Comparison of handheld Raman sensors through opaque containers

Abstract

Raman spectroscopy is a powerful tool capable of identifying unknown materials. In the past 20 years, laser sources and detectors have been getting smaller which has led to the development of handheld Raman sensors for use by the military and first responders. One of the advantages of Raman sensors is that it requires no sample preparation, however the incident laser must be able to interrogate the sample which means that the measurement must be taken in the open air or a transparent container. If an unknown material is found in an opaque container, it is typically transferred into a transparent sample jar which represents a handling hazard for the operator. More recently, a technique known as Spatially Offset Raman Spectroscopy (SORS) has shown the ability to measure Raman signals for materials stored in opaque (non-metallic) containers which would eliminate this hazard. Alternatively, advanced algorithm techniques can be used with traditional epi-illumination laser excitation to extract weak Raman signatures from noisy backgrounds or complex mixtures caused when looking at chemicals stored in Raman-active containers. For this study we compare spectral results obtained from two commercially available Raman instruments which use an epi-illumination configuration and SORS against a common set of transparent and opaque containers.