Forensic chemistry evokes in the mind, images of specialists crawling over crime scenes, taking samples, identifying fingerprints, and so on, and this version propagated by mystery movies means we often forget about the more mundane, but equally useful aspects of the field. Forensics, which by definition is the application of chemistry to obtain the identity of an unknown substance, make use of a wide array of tools, such as high-pressure liquid chromatography, gas chromatography, and endless variations of spectroscopy, in myriad fields, such as the aforementioned field of crime, as well as in the medical field, which is what I will today be talking about.
Post-mortems, also known as autopsies, have been far more frequent in modern times, and are used to determine the cause of death, not only to detect if crimes have taken place, but also to increase the medical understanding of a case, and avoid future deaths as a result of the same cause. Though post mortems are done by a pathologist, forensics are highly relevant, as certain physically obvious changes in the subject’s body can be used to identify possible causes of death; carbon monoxide poisoning leads to bright red blood, and hydrogen sulfide poisoning is indicated by a green hue in the brain. In situations where the chemical ingested is not so clearly visible, forensic specialists may be called in to use their knowledge of the metabolites (products of metabolism) to identify a substance. For example, the consumption of heroin is indicated by the presence of 6-monoacetylmorphine, a substance formed exclusively by the breakdown of heroin. A more day-to-day basis use of such techniques is to identify medicines consumed in an accidental overdose. Aspirin can be identified by its relatively low PH (~3.5) and its partial solubility, as a result of its main component being salicylic acid.
This branch of forensics is known as toxicology and has been in use for nearly 2 centuries now. Its originator was James Marsh, who developed a highly sensitive test for arsenic, once a commonplace method for murder. By combining an arsenic sample with sulfuric acid and zinc, he caused the production of arsine gas. The ignition of said arsine gas results in its decomposition to pure arsenic, which enables the detection of arsenic to 1/50 of a gram. Whether it is used to identify the poison behind a murder, or simply what caused a stomach ache, forensics has many real-world applications and should not be underestimated.
- Arnav Sherpuri
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