Application of X-ray diffraction with Rietveld refinement to quantify mineral composition including crystalline...

Area of Science:

• Mineralogy
• Analytical Chemistry
• Occupational Health

Background:

• Respirable crystalline silica (RCS) poses significant health risks.
• Accurate quantification of RCS in airborne dust is crucial for occupational safety.
• Existing methods for RCS analysis can be time-consuming or lack precision.

Purpose of the Study:

• To evaluate the efficacy of Rietveld refinement for quantifying RCS in respirable aerosol samples.
• To compare Rietveld refinement results with established methods like NIOSH 7500.
• To assess the method's performance with various mineral compositions and sample masses.

Main Methods:

• Rietveld refinement analysis applied to laboratory and field aerosol samples.
• Comparison with NIOSH 7500 method (Silica, Crystalline, by XRD) and gravimetrical measurements.
• Use of an internal standard to correct for amorphous content and unidentified phases in field samples.

Main Results:

• Rietveld refinement successfully quantified RCS and other crystalline minerals in both laboratory and field samples.
• Results were comparable to the NIOSH 7500 method for quartz.
• Linearity was observed up to 20 mg for laboratory samples, with a limit of quantification as low as 5 µg of quartz.
• Accurate quantification was achieved for field samples with up to 15 mg total mass and 1.8–11 wt% quartz content.
• A minimum sample mass of 0.5 mg was found optimal for Rietveld refinement.

Conclusions:

• Rietveld refinement is a robust and accurate method for determining RCS and other crystalline phases in respirable dust.
• The method is effective even with complex matrices and high mass loadings, offering a valuable alternative for occupational exposure monitoring.