Using lasers to detect hazardous waste

A technician inserts fragments of a toy into a machine in a lab, testing for lead. Another technician at an abandoned industrial facility collects samples of metal and building materials, looking for beryllium contamination — an extremely poisonous metal.

Both scenarios are examples of ‘green chemistry’ — chemical analysis that results in no chemical waste generation — using laser ablation technology developed by scientists at the Department of Energy’s Lawrence Berkeley National Laboratory. The technology involves aiming a laser beam at a material sample, causing a tiny amount of it to be vaporised so that spectroscopic analysis techniques can analyse the sample in seconds.

Berkeley Lab Environmental Energy Technologies Division scientist Rick Russo and his research group are pioneers of this new chemical analysis technology based on laser ablation. The two most common approaches are LIBS (laser induced breakdown spectroscopy), in which the light from a tiny plasma is directly measured and related to the chemical element and its concentration; and LA-ICP-MS (laser ablation inductively coupled plasma mass spectrometry), where tiny particles from the ablation are measured. Both approaches allow the measurement of the entire chemical composition of a sample target using a single laser pulse.

“Most samples we analyse are solid,” says Russo. “Conventional methods require an entire analysis infrastructure based on dissolving solids in strong acids so that the resulting liquid can be analysed using standard methods. This is very dirty, generates a lot of chemical waste and requires a lot of time.

“In contrast, laser ablation requires no acid dissolution and so generates no hazardous wastes. It’s ‘green’ technology. And besides eliminating chemical waste, it saves energy.”

Many nations have adopted regulations requiring the removal of hazardous materials from new and to-be-recycled electronic components (eg, RoHS and WEEE). Lead, cadmium, mercury, hexavalent chromium and organic materials PBB and PBDE are among the dangerous materials that these regulations aim to remove. Research has demonstrated that LIBS testing is more accurate than today’s X-ray fluorescence technology for quick screening of these materials.

LIBS technology can also be useful in identifying the contaminants in hazardous industrial environments such as mining sites, where information can guide waste management experts to determine the best methods to use to clean up and isolate what’s present.

LIBS testing can detect materials at concentrations of tens-of-parts-per-million. LA-ICP MS is even more sensitive, capable of detecting chemicals in parts-per-billion.