Homogeneity and evaluation of the new NIST leaf certified reference materials.

The NIST has produced and is in the process of certifying two new leaf CRMs, SRM1515 Apple Leaves and SRM 1547 Peach Leaves, as replacements for the no longer available NBS Orchard Leaves and the almost depleted Citrus Leaves. These two new materials have been processed and are being thoroughly evaluated and should provide the most advanced natural matrix botanical trace-element reference materials available. Caution should be used in determining a basis weight (drying) for these CRMs because of their very fine particle size. Homogeneity has been established by instrumental neutron activation analysis on both leaf materials for five elements, to date, to better than 1.5% (1 s) for 100-mg sample sizes.