Surface-Enhanced Raman Spectra of VX and its Hydrolysis Products

Detection of chemical agents as poisons in water supplies not only requires μg/L sensitivity, but also requires the ability to distinguish their hydrolysis products. We have been investigating the ability of surface-enhanced Raman spectroscopy (SERS) to detect chemical agents at these concentrations. Here we expand these studies and present the SERS spectra of the nerve agent VX (ethyl S-2-diisopropylamino ethyl methylphosphonothioate) and its hydrolysis products, ethyl S-2-diisopropylamino methylphosphonothioate, 2-(diisopropylamino) ethanethiol, ethyl methylphosphonic acid, and methylphosphonic acid. Vibrational mode assignments for the observed SERS peaks are also provided. Overall, each of these chemicals produces a series of peaks between 450 and 900 cm−1 that are sufficiently unique to allow identification. SERS measurements were performed in silver-doped sol-gel-filled capillaries that are being developed as part of an extractive point sensor.