RECENT DEVELOPMENTS IN NIST BOTANICAL SRMS

The National Institute of Standards and Technology (NIST) (formerly th e National Bureau of Standards (NBS)) issued the first botanical refer ence material certified for elemental content in January 1971, as Stan dard Reference Material (SRM) 1571, Orchard Leaves. In the following y ears a total of nine additional botanical certified reference material s have been issued by NIST. Each of these materials was certified for major, minor and trace elements except for SRM 2695, certified for flu orine only. Botanical SRMs issued since 1991 are significantly improve d over previous materials in a number of ways. Probably the most signi ficant change is the use of a jet-milling process to grind them to ext remely fine particles. This has resulted in botanical SRMs with signif icantly improved homogeneity. These NIST reference materials are descr ibed with information on homogeneity, drying techniques and grit conte nt.