NIST Tools for Quality Assurance in Botanical Dietary Supplement Measurements

Abstract

The accurate analysis of botanical dietary supplements presents significant challenges for the analytical laboratory. Analyte stability, extraction efficiency, the availability of calibration materials, and the use of appropriate controls are issues that must be considered in the chemical metrology of botanicals. The National Institute of Standards and Technology (NIST) has been working with the National Institutes of Health Office of Dietary Supplements (NIH/ODS) to address these challenges. NIST has developed a variety of Standard Reference Materials (SRMs) for dietary supplements, a process which includes the acquisition of appropriate materials and the characterization of their chemical composition. Mass fractions are typically reported for active and marker compounds as well as contaminants. During the certification process, NIST scientists often develop new analytical methods and generate stability and extraction data that can be useful to the dietary supplement community. In addition to the development of reference materials, NIST administers a dietary supplement laboratory quality assurance program (DSQAP); over 80 laboratories have participated in past exercises. Laboratory inter-comparison programs such as the DSQAP provide tools that allow analysts and laboratories to assess how their methods perform relative to the community and relative to an accepted value. The DSQAP identifies measurement challenges and works to bring the measurements of participants into concordance. Proper use of dietary supplement SRMs and participation in inter-comparison programs such as the DSQAP are important tools for analytical laboratories to improve and confirm method accuracy and precision.