Standard Solution SRMs Provide Traceability for Millions of Measurements

For decades, NIST has provided the SRM 3100 series single-element standard solutions. The certified values are traceable to the International System of Units (SI), enabling users to establish traceability of their measurement results to the SI. Commercial CRM producers utilize the SRMs to establish traceability of their certification results to the SI. Recent improvements in the SRM 3100 series include the implementation of “exact matching” with high-performance inductively-coupled plasma optical emission spectrometry (HP-ICP-OES), which is used as one of the certification methods. Also, a good understanding of the long-term stabilities of the SRMs is being gained by examining past and present stability data.

Literally millions of measurements of elemental composition are performed each year worldwide. The vast majority of these measurements depend upon reference materials for establishing traceability of results to the SI. Leveraged through commercial CRM producers, the NIST SRM 3100 series provides an efficient and effective way to establish this traceability. As a result, the quality of elemental determinations and comparability between laboratories are improved. Enhancements in the SRM 3100 series continue to benefit the analytical community.

“Exact matching” applied to HP-ICP-OES refers to the process of carefully matching the analyte mass fractions, internal standard element mass fractions, and matrix compositions between samples and calibration standards. HP-ICP-OES with exact matching is now being applied routinely to certification analyses for the SRM 3100 series. Results are being compared to previous HP-ICP-OES results obtained without exact matching to gain an understanding of the analytical benefits of exact matching. The effects on the certified values and associated uncertainties for the SRM 3100 series are also being assessed. Stability data for the SRM 3100 series obtained over the past decade have been collected and examined statistically for long-term trends. New data are being added as they become available.

Major Accomplishments:

• Exact matching has been shown to reduce bias and uncertainty in HP-ICP-OES analysis.
• Stability data show that the shelf-lives assigned to the 3100 series SRMs are generally appropriate.