XRF Glossary

Your A to Z guide for XRF and LIBS technology

Have questions about terminology related to XRF and LIBS? Our team of experts have put their heads together to provide you with a quick, instant reference to help answer all your questions about x-ray fluorescence (XRF) and laser induced breakdown spectroscopy (LIBS). Browse our list of terms to learn more about the science and the industries that support them; including metals, mining, consumer goods and environmental safety. Ready to learn more? Request a demo to speak with a member from our team.

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A partial or complete solid solution of two or more elements in a metallic matrix, e.g., steel (Fe + C), brass (Cu + Zn), bronze (Cu + Sn).

Alloy Grade
The name or designation of an alloy with a particular composition, e.g., C377, Forging brass (Cu 58.0-62.0, Fe 0-0.3, Pb 1.5-2.5, Zn 35.2-40.5).

API Recommended Practice 578
A recommended practice applicable to all oil and petrochemical processing systems developed by the American Petroleum Institute (API). API 578 provides guidance regarding the implementation of a material verification program (MVP). The material verification program mandates the use of positive material identification (PMI) and other methods to verify that the nominal composition of an asset, asset component, or weldment within the pressure envelope is consistent with the selected or specified construction materials.

Argon Purge
Used in LIBS, the process of replacing the air present within the sample chamber to aid in analyzing carbon. Elements such as carbon are below 200 nanometers in wavelength. The argon purge enables the optics of the LIBS spectrometer to see 200 nanometers and under.

Qualitative or quantitative analysis of a metal or ore to determine its components.

Atomic number
The number of protons in the nucleus of an atom, also sometimes called the proton number.

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When x-rays interact with low density materials (e.g., polyethylene) they can be scattered back toward the instrument and the operator.

Brominated Flame Retardant (BFR)
Bromine is commonly introduced into a product as a brominated flame retardant, which became a concern in the early 1990s when the connection was drawn between BFRs and the halogenated dioxins and furans. Some forms of BFRs, namely polybrominated biphenyls (PBBs) and polybrominated diphenyl ethers (PBDEs), have already been banned under RoHS regulations.

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Carbon Equivalency (CE)
An empirical value in weight percent, relating the combined effects of different alloying elements used in the making of carbon steels to an equivalent amount of carbon. This value can be calculated using a mathematical equation. By varying the amount of carbon and other alloying elements in the steel, the desired strength levels can be achieved by proper heat treatment. A better weldability and low temperature notch toughness may also be obtained.

Certified reference material (CRM)
A standard material that has been certified for certain elements with a given range of uncertainty. Typically, analysis has been performed by multiple methods and multiple laboratories.

Compton Normalization
An XRF technique that provides the best results for a wide range of environmental testing and some mining applications, particularly when it is necessary to measure sub-percent concentrations of heavy elements in samples composed mainly of light elements. In environmental testing projects, it is often highly desirable to be able to quickly measure low concentration levels of all of the eight Resource Conservation and Recovery Act (RCRA) heavy metals (Ag, As, Ba, Cd, Cr, Hg, Pb, Se) on site and in real time.

A thin covering over a substrate, usually to improve the surface properties such as corrosion resistance. Examples of coatings include anodized surfaces, electrochemical plating, chromate and phosphate coatings, as well as paint and enamels.

U.S. Consumer Product Safety Commission is “charged with protecting the public from unreasonable risks of serious injury or death from thousands of types of consumer products under the agency's jurisdiction.” It is the regulatory agency for enforcement of the CPSIA and endorses the use of XRF for CPSIA compliance.

Consumer Product Safety Improvement Act of 2008 (U.S.), H.R. 4040 sets in place new restrictions on permissible levels of lead in child-accessible products, reducing the permissible level of lead in paint, setting allowable levels of lead in all other materials, implementing an alternative standard for measuring lead in surface coatings, and permitting the use of XRF analyzers for screening purposes.

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Diffraction Grating
An optical component used to separate light into its constituent wavelengths.

Digital Signal Processor (DSP)
A device that shapes and produces the spectrum in XRF and LIBS instruments.

Drill Core
A “cylinder” of material taken as a sample form for geochemical analysis.

Drywall, Problematic (also Reactive Drywall)
Adverse health effects have been reported from those exposed to compounds emitted from imported drywall. XRF can facilitate screening for sulfur as an indicator of hazardous biological materials.

