Laser Chemical Elemental Analysis: From Total to Images

*Renata S. Amais, Danielle S. Francischini, Pedro S. Moreau and Marco A.Z. Arruda*

## **Abstract**

This book chapter focuses on laser ablation employed in elemental analysis and discusses the fundamentals and instrumentation of the laser-induced breakdown spectroscopy (LIBS) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) techniques. The analytical performance of such techniques, challenges related to calibration, and strategies to improve sensitivity are discussed. In addition, the processes involved in data acquisition and imaging for acquiring the elemental spatial distribution are highlighted, and some representative examples in environmental, biological, medical, and forensic researches are presented.

**Keywords:** LIBS, LA-ICP-MS, imaging, plasma, mass spectrometry, optical emission, laser ablation

## **1. Introduction**

The association of chemistry and light is so old than human being history, most probably raging from the observation of the solar spectrum to spectroscopic analysis, thus allowing the discovery of new and unknown substances. The advent of laser (acronym to Light Amplification by Stimulated Emission of Radiation) has only served to strengthen this natural bond. With the advances in electronics and computational programs, the lasers have a multitude of applications, from proteins (*i.e.* matrix-assisted laser desorption/ionization, MALDI) [1] to elemental analysis (*i.e.* laser ablation inductively coupled plasma mass spectrometry, LA-ICP-MS, or laser-induced breakdown spectroscopy, LIBS) [2]. The applications are dictated by the laser wavelengths, which, in fact, reflect their energies. For example, for biomolecules, like proteins, wavelengths higher than 350 nm are currently used, and for elemental analysis, 213 or 193 nm are most common.

Because of its modulated power, directionality, and temporal coherence, the laser has become a highly versatile tool, and used in a large variety of applications, from the study of how chemical reactions occur, then to initiate chemical reactions upon irradiation to extremely sensitive and selective means to evaluate the presence of chemical substances of interest [3]. Additionally, and as highlighted by the adage "a picture is worth a thousand words" [4], the laser ablation imaging [5] is another excellent option to greatly enhance the understanding of a studied system.

Then, this Chapter is devoted to elemental analysis, focusing on not only laser ablation ICP-MS and LIBS for qualitative and quantitative analysis, but also on imaging the results obtained from those analyses. Particular emphasis is placed on the discussion regarding the instrumentation, some processes involved in the image acquisition and formation, and also on the analytical results and figures of merit for a diversity of methods involving different areas as geochemical, environmental, biological, medical, and forensic. Some trends aspects and perspectives in the application of laser in chemical analysis are also the focus of this Chapter.
