LIBS vs XRF: comparing handheld scrap analyzers

What is XRF technology?

X-ray fluorescence (XRF) is a non-destructive technique used to determine the composition of materials. For recyclers who sort metals and alloys in applications where a precise understanding of content and composition is important, X-ray fluorescence (XRF) based handheld analyzers have been the main tool employed for material verification purposes for decades.

Benefits of handheld X-ray fluorescence (XRF)

Handheld XRF analyzers are considered by most to be the best option for applications in stainless steel and heavy metals, or for recyclers focused on plastics and e-waste sorting. Handheld X-ray fluorescence analyzers have the capability to shoot materials and send the data directly to staff, who can then easily build their blends. Designed to deliver fast light element detection for scrap recycling, basic PMI, metal manufacturing and precious metals, they also effectively measure ferrous metals, aluminum, copper, stainless steel, nickel and gold karats instantly, making these machines extra valuable for yards where sorters are doing 100 percent of the checking of material. The machines lower fatigue and increase productivity, which translates into more profit for scrap metal recyclers.

What is LIBS technology?

In recent years, laser-induced breakdown spectroscopy (LIBS) has been used increasingly in metal recycling applications, especially with aluminum and other nonferrous metals. LIBS is an analytical technique that uses a short-pulse, low-energy laser beam to cause laser ablation, providing sample surface analysis without radiation concerns.

Benefits of laser induced breakdown spectroscopy

When using LIBS, material verification results can be returned in as few as 10 seconds for increased speed and productivity. Its portability is especially valuable for operators at complex job sites with small or difficult spaces that need to be accessed for analysis. Additionally, LIBS typically samples very small amounts of material, making it almost entirely non-destructive.

What is the difference between XRF and LIBS?

In a 2015 white paper, by John I.H. Patterson, Phd., an expert on the topic of metals analysis, he compares the two technologies in detail. He writes: "For fast sorting of aluminum alloys based upon light elements, LIBS is clearly the best alternative, as well as for separating many magnesium and titanium grades. When precision and accuracy matter more, as in PMI (positive material identification) analysis and quality control or when price figures are required in scrap trading (Ni, Mo, etc.), or if your application is measuring stainless steel, high-temp alloys or other heavy metal alloys, then XRF is still the method of choice." 

To put it simply, handheld XRF analyzers use X-ray radiation to determine metal and alloy content and composition, while LIBS uses a low-energy laser pulse and optical technology, providing analysis without radiation concerns.

Overall, advances in handheld analyzers for scrap mean recyclers can now identify and sort a wider range of elements and alloys, including light elements, in the yard or in their facilities, with high speed, accuracy and safety. Both LIBS and XRF now feature smart, reliable connectivity to data analysis tools, and are designed to be lightweight, rugged and ergonomically friendly for users.

Recycling Product News asked some of the industry's leading manufacturers to provide insight on how the two technologies compare.

Bruker: A tale of two technologies

Bruker, a leading U.S.-based manufacturer of both XRF and LIBS handheld analyzers, describes XRF technology on their company website as a completely non-destructive process whereby electrons are displaced from their atomic orbital positions, releasing a burst of energy that is characteristic of a specific element. This release of energy is then registered by a silicon detector in the XRF handheld instrument, which in turn categorizes the energies by element.

With LIBS analyzers, Bruker's site describes the concept as follows: "With LIBS, a laser pulse strikes the surface of the sample and ablates an amount of material and generates a plasma plume (partially ionized gas). The energy of the laser is low, but is focused to a microscopic point on the sample to generate the plasma. In this plasma, emitted light is transmitted through optical fibres and the polychromatic radiation is dispersed in one or more spectrometers and detected by CCD chips." (CCD is an acronym for "charge coupled device", an image sensor technology that converts light into electrical charges, as used in most digital cameras.)

