Mumbai Murder — Chromatography Checks for Intoxicants

Forensic science is an important facet of the criminal justice system. It has been used to both put dangerous people behind bars and put right injustices that have placed innocent people in prison. It is critical that the results of forensic investigations are accurate and can withstand the rigors of a court trial.

There are many techniques that are used, many are known because of their exposure in modern crime shows on television. Facial reconstruction, DNA sequencing, high powered microscopy techniques like Scanning Electron Microscopy and special software to track and analyse financial transactions. One of the techniques that is perhaps not mentioned as frequently is chromatography.

Chromatography — separating innocent and guilty

Chromatography is one of the most powerful techniques available to scientists — forensic, industrial or pharmaceutical scientists all rely on the science of separation. The International Union of Pure and Applied Chemistry (IUPAC) — the international body responsible for standardizing chemistry around the world — defines chromatography as: a physical method of separation in which the components to be separated are distributed between two phases, one of which is stationary (stationary phase) while the other (the mobile phase) moves in a definite direction.

The stationary and mobile phase can range from the simple coffee filter paper and water used in schools to show which colours make black ink, to complex silica-based column packings used to separate hydrocarbons as discussed in the article, Industrial Applications of Offline and Online Comprehensive Gas Chromatography.

Mobile or stationary — what is your preference?

In all instances, the basic theory is the same. How will the components in the sample mix interact with the stationary and mobile phase? How the sample molecules interact with the phases decides how well the sample mixture is separated — and this gives the time that a particular compound is held on the column, its retention time.

By altering the type of stationary phase (for example, polar or non-polar column packings) and different properties of the mobile phase (carrier gas in gas chromatography or liquid in liquid chromatography) will alter the degree of separation. The aim is to achieve good separation, or resolution, with nice sharp peaks. Sharp peaks are one indication that a particular compound has exited the column, or eluted, in a tight band.

One of the main advantages of chromatography is the ability to change detectors or to use the eluted components as samples in a further system. Combining chromatography with mass spectrometry is one of the most powerful techniques used in analytical labs.

Solving a crime conundrum

A recent news report in The Free Press Journal indicates how chromatography can help forensic scientists. Routine forensic analysis failed to find any traces of drugs or alcohol in a potential murder victim’s blood. But, the team are now using various chromatographic techniques to determine if a crime has been committed. From simple school experiments to solving murder cases — chromatography can separate fact from fiction.