☢️ X-Ray Fluorescence (XRF)
Non-destructive analysis of elemental composition of solid and liquid materials from beryllium (Be) to uranium (U) by X-ray fluorescence method. Fast, multi-element analysis without sample dissolution.
Overview
X-ray fluorescence spectrometry (XRF — X-Ray Fluorescence) is one of the most commonly used non-destructive instrumental methods in elemental composition analysis of solids, liquids and powders. The method allows simultaneous determination of elements from beryllium (Z=4) to uranium (Z=92) at concentrations from ppm to 100%, without need for sample dissolution.
Standard PN-EN ISO 12677 defines XRF application for refractory products analysis, and PN-EN 15309 — for waste and soil characterization. However, XRF is used much more widely: in metallurgy (steel, alloy analysis), geology (rocks, minerals), cement industry, ceramics, oil industry (sulfur in fuels according to ISO 20884), environmental protection (heavy metals in soil), archaeology and art conservation.
Two types of XRF spectrometers are distinguished: WDXRF (wavelength dispersion — higher resolution and sensitivity, used in stationary laboratories) and EDXRF (energy dispersion — compact, cheaper, used in field and for screening). Portable XRF (handheld) enables field analysis — scrap sorting, soil analysis, materials verification (PMI).
Leading manufacturers are: Bruker (S8 TIGER, S1 TITAN), Malvern Panalytical (Zetium, Axios, Epsilon), Rigaku (ZSX Primus IV, Supermini200), Shimadzu (XRF-1800), Thermo Fisher (ARL PERFORM'X). Cost of laboratory WDXRF equipment: 300 000–1 500 000 PLN, portable EDXRF: 80 000–200 000 PLN.
Method principle
Sample is irradiated with X-ray beam from X-ray tube (usually rhodium Rh, 1–4 kW). Elements in sample absorb primary radiation and emit characteristic X-ray radiation (fluorescence) with energy/wavelength specific for given element (Kα, Kβ, Lα lines). In WDXRF — fluorescence radiation is dispersed on analyzing crystal (Bragg's law: nλ = 2d sinθ) and measured by detector (proportional + scintillation). In EDXRF — semiconductor detector (Si(Li) or SDD) resolves radiation directly based on energy. Intensity of fluorescence lines is proportional to element concentration.
Applications
- Chemical composition analysis of steels and metal alloys (material certificates)
- Determination of major oxides in cement, clinker, raw materials (SiO₂, Al₂O₃, CaO, Fe₂O₃)
- Soil composition analysis for heavy metals (Pb, Cd, As, Hg)
- Sulfur determination in fuels (ISO 20884) — petrochemical industry
- Materials verification (PMI — Positive Material Identification) at construction sites and refineries
- Analysis of glass, ceramics, refractory materials
- Archaeological and conservation research (pigment, metal composition)
- Quality control of galvanic coatings (coating thickness and composition)
Key parameters
| Parameter | Value |
|---|---|
| Element range | Be (Z=4) to U (Z=92) — WDXRF; Na (Z=11) to U — EDXRF |
| Concentration range | ppm – 100% (major, minor, trace constituents) |
| Limit of detection | 0.1–10 ppm (WDXRF), 10–100 ppm (EDXRF) |
| Accuracy | 0.01–0.1% abs. (major constituents), 5–15% rel. (trace) |
| Analysis time | 1–10 min (EDXRF screening), 10–30 min (WDXRF full analysis) |
| Sample preparation | Pressed pellet, fused bead (fusion) or direct (handheld) |
Standard
- Standard number
- PN-EN ISO 12677:2011 / PN-EN 15309:2007
- Title (PL)
- Analiza chemiczna wyrobów ogniotrwałych metodą XRF / Charakteryzowanie odpadów i gleby — Oznaczanie składu pierwiastkowego metodą fluorescencji rentgenowskiej
- Title (EN)
- Chemical analysis of refractory products by XRF / Characterisation of waste — Determination of elemental composition by X-ray fluorescence
Step-by-step procedure
1. Sample preparation — grinding
Grind solid sample in vibratory mill to particle size < 75 µm (for pellets) or < 200 µm (for beads). Sample weight 5–10 g.
