Determination of diagnostic levels of arsenic in animal tissue: collaborative study

The method chosen for this collaborative study is a modification of the AOAC method for As residues, 41.009-41.012. The tissue is dry-ashed overnight at 500 degrees C, and then dissolved in dilute HCl. The solution is diluted and an aliquot is reacted with zinc metal to evolve arsine gas. The gas is trapped in AgDDC solution and As is quantitated at 540 nm. Nine collaborating laboratories performed single analyses on 4 blind duplicate pairs of bovine liver samples which were spiked at 0, 4.3, 10.8, or 21.6 mg As/kg liver. A National Bureau of Standards control (SRM 1566 Oyster Tissue, 13.4 +/- 1.9 mg As/kg) and a 1000 mg As/L standard were also submitted to the collaborators. Intralaboratory coefficients of variation ranged from 7.7 to 17.8%; interlaboratory coefficients of variation ranged from 10.9 to 19.0%. The method has been adopted official first action.