Laser-induced breakdown spectroscopy, abbreviated as LIBS analysis, is a versatile technique used to interrogate the elemental composition of a sample. Until recent decades, it was regarded as a scientific curiosity due to the availability of existing atomic emission spectroscopic (AES) methods like X-ray fluorescence (XRF) and inductively-coupled plasma (ICP) analysis.
However, renewed interest in the technology helped laser-induced breakdown spectroscopy carve out a rapidly-growing niche in the AES space. This was supported by innovative development of the method’s underlying components, such as the optical detector arrays and spectrographs. The ability to manufacture compact, portable LIBS analyzers with comparable accuracy and sensitivity to conventional techniques cemented laser-induced breakdown spectroscopy as one of the world’s foremost AES technologies.
Working Principles of Laser-Induced Breakdown Spectroscopy
The fundamental principles of AES were established in 1913 by the Bohr theory of hydrogen (H), which posited a link between the structure and spectra of atoms. This proved correct, forming the basis of many essential technologies in materials characterization.
Generally, AES involves the atomization of the uppermost surface layer/s of a sample using a high energy source of radiation. This causes atomic excitation and the emission of characteristic radiation, which is detected and resolved for intensity or mass before a full emission spectrum is determined. Laser-induced breakdown spectroscopy follows this basic premise to characterize sample chemistry with extremely low limits of detection. With LIBS one can also detect lighter elements such as Li, Be that cannot be detected with the XRF.
A typical LIBS analyzer uses a solid-state laser excitation source that generates a near-infrared (NIR) beam of energy with a wavelength of either 1030 or 1064 nanometers (nm). This focused laser is pulsed on an order of nanoseconds, heating extremely specific sample areas to temperatures up to 30,000K. Small volumes of surface material are ablated and energized by the latter portion of the laser pulse, creating a plume of highly energized plasma. In this state, electrons in the outer atomic orbits are readily ejected.
After this initial excitation phase, the laser pulses are ceased, and the plasma begins to cool. The vacancies left by ejected electrons are filled by others cascading down from outer atomic orbits. When an electron moves down from one band to another, excess energy is released in the form of characteristic radiation with discrete spectral peaks. Laser-induced breakdown spectroscopy can reliably resolve the emission spectrum of samples across the ultraviolet (UV), visible (Vis), and NIR electromagnetic spectrum to detect virtually any element in the periodic table by their distinct spectral fingerprints. It also enables concentration measurements down to the trace level, by simultaneously measuring the peak intensity.
Today, laser-induced breakdown spectroscopy is one of the chief technologies used in materials science applications and more rugged working environments due to its outstanding precision and excellent real-world applicability. Unlike many analytical technologies, LIBS analyzers are optimized for in-field analysis of materials and products with no loss of functionality. Given that the extreme temperatures of laser-induced breakdown analysis are limited to the contained plasma plume, samples do not get hot to the touch and can subsequently be handled throughout the analytical process. This makes it the ideal technology for handheld analytical instrumentation.
The NanoLIBS range of handheld laser-induced breakdown spectroscopy tools from B&W Tek is a state-of-the-art product line developed for minimally-invasive materials characterization and quality control applications. The NanoLIBS is optimized for raw material identification of monatomic salts commonly used in the pharmaceutical industry, with unambiguous analysis, ensuring peace of mind in your R&D or QC processes.
Miziolek, A., Palleschi, V., & Schechter, I. (Eds.). (2006). Laser-Induced Breakdown Spectroscopy. Cambridge: Cambridge University Press. doi:10.1017/CBO9780511541261