Laser-induced breakdown spectroscopy (LIBS) is a type of atomic emission spectroscopy which uses a highly energetic laser pulse as the excitation source. [1] [2] The laser is focused to form a plasma, which atomizes and excites samples. The formation of the plasma only begins when the focused laser achieves a certain threshold for optical breakdown, which generally depends on the environment and the target material. [3]
From 2000 to 2010, the U.S. Army Research Laboratory (ARL) researched potential extensions to LIBS technology, which focused on hazardous material detection. [4] [5] Applications investigated at ARL included the standoff detection of explosive residues and other hazardous materials, plastic landmine discrimination, and material characterization of various metal alloys and polymers. Results presented by ARL suggest that LIBS may be able to discriminate between energetic and non-energetic materials. [6]
Broadband high-resolution spectrometers were developed in 2000 and commercialized in 2003. Designed for material analysis, the spectrometer allowed the LIBS system to be sensitive to chemical elements in low concentration. [7]
ARL LIBS applications studied from 2000 to 2010 included: [5]
ARL LIBS prototypes studied during this period included: [5]
LIBS is one of several analytical techniques that can be deployed in the field as opposed to pure laboratory techniques e.g. spark OES. As of 2015 [update] , recent research on LIBS focuses on compact and (man-)portable systems. Some industrial applications of LIBS include the detection of material mix-ups, [8] analysis of inclusions in steel, analysis of slags in secondary metallurgy, [9] analysis of combustion processes, [10] and high-speed identification of scrap pieces for material-specific recycling tasks. Armed with data analysis techniques, this technique is being extended to pharmaceutical samples. [11] [12]
Following multiphoton or tunnel ionization the electron is being accelerated by inverse Bremsstrahlung and can collide with the nearby molecules and generate new electrons through collisions. If the pulse duration is long, the newly ionized electrons can be accelerated and eventually avalanche or cascade ionization follows. Once the density of the electrons reaches a critical value, breakdown occurs and high density plasma is created which has no memory of the laser pulse. So, the criterion for the shortness of a pulse in dense media is as follows: A pulse interacting with a dense matter is considered to be short if during the interaction the threshold for the avalanche ionization is not reached. At the first glance this definition may appear to be too limiting. Fortunately, due to the delicately balanced behavior of the pulses in dense media, the threshold cannot be reached easily.[ citation needed ] The phenomenon responsible for the balance is the intensity clamping [13] through the onset of filamentation process during the propagation of strong laser pulses in dense media.
A potentially important development to LIBS involves the use of a short laser pulse as a spectroscopic source. [14] In this method, a plasma column is created as a result of focusing ultrafast laser pulses in a gas. The self-luminous plasma is far superior in terms of low level of continuum and also smaller line broadening. This is attributed to the lower density of the plasma in the case of short laser pulses due to the defocusing effects which limits the intensity of the pulse in the interaction region and thus prevents further multiphoton/tunnel ionization of the gas. [15] [16]
For an optically thin plasma composed of a single, neutral atomic species in local thermal equilibrium (LTE), the density of photons emitted by a transition from level i to level j is [17]
where :
The partition function is the statistical occupation fraction of every level of the atomic species :
Recently, LIBS has been investigated as a fast, micro-destructive food analysis tool. It is considered a potential analytical tool for qualitative and quantitative chemical analysis, making it suitable as a PAT (Process Analytical Technology) or portable tool. Milk, bakery products, tea, vegetable oils, water, cereals, flour, potatoes, palm date and different types of meat have been analyzed using LIBS. [18] Few studies have shown its potential as an adulteration detection tool for certain foods. [19] [20] LIBS has also been evaluated as a promising elemental imaging technique in meat. [21]
In 2019, researchers of the University of York and of the Liverpool John Moores University employed LIBS for studying 12 European oysters ( Ostrea edulis , Linnaeus, 1758) from the Late Mesolithic shell midden at Conors Island (Republic of Ireland). The results highlighted the applicability of LIBS to determine prehistoric seasonality practices as well as biological age and growth at an improved rate and reduced cost than was previously achievable. [22] [23]
Analytical chemistry studies and uses instruments and methods to separate, identify, and quantify matter. In practice, separation, identification or quantification may constitute the entire analysis or be combined with another method. Separation isolates analytes. Qualitative analysis identifies analytes, while quantitative analysis determines the numerical amount or concentration.
Inductively coupled plasma mass spectrometry (ICP-MS) is a type of mass spectrometry that uses an inductively coupled plasma to ionize the sample. It atomizes the sample and creates atomic and small polyatomic ions, which are then detected. It is known and used for its ability to detect metals and several non-metals in liquid samples at very low concentrations. It can detect different isotopes of the same element, which makes it a versatile tool in isotopic labeling.
An ion source is a device that creates atomic and molecular ions. Ion sources are used to form ions for mass spectrometers, optical emission spectrometers, particle accelerators, ion implanters and ion engines.
Gold fingerprinting is a method of identifying an item made of gold based on the impurities or trace elements it contains.
