What is laser induced breakdown spectroscopy?
Laser-induced breakdown spectroscopy (LIBS)
is a type of atomic emission spectrometer. It allows qualitative and quantitative analysis of almost all elements in solid-, liquid- and gas-phase matrices. Unlike conventional detection methods such as ICP-OES or XRF, LIBS
eliminates the need for complex sample preparation during the detection process.
To achieve the objective without complicated sample preparation, LIBS spectroscopy
uses a high-energy focused pulsed laser beam to excite the sample to the plasma state, which generates the corresponding elemental emission spectrum for analysis. The wavelength of the elemental emission spectrum is directly related to the type of element, while the intensity of the elemental spectral lines is related to the content of the element.
Laser-induced breakdown spectroscopy principle
The development of laser technology has greatly contributed to the development of spectroscopy. The laser-induced breakdown spectroscopy (LIBS) technique
, also known as laser-induced plasma spectroscopy (LIPS)
, is a new method for the analysis of matter elements. It is a new analytical method in the field of spectroscopy, which was proposed and realized by David Cremers' group at Los Alamos National Laboratory in 1962. It is a new analytical tool in the field of spectral analysis.Laser-induced breakdown spectroscopy
uses a high peak power pulsed laser to irradiate the sample and the beam is focused to a very small analysis spot (typically 10-400 microns in diameter). In the area of the laser irradiated spot, the material in the sample is ablated away and a cloud of nanoparticles is formed above the sample. Since the peak energy of the laser beam is quite high, its absorption and multiphoton ionization effects increase the opacity of the gas and aerosol clouds generated above the sample, even in the case of only very short laser pulse excitation. As the laser energy is significantly absorbed by the cloud, the plasma is gradually formed. The high-energy plasma melts the nanoparticles, excites the atoms in them, and emits light. The light emitted by the atoms can be captured by the detector and recorded as a spectrum, which can be analyzed to obtain information about which elements are present in the sample, and further qualitative (e.g., material identification, PMI) and quantitative (e.g., the amount of an element in the sample) analyses can be performed by software algorithms.
A. Basic principle of laser-induced emission spectroscopy
The high-power pulsed laser beam generated by the laser is focused on the surface of the sample, and the atoms in the sample are excited to form a high-temperature plasma spark. The excited atoms and ions emit characteristic spectral lines of atoms and kaons during the de-excitation process, and then the wavelength (UV to NIR) and intensity of the characteristic spectral lines of atoms are measured by a spectrometer for qualitative or quantitative analysis of the elements.
Limit of detection and quantitative analysis
The detection limits of LIBS are highly dependent on the type of sample to be measured, the specific elements, and the laser/spectral detector configuration of the instrument. For these reasons, the detection limits of LIBS can range from a few ppm up to the % level. For most routine applications, LIBS detection limits can be achieved from 10 ppm to 100 ppm for most elements, and for quantitative analysis, the relative standard deviation of measurements obtained by LIBS can be within 3-5%, and typically within 2% or even <1% for homogeneous materials.
B. The process of plasma spark generation
Under the action of a strong excitation pulse, atoms and fractions in the laser's focus region are ionized by multi photons to produce initial free electrons. As the focus laser increases, the atoms continue to absorb photons and ionize, producing a large number of primary electrons. When the laser power is strong enough, the pulse duration is long enough for the free electrons to accelerate under the action of the laser. When the electrons have enough energy to bombard the atoms, the atoms ionize and produce new electrons. The acceleration of these electrons also causes the atoms to continue ionizing, resulting in an avalanche effect and a rapid increase of electrons in a very short period. At the same time, this leads to continuous ionization of the atoms, resulting in a large number of free electrons and ions, and an overall approximately electrically neutral plasma. Excitation plasma is a light-emitting source that irradiates photons at specific frequencies to produce characteristic spectral lines. Its frequency and intensity distributions contain information about the species and concentration of the analyzed objects.
