Diluted Blends of Single Element Standards

Jan uses 1000 or 10000 ppm stock solutions of single elements and combines them to create her own elemental standards. The concentrations of the elements are typically less than 25 ppm. She blends them in acidic matrices, somtimes with a metal matrix. Jan wanted any information Paul could offer regarding these diluted standards. She was also curious about the shelf life and expiration date of her own custom blends.

	RE: Diluted Blends of Single Element Standards Dear Jan,      The chemical stability of mixed elemental standards is a function of the elements in the blend, the matrix, and the container. For example, Ag in nitric acid in a LDPE container shows no signs of chemical instability and appears to be chemically stable indefinitely. However, when Ag is diluted into HCl, it forms the soluble chloride complex (Ag < 10 ppm and HCL > 10%). This complex is photosensitive with a stability of several weeks to a few months. The elements that cause the greatest problem are the refractories (including Si, Sb, and Sn); the precious metals; and the most problem-prone, Hg.      For chemical compatibility information, please reference our Analytical Periodic Table -- it has all of the data you'll need for the most important elements.      The blends that we manufacture at IV are grouped in such a manner that the chemical stability is projected to be indefinite. The expiration dates of such blends are generally one year. To better understand the reasoning behind these timeframes, see Shelf-Life vs. Expiration Date. Let me know if you need further assistance.     Paul R. Gaines, Ph.D. Serving you in chemistry