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A substance composed of only one type of atom, e.g., iron (Fe), copper (Cu), gold (Au).

Empirical Calibration
In empirical calibration, the user must first analyze known samples to obtain the count intensity, which is then plotted using off-line software to generate the calibration curve. This curve data is then put back onto the analyzer which can then be run to provide results. Empirical testing modes are only suited for measuring samples for which chemical compositions will fall within the narrow calibration range, and interferences (spectral and matrix) must be taken into consideration within the calibration.

End-of-Life Vehicles (ELV) Directive (2000/53/EC)
A requirement that certain automotive products be free (except for trace impurities) of mercury, cadmium, and lead as of July 1, 2003. Lead can still be used as an alloying additive in copper, steel, and aluminum and in solderable applications.

Energy Dispersive X-Ray Fluorescence (EDXRF)
EDXRF is designed to analyze groups of elements simultaneously. This type of XRF instrumentation separates the characteristic x-rays of different elements into a complete fluorescence energy spectrum which is then processed for qualitative or quantitative analysis. Filters positioned between sample and detector are used to improve signal, background reduction, and focus on certain regions of the spectra.

Environmental Lead Proficiency Analytical Testing program (ELPAT)
The process of accrediting laboratories that analyze environmental samples for lead in soil, paint, air filters, and dust to help ensure that the lab’s process and protocols will produce accurate, repeatable, reliable results.

EPA Method 6200
A field-screening method for analysis of in-situ and ex-situ soil test samples.

Ex Situ
Latin phrase meaning off-site. Often a soil sample is removed from its original location, prepared (dried, ground, sieved, and cupped), and then analyzed ex-situ.

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1. A mechanism built into the XRF instrument that allows modification of the x-ray energy to preferentially enhance the analysis of certain elements in certain matrices.
2. A thin support mechanism for sample collection, such as a 37mm air filter.

High filter – the filter used in the instrument to preferentially fluoresce many of the heavy elements (Z = 47-56).
Light filter – the preferred filter used in the instrument to fluoresce light elements if Z < 17.
Main filter – the preferred filter used in the instrument to fluoresce the transition elements, which include groups 3-12 on the periodic table (all of the first row and some of the second row).

Flow Accelerated Corrosion (FAC)
A well-known source of problems in nuclear and fossil-fuel power plants. FAC occurs when carbon steel piping and components are degraded in the presence of flowing water or steam water with low-dissolved oxygen. As the water flows against the carbon steel material, the stable surface oxide layer (typically Fe3O4) is dissolved into the flowing stream – thinning the walls of piping over time and resulting in catastrophic failures due to rupturing.

Fundamental Parameters (FP)
For measuring samples of unknown chemical composition in which concentrations of light and heavy elements may vary from ppm to high percent levels, Fundamental Parameters (FP) analysis is used to simultaneously compensate for a wide variety of geometric effects (including small and odd-shaped samples), plus x-ray absorption, and secondary and tertiary fluorescence effects. FP is the preferred analysis tool for mining, precious metals and all metal alloy testing applications.

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Chemical composition of the earth's crust and the chemical changes that occur there; in particular “the study of the absolute and relative abundances of chemical elements in the minerals, soils, ores, rocks, water, and atmosphere of the earth and the distribution and movement of these elements from one place to another as a result of their chemical and physical properties.” [http://encyclopedia2.thefreedictionary.com/geochemistry]

GIS (Global Information System)/ GPS (Global Positioning System)
Tools used in field mapping systems to plot geochemical data on maps in real time, reach infill and step-out decisions, and make more informed decisions.

Grade Control
The measurement and adjustment of mined materials to keep the elements of interest within a specific concentration range.

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The generic name for a group of non-metal elements from Group 17 (formerly VII, VIIA) of the periodic table, comprising F, Cl, Br, I, and At.

Halogen Free
According to IEC 61249-2-21, the accepted definition of halogen free is 900 ppm maximum Cl, 900 ppm maximum Br, or 1,500 ppm maximum total halogens.

Helium purge
1. The process of replacing the air present surrounding the x-ray tube and detector with helium gas to permit the direct analysis of magnesium, aluminum, silicon, phosphorus and low levels of sulfur in a variety of sample types. 
2. The method preferred over vacuum purge systems for analysis of magnesium, aluminum, silicon, phosphorus and sulfur resulting from its higher reliability and reduced potential for instrument contamination.

