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Interlaboratory and intralaboratory variabilities in the Environmental Lead Proficiency Analytical Testing (ELPAT)
P C Schlecht1, R Song, J H Groff
1U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Robert A. Taft Laboratories, Cincinnati, OH 45226, USA.
American Industrial Hygiene Association Journal
|November 28, 1997
Summary
This study analyzed laboratory variability in lead testing. Interlaboratory variation in lead measurements was found to be greater than intralaboratory variation, impacting overall accuracy.
Area of Science:
- Environmental Science
- Analytical Chemistry
- Occupational Health
Background:
- The Environmental Lead Proficiency Analytical Testing (ELPAT) Program assesses lead measurement accuracy in over 400 laboratories.
- Previous research identified small biases between instrumental methods but not digestion techniques.
Purpose of the Study:
- To examine total sample variability and its components (interlaboratory and intralaboratory) in lead testing.
- To compare variation components across different analytical methods and lead concentrations.
Main Methods:
- Utilized a correlation model to estimate variation ratios and separate interlaboratory and intralaboratory variability.
- Expanded upon previous National Institute for Occupational Safety and Health (NIOSH) study using ELPAT data.
Main Results:
- No significant change in the contribution of variation components with varying lead levels.
- No significant differences in variation components among the three most common analytical methods.
- Interlaboratory relative standard deviation was approximately 1.7 times the intralaboratory relative standard deviation.
Conclusions:
- Both interlaboratory and intralaboratory variations are significant contributors to total variability in lead measurements.
- Laboratory-to-laboratory differences (interlaboratory) are a greater source of variation than within-laboratory differences (intralaboratory).