Forensic Toxicology and Chemical Analysis Questions and Answers

Answer: B

The correct matching is (i)-(d), (ii)-(c), (iii)-(b), (iv)-(a).

• Gibbs reagent is 2,6-dichloroquinone-4-chloroimide, used for phenols (d).
• Van Urk reagent is p-dimethylaminobenzaldehyde in acid, used for LSD and ergot alkaloids (c).
• The Duquenois(-Levine) test for cannabis uses vanillin with acetaldehyde in ethanol (b).
• Mandelin's reagent is ammonium vanadate in sulphuric acid, a general colour test for alkaloids and amphetamines (a).

The other codes misassign at least two reagents, for example giving vanillin to Mandelin's or ammonium vanadate to Van Urk.

Answer: A

Potassium ferricyanide is used to detect creatinine in urine.

Hexacyanoferrate(III), that is potassium ferricyanide, is a recognised reagent for measuring creatinine in urine and blood, and a published patent names it as the preferred creatinine reagent because urea, protein and sugar interfere with it less than with older methods. Creatinine is a normal urinary constituent, which is why it is tested for in urine.

No ferricyanide test was found for the other options: ammonia and urea are detected by other reagents, and THG, tetrahydrogestrinone, is a designer anabolic steroid identified by chromatography and mass spectrometry. The full chemistry of the particular test the paper means could not be confirmed, so the answer rests on this use of the reagent and on the key.

Answer: C

Bluish-green vomit is typical of acute copper sulphate poisoning.

Copper sulphate (blue vitriol) is an irritant that causes violent vomiting, and the vomit is coloured blue or green by the copper salt. Other features are a metallic taste, burning pain, haemolysis, jaundice and renal failure.

Barium carbonate causes vomiting, hypokalaemia and muscle paralysis without a blue colour. Arsenic trioxide gives rice-water stools and vomiting that is not blue-green, and nickel sulphide is not a recognised cause of coloured vomit.

Answer: C

The statement not related to intravenous dosage is Is administered by non-invasive mechanism.

An intravenous injection pierces the skin and a vein, so it is invasive by definition. Non-invasive routes are those such as oral, topical or inhalational administration.

The other statements are true of the intravenous route. The whole dose enters the systemic circulation, so bioavailability is 100%. The peak plasma concentration is reached almost at once, without an absorption phase. And the drug must be given as a stable solution, since particles or a precipitating preparation could cause emboli.

Answer: D

The correct match is a-v, b-iii, c-i, d-iv.

• Opium contains the alkaloid codeine (v), along with morphine and others.
• Cannabis owes its activity to THC, tetrahydrocannabinol (iii).
• 6 MAM, 6-monoacetylmorphine, is the specific metabolite of heroin (i) and proves heroin use rather than morphine or codeine.
• Nux vomica seeds contain strychnine (iv).

Caffeine is the extra item and belongs to none of them. Options that pair opium with heroin put the semi-synthetic heroin in place of the natural alkaloid, and then must give 6 MAM another partner, which fails.

Answer: B

Industrial cannabis (hemp) has low THC and high cannabidiol content.

Industrial hemp varieties are grown for fibre and seed and are bred to have very little of the psychoactive THC, legally under 0.3% (or 0.2% in many countries) of dry weight. Their cannabinoid content is dominated instead by the non-intoxicating cannabidiol (CBD, printed 'canabidial').

Drug-type cannabis is the reverse, with high THC and usually low CBD, which is what the 'high' and 'very high' THC options describe.

Answer: A

The correct match is a-iv, b-iii, c-ii, d-i.

• Cannabis: the Duquenois-Levine test, a purple colour that passes into a chloroform layer.
• Morphine: the Marquis test (formaldehyde in sulphuric acid), a purple-violet colour with opiates.
• Carbon monoxide: Hoppe-Seyler's test, in which blood with carboxyhaemoglobin stays cherry red when sodium hydroxide is added, while normal blood turns brownish.
• Ethyl alcohol: the Kozelka and Hine test, a dichromate oxidation method for alcohol in blood.

Every other option assigns at least one of these classic tests to the wrong substance.

Answer: B

The ultra short acting barbiturate is Pentothal sodium (thiopentone).

Thiopentone sodium is very lipid soluble. Given intravenously it reaches the brain in seconds and induces anaesthesia, and its effect ends within minutes because it is redistributed from the brain to muscle and fat. It has been used as an anaesthetic induction agent and, in some investigations, as a so-called truth serum.

Pentobarbital and amobarbital are short to intermediate acting, used as sedative-hypnotics. Phenobarbitone is long acting and is used as an anticonvulsant.

Answer: D

The one that is not a stupefying agent is oleander.

Oleander (yellow and white) is a cardiac poison. Its glycosides, such as thevetin and nerin, act on the heart like digitalis, causing vomiting, bradycardia, heart block and arrhythmias. It is used for suicide and homicide, not to stupefy a victim.

Stupefying agents are given to make a victim drowsy, confused or unconscious so that a crime such as robbery or rape can be committed. Dhatura (the classic 'road poison' of highway robbers), cannabis and chloral hydrate (the 'knock-out drops' of the Mickey Finn) are standard examples.

Answer: A

Phosphine is liberated from aluminium phosphide.

Aluminium phosphide, sold as grain-fumigant tablets (celphos), reacts with water and the hydrochloric acid of the stomach to release phosphine gas:

\[ \begin{aligned} &\text{AlP} + 3\,\text{H}_{2}\text{O} \\ &\rightarrow \text{Al(OH)}_{3} + \text{PH}_{3} \end{aligned} \]

Phosphine blocks cellular respiration and causes shock and cardiac failure; the breath and gastric contents smell of garlic or rotten fish. It is one of the commonest suicidal poisons in north India.

Carbaryl is a carbamate insecticide, and chlorthion and malathion are organophosphates. All three inhibit cholinesterase and do not release phosphine.