Chemometrics-enhanced fiber optic Raman detection, discrimination and quantification of chemical agents simulants concealed in commercial bottles

Abstract

a b s t r a c tChemometric techniques such as partial least squares combined with discriminant analysis (PLS-DA) and artificial neural networks (ANN) analysis were used to enhance the detection, discrimination and quantification of chemical warfare agents simulants. Triethyl phosphate (TEP) mixed with commercial products in their original containers was analyzed through the container walls using fiber-optic-coupled Raman spectroscopy. Experiments were performed by employing a custom built optical fiber probe operating at 488 nm. Detection was accomplished using mixtures of the contents of the commercial bottles and water. The bottle materials included green plastic, green glass, clear plastic, clear glass, amber glass and white plastic. To account for the low scattering-peak intensities of some bottle materials, integration times were increased. Short integration times provided no information for amber glass and white plastic. The limits of detection were on the order of 1-5%, depending on bottle materials and contents. Good discrimination was achieved with PLS-DA when models were generated from a dataset originating from the same type of bottle material. ANN performed better when large sets of data were used, discriminating TEP from bottle materials and contents, as well as accurately classifying over 90% of the data.

Raman Scattering Techniques for Defense and Security Applications

“…Raman spectroscopy is a good candidate for applications for detection at a distance, thanks to its ability to be able to acquire signals over potentially very long distances using intrinsically collimated lasers and the ability to be coupled with fiber optics. The examples for biohazard detection remotely using optical fibres are limited though. , This could be due to the high background from silica based optical fibers but recent hollow core fiber technologies offer hope. , Nevertheless, technologies such as portable Raman spectrometers permit the design of compact robotic devices that can be mounted on unmanned ground vehicles (UGVs). , Raman is not without drawbacks for such applications, however. The greatest issue for fielding Raman as a stand-off or proximal detection system is the collection of the signal from the sample.…”

Mid-Infrared Laser Spectroscopy Detection and Quantification of Explosives in Soils Using Multivariate Analysis and Artificial Intelligence

“…The noise level was measured by collecting 20 spectra of a blank (KBr) and calculating the average of the standard deviations for all wavenumbers. The LOD was estimated using Equation (3) [60,61]:…”

Mid-infrared Laser Spectroscopy Detection and Quantification of Explosives in Soils Using Multivariate Analysis and Artificial Intelligence

“…Noise was measured by collecting 20 spectra of a blank (KBr) and calculating the average of the standard deviations for all wavenumbers. The LOD was estimated using the following equation [60,61]:…”