Airports Are Using Chromatography to Detect Bombs. Find Out How

Most people who have travelled by plane in the past fifteen years have experienced increased security checks. This is as a result of the terrorist attacks in 2001 in which four aeroplanes were hijacked and crashed in the United States. Although the aeroplanes hijacked on September 11^th 2001 were used as the weapons of destruction, there is a history of explosives being detonated on aircraft to kill and maim innocent people. Pan Am Flight 103 exploded over Lockerbie, Scotland in 1988 killing 270 people. The bomb is thought to have been hidden in a radio-cassette player packed into a suitcase.

So how can airport security keep us safe in the air? Physically checking every case and bag would take too long — so automatic detectors are needed. And that’s where chromatography can help. But first...

What is Chromatography?

Chromatography is the separation of a sample into its component parts — remember when you separated ink spots using filter paper and water at school — so the components can be identified and quantified. There are several branches of chromatography, with gas chromatography (GC) and liquid chromatography (HPLC) being the most common techniques. All rely on the principle that the individual components, or molecules, have a different attraction for the different materials used to carry out the separation.

When searching for explosives, GC is commonly used as this technique is best for analysing the volatile substances found in explosives. GC uses a gas mobile phase to carry the sample through a column containing the stationary phase. As the sample is injected onto the column it vaporizes and is carried along by the mobile phase, typically an inert gas such as helium. As the molecules move through the column some prefer the mobile phase and some the stationary phase. Thus the different molecules are separated depending on their affinity for the different phases. At the end of the column the different molecules exit at different times and are detected and quantified. For highly sensitive analysis, GC-MS is a widely used technique which couples GC with mass spectroscopy (MS) as discussed here.

Airport Detectors

There are many different types of detection method used in airports. Some methods involve a swab being taken from suspicious bag or person, with the swab being analysed by GC. Explosives can be detected in this way in under 20 seconds, but the method relies on airport security personnel to detect suspicious persons or bags and cannot be used on every bag or person.

Current interest is in using “puffer machines” which work by blowing air across a person or bag as it passes through a gate. On the opposite side is a detector which takes a sample of the air and runs a GC-MS on it — this can automatically detect explosives. Using these machines means a much higher percentage of passengers and baggage can be screened. So next time you walk through a security see if you feel a puff of air — you might have been sampled.

Image Source: Airplane