Why is chromatography useful in forensics

Because a high-pressure pump is moving the substance through liquid instead of gas, it keeps the substance in its most pure state to ensure accuracy. Forensic scientists employ two types of planar chromatography: paper chromatography and thin-layer chromatography. This method can be helpful for analyzing fingerprints and some bodily fluids.

The process of thin-layer chromatography TLC , unlike the paper stationary phase, is characterized by a thin-layer cell. Similarly, high-performance liquid chromatography will be ideal if they need a quick answer, as the high-pressure pumps significantly speed up the process. In each of these methods, the injected mixture is separated from the solvent, which allows forensic scientists to gain specific results.

On the other hand, there are benefits to using one of the planar chromatography methods. For example, if a lab trying to determine if fingerprints match a crime scene, paper chromatography may be the most efficient choice. Another common use for paper chromatography is ink analysis. For example, forensic scientists can analyze a check at a bank for forgery. This method of chromatography allows lab technicians to separate the pen ink from the document to determine if the ink matches what the suspect had with them.

Chromatography in forensic science has many applications, from toxicology to pathology to crime scene investigations. Forensic laboratories use chromatography applications every day and must have equipment that performs well and produces accurate results for quality analysis. Researchers discover new approach to reform plant breeding and genetics. Determining class A drug use from a single fingerprint. Novel technique helps researchers in single-organelle characterization.

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It is unlikely that consumers who choose free range or organic eggs over less expensive barn ones often think about whether they are getting exactly what they pay for. Cases of passing barn eggs off as higher-welfare varieties and pocketing the price difference have been recorded, but no one knows how common this type of complex food fraud is.

David Thompson, a forensic chemist at the University of Keele in the UK, is collaborating with researchers at the National Institute for Poultry Husbandry at Harper Adams University in Shropshire, UK, in developing methods for discriminating between barn, free-range and organic eggs using chromatography-based metabolic profiles.

Recent events around the Rio Olympics, and particularly the fate of the Russian athletes, illustrated the high stakes involved in keeping major sporting events free of performance-enhancing drugs. Urine samples from thousands of athletes were screened for over illicit substances using LC coupled to high resolution mass spectrometry, and for many other prohibited substances using GC coupled to tandem mass spectrometry.

Clearly, this type of fraud could have been detected easily using an analytical technique that could link each urine sample to an individual athlete. And these techniques do now exist.

This can enable an identification to be made from the tiniest samples of DNA, such as might be extracted from fingerprints at a crime scene. Chemical analysis of the same fingerprints will also be used to identify substances that the suspect had handled.

And it is this technique — the sequencing of the soluble DNA fragments found at very low concentration in the urine of healthy individuals — that could prevent a scam such as that at the Sochi winter Olympics from happening again. However, the extreme sensitivity of modern DNA profiling techniques and, to a lesser extent, chromatography techniques can have disadvantages.

Avoiding sample contamination is now even more essential. It is very likely that contamination of blood samples at the crime scene led to the repeated prosecutions and acquittals in the still-controversial case of the British student Meredith Kercher, murdered in Italy in Syndercombe-Court describes a similar case in the UK where DNA evidence appeared to implicate a man in a rape in Manchester despite his swearing that he had never been there.

Real-life cases like these, as well as fairly realistic portrayals of the forensic sciences in books and TV series have driven a burgeoning public interest in the role of science in detection. This, in turn, will have contributed to an increasing interest in forensic science and forensic chemistry as a career. With pure chemistry courses sadly in decline, some institutions in the UK and elsewhere have converted chemistry degrees into forensic chemistry ones or added an option in the subject.

Interestingly, this can present more challenges to academic than to forensic chemists. Typically columns contain a silica-based stationary phase, with different bonded substances depending on the type of analytes to be separated. This is equally the case with the type of mobile phase used the liquid used to carry the sample through the column.

For instance, normal phase HPLC will use a polar stationary phase with a non-polar mobile phase, whereas reverse-phase chromatography uses the opposite. The purpose of this is to detect components of the sample as they leave the HPLC column, allowing the analyst to identify and quantify the components of the sample. Gas Chromatography Gas chromatography GC is a method of separating compounds in order to aid in the identification and quantification of a substance.

There are numerous possible routes of injection of a sample, each of which may be considered depending on the type and amount of sample available for analysis. As the sample is introduced into the GC, it is vaporised and swept onto the analytical column by the carrier gas.

The carrier gas is the mobile phase in gas chromatography, and is always an inert substance such as hydrogen, helium or nitrogen. The gas supply lines are often coupled with various devices to trap moisture, oxygen and hydrocarbon impurities that can interfere with samples and damage instruments, a feature particularly vital in forensic analyses. Within the column is a stationary phase — most commonly in gas chromatography a capillary column is used in which the stationary phase coats the inner walls of the column.

As the analytes pass through the column, components will interact with the gaseous mobile phase and the stationary phase to a different extent, resulting in components remaining in the column for varying lengths of time depending on certain properties, thus having different elution times the time taken for a component to leave the column and be detected. The process of gas chromatography alone is not particularly beneficial, thus it is often coupled with some form of detector, which will allow for the eluting components to be represented by a peak in a chromatogram.

The retention time of these peaks can be useful in identifying the compound, and the size typically peak area rather than height can be used in quantification.