GASES FOR CRIME-FIGHTING

The perpetrator can be as cunning as he likes: some lint or a grain of sand is all it takes for him to end up in handcuffs. Because sophisticated scientific methods can transform the most negligible clue into valuable incriminating evidence. State-of-the-art technologies and gases are used here in various applications.

For the analysis of inorganic particles, for example, a scanning electron microscope is used: and its X-ray semiconductor detector is cooled with liquid nitrogen. The sample chamber is cleaned by flushing it with gaseous nitrogen to eliminate any risk of spoiling the sample. In this way the experts examine, among other things, filaments from car headlights or traces of powder formed when firing a weapon.

The spectrophotometry lab examines microparticles found on the evidence. These include all textile fibers and the tiniest flecks of rubber, plastic or nail polish, which can provide clues about possible perpetrators. In the case of the infrared photometer used here, the interior of the device is cleaned with gaseous nitrogen.

Organic chemists, too, use state-of-the-art methods and technologies that cannot deliver detailed findings without the help of gases.Samples are first dried with nitrogen if necessary.In gas chromatography, nitrogen, hydrogen, helium and compressed air are used as flushing gases, carrier gases or operating gases for mass spectrometers, gas chromatographs and flame ionization detectors.In addition, ultra-pure calibration gases are used for reference purposes.