Portable SERS Instrument for Explosives Monitoring

摘要

The costs for initial characterization, remediation monitoring, and long-term, post-remediation monitoring of groundwater contaminated with explosives are increasing as live firing ranges, ammunition depots, ordnance test facilities, and other Department of Defense sites come under ever closer scrutiny. Major elements of the expense for characterization and monitoring are collection, packaging, shipping, and laboratory analysis of samples. However, most samples test blank. Those samples that do test positive can be characterized by analyzing for just a few explosives, most notably TNT, 2,4-DNT, and RDX, obviating the need for a complete Method 8330 analysis. Furthermore, the conventional approach is not well suited for monitoring active remediation processes such as pump-and-treat systems because turnaround times for laboratory results are too slow for process control. In this project, a new method based on surface-enhanced Raman spectroscopy (SERS) has been developed. Raman is a vibrational spectroscopic method that produces a unique 'fingerprint' spectrum for each analyte, allowing the components of a mixture to be discriminated in a single test. Normally a weak phenomenon, the Raman signal is enhanced up to 106 by adsorbing analytes onto a noble metal surface (colloidal gold, in this case), rendering it suitable for trace analysis. This project was designed to field and demonstrate the potential of SERS to reduce the time, cost, and waste generated per analysis while providing discriminate quantification of multiple analytes in a single measurement.