Researchers at the US Department of Energy’s Idaho National Engineering and Environmental Laboratory have discovered a method of detecting part-per-million levels of chemical warfare agents using a novel ion-trap secondary ion mass spectrometer (IT-SIMS).
Using IT-SIMS, researchers bombard the surface of a sample with a polyatomic projectile to lift or ‘sputter’ off molecules adhering to the sample surface.
The sputtered molecules (secondary ions) retain the chemical characteristics of the chemical warfare agent stuck to the surface of the soil. The secondary ions are filtered by mass and then counted.
That data is displayed as a bar graph that plots the number of ions versus their mass (spectra) that researchers then use to identify the chemicals. Each chemical has its own unique, signature spectra-similar to that of a fingerprint.
The current standard for verifying the presence of chemical warfare agents is gas or liquid chromatography in conjunction with mass spectrometry.
Samples must be extracted from soils, plants or concrete prior to analysis, which is a labour intensive process that can destroy or bias the original sample. Ion Trap SIMS offers distinct advantages to this conventional process.
One advantage of IT-SIMS is that once a surface contaminant is sputtered into the gas phase, researchers capture and retain the ions specific to certain chemical agents and screen out everything else.
Then, researchers subject the target ions to precisely chosen electromagnetic frequencies, called tickle voltages, to fragment the ions into still smaller pieces.
The researchers have also developed a bombarding projectile, called the primary ion, which reportedly lends an additional edge to the INEEL IT-SIMS design.
The team uses a rhenium/oxygen molecule, called a perrhenate ion, instead of an atomic particle such as cesium or gallium. The substantial size of the perrhenate ion makes the sampling process more efficient.
The perrhenate ion can sputter off intact molecules from a sample surface, giving researchers more accurate molecular information.
Additionally, the mechanism used to launch the perrhenate ion is small, which may enable researchers to miniaturise the entire IT-SIMS instrument for more convenient field use in the future.