The Road to Complete Chemical Analysis
New analytical technology combinations promise simultaneous solvent-free measurement of every element on the periodic chart. And that’s something worth shouting about.
Can one technology or instrument measure every element and isotope on the periodic chart? Yes, it can.
Our laser technologies research group has found that such capability exists by combining laser ablation sampling with optical and mass detection in a single instrument. Laser induced breakdown spectroscopy (LIBS) provides light elements, halogens and major concentrations, while inductively-coupled plasma mass spectroscopy (ICP-MS) simultaneously provides trace elemental and isotopic analysis. The approach makes it possible to measure, for example, hydrogen, nitrogen, fluorine and carbon at the same time as uranium and thorium isotopes.
Another beautiful aspect of the single instrument approach is the ability to predict interferences in each of the technologies and develop correction factors. For example, identifying the elemental contaminants measured by LIBS that lead to isobaric interferences in the mass spectrometer.
We are working on a technology platform that advances LIBS called laser ablation molecular isotopic spectroscopy (LAMIS). It measures molecular spectra appearing after the ablation laser pulse. With LAMIS, the isotopes of light elements (for example, carbon, nitrogen, hydrogen, chlorine) become part of the analysis package. Therefore, we can eliminate the need for multiple analytical technologies to characterize samples fully using this new approach: tandem LA-LIBS/LAMIS-ICP can do the job of glow discharge (GD), X-ray fluorescence (XRF), carbon, and mercury analyzers, optical emission spectroscopy (OES) and MS at the same time.
Rapid chemical imaging, analysis and depth profiling with high spatial resolution at atmospheric pressure are additional benefits that underlie the complete elemental/isotopic analysis capabilities that we have studied and developed. Notably, performance (for example sensitivity) is driven by the application; the instrument can be optimized for a specific element or isotope or optimized for best sensitivity over the entire periodic chart of elements.
Another benefit is that there is no need for solid sample digestion, eliminating the use of hazardous and costly acid or other solvent dissolution and purification procedures before analysis – laser ablation does all the sampling you need. We have found the technology is also suitable for liquid and gas analysis, but the real value is in changing the solid-sample analysis paradigm away from conventional dissolution. What about heterogeneity? Well, instead of being a challenge it becomes a feature, measurable through spatial mapping or averaged to present a bulk analysis.
The LIBS/LAMIS combination is an all-optical elemental/isotopic analytical technology that is suitable for real-time standoff measurements. For example, NASA has proven that LIBS can work on Mars with a standoff distance of about 7 meters – a very successful demonstration of real-time elemental analysis in a challenging environment. And we think that many industrial applications can benefit from standoff in-line elemental analysis; for example, raw material feedstock analysis, pharmaceutical inspection, Li-ion batteries, steel, polymers, food.
Something that I find puzzling is the fact that laser ablation has been studied and developed for more than 50 years, has been adopted in many applications (surgery, cutting, welding, nanomaterials, and so on) – and yet, for chemical analysis, it is not a mainstay approach. In my view, the main impediment is the need for a paradigm shift in thinking.
Reliable commercial instruments with data analysis software are available, making the value proposition for this technology compelling. Does the ability to measure every element and isotope with a single instrument, no sample preparation and rapid turn-around time not sound good to you? Certainly, paradigm shifts require risk takers – just like giving up a typewriter to use a computer. You don’t see many typewriters these days...
I think another hindrance to laser ablation adoption for chemical analysis has been the component approach to applications, which has led people to ask the wrong question: “What is the best laser and or detector?” Although components are critical to the application, the real question is “What are the requirements of the analysis?” In this way, performance metrics are guaranteed. I think it is only a matter of time before industry will realize the benefits of this rapid, flexible, single instrument approach.
Rick Russo has studied the fundamental properties of laser material interactions and related applications for over 30 years. He received a BS degree in Chemistry from the University of Florida in 1976 and a PhD in Chemistry from Indiana University in 1981, where he also completed his postdoctoral studies. Since 1982, he has held various positions at the Lawrence Berkeley National Laboratory in Berkeley, California, where he is currently a Senior Scientist. His research has included: fundamental studies of laser heating and laser ablation processes; improved chemical analysis using laser ablation; fiber sensors for monitoring organic and radioactive species in groundwater; Raman, fluorescence, and photothermal spectroscopy of rare-earth and actinide ions. He is co-inventor of the ion-assisted pulsed laser deposition (IBAD) and ion-texturing (ITEX) processes, and holds the world record for the highest critical current density (Jc) HTSC film on polycrystalline substrate. Rick is co-discoverer of the nanowire laser, highlighted by a Science article and patent application in 2002. Rick is also CEO and founder of Applied Spectra.
