Rapid XRD Screening of Asbestos Reference Samples on Aeris Using the 1Der High-Energy-Resolution Detector

Abstract

This note summarizes a feasibility study measuring two JAWE asbestos reference samples (tremolite and chrysotile) on an Aeris X-ray diffractometer equipped with the 1Der energy-dispersive solid-state strip detector. With ~340 eV energy resolution, 1Der uses programmable energy windows to suppress unwanted radiation (white radiation, Kβ, and sample fluorescence). This reduces background to levels close to an empty zero-background holder, improving visibility of low-level asbestos peaks. A single 33-minute overview scan enabled detection of 0.5 wt.% tremolite and 0.8 wt.% chrysotile above the limit of detection (LOD) criterion, and multiple repetitions of this measurement (5×33 min) improved signal-to-noise ratio, making it possible to reach the limit of quantification (LOQ) for both tremolite and chrysotile. These results match the requirements summarized in the recently released USP <901>.

1. Background and objective

The need to identify and quantify trace amounts of asbestos within materials such as talc has become increasingly important in recent years, with the requirement for quantification found in both the mining and pharmaceutical industries, the latter now having USP <901> in place. This regulation explicitly mentions X-ray diffraction (XRD) as a mandatory technique to detect the presence of asbestos in pharmaceutical talc.

XRD identification of asbestos phases can be limited by elevated background from fluorescence and other parasitic radiation components. The objective of this study was to assess whether high-energy-resolution detection on Aeris can electronically reject these contributions and improve detection performance for low-level asbestos presence in a crystalline matrix.

2. Instrumentation and concept

• Aeris benchtop XRD with 1Der detector (127 channels) operating with CSS and ER modes
• Energy resolution (~340 eV) enables programmable energy windows acting as an electronic secondary monochromator
• Unwanted radiation suppressed from (i) the source (white radiation/Kβ), (ii) the sample (fluorescence), and (iii) background contributions, eliminating the need for a Kβ-filter

3. Sample preparation

Two JAWE reference samples containing the phases in question were used: JAWE 1113 – tremolite (0.5 wt.%) and JAWE 1213 – chrysotile (0.8 wt.%).

Sample preparation:

• A small amount of sample was filled using a top-loading technique into the holder cavity of a 16 mm silicon zero-background plate.
• Gently press using a glass slide to make sure no loose powder is on the surface of the sample holder. Applying more pressure might result in inducing undesired preferred orientation in the sample.
• Remove the glass slide and mount the holder in the sample ring.

4. Measurement method (overview scan)

Parameter	Setting
Geometry	Reflection mode (Bragg-Brentano)
Primary optics	No Kβ-filter, 1/4° divergence slit; 0.04 rad Soller slits, beam mask 13 mm; beam knife in “low” position
Secondary optics	Anti-scatter slit 7 mm; Soller slits 0.02 rad
Detector	1Der high-energy-resolution detector
Tube	Cu anode; 40 kV, 15 mA (600 W)
Scan range / step	3° to 70° 2θ; step size 0.0138°
Time	33 min per scan

5. Results

Raw diffractograms showed very low background in the crystalline matrix, reported to be close to an empty zero-background holder measured under identical conditions. Both tremolite and chrysotile peaks were visible in a 33-minute overview scan.

• Signal-to-noise ratio (S/N) criteria used: LOD when S/N > 3; LOQ when S/N > 10
• Single scan (33 min): tremolite S/N = 8.9 (above LOD); chrysotile S/N = 8.0 (above LOD)
• Summed scans (5×33 min = 165 min): tremolite S/N = 17.2 (above LOQ); chrysotile S/N = 15.6 (above LOQ)
• LOD for tremolite is 0.17 wt.% after 33 minutes and 0.09 wt.% after 165 minutes
• LOQ for tremolite is 0.56 wt.% after 33 minutes and 0.30 wt.% after 165 minutes
• LOD for chrysotile is 0.30 wt.% after 33 minutes and 0.15 wt.% after 165 minutes
• LOQ for chrysotile is 1.00 wt.% after 33 minutes and 0.50 wt.% after 165 minutes

6. Practical guidance for routine screening

• Use a short overview scan to confirm matrix/background behavior; then focus on specific diffractogram regions (containing high-intensity reflections of the phases in question) to reduce total measurement time.
• With the 1Der detector’s background suppression, detection limits below 1 wt.% are readily achievable for the demonstrated reference materials.
• For improved confidence at very low levels, combine repeated short scans or extend counting time in the selected 2θ windows.

7. Conclusions

• Aeris equipped with 1Der provides strong electronic suppression of unwanted radiation, lowering background and improving trace phase visibility.
• In this feasibility study, the required limit of detection for USP <901> for asbestos (0.2 wt.%) was achieved with the Aeris compact XRD, showing that it is on par with the floor-standing systems that were used for generating the norm.
• Targeted short-range scans are recommended to shorten routine workflows after identifying key peak positions.