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Inductively Coupled Plasma (ICP)
Traditional testing method, which is generally accepted as accurate, but also destructive and time consuming. Ultimately, this makes the method inefficient.

Taking readings at a higher rate to more closely define the elemental composition of an area of interest; an exploration technique.

In Situ
Latin phrase meaning in place; the XRF instrument may be used directly on a sample without moving or preparing it, e.g., taking a soil reading in-situ.

Instrument Detection Limit (IDL)
The best possible limit of detection, calculated from a “clean” sample, i.e., one with no interferences.

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Laser Induced Breakdown Spectroscopy (LIBS)
A form of atomic emission spectroscopy that users a laser to ablate the surface of a sample to obtain elemental data. A plasma is caused by the laser ablation process and emits light as it cools. The light is then collected and analyzed with a spectrometer for qualitative and quantitative material analysis.

Light Elements
Elements below atomic #17.

Limit of detection (LOD)
The smallest concentration of an element that can be detected with reasonable certainty. It is generally regarded as indicating whether an element is present or not and does not imply that a value obtained is accurate. LODs are usually calculated using 3 sigma.

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Mill Heads and Tails
XRF analyzers are valuable assets in mills and refineries, providing fast, accurate analysis of feedstocks (heads), concentrates, and tailings (finely ground rock separated from the ore minerals) to quickly and easily gauge the efficiency of extraction and enrichment processes.

Mine Mapping
The identification of ore boundaries.

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Optical Emission Spectroscopy (OES)
An elemental analysis technique that uses an electric arc, spark or laser to stimulate atoms to emit a characteristic spectrum of light for each element within the sample. While both LIBS and OES use similar scientific principles, OES offers limited mobility. Existing configurations include benchtop instrumentation, or a mobile cart.

A mineral or an aggregate of minerals from which a valuable constituent, especially a metal, can be profitably mined or extracted.

A portion of bedrock or other stratum protruding through the earth’s surface, i.e., the soil level.

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Pathfinder Elements
Elements with better geochemical or analytical characteristics than the main metal, can be used as a pathfinder in the search for Au.

Performance Characteristic Sheet (PCS)
Third-party-developed testing design, data management, and statistical methodology for performance characteristic conformance.

Phthalates are often used to soften plastics such as the normally-rigid polyvinyl chloride plastics (PVC). They are a group of chemical compounds that are mainly used as plasticizers as in plastic fishing lures, nail polish, adhesives, caulk, paint pigments, and some soft toys made of so-called "jelly rubber." Prohibitions of certain phthalates are delineated in Section 108 of the CPSIA.

An electrically neutral gas made up of ions and electrons.

Platinum Group Metals (PGM)
A group of six (6) precious metals (Ru, Rh, Pd, Os, Ir and Pt) all having similar chemical and physical properties.

Positive Material Identification (PMI)
Inspection process by which alloy chemistry and alloy grade is verified; XRF and LIBS are the standard methods used.

Priority Pollutants
Mercury by EPA method 245.1, antimony, arsenic, beryllium, cadmium, chromium, copper, lead, mercury, nickel, selenium, silver, thallium, zinc.

Product Safety Enforcement Forum of Europe (PROSAFE)
The European Union's overseer for the safety of consumer products.

Proposition 65 
California's Safe Drinking Water and Toxic Enforcement Act of 1986 promotes clean drinking water and keeping cancer-causing and birth defect-related toxic substances out of consumer products.

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Rare Earth Elements (REE)
A collection of 17 elements, Sc (21), Y (39), and the lanthanoids (57-71).

RCRA Metals
Arsenic, barium, cadmium, chromium, lead, mercury, selenium, silver.

Reasonable Testing Program
A set of procedures that are employed to provide reasonable certainty that products made follow all applicable rules, bans, and standards (CPSC definition).

A measure of the variation in results obtained when the same sample is run by the same person on the same instrument under identical conditions, generally over a short time period.

A measure of the variation in results obtained by different people running different instruments. Reproducibility is generally worse that repeatability in absolute terms.