Bruker: S1 TITAN (XRF)

The S1 TITAN Handheld XRF Spectrometer is among the lightest tube-based handheld XRF analyzers on the market today, according to its manufacturer Bruker, at 1.5 kg, including battery. Fast analysis speed and exceptional accuracy are two key attributes that help define the S1 TITAN. Other innovative features include an integrated touch-screen colour display, 50 kV X-ray tube, SMART Grade timing, SharpBeam optimized X-ray geometry, Silicon Drift Detector (SDD), and an extremely tough housing that is sealed against humid and dusty environments. 

The S1 TITAN series is available in five configurations: models 800, 600, 500, 300 and 200. All models use Bruker's SharpBeam technology. The S1 TITAN 800 and 600 use a large area CUBE SDD detector to provide incredibly fast analysis times, while the S1 TITAN 500 is configured with a fast, accurate, and affordable standard SDD detector. The S1 TITAN 200 and 300 are configured with an economical Si-PIN detector. In addition, the S1 TITAN can be configured with calibrations that are optimized for a variety of sample materials, including a wide range of alloys, a variety of mining and environmental samples, as well as restricted materials.

Bruker: EOS 500 - Handheld (LIBS)

Bruker's new EOS 500 is a handheld Laser Induced Breakdown Spectroscopy (HH-LIBS) system. The EOS 500 is based on laser excitation of a metal sample followed by quantitative analysis of the light generated in the plume. This technology provides quick (3 to 5 seconds) analysis of alloys including aluminum, titanium and magnesium.

The EOS is especially well suited to scrap sorting of these alloys because of its quick and user-friendly operation. In addition to common elements detectable with XRF analyzers, the EOS is capable of measuring very light elements such as Li, Be and B, as well as laser-fast analysis of Mg, Al and Si.

TSI's ChemLite LIBS analyzer provides high accuracy and speed for light metals

Todd Hardwick is the global marketing manager for TSI Incorporated, a company focused on the manufacture of LIBS handheld analyzers."XRF cannot compete with LIBS when it comes to speed, ease of operation and cost of ownership," says Hardwick. "Our ChemLite LIBS analyzers precisely identify metals in one to two seconds, much faster than with XRF." Hardwick says that because there are no radiation concerns and their units use an eye-safe Class 1M pulsed laser, ChemLite "gun" owners avoid regulatory hassles - such as radiation licensing and the paperwork that comes with it.  

"LIBS requires no special training or storage and ChemLite LIBS guns do not need argon gas to operate," he continues. "When you add up the extra time, fees, training and supplies that XRF requires, the cost of ownership is often lower for LIBS." 

Hardwick does add though that LIBS is not a viable option for plastics recycling or e-waste applications according to their experience, whereas XRF technology is a viable tool for use in these applications.

TSI: ChemLite Plus (LIBS) 

ChemLite Plus is TSI's newest handheld LIBS metals analyzer. Units are designed to be accurate and fast, with 1 to 2 second readings and eye-safe, Class 1M lasers. Because there's no radiation, there are no regulation requirements, and compared to XRF units, ChemLite is easy and safe for any operator. Additionally, ChemLite analyzers have the largest laser spot size available, and a built-in cleaning mode.

ChemLite guns identify Al, Mg, Ti, Fe, Ni, and Cu alloys, and are able to separate close Al alloys that XRF cannot. TSI LIBS analyzers can also detect tramp elements, like Li and Be, down to 1 ppm and can measure Be copper alloys.

Olympus LIBS analyzer aims to enhance existing XRF technology

According to Ted Shields, portable products manager, analytical instruments division, Olympus Scientific Solutions Americas, LIBS is best viewed as a complimentary machine to more traditional handheld XRF, and each type of machine does certain things well. 

"The most intriguing thing about LIBS is the ability to measure elements that you cannot measure with XRF," says Shields. "Carbon, beryllium and lithium are all possible, and recent advances are making carbon in L-grades achievable for some LIBS analyzers." 

