Raman Method Detects Liquid Explosives

A foiled plot in August 2006 raised the specter of terrorists smuggling liquid explosives onto commercial airline flights. Pavel Matousek and coworkers at Rutherford Appleton Laboratory, in Didcot, England, show that automated spatially offset Raman spectroscopy (SORS) could easily be used in airports to detect such explosives (Anal. Chem., DOI: 10.1021/ac071383n). In SORS, Raman spectra are collected from locations in the sample that are spatially offset from the focal point of the incident laser beam light source. The researchers configured their system so the laser beam passes through a container wall to a focal plane several millimeters below the liquid sample surface. They collect two spectra at the container surface, one laterally offset from the other by 10 mm. By subtracting the zero-offset spectrum from the offset spectrum, contributions from the container wall to the spectrum can be eliminated. The researchers successfully used SORS to detect hydrogen peroxide, a key component of homemade liquid explosives, in different types of clear and colored plastic containers.