Forensic Toxicology and Chemical Analysis Questions and Answers

Answer: D

The formula showing the simplest ratio of atoms is the empirical formula.

The empirical formula gives the smallest whole-number ratio of the atoms of each element in a compound. Glucose, for example, has the empirical formula CH₂O, while its molecular formula is C₆H₁₂O₆.

The molecular formula gives the actual number of each kind of atom in a molecule, a whole-number multiple of the empirical formula. A structural formula shows how the atoms are bonded. A rational (condensed) formula groups atoms by functional groups, such as CH₃COOH for acetic acid.

Answer: C

Aldrich-Mees lines are seen in subacute poisoning by arsenic.

Mees' lines are transverse white bands across the nails, appearing a few weeks after exposure as the nail grows out. They are a classic sign of subacute or chronic arsenic poisoning, along with raindrop pigmentation of the skin, hyperkeratosis of the palms and soles, and peripheral neuropathy. The position of the band along the nail can help estimate when the exposure occurred.

Thallium poisoning can produce similar lines, but none of the other listed metals is the classic cause. Antimony resembles arsenic in some respects, and manganese and nickel cause different syndromes.

Answer: B

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

Once ketamine is paired with Kit Kat and PCP with angel dust, only the second code fits. Each of the other codes pairs PCP or methamphetamine with the wrong name.

Answer: C

Hunter-Russell syndrome is caused by chronic exposure to methyl mercury.

Described by Hunter and Russell in 1940 in workers making methyl mercury fungicides, the syndrome is a triad of ataxia, constricted visual fields and difficulty in speech (dysarthria), from damage to the cerebellum and visual cortex. The Minamata disaster in Japan was a mass outbreak of the same poisoning.

Tetramethyl lead causes organic lead poisoning with different, mainly psychiatric, features, and dimethyl zinc and 'methyl nickel' are not linked with this syndrome.

Answer: D

Synergism takes place when two different drugs are taken at the same time and their effect is magnified.

In synergism the combined effect of two substances is greater than the sum of their separate effects, as when alcohol is taken with benzodiazepines or opioids and breathing is dangerously depressed. It is important in forensic toxicology when deaths occur at individually non-fatal levels.

Taking more of a drug for the same effect is tolerance, and being addicted is dependence. A drug being metabolised into two products is biotransformation, not synergism.

Answer: C

The non-distilled alcoholic beverage is wine.

Wine is made by fermenting grape juice and is not distilled, so its alcohol content is limited by the yeast, usually to about 9 to 15 per cent.

Gin and rum are distilled spirits, made by distilling a fermented liquid to concentrate the alcohol. Sherry is a fortified wine: distilled grape spirit is added to it, which is why it is not the non-distilled beverage here.

Answer: C

The best matrix is meconium.

Meconium, the newborn's first stool, begins to form around the twelfth week of pregnancy and accumulates drugs and metabolites that the fetus is exposed to from then until birth. Testing it reveals maternal drug use over the second and third trimesters.

Fetal or newborn blood and urine reflect only the last few days before birth, and 'fetal breath' is not a usable matrix. Meconium gives the longest and most reliable window of exposure.

Answer: D

Dichlorprop is not a trade name of aluminium phosphide.

Dichlorprop is a chlorophenoxy herbicide, a weedkiller related to 2,4-D, with no connection to phosphide fumigants.

Aluminium phosphide, the grain fumigant that releases phosphine gas and is a common cause of fatal poisoning in India, is sold under many brand names, Celphos, Quickphos and Phostoxin among the best known. Whatever brand names the other options stand for, Dichlorprop is a different chemical altogether, so it is the one that cannot be a name for aluminium phosphide.

Answer: A

Nalorphine is an antidote for opium poisoning.

Nalorphine is an opioid antagonist that reverses the respiratory depression of opium and its alkaloids such as morphine. It has largely been replaced by naloxone, but it is still the classic answer in toxicology texts; it was also used in the nalorphine test for opioid addiction.

Cocaine poisoning is treated with sedation and supportive care, dhatura (atropine-like alkaloids) with physostigmine, and strychnine with barbiturates or diazepam and muscle relaxants. Nalorphine does not counteract any of them.

Answer: B

Gunzberg's test ascertains the presence of vomit.

Gunzberg's reagent (phloroglucinol and vanillin) detects free hydrochloric acid, which comes from the stomach. A positive result on a stain therefore indicates gastric contents, that is vomit, which may matter in cases of poisoning or aspiration.

Saliva is identified by its amylase, urine by urea or creatinine, and faecal matter by urobilinogen or microscopic food residues. None of these is identified by Gunzberg's test.