text: In 1977, Edmonds et al. reported the identification, isolation, and synthesis of major arsenic-containing substance in sea organisms, the arsenobetaine. In 1999, NRC certified arsenobetaine in the dogfish muscle material DORM-2, which became the first matrix reference material certified for arsenobetaine. Before DORM-2, DORM-1 (issued in 1986) served as the reference material for which the concentration of arsenobetaine was widely reported in scientific literature. Besides arsenobetaine, NRC currently offers matrix reference materials certified for methylmercury (TORT-3), dibutyltin, and tributyltin (PACS-3).
  * Biological tissues and sediments
  ** CARP, fish for dioxins, furans, and PCBs
  ** DOLT, dogfish liver for methylmercury
  ** DORM, fish protein for methylmercury
  ** TORT, lobster hepatopancreas for methylmercury and arsenobetaine
  ** PACS and SOPH, marine sediment for dibutyltin and tributyltin
  ** SELM, selenium-enriched yeast for methionine and selenomethionine