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

Abstract

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 plasma is in local thermodynamic equilibrium (LTE). Even in this case, the transient nature of the plasma and its spatial inhomogeneity need to be considered and overcome in order to justify the theoretical assumptions made. This first article focuses on the basic diagnostics aspects and presents a review of the past and recent LIBS literature pertinent to this topic. Previous research on non-laser-based plasma literature, and the resulting knowledge, is also emphasized. The aim is, on one hand, to make the readers aware of such knowledge and on the other hand to trigger the interest of the LIBS community, as well as the larger analytical plasma community, in attempting some diagnostic approaches that have not yet been fully exploited in LIBS.

Recent Advances and Remaining Challenges for the Spectroscopic Detection of Explosive Threats

“…together which may cause undesirable matrix effects. 39 It is fair to say that, in its current state, LIBS fails to provide the confidence necessary in chemical analysis for weapons intelligence purposes and ultimately attribution. Since there are a number of additional optical or spectroscopic techniques that could be applied to the problem of standoff detection on surfaces that do not suffer from these issues, military interests in and pursuit of LIBS has waned and was therefore excluded from this ATO effort.…”

Quantitative detection of metallic traces in water-based liquids by microwave-assisted laser-induced breakdown spectroscopy

“…LIBS has achieved enormous popularity and has established itself as an analytical spectroscopic tool in several applications in the last decade. The popularity of this method is due to the fact that almost no sample preparation is needed along with the ability to perform in situ analysis in real time [5,6], making it an ideal candidate for the previously mentioned applications. In spite of its potential benefits, liquid analysis using LIBS can result in significant problems such as poor repeatability, low sensitivity, extinction of emission, surface movements, splashing and a shorter plasma lifetime due to rapid cooling [4,7].…”

Dispersive liquid–liquid microextraction for metals enrichment: A useful strategy for improving sensitivity of laser-induced breakdown spectroscopy in liquid samples analysis

“…Moreover, due to the striking technological improvements in lasers and spectrometers during the last decades, a number of portable and easily automatable commercial LIBS instruments are currently available in market [5][6][7], which makes this technique especially suitable for field measurement. However, in spite of its numerous advantages, the low sensitivity of LIBS when compared with other well established atomic spectrometric techniques constitutes its most important limitation for (ultra) trace elemental analysis, in special for liquid samples analysis [8][9][10][11].…”