WDXRF Frequently Asked Questions

WDXRF (Wavelength Dispersive X-ray Fluorescence) is an analytical technique that measures fluorescent X-rays emitted from a sample when irradiated by primary X-rays. These fluorescent X-rays are diffracted by an analyzing crystal, allowing separation by wavelength according to Bragg’s law. Because each element emits X-rays with characteristic wavelengths, WDXRF enables reliable qualitative and quantitative analysis.

Key characteristics include:

• High spectral resolution, minimizing peak overlaps and enabling accurate multi-element analysis
• Excellent light-element sensitivity, made possible by optimized optics and analyzing crystals
• Outstanding long-term stability and reproducibility, supported by stable X-ray optics and digital signal processing

Reference: What XRF Can and Can’t Analyze: A Guide for Beginners

WDXRF accommodates a broad range of sample forms—including solids, powders, liquids, and thin films—and is used extensively across industries such as:

• Metals and alloys (ferrous and non-ferrous)
• Cement, glass, ceramics, and minerals
• Petroleum products, fuels, and related refinery processes
• Battery materials and electronic device materials
• Environmental samples such as soils, sludge, and waste materials

The versatility of WDXRF stems from its ability to achieve high accuracy, high sensitivity, and high throughput across diverse matrices, as emphasized in Rigaku’s product and application materials.

References:

• What XRF Can and Can’t Analyze: A Guide for Beginners
• All industries

Each method possesses distinct strengths.

WDXRF

• Uses a crystal to disperse fluorescent X-rays, giving superior peak separation and high quantitative accuracy
• Provides high sensitivity for light elements, particularly when measured under vacuum or helium atmosphere
• Ideal for long-term quantitative analysis in quality control environments

EDXRF

• Uses energy-dispersive detection rather than wavelength dispersive optics
• Compact and simple architecture
• Short measurement times suitable for screening or field applications

ICP-AES / ICP-MS

• Requires solution sample preparation, but delivers extremely low detection limits (ppb and below)
• Enables simultaneous multi-element detection at high sensitivity
• Needs sample digestion and chemical handling

Reference: What XRF Can and Can’t Analyze: A Guide for Beginners

Depending on the instrument configuration and measurement parameters, WDXRF can quantify elements typically ranging from Be (Z=4) to Cm (Z=96).

Concentration ranges:

• Major components: several mass% to 100%
• Minor/trace components: several ppm
• Optimized conditions: sub-ppm detection may be possible for certain elements

These performance capabilities align with Rigaku’s demonstrations of high-sensitivity WDXRF systems using optimized crystals, Soller slits, and digital signal processing.

Reference: What XRF Can and Can’t Analyze: A Guide for Beginners

Sequential WDXRF spectrometers measure elements one at a time by scanning the diffracted fluorescent X-rays across different optical conditions—such as analyzing crystals, Soller slits, and detectors—to obtain each element’s intensity.

This approach provides high spectral resolution, excellent flexibility, and the ability to optimize measurement time and optical settings for each element individually.

Simultaneous WDXRF spectrometers, on the other hand, use multiple fixed optical channels, with each channel dedicated to a specific element. Because all elements are measured at the same time, simultaneous systems offer very high throughput, making them ideal for routine, high-volume quality control applications.

In summary:

• Sequential WDXRF:
  • Measures elements sequentially
  • Highly flexible for different applications and matrices
  • Enables optimal selection of analyzing crystals and measurement conditions
• Simultaneous WDXRF:
  • Measures multiple elements simultaneously
  • Extremely fast and stable for fixed sets of elements
  • Suitable for production and continuous process control

Reference: Compare all WDXRF

The quality of WDXRF results is governed by:

Measurement Time

Longer measurement time improves counting statistics, reducing relative error.

Optical Conditions

Key settings include:

• X-ray tube voltage and current
• Analyzing crystal (e.g., LiF(200), PET, Ge)
• Collimator/Soller slit
• Filters to stabilize background and prevent interferences

Calibration Models

Constructing appropriate calibration curves and applying matrix corrections such as FP (Fundamental Parameters) are essential for accurate quantitative analysis.

These considerations match Rigaku’s documentation showing how automatic setting of measurement/correction conditions enhances reliability.

The level of preparation depends on the required analytical precision and sample characteristics.

Metals

• Surface polishing is typically essential to remove oxidation or contaminants
• For cast materials, melting or homogenizing chips may be needed
• Ensuring that the surface condition of both standard and unknown samples is prepared in the same manner is important for consistent results 

Powders

• First, grind sufficiently (aim for approximately 50 µm), then either pack directly into the cell or form into pellets.
• For higher precision, melt it with a flux to form glass beads.
• Grind to achieve uniform particle size (≤ 50 µm recommended)
• Measure as loose powder or press into pellets
• For highest accuracy, prepare fusion beads

• Use a dedicated liquid cell and measure under helium atmosphere
• For trace elements, pipette onto filter paper, dry, and measure in vacuum

Reference: Sample Preparation Videos

Measurement time varies based on target elements, required precision, and optical conditions:

• Routine QA/QC: several tens of seconds to several minutes per element
• Trace/critical analyses: several minutes to more than ten minutes

High-capacity auto-samplers can significantly enhance throughput, enabling continuous unattended operation.

Organizing costs into the following categories facilitates consideration:

Cost factors can be viewed in two categories:

Initial installation

• Instrument price (X-ray tube rating, optical components, available options)
• Required infrastructure: power capacity, cooling (if required), installation space, floor load

Running costs

• Gases such as helium or P-10
• Consumables such as sample cups, films, flux, and pellets
• Replacement intervals for X-ray tubes and detectors

Reference: How Much Does an XRF Spectrometer Cost?