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Microheterogeneity evaluation of polycyclic aromatic hydrocarbons in particulate standard reference materials
Katrice A Lippa1, Michele M Schantz
1Analytical Chemistry Division, Chemical Science and Technology Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899, USA. katrice.lippa@nist.gov
Assessing material homogeneity is crucial for accurate microanalysis. This study found diesel particulate matter (SRM 1650b) to be homogeneous for certain polycyclic aromatic hydrocarbons (PAHs), while urban dust (SRM 1649a) showed greater heterogeneity.
Area of Science:
- Environmental Chemistry
- Analytical Chemistry
- Materials Science
Background:
- Microanalysis of natural-matrix materials requires homogeneity assessment at small sample sizes.
- Emerging analytical techniques necessitate evaluation of sampling levels for accurate results.
Purpose of the Study:
- To determine sampling constants and evaluate the homogeneity of polycyclic aromatic hydrocarbons (PAHs) in particulate standard reference materials.
- To assess material heterogeneity using milligram sampling levels for urban dust and diesel particulate matter.
- To establish analyte-specific minimum sample masses for reliable analytical uncertainty.
Main Methods:
- Pressurized liquid extraction (PLE) coupled with gas chromatography/mass spectrometry (GC/MS).
- Determination of sampling constants (K (S)) to quantify material homogeneity.
- Analysis of ten individual PAHs in SRM 1649a Urban Dust and SRM 1650b Diesel Particulate Matter.
Main Results:
- SRM 1650b Diesel Particulate Matter showed homogeneity for fluoranthene, pyrene, benz[a]anthracene, and benzo[e]pyrene (K (S)<100 mg).
- SRM 1649a Urban Dust exhibited greater heterogeneity for all analyzed PAHs (K (S)>100 mg).
- Nonlinear power law relationships were identified between subsampling error and sample mass for predicting minimum sample masses.
Conclusions:
- The homogeneity of particulate reference materials varies significantly, impacting microanalysis.
- Sampling constants effectively differentiate homogeneous and heterogeneous materials.
- Predictive models for minimum sample mass are essential for achieving desired analytical uncertainty in PAH microanalysis.