A very high-power density, which can exceed 1GW/cm2, is used in the process of generating plasma. A few micrograms of material on the surface are instantaneously heated by the laser to 10,000 degrees Celsius and ejected to form a very short-lived but extremely bright plasma. These ejected plasma bodies have been polarized by the laser into excited atoms or ions. At the end of the laser pulse, the plasma cools down as quickly as it began to expand. During the cooling process, the excited atoms or ions return from the high-energy state to the low-energy state and emit optical radiation with their characteristics. The detection and analysis of these spectral emissions by a sensitive spectrometer gives information on the elemental composition of the substance.
Laser-induced breakdown spectroscopy applications
Laser-induced breakdown spectroscopy, as new material identification and quantitative analysis technology, can be used in the laboratory as well as applied to online inspection in industrial sites. Its main features are as follows.
a. Fast and direct analysis with almost no sample preparation required.
b. Detects almost all elements.
c. Simultaneous analysis of multiple elements.
d. Matrix morphology versatility - almost any solid sample can be detected.
LIBS spectroscopy makes up for the shortcomings of traditional elemental analysis methods, especially in applications such as micro-area material analysis, plating/film analysis, defect detection, jewelry identification, forensic evidence identification, powder material analysis, alloy analysis, etc. LIBS laser can also be widely applied to applications in different fields such as geology, coal, metallurgy, pharmaceuticals, environment, and scientific research.
In addition to the traditional laboratory applications, libs laser induced breakdown spectroscopy is one of the few elemental analysis technologies that can be made into handheld portable devices. It is considered the only elemental analysis technology that can do so online analysis. This will enable the analysis technology to expand greatly from the laboratory field to the outdoor, field, and even the production process.
Applications of Laser-Induced Breakdown Spectroscopy (LIBS)
emote non-destructive analysis, characterization, and identification of materials.
b. Remote detection and elemental analysis of hazardous materials (high temperature, radioactive, chemically toxic materials).
c. On-site detection of radioactive contamination of storage containers (glassy high-grade scrap, intermediate-grade scrap).
d. On-site composition analysis of steel in inaccessible environments (e.g. nuclear reactor pressure vessels).
e. Rapid identification of metals and alloys in the scrap recycling process.
f. Metal identification of critical components during manufacturing and assembly.
g. Online composition analysis for process control of liquid metals and alloys (e.g. determination of carbon, silicon, and phosphorus content in steel).
h. On-line composition analysis for process control of liquid glass (e.g. determination of iron and lead content).
i. On-site identification of materials submerged in water (e.g. metals, alloys, ceramics, minerals, radioactive materials).
j. Deep profile analysis and composition analysis of surface coatings (e.g. plated steel, plastic film layer, heavy metals in paint).
k. Online monitoring of airborne particles (e.g. stack emission monitoring).
l. Component analysis of complex shaped objects.
Laser induced breakdown spectroscopy features
a. Laser-induced breakdown spectrometer can measure almost all-natural elements, including H, Li, Be, C, N, O, S, etc., which are difficult to analyze by conventional methods.
b. The sample preparation process is very simple and also allows the sample surface to be cleaned or the surface coating to be removed using repeated pulses.
c. High throughput analysis can be performed with only a small amount of sample (1-10g), which greatly reduces the cost of analysis.
d. With ppm-level detection limits and high sensitivity, detection accuracy, and degree.
e. Truly non-destructive detection. Only consume a tiny amount of sample, and there is almost no heating effect when the laser is incident on the sample.
f. The possibility of elemental analysis of samples in any physical state, including solids, liquids, gases, and various mixtures.
g. Virtually unaffected by spectral interference.
h. Reduced analysis time to approximately 20 seconds for all detectable elemental colleague determinations, which is a significant advantage relative to other analytical techniques.
i. Good environmental adaptability with almost no special requirements. It works when connected to the power supply and does not require water cooling or compressed air. This means it can meet the requirements of field experiments.
j. Consumables without periodic replacement and the configuration of the laser can be used more than 600000 times continuously.
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