Tandem LA-LIBS – All in One Solid Sample Analyzer
By Dr. Rick Russo
Chemical analysis is vital to the world economy – the elemental and isotopic composition of everything determines if it is safe or harmful, meets requirements or not, valuable or worthless. Spatial distribution of the elements in a material also is critical; does heterogeneity establish or compromise integrity?
Inductively Coupled Plasma (ICP) with Optical Emission Spectroscopy (OES) and Mass Spectrometry (MS) are fantastic instruments for multi-elemental analysis. I believe that the ICP is one of the most significant developments of the 20th century, and a powerhouse for 21st century elemental and isotopic analysis.
It is the sample preparation process that is obsolete.
If a sample is liquid, it can be analyzed directly or with nominal dilution using the ICP. However, there are millions of solid samples that must be digested before analysis, generally requiring the use of acids, microwave ovens and high temperature. Solid sample preparation is laborious, hazardous, creates waste and is costly. Also, dissolving the sample precludes knowledge of heterogeneity.
ICP with laser ablation (LA) is a paradigm change for solid sample analysis.
Instead of the analyst having to digest the sample, the laser does the work in removing a small amount of the sample that is then directly injected into the ICP. Analysis using LA requires only micrograms or less of sample whereas sample digestion in acid requires milligrams to grams.
Some people have said that LA sampling does not give representative analyses because it is a micro-sampling technique. You can spin this around and say that LA measures spatial heterogeneity. If bulk analysis is required, then repetitive laser pulses over a representative area will provide the bulk composition.
ICP-TOF-MS transient signal of selected isotopes produced by high repetition rate femtosecond laser ablation of NIST 612 and granite at 6 mm spot size, 40 mm s-1 and 20 kHz.
Each community has established how much mass is required to be digested for representative analysis; the same can be established for LA. In cases where large quantities are required, simple grinding and mixing to prepare a representative bulk sample would eliminate the acid and microwave digestion steps. These are the messy steps and bottlenecks to rapid efficient clean analysis.
ICP measurements do not provide analysis for every element that can be present in a sample, and ICP-MS is generally not suitable for major concentrations. An innovative approach to provide these capabilities is to combine LA-ICP with laser induced breakdown spectroscopy (LIBS); the basis of the Applied Spectra J200 Tandem LA-LIBS Instrument.
With LIBS, elemental analysis of the sample is measured by the emission spectra from the tiny plasma created by the laser during sampling. The laser sampling process produces a plasma (optical emission) simultaneous with the aerosol for the ICP.
What an ideal case – two simultaneous technologies that exist for every laser pulse!
LIBS measures light elements, halogens and concentrations of major constituents. The ICP-MS is ideal for measuring the heavier elements and isotopes at trace levels. Normally, three to five separate analytical instruments would be needed to achieve the capabilities provided by the J200 Tandem, requiring substantially more sample, time and cost to achieve similar results. Even using multiple instruments, all the elements/isotopes in a sample could not be measured from a single location in a heterogeneous material.
No other analytical instrument offers the compelling capabilities to spatially measure every element in the periodic chart.
The J200 Tandem is an integrated user friendly instrument with internal data analysis software. The user can select which mode(s) (LA and/or LIBS) to process data. There is no burden in measuring the simultaneous spectra and all data are available for use (or not) depending on the application.
Simultaneous measurements also can be used for signal correlation and data fusion. Data fusion of correlated measurements can provide improvements in accuracy, precision, normalization for calibration and quantitative analysis by identifying appropriate internal standards. In addition, based on LIBS measurements, the software interface can display warning signals for ICP-MS isobaric interference.
The J200 Tandem instrument addresses numerous applications.
Some example measurement capabilities in these application areas include biological imaging, geochemical age dating, forensics, mining, energy, environmental remediation, advanced batteries, nonproliferation, safeguards and advanced industrial manufacturing.
