How does X-ray fluorescence work?

X-ray fluorescence (XRF) is a nondestructive analytical technique used to identify and quantify elements in various sample types. The sample is exposed to X-rays, causing its atoms to emit fluorescence back to a detector. This fluorescence is measured to identify the elements present and determine their concentrations. XRF is widely used in fields such as materials science, environmental analysis, archaeology, and mining due to its ability to quickly and accurately analyze solids, liquids, and powders. Its main advantages include fast results, minimal sample preparation, and the ability to analyze a broad range of materials. Learn more about XRF and how it works in this blog article.

Click to go directly to a topic:

• What is X-ray fluorescence?
• What are the main components of an XRF analyzer?
• What are the advantages of XRF?
• XRF applications
• XRF in process analysis
• What are the advantages of XRF in process analysis?

What is X-ray fluorescence?

X-ray fluorescence, or XRF, is a nondestructive technique used to analyze the elemental composition of a material. The process begins when a sample is exposed to X-rays, which excites the atoms within it. This excitation causes the atoms to release energy in the form of characteristic X-rays. The emitted X-rays are unique to each element and are detected and measured to identify the elements present in the sample and determine their concentrations.

XRF can be easily described in four steps:

1. Emission: The XRF analyzer emits X-rays with an X-ray tube.
2. Excitation: X-rays hit the sample and it fluoresces, sending X-rays back to the detector in the XRF analyzer.
3. Measurement: The returning X-rays are counted by the detector. The detector measures the energy of each X-ray, creating a spectrum. This information reveals which elements are present and how much of each element is there.
4. Results: The energy spectrum is processed via software and displayed as the elemental composition of the sample. The composition of the sample can be determined in as little as two seconds.

What are the main components of an XRF analyzer?

XRF instruments include the following core components: 

X-ray source

An X-ray tube (Figure 1) converts electricity into X-rays, similar to how a lightbulb converts electricity into light. X-rays are produced only when a current flows through the tube. The tube contains a filament which can be made from various materials such as rhodium, tungsten, gold, or silver. No single filament material is superior to others; the choice depends on the specific application for which the X-ray tube is used.

X-ray detector

An X-ray detector (Figure 1) captures and measures the X-rays re-emitted by the sample. It functions similarly to the digital camera in a smartphone, converting the X-rays into an electrical signal. The most common detectors for XRF analysis are the proportional counter (prop counter), silicon PIN (Si-PIN) detector, and silicon drift detector (SDD). Of these, the SDD offers the best performance and sensitivity.

Internal processor

The internal processor manages the X-ray tube, X-ray detector, advanced calibration, touch screen, wireless capabilities, and all other components. It controls the operation of the X-ray tube and converts the detector's counts into the displayed chemical composition.

Measuring cell

A measuring cell may be used in online XRF process analyzers, which are programmed to automatically extract samples from the process line at predefined intervals. The extracted sample is then transferred to a measuring cell (Figure 1), where it is exposed to X-rays generated by the X-ray source. The atoms within the sample absorb these X-rays and re-emit them at specific energies that are characteristic of the elements present. Once the analysis is complete (typically within a few seconds), the sample is either returned to the process stream or disposed of. To ensure more accurate analysis, the sample may also undergo preconditioning steps such as filtration to remove particulate matter. These preconditioning steps are automated to optimize the analysis process.

What are the advantages of XRF?

X-ray fluorescence analysis provides many advantages to field and lab professionals. Benefits of XRF include: 

• Nondestructive testing: XRF is a nondestructive technique that will neither alter nor damage samples, enabling analysis without changing the chemical composition. This keeps the sample in its original state from the beginning to the end of the analysis.
• Fast results: XRF provides rapid results, typically within seconds to minutes, making it ideal for real-time analysis and quick decision-making across a wide range of applications. It significantly reduces analysis time compared to traditional wet chemistry techniques.
• Multi-elemental analysis: XRF allows for the detection and quantification of multiple elements from a single sample measurement, enabling efficient and comprehensive elemental analysis.
• Versatility: XRF can analyze a variety of samples, including solids, liquids, and powders. Its versatility makes it suitable for use in many industries, such as mining, metal production, electronics, environmental testing, petrochemicals, energy production, and more. 

XRF applications

X-ray fluorescence is fundamentally an elemental analysis technology. This means that the applications of XRF for compositional analysis are almost unlimited. Since XRF is an elemental analysis—and everything is made up of atoms—nearly any material can be analyzed with XRF. 

As XRF is a nondestructive technique, even valuable or fragile samples can be evaluated without any detrimental effect. The portability and ease of use of handheld XRF analyzers make these devices particularly valuable for on-site or in situ investigations, where quick, accurate, and minimally invasive analyses are required.

Common XRF applications include: 

From the mine to metalworks, plants to playgrounds, and coins to consumer products, XRF plays a valuable role in nondestructive material analysis. 

XRF in process analysis

In general, process analysis is the method of examining how a task is done. The ultimate goal is to ensure the work meets its objectives while finding ways to improve on the quality, efficiency, and safety of the process at hand. XRF technology can be a critical tool to help accomplish these goals. This technology is not limited to any specific industry and can be used on solid or liquid samples. Industrial applications such as mining, forging, cement production, oil and gas (petrochemicals), batteries (energy), manufacturing, and recycling can benefit from utilizing XRF. 

Optimizing zinc-nickel plating baths

Online XRF process analyzers are designed for the continuous monitoring of liquid samples in various industries where elemental analysis is essential. One specific area where online XRF process analyzers excel is in the zinc-nickel plating industry.

In the metal plating industry, online XRF process analyzers have transformed the way plating processes are monitored and controlled.

Historically, manual titrations were performed every six hours to analyze zinc and nickel content in zinc-nickel plating baths. This method offers limited data points (Figure 5), making it difficult to identify trends or process disruptions. Consequently, this method can lead to suboptimal performance, increased waste, and inconsistent product quality. 

In contrast, online XRF process analyzers provide real-time, high-resolution data of the metal ion concentrations in zinc-nickel plating baths (Figure 6). These instruments enable precise process control, enhanced product quality, reduced chemical consumption, and minimized environmental impact.

What are the advantages of XRF in process analysis?

Conclusion

XRF's versatility and ability to perform on-site analysis make it a valuable tool across various industries. Whether used in refining, plating, cement production, electronics manufacturing, mining, or archaeology, portable XRF technology offers a powerful and practical solution for elemental analysis. When automated in process analysis, XRF technology adds value by enabling manufacturers to achieve significant improvements in their operations. By obtaining real-time insights into critical process parameters, manufacturers can optimize resource utilization, enhance product quality, reduce downtime, and make data-driven decisions for enhanced efficiency and environmental performance. 

Your knowledge take-aways

Flyer: Efficient Bath Quality Control with XRF – Online analysis of zinc and nickel for process control

Flyer: Efficient Li-ion battery production with XRF – Online analysis of metals in cathode active material (CAM)

Brochure: 2060 XRF Process Analyzer

Application Note: Online monitoring of cyanide and gold in gold leaching solution

Application Note: Online analysis of copper, tin, and zinc in white bronze baths by XRF

On-demand webinar: Online analysis of copper, tin, and zinc in white bronze baths by XRF