The chemical measurement of plutonium in nuclear fuel cycle materials ranges from highly precise titrimetric methods applied to homogeneous products to less precise methods applied to heterogeneous scrap materials. A system under development for analyzing scrap materials involves a combination of high-temperature pressurized acid-dissolution attack, a gamma assay for low levels of plutonium in any resulting residue, and an automated spectrophotometer for measuring plutonium in the liquid fraction. A review of chemical standards, that are essential for calibrating methods to maintain unbiased plutonium-assay measurements, indicates that a greater variety is needed for application to nuclear safeguards materials.