Comparison of sample digestion procedures for the determination of arsenic in certified marine samples using the FI-HG-AAS technique

High-pressure digestion and a closed-vessel microwave heated system, both employing a mixture of nitric acid and hydrogen peroxide as digesting agent, were tested for decomposing the certified samples of BCR 278 mussel tissue (Mytilus edulis) and of BCR 422 cod muscle to determine arsenic by use of FI-HG-AAS. While the microwave system is insufficient to mineralize arsenic in marine samples (arsenic recoveries of 13 +/- 10% in BCR 278, 2 +/- 1% in BCR 422; n = 4), high-pressure ashing at 300 degrees C results in recovery percentages of 56 +/- 15% (n = 4) in mussel tissue (BCR 278) and of 25 +/- 10% (n = 4) in cod muscle (BCR 422). A dry ashing procedure is given as a reference digestion, yielding complete recoveries of arsenic for both materials. The nitrite interference arising during measurement can be entirely overcome by using an amino sulfuric acid concentration of about 350 mmol/L in the solutions for measurement.