The first part of this two-part review focused on the fundamental and diagnostics aspects of laser-induced plasmas, only touching briefly upon concepts such as sensitivity and detection limits and largely omitting any discussion of the vast panorama of the practical applications of the technique. Clearly a true LIBS community has emerged, which promises to quicken the pace of LIBS developments, applications, and implementations. With this second part, a more applied flavor is taken, and its intended goal is summarizing the current state-of-the-art of analytical LIBS, providing a contemporary snapshot of LIBS applications, and highlighting new directions in laser-induced breakdown spectroscopy, such as novel approaches, instrumental developments, and advanced use of chemometric tools. More specifically, we discuss instrumental and analytical approaches (e.g., double- and multi-pulse LIBS to improve the sensitivity), calibration-free approaches, hyphenated approaches in which techniques such as Raman and fluorescence are coupled with LIBS to increase sensitivity and information power, resonantly enhanced LIBS approaches, signal processing and optimization (e.g., signal-to-noise analysis), and finally applications. An attempt is made to provide an updated view of the role played by LIBS in the various fields, with emphasis on applications considered to be unique. We finally try to assess where LIBS is going as an analytical field, where in our opinion it should go, and what should still be done for consolidating the technique as a mature method of chemical analysis.

https://journals.sagepub.com/doi/pdf/10.1366/11-06574

Laser-induced breakdown spectroscopy (LIBS), part II: review of instrumental and methodological approaches to material analysis and applications to different fields.

Laser-induced breakdown spectroscopy (LIBS) has become a very popular analytical method in the last decade in view of some of its unique features such as applicability to any type of sample, practically no sample preparation, remote sensing capability, and speed of analysis The technique has a remarkably wide applicability in many fields, and the number of applications is still growing From an analytical point of view, the quantitative aspects of LIBS may be considered its Achilles' heel, first due to the complex nature of the laser–sample interaction processes, which depend upon both the laser characteristics and the sample material properties, and second due to the plasma–particle interaction processes, which are space and time dependent Together, these may cause undesirable matrix effects Ways of alleviating these problems rely upon the description of the plasma excitation-ionization processes through the use of classical equilibrium relations and therefore on the assumption that the laser-induced 

Laser-Induced Breakdown Spectroscopy (LIBS), Part I: Review of Basic Diagnostics and Plasma–Particle Interactions: Still-Challenging Issues Within the Analytical Plasma Community

Ozonolysis is a major tropospheric removal mechanism for unsaturated hydrocarbons and proceeds via "Criegee intermediates"--carbonyl oxides--that play a key role in tropospheric oxidation models. However, until recently no gas-phase Criegee intermediate had been observed, and indirect determinations of their reaction kinetics gave derived rate coefficients spanning orders of magnitude. Here, we report direct photoionization mass spectrometric detection of formaldehyde oxide (CH(2)OO) as a product of the reaction of CH(2)I with O(2). This reaction enabled direct laboratory determinations of CH(2)OO kinetics. Upper limits were extracted for reaction rate coefficients with NO and H(2)O. The CH(2)OO reactions with SO(2) and NO(2) proved unexpectedly rapid and imply a substantially greater role of carbonyl oxides in models of tropospheric sulfate and nitrate chemistry than previously assumed.

http://science.sciencemag.org/content/sci/335/6065/204.full.pdf

Direct Kinetic Measurements of Criegee Intermediate (CH2OO) Formed by Reaction of CH2I with O2

Kinetics of elementary reactions in low-temperature autoignition chemistry

Laser-induced breakdown spectroscopy is reviewed by dividing the literature into three categories according to target phase: solid, liquid, or gas. Within each category, the literature is ...

Fundamentals and Applications of Laser-Induced Breakdown Spectroscopy

We have developed a multiplexed time- and photon-energy?resolved photoionizationmass spectrometer for the study of the kinetics and isomeric product branching of gasphase, neutral chemical reactions. The instrument utilizes a side-sampled flow tubereactor, continuously tunable synchrotron radiation for photoionization, a multi-massdouble-focusing mass spectrometer with 100percent duty cycle, and a time- and positionsensitive detector for single ion counting. This approach enables multiplexed, universal detection of molecules with high sensitivity and selectivity. In addition to measurement of rate coefficients as a function of temperature and pressure, different structural isomers can be distinguished based on their photoionization efficiency curves, providing a more detailed probe of reaction mechanisms. The multiplexed 3-dimensional data structure (intensity as a function of molecular mass, reaction time, and photoionization energy) provides insights that might not be available in serial acquisition, as well as additional constraints on data interpretation.

/pdf/the-multiplexed-chemical-kinetic-photoionization-mass-42wjle6z64.pdf

The multiplexed chemical kinetic photoionization mass spectrometer: a new approach to isomer-resolved chemical kinetics.

Implementation of laser-induced breakdown spectroscopy as a continuous emissions monitor for toxic metals

Optimal temporal gating for laser-induced breakdown spectroscopy (LIBS) analysis was investigated for a select group of toxic metals, namely the Resource Conservation and Recovery Act (RCRA) metals arsenic, beryllium, cadmium, chromium, lead, and mercury. The differing rates of decay between the continuum plasma emission and the atomic emission were used as a means to maximize the signal-to-noise ratio of the atomic emission lines for these six metal species. Detection windows were investigated corresponding to delay times from 2 to 50 μs following the plasma-initiating laser pulse. For the current experimental conditions, it is concluded that the relatively short delay time of 12 μs is optimal for the detection of arsenic, beryllium, cadmium, and mercury, while a longer delay time of 50 μs is optimal for the detection of chromium and lead. The reduced atomic emission intensity at relatively long delay times is compensated for by the use of long detector gate widths. Estimated detection limits are reporte...

Temporal Gating for the Optimization of Laser-Induced Breakdown Spectroscopy Detection and Analysis of Toxic Metals

An aerosol generation system is described that enables the production of precise mass flow streams of well-characterized, submicron-sized aerosol particles. A pneumatic-type nebulizer is used to nebulize aqueous solutions of dissolved metals, which subsequently dry in a gaseous co-flow, producing a gaseous stream of dispersed, fine solid particles with a known mass concentration. Gravimetric calibration of nebulizer demonstrates the precise nature of the device for aerosol generation. Representative iron-based (spherical) and titanium-based (nonspherical) particles are analyzed using transmission electron microscopy and x-ray diffraction. Both aqueous metals form metallic oxides, namely, FeO and TiO, and the measured particle sizes are in the range 10–100 nm. The measured particle size and composition are used to calculate the size distribution of droplets produced by the nebulizer, which yield a mean droplet diameter of 524 nm. The nebulizer droplet distribution is well described by a log–normal distribution. Using the aerosol generator as a calibration source of aerosol particles for laser-induced breakdown spectroscopy, linear calibration curves were produced for titanium over mass concentrations ranging from 0 to 4425 μg/m3.

Howard A. Johnsen

Papers

The multiplexed chemical kinetic photoionization mass spectrometer: a new approach to isomer-resolved chemical kinetics.

Implementation of laser-induced breakdown spectroscopy as a continuous emissions monitor for toxic metals

Temporal Gating for the Optimization of Laser-Induced Breakdown Spectroscopy Detection and Analysis of Toxic Metals

Aerosol generation system for development and calibration of laser-induced breakdown spectroscopy instrumentation

A laser-based technique to continuously monitor metal aerosol emissions