Uncertainty determination for nondestructive chemical analytical methods using field data and application to XRF...

Area of Science:

• Environmental Science
• Analytical Chemistry
• Occupational Health

Background:

• Laboratory validation of air sampling methods has limitations in reflecting real-world field uncertainties.
• Field evaluations are challenging due to uncontrolled conditions, hindering method comparison and variance assessment.
• Nondestructive field methods allow for direct comparison with reference laboratory techniques using the same samples.

Purpose of the Study:

• To evaluate a portable X-ray fluorescence (XRF) analyzer for lead content determination in air samples.
• To develop and assess statistical approaches for analyzing field data, accounting for non-normal distributions and outliers.
• To establish acceptance criteria for field analytical methods based on accuracy and reliability.

Main Methods:

• Air filter samples were analyzed using a portable X-ray fluorescence (XRF) analyzer.
• The same samples underwent reference laboratory analysis for comparison.
• Two statistical methods, ISO GUM and bootstrap procedure, were employed to evaluate data and determine accuracy ranges, considering outliers.

Main Results:

• The portable XRF method demonstrated faster decision-making capabilities compared to off-site laboratory analysis.
• Both the ISO GUM and bootstrap statistical approaches yielded similar accuracy ranges.
• The portable XRF analyzer met the proposed field evaluation criterion of a 35% symmetric accuracy range.

Conclusions:

• The portable XRF analyzer is suitable for routine air lead evaluation in workplaces.
• The developed statistical methods effectively handle non-normal data and outliers in field evaluations.
• Nondestructive analysis allows for subsequent testing of samples near decision points, enhancing compliance monitoring.