Guanine, not less than 75 percent.
Hypoxanthine, not more than 25 percent.
Ash (ignition at 800 °C), not more than 2 percent.
Lead (as Pb), not more than 20 parts per million.
Arsenic (as As), not more than 3 parts per million.
Assay, not less than 96 percent total purines.
Mercury (as Hg), not more than 1 part per million.
21 C.F.R. §73.1329