An inductively coupled plasma (ICP) or transformer coupled plasma (TCP) is a type of plasma source in which the energy is supplied by electric currents which are produced by electromagnetic induction, that is, by time-varying magnetic fields.
Laser ablation or photoablation is the process of removing material from a solid surface by irradiating it with a laser beam. At low laser flux, the material is heated by the absorbed laser energy and evaporates or sublimates. At high laser flux, the material is typically converted to a plasma. Usually, laser ablation refers to removing material with a pulsed laser, but it is possible to ablate material with a continuous wave laser beam if the laser intensity is high enough. While relatively long laser pulses can heat and thermally alter or damage the processed material, ultrashort laser pulses cause only minimal material damage during processing due to the ultrashort light-matter interaction and are therefore also suitable for micromaterial processing. Excimer lasers of deep ultra-violet light are mainly used in photoablation; the wavelength of laser used in photoablation is approximately 200 nm.
Infrared multiple photon dissociation (IRMPD) is a technique used in mass spectrometry to fragment molecules in the gas phase usually for structural analysis of the original (parent) molecule.
In nonlinear optics, filament propagation is propagation of a beam of light through a medium without diffraction. This is possible because the Kerr effect causes an index of refraction change in the medium, resulting in self-focusing of the beam.
Inductively coupled plasma atomic emission spectroscopy (ICP-AES), also referred to as inductively coupled plasma optical emission spectroscopy (ICP-OES), is an analytical technique used for the detection of chemical elements. It is a type of emission spectroscopy that uses the inductively coupled plasma to produce excited atoms and ions that emit electromagnetic radiation at wavelengths characteristic of a particular element. The plasma is a high temperature source of ionised source gas. The plasma is sustained and maintained by inductive coupling from electrical coils at megahertz frequencies. The source temperature is in the range from 6000 to 10,000 K. The intensity of the emissions from various wavelengths of light are proportional to the concentrations of the elements within the sample.
An electric spark is an abrupt electrical discharge that occurs when a sufficiently high electric field creates an ionized, electrically conductive channel through a normally-insulating medium, often air or other gases or gas mixtures. Michael Faraday described this phenomenon as "the beautiful flash of light attending the discharge of common electricity".
Velmer A. Fassel was an American chemist who developed the inductively coupled plasma (ICP) and demonstrated its use as ion source for mass spectrometry.
Atomic emission spectroscopy (AES) is a method of chemical analysis that uses the intensity of light emitted from a flame, plasma, arc, or spark at a particular wavelength to determine the quantity of an element in a sample. The wavelength of the atomic spectral line in the emission spectrum gives the identity of the element while the intensity of the emitted light is proportional to the number of atoms of the element. The sample may be excited by various methods.
Chemistry and Camera complex (ChemCam) is a suite of remote sensing instruments on Mars for the Curiosity rover. As the name implies, ChemCam is actually two different instruments combined as one: a laser-induced breakdown spectroscopy (LIBS) and a Remote Micro Imager (RMI) telescope. The purpose of the LIBS instrument is to provide elemental compositions of rock and soil, while the RMI will give ChemCam scientists high-resolution images of the sampling areas of the rocks and soil that LIBS targets. The LIBS instrument can target a rock or soil sample from up to 7 m (23 ft) away, vaporizing a small amount of it with about 30 5-nanosecond pulses from a 1067 nm infrared laser and then observing the spectrum of the light emitted by the vaporized rock.
Resonance ionization is a process in optical physics used to excite a specific atom beyond its ionization potential to form an ion using a beam of photons irradiated from a pulsed laser light. In resonance ionization, the absorption or emission properties of the emitted photons are not considered, rather only the resulting excited ions are mass-selected, detected and measured. Depending on the laser light source used, one electron can be removed from each atom so that resonance ionization produces an efficient selectivity in two ways: elemental selectivity in ionization and isotopic selectivity in measurement.
Glow-discharge optical emission spectroscopy (GDOES) is a spectroscopic method for the quantitative analysis of metals and other non-metallic solids. The idea was published and patented in 1968 by Werner Grimm from Hanau, Germany.
Candice Mae Bridge is an American chemist and Associate Professor of Chemistry and Forensic Science at the University of Central Florida. Her research considers the development of mass spectroscopy for forensic analysis, including the characterization of lubricant from rape victims and residue from gunshots, as well as the identification of drugs in urine samples.
Dmitry Bandura is a Soviet-born Canadian scientist, notable for being one of the co-inventors of the Mass cytometry technology. Bandura co-founded DVS Sciences in 2004 along with Drs Vladimir Baranov, Scott D. Tanner, and Olga Ornatsky.
Vladimir Baranov is a Soviet born Canadian scientist and one of the original co-inventors of Mass cytometry technology...
Scott Tanner is a Canadian scientist, inventor, and entrepreneur. His areas of expertise include mass spectroscopy, especially inductively coupled plasma mass spectrometry (ICP-MS), and mass cytometry.
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