Vapor phase detection of plastic explosives using a SAW resonator immunosensor array

We present the results of a series of experiments demonstrating on-the-spot detection of low vapor pressure plastic explosives containing nitro groups such as RDX, TNT, and their analogous substances, facilitated by the Transportation Security Administration (TSA) Lab. A set of antibody coated SAW resonators inside the flow cell detect the presence of the target molecules diffusing from the sample. Monoclonal anti-RDX and anti-TNT antibodies are immobilized on the metal electrodes of the device surface via protein-A cross linker. The SAW immunosensor response was monitored and a baseline frequency shift was observed. To minimize possible spurious responses arise from the undesirable perturbation such as air pressure or temperature changes, a non-specific reference sensor is employed and subjected to the exactly same physical environment as the detecting sensors. We could observe a distinctive signature accompanied by baseline shift from the target analytes, and also could verify a certain degree of the cross activity of anti-TNT and anti-RDX antibodies towards nitro groups of molecules