 1.0 mol of propan-1-ol and 0.5 mol of ethanol are mixed? Assume the mixture behaves like an ideal solution, i.e. it obeys Raoult's law.

Mole fraction of propan-1-ol = 1.0 ÷ 1.5 = 2/3, mole fraction of ethanol = 0.5 ÷ 1.5 = 1/3.
P(propan-1-ol) = 2/3 x 13.3 = 8.87 kPa; P(ethanol) = 1/3 x 29.3 = 9.77 kPa
P(total) = 8.87 + 9.77 = 18.6 kPa

 

Many pure drugs are solids at room temperature. In order to obtain their 1H NMR spectra they are often made into a solution by dissolving in deuterated trichloromethane, CDCl3. Which statement explains why deuterated trichloromethane, CDCl3 rather than normal trichloromethane, CHCl3 is used as the solvent. 

Because CDCl3 contains no protons it does not give any signals in an 1H NMR spectrum so all the signals can be attributed to the protons in the drug.

 

Which gases may be used as the mobile phase in gas-liquid chromatography?

I. oxygen

II. nitrogen

III. helium

 

The mobile phase used to carry the sample through the column must be an inert gas. Oxygen might react either with the sample or with the material used to make the stationary phase.

 

Which will change the Rf value of a component during thin layer chromatography?

The Rf value depends upon how the component distributes itself between the mobile and stationary phases. Altering the polarity of the mobile phase will affect this distribution.

 

An analysis of a urine sample from a patient was undertaken. Which observations support the fact that paracetamol (acetaminophen) was present in the urine sample.

I.   The 1H NMR spectrum of one of the components showed four signals with an integration trace ratio of 1:1:4:1.

II.  The infrared spectrum of one of the components showed a broad absorption between 3200 - 3600 cm−1.

III. The 1H NMR spectrum of one of the components showed three singlets together with one more complex signal.

The absorption at 3200 - 3600 cm−1 shows the presence of an -OH group. Paracetamol will have three singlets and one more complex signal but the integration trace for these four signals will be 1:1:4:3.

 

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