Metal content of shark muscle powder biological reference material.

: Powdered dried shark muscle (Cephaloscyllium umbratile) is a promising biological reference material for metal analysis. Homogeneity indices (CV%) for Na, K, Zn, As, Ca, and Hg of the shark powder were within 5%. Mercury and arsenic concentrations (total Hg, 9.1 ppm dry wt, As, 99 ppm dry wt) in shark powder are relatively high. Muscle can be obtained inexpensively, and the powder can be preserved indefinitely if kept cold.