Real-time fingerprinting of structural isomers using laser induced breakdown spectroscopy

Abstract

Laser induced breakdown spectroscopy (LIBS) has surfaced as an attractive alternative to mass spectrometry and wet chemistry methods for chemical identification, driven by its real-time, label-free nature. Rapid analysis needs, especially in high-energy materials and pharmaceutical compounds, have further fueled an increasing number of refinements in LIBS. Yet, isomers are seldom identifiable by LIBS as they generate nearly identical spectra. Here we employ a suite of chemometric approaches to exploit the subtle, but reproducible, differences in LIBS spectra acquired from structural isomers, a set of pyrazoles, to develop a sensitive and reliable segmentation method. We also investigate the possible mechanistic principles (causation) behind such spectral variations and confirm their statistically significant nature that empowers the excellent classification performance.

Time-Dependent Intensity Ratio-Based Approach for Estimating the Temperature of Laser Produced Plasma

“…Dispersion of the emitted light can provide insights into the atomic constituents of the target material. Understanding the relaxation mechanism can be of great interest, as it can enhance the analytical capabilities of techniques that exploit light emanating from it, for example, laser-induced breakdown 1 Advanced Centre of Research in High Energy Materials, University of Hyderabad, Hyderabad, India 2 LUT School of Engineering Science, Lappeenranta University of Technology, Lappeenranta, Finland 3 Ishlinsky Institute for Problems in Mechanics, Russian Academy of Sciences, Moscow, Russia 4 Tomsk State University, Tomsk, Russia spectroscopy (LIBS), 3,5 laser induced fluorescence (LIF), 6,7 pulsed laser deposition (PLD), 8 and generation of the plasma light sources, etc. 9 After the termination of the laser pulse on the sample, the LIP plume will continue to expand into the ambient environment.…”

“…During this breakdown, a very high temperature occurs (usually > 6000 K) that leads to the formation of plasma containing neutrals, ions, and electrons. 3,4 This is referred to as laser-induced plasma (LIP). Further plasma shielding is also possible if the number density of the electrons is high where plasma temperature increases due to the absorption of the trailing part of the laser pulse.…”

“…Dispersion of the emitted light can provide insights into the atomic constituents of the target material. Understanding the relaxation mechanism can be of great interest, as it can enhance the analytical capabilities of techniques that exploit light emanating from it, for example, laser-induced breakdown spectroscopy (LIBS), 3,5 laser induced fluorescence (LIF), 6,7 pulsed laser deposition (PLD), 8 and generation of the plasma light sources, etc. 9…”

Femtosecond laser induced breakdown spectroscopy based standoff detection of explosives and discrimination using principal component analysis

“…In contrast, laser based spectroscopic techniques such as Raman spectroscopy, laser induced breakdown spectroscopy (LIBS), terahertz spectroscopy and laser induced fluorescence possess high potential for in situ remote/standoff detection of explosives, biological warfare agents and hazardous substances [3][4][5][6][7][8][9]. Laser induced breakdown spectroscopy has been extensively used in various fields owing to it's robust in situ elemental analysis, such as space exploration, pharmaceutical, soil and nutrient analysis and identification/discrimination of explosives [10][11][12][13][14][15][16][17][18]. To this end, nanosecond (ns) LIBS has been extensively used in analysing aerosols [19], process control and monitoring in metallurgical industry [20], planetary missions and detection of explosive residues [21][22][23][24] [29][30][31][32].…”

An Approach to Reduce the Sample Consumption for LIBS based Identification of Explosive Materials

“…While the elemental analysis utilises calibration 9 , calibration -free 10,11 or multivariate methods 12 , classification/identification relies predominantly on the multivariate methods 3,12 . LIBS has added a new paradigm in various fields like space 13 , archaeology 14 , biology 15 , isomer identification 16 biomedical 17,18 , industrial 19 , defense 2,20 , food processing 21 , nuclear waste 22 and forensics 23,24 . LIBS received a boost with the availability of the compact, high power lasers and Echelle type gratings for the applications related to classification and identification of materials.…”