- Forensics
- LA-ICP-MS: U, Pb
- LIBS: Ca, Si, C, O, N, H
- Geological, Environmental
- LA-ICP-MS: Pb, U, Th, REE’s, Sr, Se, As
- LIBS: O, N, H, Li, Be, Na, K, Ca, Si, Al, Fe, Cl, Br, F, Ar, Ti, Sr, Rb, Mg, B
- Energy (batteries, solar)
- LA-ICP-MS: Fe, Cu, Ni, Zn, Pb, Cd, etc.
- LIBS: C, H, Si, Li, Pt, Rh etc.
- Nuclear
- LA-ICP-MS: U, Pu, Th, Pb
- LIBS: Be, Li, O, H, D, B, F, N
- Food
- LA-ICP-MS: Low concentration metals, As, Se
- LIBS: C, S, N, Na, Li, K
- Metallurgic
- LA-ICP-MS: Fe, Al, Ta, Cr, Zn, etc.
- LIBS: C, S, P, H, O, N
- Coal
- LA-ICP-OES: Ideal, too much carbon deposits issues for MS
- LIBS: H, C, N, O; H/C ratio
- Petroleum (crude oil derivatives, catalyst)
- LA-ICP-OES: Ideal, too much carbon deposits issues for MS
- LIBS: H, C, N, O; H/C ratio
- Semiconductor
- LA-ICP-MS: Ti, V, Mn, Fe, Ni, Cr, Zn, etc.
- LIBS: C, H, Si, Cu, Au, Ta
- Bio-medical
- LA-ICP-MS: Cu, Zn, Pt, Au
- LIBS: C, S, P, H, O, N
Layer-by-layer contour elemental maps obtained by simultaneous LIBS/LA-ICP-MS. (a and b) LIBS and (c–d) LA-ICP-MS maps as a function of depth.2
The J200 Tandem instrument is a new paradigm for chemical analysis. Paradigm shifts take time but once adopted, they change the world.
Hardly any corrective eye surgeries are done using a scalpel since LASIK was adopted. NASA is showing the benefits of an advanced technology like LIBS for chemical analysis. They have recorded almost 500,000 spectra since landing the Curiosity rover on Mars, mitigating their reliance on robotic sampling and analysis.
Did I use a typewriter to write this article or a computer? This is not a question but a comment – if an advanced technology is available – is there really a choice if one wants to remain competitive.
This is the way I view the innovative new technology by Applied Spectra. Laser ablation (LA) replaces acid digestion and the J200 Tandem measures every element in the sample. No more multiple instruments to measure light and heavy elements or to measure major to trace concentrations, and no more sample preparation.
Chemical analysis has changed – have you?
About the Author
Richard E. Russo, Ph.D – Executive Chairman at Applied Spectra. Dr. Russo has studied laser ablation, LIBS and general atomic and molecular spectroscopy for over 35 years. He also is a senior scientist at the Lawrence Berkeley National Laboratory and has published more than 325 manuscripts in a variety of places including the Journal of Analytical Atomic Spectrometry, Spectrochimica Acta B, Applied Physics, Applied Spectroscopy and Talanta. He also has a number of patents, book chapters, and presentations to his name, and was given an R&D 100 Award in 2006 and 2012. His technical and scientific expertise is a driving factor in Applied Spectra’s emerging role in the LIBS and LA-ICP-MS industry.
Journal Reference
1. Jhanis J. Gonzalez, Dayana D. Oropeza, Henry Longerich, Xianglei Maoa and Richard E. Russo. Rapid bulk analysis using femtosecond laser ablation inductively coupled plasma time-of-flight mass spectrometry. J. Anal. At. Spectrom., 2012, 27, 1405.
2. Jose R. Chirinos, Dayana D. Oropeza, Jhanis J. Gonzalez, Huaming Hou, Mark Morey, Vassilia Zorbaa and Richard E. Russo. Simultaneous 3-dimensional elemental imaging with LIBS and LA-ICP-MS. J. Anal. At. Spectrom., 2014. DOI: 10.1039/c4ja00066h