Residual Element Analysis
Residual element concentrations in carbon steel pipe can be a critical indicator of the expected life and performance of finished components in petrochemical applications. Particular elements of interest include Cr, Cu, and Ni, as well as Mo, Sn, V, Sb, As, and Pb. HF alkylation units can be subject to selective corrosion in a unique manner resulting from elevated levels of residual Cr, Cu, and Ni.

Restriction of Hazardous Substances (RoHS) Directive
A requirement that certain electrical and electronic products be free (except for trace impurities) of mercury, cadmium, hexavalent chromium, PBB, PBDE and lead as of 2006-7-1. Certain exemptions are allowed such as lead used as an alloying additive in copper, steel, and aluminum. Also, China RoHs and US RoHS (effective July 1, 2010 – Environmental Design of Electrical Equipment Act (HR 2420) states that no electrical equipment shall be placed on the US market (manufactured or imported) unless it meets RoHS compliance (6 elements per European RoHS).

Resource Conservation and Recovery Act (RCRA)
A U.S. federal law enacted in 1976 that governs the disposal of waste (solid and hazardous).

Renovation, Repair, and Painting (RRP) Rule 
A U.S. Environmental Protection Agency (EPA)- issued rule requiring the use of lead-safe practices and other actions aimed at preventing lead poisoning. Under the rule, beginning in April 2010, contractors performing renovation, repair, and painting projects that disturb lead-based paint in homes, child care facilities, and schools built before 1978 must be certified and must follow specific work practices to prevent lead contamination.

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The by-product formed by oxidation at the surface of molten metals. In the production of iron and steel, slag’s primary purpose is to purify the iron product through removal of oxides while acting as a protective blanket that stabilizes melt temperatures and helps prevent re-oxidation. Slag chemistry is controlled closely to maximize furnace efficiency, reduce impurities in the product, and prolong the life of the refractory lining of the furnace. After the refining process, slags can be recovered and used for commercial purposes such as ballasts, road fill, or mixed with cement for structural applications.

The visual representation of signal intensity plotted against wavelength or frequency.

Standard Deviation or Sigma
A measure of the variability within a sample set. The smaller the value, the closer all the results are to one another. It is calculated by taking a data set and first calculating the mean. Then the mean is subtracted from each individual reading and the calculated value is squared (this gets rid of any negative numbers). Next, these calculated values are averaged and the square root is calculated. This square root is sigma, or one standard deviation. It may also be calculated easily in spreadsheets such as Excel, in Excel use “=stdev (highlight cells of interest)”.

Standard Reference Material (SRM)
Material or substance whose property values (one or more) are sufficiently homogeneous and well established for use in the calibration, the assessment of a measurement method, or for assigning values to materials.

Base materials, including plastic, wood, metal, and ceramics.

Corrosion of metals resulting from reaction with sulfur compounds in high temperature environments. Sulfidation corrosion of piping and equipment within the refining industry continues to be a significant cause of leaks leading to equipment replacements, unplanned outages, and incidents associated with large property losses and injuries. Carbon steels with low silicon (< 0.10%) content can corrode at an accelerated rate when exposed to hydrogen-free sulfidation corrosion conditions. [from API-939-C Guidelines, version 5.0, Jan. 2008]

High-performance alloys that can tolerate high temperatures; corrosion and oxidation resistant.

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Tin Whiskers
The main danger posed by the presence of high-purity tin or lead-free tin solder is its tendency to produce filamentary corrosion – more commonly known as “whiskering.” Whiskering is a naturally occurring phenomenon that results in the spontaneous and unexplainable growth of tiny, needle-like protrusions. In turn, they break loose, short circuiting system boards and terminals, seriously crippling or destroying entire systems, especially those involved in reliability critical applications such as aircraft, spacecraft, military weapons systems, and electronic medical devices.

Trace Element
Element present in a sample very small quantities (usually less than 100 ppm).

Tramp Element
Element found in minute quantities in metal, which can adversely affect its properties.

True Value
The actual or certified value of a sample.

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Vacuum Purge
1. The process of evacuating the air present surrounding the x-ray tube and detector to permit the direct analysis of magnesium, aluminum, and silicon in metal alloys. 
2. An inferior method for light element analysis, as compared to helium purge, because of its reduced reliability and higher potential for instrument contamination.

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X-Ray Fluorescence (XRF)
1. The emission of x-rays from a substance during exposure to an external source of x-rays. 
2. The process by which a nondestructive test for material composition is performed.

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