Have you ever wondered what X-ray fluorescence (XRF) instruments can and can’t analyze, or why it might be better suited for certain materials than other techniques? XRF is only one of many elemental analysis tools, and has strengths and weaknesses. As someone who’s spent years working with XRF and teaching new users how to get the best results, I know firsthand how confusing it can be for beginners to grasp what this powerful tool can do—and where its limits are.
In this guide, I will walk you through the essentials of XRF, explaining its advantages and limitations and how to decide when it's the right tool for the job. Whether you're just starting out or looking to refine your understanding, this article will help you feel more confident in applying XRF to your work.
XRF is a non-destructive analytical technique used to determine the elemental composition of materials. When a sample is exposed to high-energy X-rays, the atoms in the sample scatter energy in the form of secondary (or fluorescent) X-rays. Each element emits X-rays at characteristic energies, which allows the instrument to identify and quantify the elements in the sample. Depending on how the energy of the fluorescent X-rays is analyzed, XRF instruments are categorized into EDXRF (Energy Dispersive XRF) and WDXRF (Wavelength Dispersive XRF).
Now that we know how XRF works, let’s take a look at what it can analyze.
Range of elements
XRF can analyze a wide range of elements, typically from sodium (11Na) to curium (96Cm), depending on the instrument and its configuration. WDXRF instruments can often analyze starting with beryllium (4Be).
The technique works best for mid- to high-atomic-number elements, as lighter elements like sodium, magnesium, and aluminum produce lower-energy X-rays that are harder to detect. The detectable and quantifiable concentration range can vary widely but is generally between parts-per-million (ppm) levels and 100%, making XRF useful for both trace analysis and bulk composition determination.
High-power WDXRF instruments, which typically operate with X-ray tubes up to about 4 kW, can achieve exceptional sensitivity and precision, allowing them to detect and quantify elements at parts-per-million (ppm) to sub-ppm (hundreds of parts-per-billion (ppb)) levels. This level of sensitivity is achieved through high-power excitation for greater X-ray intensity, optimized optics for efficient wavelength dispersion, and advanced detectors for capturing weak signals from trace elements. Also, extra care should be taken during the sample preparation to achieve ppb-level analysis.
Forms of samples
XRF is versatile in the forms of samples it can analyze. It can handle solids such as metals, ceramics, and plastics; powders like geological samples and cement; and liquids including oils and chemical solutions. Gaseous samples are generally not suitable for XRF because they lack the necessary density for effective X-ray interaction.
XRF, especially EDXRF, is very forgiving and can analyze various forms of samples for identification or semi-quantitative analysis. However, the sample must be prepared appropriately to ensure a flat and uniform surface for consistent X-ray excitation and detection. For these purposes, pressed pellets or fused beads are often prepared for more consistent results.
Industries and applications
XRF is used across various industries, typically for quality control, process monitoring, regulatory compliance, and research. Here are some examples:
Mining and geology
Cement and building materials
Metals and alloys
Coatings
Petrochemicals
Environmental science
Electronics and semiconductors
Food and agriculture
Pharmaceuticals and healthcare
Energy and battery materials
Art and archaeology
XRF's versatility, speed, and non-destructive nature make it an indispensable tool across these industries for ensuring product quality, meeting regulations, and advancing research.
While XRF is a versatile technique, it has certain limitations. These include elements, trace levels, and sample forms that are beyond its capabilities. It’s important to understand these limitations so you know when XRF might not be the best option for your analysis.
Elements XRF cannot analyze
Sample forms XRF cannot analyze
Other Limitations
While XRF is excellent for rapid and non-destructive elemental analysis, its limitations mean that alternative techniques like ICP-MS, GC, or mass spectrometry are required for noble gases, isotopic analysis, and ultratrace element detection.
Depending on what you want to use XRF for and in which environment, there are a few key considerations.
Quality control
For quality control (QC) applications using XRF, key considerations include ensuring sample consistency and proper preparation (e.g., homogenizing powders, polishing solids), choosing appropriate calibration standards, and understanding matrix effects.
It's important to select the right type of XRF (EDXRF or WDXRF) based on the required sensitivity and precision and to configure the instrument for the elements being analyzed. Accurate detection limits should be met for contaminants while ensuring that the measurement time is efficient for high-throughput environments. Consistency and reproducibility are critical for QC, as well as integrating data into statistical process control (SPC) systems for ongoing monitoring and trend analysis.
Lastly, complementary techniques may be needed for trace elements below the detection limits of XRF.
Research and development
For research and development (R&D) applications using XRF, key considerations include ensuring precise sample preparation to maintain homogeneity and minimize matrix effects, as R&D often requires detecting minor variations in elements.
The instrument should be configured for high resolution and sensitivity and scans should be set longer, particularly when analyzing a small amount of sample, complex materials, or trace elements. Accurate calibration with reference materials closely matching the sample matrix is crucial to obtain reliable results.
In R&D, it's important to balance measurement time with the level of detail required, as detailed analysis may need longer measurement times. Additionally, XRF's limitations in distinguishing oxidation states or isotopic compositions must be considered, and complementary techniques may be necessary for more specialized analyses.
XRF is a versatile and indispensable tool across a wide range of industries, offering fast, accurate, and non-destructive analysis of various materials. While it excels at analyzing metals, geological samples, and consumer products, it does have some limitations, such as difficulty detecting light elements and limited depth of penetration.
By understanding what XRF can and can’t do, you’ll be better equipped to decide when it’s the right tool for your needs. Whether you're just starting out or looking to deepen your understanding, mastering XRF can open doors to improving processes, ensuring quality, and staying compliant in your field.
Our team of experts can help you if you have any questions or need help deciding which technique is the right solution for you. Talk to one of our XRF experts by clicking the "Talk to an expert" button at the top right of the page or contact us at info@rigaku.com.
Curious about how XRF and XRD compare? Download our free cheat sheet to quickly understand the key differences and choose the right technique for your analysis.