EDS vs WDS: Understanding Modern X-ray Microanalysis

What is WDS?

WDS is a high resolution technique that physically diffracts X-rays using a crystal and measures them with very fine energy discrimination.

Traditionally, this enabled:

Separation of closely overlapping peaks
Trace and minor element quantification
High precision quantitative analysis
High resolution elemental mapping

However, WDS systems are:

Complex to use
Slow (sequential acquisition)
Expensive to purchase and maintain
Limited in field of view when mapping

WDS remains valuable where the very lowest detection limits are required and where acquisition time is less important.

What is EDS?

EDS detects X-rays using a semiconductor sensor. In earlier decades, EDS was limited by:

Broader peak shapes
Higher noise
Peak shift at high count rates
Semi-quantitative results

As a result, older EDS could not match WDS performance - especially for overlaps and low level detection. Modern EDS has changed dramatically, with innovations such as:

Large area SDDs for high count rates
Digitally sampled pulse processing
Novel technologies for spectrum processing and quantitative analysis that include:
- Tru-Q unified engine that combines multiple advanced algorithms—FLS background removal, QCAL peak characterisation, XPP matrix correction, PPC pile‑up prediction, and AutoID peak‑based element identification
- Latest Tru‑Q IQ unified engine thar keeps all the strengths of Tru-Q - but adds a critical new capability:
- Unlike earlier approaches that used averaged detector‑type models, TruQ‑IQ measures and embeds the full spectral behaviour of each individual detector
- Per‑detector calibration enables more accurate peak fitting, cleaner deconvolution of overlapping lines, improved trace‑element sensitivity and stable quantitative results from low‑kV analysis to count rates approaching one million cps.
- By unifying hardware performance with detector‑specific modelling, Tru-Q‑IQ delivers a new standard of automatic, real‑time EDS accuracy previously achievable only through expert‑driven optimisation

EDS now achieves fast, reliable, accurate quantification across major, minor and trace elements, including difficult overlaps.

How Modern EDS Matches WDS for Challenging Quantitative Measurements

Modern EDS systems now deliver quantitative performance previously achievable only with WDS, even for low‑level and heavily overlapped elements. The recent publication demonstrates the following capabilities:

Trace‑Element Quantification Down to 0.1 wt%
Detection Limits Near 0.01 wt% (≈100 ppm)

Accurate Quantification Under Severe Peak Overlap
High‑Count‑Rate Quant Accuracy (up to 800 kcps)

Points	Al	Si	Ti	Cr	Mn	Fe	Co	Ni	Mo	Total
1	1.31	0.15	1.17	17.76	0.1075	34.25	0.15	42.86	3.22	100.99
2	1.30	0.16	1.18	17.69	0.0982	34.03	0.18	42.71	3.27	100.63
3	1.30	0.16	1.47	17.63	0.0870	33.72	0.16	42.49	3.34	100.37
4	1.30	0.15	1.11	17.68	0.0859	34.35	0.19	42.57	3.11	100.54
Average	1.30	0.16	1.23	17.69	0.0947	34.09	0.17	42.66	3.24	100.63
Standard Deviation	0.01	0.01	0.16	0.05	0.0102	0.28	0.02	0.16	0.10	0.01
Nominal	1.27	0.15	1.25	17.00	0.0500	33.88	0.09	42.80	3.41	99.90

Table 1. WDS/EDS reference measurements for XPE16 standard (all values in wt%). Mn is measured by WDS and serves as a reference for accessing the quality of EDS measurements under challenging analytical conditions. The average measured Mn concentration with WDS in XPE16 standard is 0.0947 ± 0.0102 wt%, and further EDS data shows characterisation down to this concentration levels is possible.

How Modern EDS Matches WDS for Challenging Trace‑Element Mapping

This figure demonstrates how advanced EDS spectrum processing can now achieve WDS‑level accuracy even in extremely challenging analytical situations. The furnace‑slag sample contains trace Mn whose main X‑ray line (Mn Kα) lies only 48 eV from a major Cr peak (Cr Kβ), producing severe peak overlap and additional distortion from multiple Cr sum peaks. These conditions traditionally make Mn impossible to quantify with conventional EDS, especially during high‑count‑rate mapping.

EDS Window-Integral Map

WDS Map

Left: WDS Map (Reference Standard): WDS does not suffer from the Mn–Cr overlap or pulse‑pile‑up interference, so it provides the “true” Mn distribution for comparison.

Right: EDS Window‑Integral Map: A simple window map incorrectly shows Mn following the Cr‑rich regions, illustrating how raw EDS signals are dominated by Cr‑related overlaps and uncorrected sum peaks.

EDS Pulse‑Pile‑Up‑Corrected Map

EDS Peak‑Deconvolution Map

Left: EDS Peak‑Deconvolution Map: Removing the continuum and deconvolving the peaks improves the result but still falls short of WDS because uncorrected pulse‑pile‑up boosts the Mn intensity.

Right: EDS Pulse‑Pile‑Up‑Corrected Map: With full pulse‑pile‑up correction and peak deconvolution applied at every pixel, the Mn distribution matches the WDS map, capturing both the reduced Mn in Cr‑rich regions and the Mn present in surrounding phases.

This example highlights a critical point: modern EDS equipped with detector‑specific calibration (e.g., TruQ‑IQ) can now resolve severe overlaps and recover true trace‑element information at high count rates, enabling WDS‑level mapping performance in many real‑world scenarios.

Bringing WDS Capability to Your SEM Using Modern EDS

How to Achieve WDS Data Quality with a Modern EDS Detector

Webinar

A detailed comparison of WDS and EDS performance, including peak overlap solutions, trace element quantification and practical workflows.

How to Bring WDS Capability to Your SEM Using the Latest EDS Technology

Presentation

Explains how advances in SDD hardware, digital pulse processing and Tru-Q/Tru-Q IQ algorithms enable WDS level data on a standard SEM.

Summary

Advances in EDS technology over the past two decades mean that most SEM WDS use cases can now be addressed more efficiently using modern EDS.

Oxford Instruments’ latest detectors and Tru-Q IQ processing provide:

Artefact-Free Maps with Cleaner Element Detection at maximum throughput

Reliable deconvolution of complex overlaps

Accurate quantification including complex environment (trace elements, overlaps and high count rates)

Superior AutoID even in case of trace detection

User friendly operation with guided workflows

Consistent, reliable results across all conditions

Discover More with our Product Range

Ultim Max Infinity

Ultim Max Infinity SDD detectors unlock the infinite potential of EDS - including the world's largest area SDD at 170 mm2, and guaranteed Carbon resolution of 46eV or better for all sensor sizes.

Ultim Extreme Infinity

Ultim Extreme Infinity is a unique windowless detector that enables EDS data collection at very low kV (e.g. 1-3 kV) and very short working distance to provide elemental analysis under the conditions required to analyse nanomaterials and surfaces at the highest SEM resolution.

Unity

Unity is the world’s first Backscattered Electron and X-ray (BEX) Imaging detector includes both backscattered electron and X-ray imaging detector. It is located directly beneath the pole piece and has been engineered to maximise signal collection.

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