Over the last few years, the LIBS technology has changed from a fairly niche laboratory process to a widely-used field-based analysis methodology.
The principle behind Laser Induced Breakdown Spectroscopy (LIBS) is that a pulsed laser is focused on a small area of a sample, generally about 100 µm in diameter and 5-10 µm deep. This contact forms a plasma plume that releases light in cooling. The light emitted has a spectrum of ultraviolet, visible and infrared, and the collected light is sampled using one or more integrated spectrometers, depending on the analytical range required.
The advancement in LIBS has been significantly influenced by the advancement in the laser technology, which has led to the recent increase in the application of the technology. To make LIBS viable in the field, systems had to be fast, portable, battery-powered, and capable of operating in a wide temperature range, yet provide high pulse energies and high repetition rates. The development required a lot of effort to achieve all these requirements in a single device, but eventually resulted in successful commercial solutions.
READ “HANDHELD LIBS – THE LATEST SUCCESS STORY IN PORTABLE ANALYTICAL INSTRUMENTATION” BY DON SACKETT, SCIAPS CEO, IN THE RECENT EDITION OF SPECTROSCOPY MAGAZINE.
An example of this is the use of lasers with a power of about 6-8 millijoules per pulse and a frequency of 50 Hz with a pulse width of 2 nanoseconds and a temperature range of 25–45°C, in modern instruments like those made by SciAps. This performance is critical to be comparable with analytical performance of well-known field methods like spark optical emission spectroscopy and handheld X-ray fluorescence.
The handheld LIBS systems have now become well accepted in a number of significant applications. Among the biggest applications is in the analysis of carbon content in steel and stainless steel alloys. Numerous industries rely on correct values of carbon equivalents to maintain the correct welding process and low-carbon stainless steels are frequently demanded in the chemical processing and energy industries. LIBS is the only portable analytical technique that can measure carbon in this type of measurement. This has led to the wide usage of handheld LIBS devices in industries that deal with steel production and fabrication across the globe and have disrupted the traditional mobile spark OES systems.
The other expanding field of use is in the green economy especially in the sector of electric cars. LIBS is the sole mobile field method that can be used to measure levels of lithium in soils, ores, and brines. This has enabled it to be a significant instrument in the exploration of lithium, as it assists in the endeavor to expand battery material to electric vehicles. It is also in application in recycling and recovery of used batteries.
One of the benefits of handheld LIBS is that it is more flexible than other field analysis techniques. As LIBS can produce emission signals of all stable elements in the periodic table, systems can be optimized to the analytical requirements. Rather than operating with a full-spectrum system with wavelengths ranging 190 nm to 950 nm, users are able to choose specific configurations that are optimized to specific spectral ranges, saving money without compromising performance to applications with specific spectral requirements.
Recent advancements involve instruments that have been equipped with a single spectrometer that has a wavelength in the 580-780 nm range of detecting fluorine. The systems are deployed to screen PFAS (per- and polyfluoroalkyl substances) in packaging and consumer products in the field. Other configurations have been fabricated to identify beryllium in soil and dust when performing site remediation tasks, such as the remediation of older U.S. weapons production establishments. Other specialized uses include the measurement of light elements like fluorine, sodium and boron in all kinds of mineral samples.
In addition to industrial applications, handheld LIBS has found some adoption in academia as well. It has been applied to teaching in the fields of chemistry, physics, geoscience, and metallurgy due to its capability to both analyse and teach quantitative fields as well as to educate. In the last ten years, university researchers and government laboratories have explored a wide range of applications which have helped to broaden the range of this technology.
On the whole, the last 5-10 years have been associated with the development of handheld LIBS as a proven and useful portable analytical instrument. It has found a footing in the conventional industries like chemical processing, petrochemical operations and oil and gas and also complementing the more recent industries like electric vehicles, strategic metals and environmental monitoring of fluorine-based compounds.
Early LIBS applications were in alloy analysis, but have since been used in fields such as electric mobility, environmental cleanup, and, most recently, space-related studies.
Russell Harmon has also pointed out the potential of LIBS in facilitating in-field chemical analysis in a wide range of applications, in terms of the greater effect of portable analytical technologies.
RUSSELL HARMON IS ADJUNCT ASSOCIATE PROFESSOR, DEPARTMENT OF MARINE, EARTH, & ATMOSPHERIC SCIENCES, NORTH CAROLINA STATE UNIVERSITY
The progress, up-to-date developments, and future perspectives of LIBS technology are also found in Spectrochimica Acta Part B: Atomic Spectroscopy (Volume 175, 2021). Also, David Day has written Chapter 13 of the Portable Spectroscopy and Spectrometry: Volume One (Wiley), which covers handheld LIBS, explaining its development and the technical details.
