Forensic Toxicology and Chemical Analysis Questions and Answers

Answer: A

The Fujiwara test is applied for the detection of halogenated hydrocarbons such as chloroform, carbon tetrachloride and trichloroethylene. The sample is heated with pyridine and strong alkali, and a pink to red colour appears in the pyridine layer.

The Koppanyi Zwikker test, with cobalt acetate and an amine, detects barbiturates. Sodium nitroprusside is used for acetone and some amines. Cobalt thiocyanate detects cocaine. None of them is a test for halogenated hydrocarbons.

Answer: A

Amanita phalloides, the death cap, is a poisonous mushroom whose toxins, amatoxins and phallotoxins, damage the liver and are often fatal.

Morchella esculenta is the edible morel, Boletus edulis is the edible porcini or cep, and Cantharellus cibarius is the edible chanterelle. All three are prized for food, so the only poisonous species in the list is Amanita phalloides.

Answer: D

Scott's test is applied for the detection of cocaine. The sample is treated with cobalt thiocyanate, which gives a blue precipitate, and then with hydrochloric acid and chloroform, in which a blue colour in the chloroform layer indicates cocaine.

Amphetamines are tested with Marquis or Simon's reagent. Barbiturates are tested by the Koppanyi Zwikker test. Opiates are tested with Marquis or Froehde reagents. None of these uses the cobalt thiocyanate and chloroform sequence.

Answer: A

The active ingredients of cannabis are collectively known as cannabinoids, a group of compounds that includes delta-9-tetrahydrocannabinol, cannabidiol and cannabinol. THC is the main psychoactive one.

Annabinoids, Cannazoids and Cannatedois are not names used in chemistry or pharmacology; they are distractors that imitate the spelling of the real term. Only cannabinoids is the accepted name.

Answer: A

Acetic anhydride is the acetylating reagent used to prepare heroin. Morphine is heated with it and the two hydroxyl groups are acetylated, giving diacetylmorphine, which is heroin.

Sodium hydroxide and ammonium hydroxide are bases, used to precipitate morphine from solution or to adjust the pH, and they do not acetylate. None of the above is wrong because acetic anhydride is the correct reagent.

Answer: A

Blood alcohol concentration is measured in weight by volume percent, for example 0.08 g of alcohol in 100 ml of blood, written 0.08 percent w/v. Forensic reports also state it as mg per 100 ml.

Volume by volume percent is used to state the strength of alcoholic drinks, and weight by weight percent is used in some countries but is not the standard in Indian reports. None of above is wrong because the first option is the accepted unit.

Answer: C

The main ingredient of Mandrax is methaqualone, option C. Mandrax is a sedative hypnotic tablet that combines methaqualone with diphenhydramine and is misused as a drug of abuse. PCP (A), phencyclidine, is a dissociative anaesthetic known as angel dust, STP (B), or DOM, is a hallucinogenic amphetamine, and GHB (D), gamma hydroxybutyrate, is a central nervous system depressant. None of them is the main ingredient of Mandrax.

Answer: C

Dry ashing is used for the extraction of metallic poisons from viscera, option C. The tissue is heated in a muffle furnace to burn away the organic matter, which leaves the metals as ash that can be dissolved in acid and analysed. The organic poisons, whether volatile (A) or non-volatile (B), would be destroyed or lost by this heating, so they are extracted by distillation or by solvent methods such as the Stas-Otto process instead. For the non-volatile organic poisons, the Stas-Otto method is used, and for the volatile ones, distillation or steam distillation, which is why the key leaves dry ashing for the metals.

Answer: D

All three colour tests are applied for the detection of opiates, so the answer is option D. Marquis reagent, formaldehyde in sulphuric acid, gives a purple colour with morphine and its relatives, Mecke reagent, selenious acid in sulphuric acid, gives a green colour, and Froehde reagent, molybdic acid in sulphuric acid, gives a purple to green colour. Since each of A, B and C is a test for opiates, the combined option is correct.

Answer: A

Lysergic acid is found in the ergot fungus, option A. Ergot, Claviceps purpurea, grows on rye and other cereals and contains ergot alkaloids, from which lysergic acid is obtained, and LSD is made from it. Psilocybe mexicana (B) contains psilocybin, and Lophophora williamsii (C), the peyote cactus, contains mescaline, so they are different hallucinogens. The plant name in option D is not a source of lysergic acid.