2. Drying
Dry sample in oven at 105°C to constant weight. For loss on ignition (LOI) determination — calcine at 1050°C for 1 h.
3. Pressed pellet preparation (alternative A)
Mix 8 g sample with 2 g binder (Hoechst C wax). Press in hydraulic press at 200–300 kN (20–30 tons). Pressing time 30 s.
4. Fused bead preparation (alternative B)
Weigh 0.5–1 g sample + 5–10 g flux (Li₂B₄O₇/LiBO₂). Place in Pt/Au crucible. Fuse at 1050°C for 10–15 min with automatic stirring.
5. Spectrometer calibration
Perform calibration using CRM series (min. 10 standards covering expected concentration range). Apply matrix corrections (alpha/FP).
6. Sample measurement
Place pellet/bead in spectrometer. Start measurement program. WDXRF: sequential measurement of Kα/Lα lines of each element.
7. Results calculation
Software converts line intensities to concentrations taking into account matrix corrections (absorption and enhancement effects). Results in % oxides or ppm elements.
8. Quality control
Analyze control CRM (independent from calibration) in each series. Deviation from certified value < 2× CRM uncertainty.
9. Validation / verification
Check linearity, repeatability (RSD < 1% for major constituents), reproducibility, LOD/LOQ. Oxide balance 99.0–100.5%.
10. Report
Prepare report with results in % (oxides) or ppm (elements), uncertainty, sample identification and preparation method.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| WDXRF spectrometer | Bruker S8 TIGER Series 3, Malvern Panalytical Zetium, Rigaku ZSX Primus IV | 400 000–1 500 000 PLN |
| EDXRF spectrometer | Bruker S2 PUMA, Malvern Panalytical Epsilon 4, Shimadzu EDX-7200 | 100 000–400 000 PLN |
| Portable XRF (handheld) | Bruker S1 TITAN 800, Thermo Niton XL5, Olympus Vanta | 80 000–200 000 PLN |
| Hydraulic press for pellets | Fluxana Vaneox, Herzog TP-40, Specac Atlas | 20 000–60 000 PLN |
| Fusion device (fused beads) | Claisse M4 Fluxer, PANalytical Eagon2, Katanax X-600 | 80 000–200 000 PLN |
| Vibratory/ball mill | Retsch RS 200, Fritsch Pulverisette 6, Herzog HSM 100 | 30 000–80 000 PLN |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| Lithium tetraborate (Li₂B₄O₇) | 12007-60-2 | Flux for fused bead preparation (fusion at 1050°C), Claisse / Fluxana, ~300 PLN/kg |
| Lithium metaborate (LiBO₂) | 13453-69-5 | Flux — mixture with tetraborate (66:34) ensures optimal bead viscosity |
| Boric acid (H₃BO₃) | 10043-35-3 | Binder for pressed pellets, bottom layer (backing), ~50 PLN/kg |
| Microcrystalline wax (Hoechst C) | — | Binder for pressed pellets (1–3% addition), facilitates pressing |
| CRM standards | — | Certified reference materials (e.g. NIST SRM, BAS, IPT) — cement, steel, ores, soil — 200–800 PLN/pc |
| Lithium iodide (LiI) | 10377-51-2 | Release agent — prevents bead sticking to platinum crucible (0.5–1% in mixture) |
Health and safety (OHS)
- X-ray radiation — spectrometer has shields and interlocks, do not open chamber during tube operation
- Fusion at 1050°C — platinum crucible very hot, use tongs and heat-resistant gloves
- Borate fluxes (Li₂B₄O₇) — irritating, avoid dust inhalation, gloves
- Hydraulic press — crushing risk, do not insert hands during pressing
- Vibratory mill — noise, hearing protection; dust — P2 mask
- Portable XRF — never point beam at people, use backscatter shield