Speaker
Description
Knowing the chemical composition of samples is essential to science and beyond, so much so that chemical analysis facilities are widespread within government agencies, universities, and industry. One of the enduring needs within the scientific community has been a capability for in situ chemical analysis for routine use outside the traditional analytical laboratory. Such instrumentation must be readily portable and lightweight to facilitate use by an individual as well as robust and ruggedized for use in the remote and harsh environments in which materials often need to be analyzed. Laser-induced breakdown spectroscopy (LIBS) is one of the few current technologies that meets this need, having a capability to detect and measure every element in the periodic table above its intrinsic material specific Limit of Detection (LOD). Although initially developed over 50 years ago (Brech and Cross, 1962), the common application of LIBS within the sciences began about two decades ago. This has been facilitated first through the development of mobile and stand-off LIBS systems for use outside of the conventional laboratory setting for in situ analysis in the ambient environment by both close-in or stand-off approaches and then strongly accelerated over the last decade by the development of commercial handheld (h)LIBS analyzers.
Atomic emission spectroscopy is a technique for chemical analysis that measures the intensity of light emitted from a flame, spark, arc or plasma to determine the presence or mass fraction of an element in a sample. LIBS is a specific form of atomic emission spectroscopy that offers rapid, multi-element analysis in real-time with minimal sample preparation. In LIBS, a rapidly-pulsed low energy laser beam is tightly focused on a sample to create a plasma in which constituent elements can be detected and identified through spectral analysis of emitted light. LIBS can detect most elements, particularly light elements, in the periodic table at high sensitivity with a single laser shot. Quantitative analysis by LIBS is readily achieved using calibration curves generated from matrix-matched standards or through calibration-free methodologies and, when used in conjunction with chemometric techniques and pre-established databases, LIBS spectral analysis is capable of identifying and discriminating unknown materials. LIBS can also be used for rapid microscale compositional imaging at high spatial resolution.
As every element in the periodic table has one or more optical emission lines in the broadband spectral regions between 190 to 900 nm, LIBS is ideally suited for the multi-element analysis of all types of media, because offers with a single laser pulse simultaneous detection of all chemical elements in solids, liquids and gases with little to no sample preparation. It is notable and important that LIBS is particularly sensitive to the elements of low atomic number – H, Li, Be, B and C, that cannot be readily determined by many other analytical methods and to first-row transition elements of the periodic table. Most elements of the periodic table have been observed in LIBS spectra of different media, and although LIBS LODs have been steadily improving over the past two decades concomitant with technological progress in LIBS instrumentation, it is important to understand that they are highly dependent on sample matrix and the operational capabilities of the LIBS system used for an analysis.
In this work, a practical example of application of hLIBS used to identify the qualitative and quantitative composition and the compositional micro-maps of a suite of iron meteorite samples is reported.
Brech, F. and Cross L. (1962) Optical micro-emission stimulated by a ruby MASER. Applied Spectroscopy, 16: 59-64.