He says however that LIBS analyzers struggle with some elements that XRF excels at. Notably, he says, these include refractory metals, such as Cr, Zr, Mo, Ta and other common and commercially important alloying elements. "LIBS has a much smaller spot size than XRF," continues Shields. "This is good in the sense that the burn mark left behind is small. But it makes it much harder to get the same answer when you test twice in a row. This is because the sample varies across the small scale of the LIBS spot." 

Olympus: VANTA (XRF)

The Vanta analyzer is Olympus' most advanced handheld X-ray fluorescence (XRF) device and provides rapid, accurate element analysis and alloy identification to laboratory-quality results in the field. Units are military-standard drop tested, IP64 or IP65 rated, and designed with a large, gesture-capable touch screen, wireless communication, access to the Olympus Scientific Cloud, and direct PDF creation. They are also designed to be easy to use with minimal training, and to provide high throughput. 

The latest Vanta VMR model analyzers' come with a graphene detector window making them even more sensitive for magnesium, aluminum and silicon. Units provide very fast grade identification and are combined with Axon technology for high x-ray count. Other key features include: SmartSort and Grade Match Messaging; IMX processor; a metal detector shutter; intuitive navigation and configurable software.

Hitachi High-Technologies' calibration options suit various recycling applications

Hitachi High-Technologies: X-MET8000 (XRF)

Hitachi High-Tech's latest handheld XRF analyzer, the X-MET8000, is typically used in metal recycling and scrap yards when accurate on-site alloy identification and chemistry are required. 

"The optimized combination of a high performance X-ray tube and large area silicon-drift detector (SDD) delivers the results required in even the most demanding metals applications," says McKernan. "The X-MET8000 is used for analysis of light elements (Mg to S) and most commercial alloys, including aluminum, titanium, bronze and high temperature alloys. The low limits of detection provide accurate grading and determination of impurities and penalty elements." 

McKernan adds that unlike Hitachi-High Tech's LIBS model (Vulcan), its X-MET8000 HH-XRF analyzer is available with calibration options that suit various recycling applications. The X-MET8000's plastic FP calibration, for example, is optimized for the determination of a wide range of elements (Cl, Cd, Hg, Pb and many others). "In instances where separation of chlorinated from non-chlorinated plastics is required, The X-MET8000 can be used to ensure that materials such as PVC are not incinerated, preventing damage to the incinerator's masonry as well as the release of harmful dioxins into the atmosphere," explains McKernan. 

Hitachi High-Technologies: Vulcan (LIBS)

For Hitachi High-Tech's latest LIBS analyzer (the Vulcan) speed is the biggest asset to scrap metal recyclers as this maximizes their operational efficiency during metal sorting. According to Sean McKernan of Non-Destructive Testing (NDT) Products, an Ontario-based distributor for Hitachi High-Technologies analyzers; "by employing point and shoot operation, Hitachi High-Tech's Vulcan LIBS technology, creates a simple, fast routine for recyclers which eliminates user related errors and ensures consistency of results.

SciAps offers both LIBS and X-ray technologies 

SciAps: Z-200 (LIBS)

The Z-200 LIBS model uses a laser pulse of 5-6 mJ/pulse, with a 50 Hz repetition rate. According to SciAps, it is the world's only handheld LIBS capable of carbon analysis, and the only handheld analyzer with integrated argon purge, allowing for operation in both air-based analysis for quick screening, or argon-purge for highly sensitive, precise measurements. The Z model is ideal for analysis of aluminum scrap, particularly where low concentrations of Li, Be and/or B are important, for upgrading stainless into low-carbon or straight grades, and for sorting carbon steels.  

SciAps: X-250 (LIBS)

Complementing the LIBS model, SciAps' latest XRF model is the X-250, which provides quick analysis of stainless, high temperature- and red metals. The X-250 also excels in the analysis of aluminum alloys, in four seconds, including Al alloys that historically get mixed by other X-ray guns. Additionally, the X-250 offers leading performance on other light elements including S, P, Al and Si. 

This is an updated article; an earlier version was published in the March 2018 edition of Recycling Product News, Volume 26, Number 2.