Comparison of quantitative techniques for analysis of bulk asbestos proficiency testing materials
The methods used by NIST for quantitative analysis of NVLAP bulk asbestos PTMs are described. Quantitative XRD using the method of standard additions is the most generally applicable tool used. PTMs are also analyzed gravimetrically using acid dissolution and ashing to remove the matrix quantitatively. Gravimetry is used for many samples, even when the matrix cannot be completely removed. Point counting is performed on all the PTMs, but the results are used primarily to adjust acceptance ranges and not to provide reference values. The general application of these analytical methods to the analysis of the PTMs is described, and the results from multiple techniques are compared for selected samples. The reliability of each method is described, along with precautions that must be exercised to obtain accurate results. Results from Research Triangle Institute using the same general methods on the same PTMs are compared with results from NIST.