Laser Induced Breakdown Spectroscopy (LIBS) is the core technology behind the groundbreaking FOSS Micral™ analyzer. But even though Micral is the first fully automated solution to measure elements in a broad variety of agricultural samples such as feed and forage, the method is not completely new.
We spoke to scientist, PhD Jens Frydenvang from the University of Copenhagen. With a background in physics and a PhD in analytical chemistry focusing on LIBS, and extensive experience using LIBS for geochemical observations on the planet Mars in collaboration with NASA, Jens Frydenvang is quite the expert on LIBS. We called him up to discuss the challenges and the future potential of LIBS technology on our own planet, and why accuracy isn’t always the most important parameter when choosing a method for element analysis.
On Mars, both the Chemcam and the Supercam LIBS instruments shoot lasers onto the Martian surface within a 5-6 meter radius of the rover on which they are mounted. But when it comes to using LIBS in a populated setting on planet Earth, it’s not that simple. The main drawback of using an open laser path on Earth like on Mars has to do with eye safety concerns.
“So that's obviously an issue for use cases of LIBS on Earth. Either everyone around it needs to wear protective goggles, or you have the laser path completely incased in the hardware itself. But in essence, there's no real issue in using LIBS on Earth, similar to what we do on Mars,” says Jens Frydenvang.
Apart from safety concerns, the potential of using LIBS on Earth all depends on the use case, he explains. “LIBS has a unique strength because it can provide quick measurements, and that strength comes from the fact that we have this quick heating of the sample to make that spark.” However, achieving a stable result with LIBS is challenging. For example, the way samples are handled, and the quality of calibrations are an essential part of achieving accurate and stable results.
“For a long time, there was a lot of doubt about whether you could get to something that was sufficiently accurate to be useful for many cases. But what we've seen, especially on Mars, is that if you have a good enough calibration, then we can move from the purely qualitative into a quantitative realm of LIBS usage,” explains Jens Frydenvang.
“If at all possible, some kind of sample preparation is beneficial to overcome some of the limitations that come from the very quick LIBS measurements, but you need to be able to do it quite consistently – and obviously in a way that doesn’t jeopardize the strengths that LIBS provide over other techniques” he adds.
To succeed with LIBS, you need full control of your sample preparation, you need the right lasers and the right spectrometer, and from that point on, it's really the calibration that make the difference.
“You'll never get to an ICP-MS level, but you can get to a level where you have sufficient information to meet the goal of the analysis. What is achievable depends on what the element of interest is. If you're looking for lithium, for example, then XRF won't help you. But LIBS is very sensitive to the light elements due to the physical nature of these. Overall, the question is if you can create an instrument that has good enough accuracy and precision for what you need, and second, if you have a use case where you need the unique strength that LIBS can provide, e.g., a high throughput, either because it drives down prices or because you have a fast process that needs to be continuously analyzed? Then you really have a fantastic case for using LIBS.”
Good enough accuracy
A LIBS measurement may not have the same accuracy as ICP-MS or XRF, so when Jens Frydenvang talks about good enough accuracy, what does that actually mean?
“Even if you talk ICP-MS, there's a huge range in terms of the accuracy that different laboratories can provide. It is often the case that ICP-MS (or optical emission spectroscopy) has become the gold standard. But, as soon as you start looking into the actual accuracy of different labs, then you realize that that they're not 100% accurate at all. And that's why it's a difficult question to answer. You could look at it like this, do you need 4 decimals for these results? Or maybe you don't need any decimals in order to make a decision? So, that's the kind of question we are asking here,” Jens Frydenvang explains.
So rather than focusing on getting the highest level of accuracy, sometimes getting to a level where you are able to make the right decisions without delay is more important.
“If you don't need 4 decimals then ICP-MS might be overkill and then you can do it much more quickly with LIBS because you don't need to dissolve the sample. So, if you don't need 4 decimals but you rather want something that is quick, then LIBS would be in an ideal scenario,” Jens Frydenvang continues.
Another aspect to consider is the fact that faster results and a higher throughput can provide more information.
“If a method would mean that you could get information from 1000 points instead of 100 points on an area, then even though each point has a lower accuracy, the fact that you can get information from a wider area might be even more important,” he concludes.
Future use cases
Looking into the future, what we will be able to detect with LIBS is constantly evolving. Jens Frydenvang talks about the possibility to potentially measure even minor elements such as fluorine.
