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, b oth employing a mixture of nitric acid and hydrogen peroxide as digest ing agent, were tested for decomposing the certified samples of BCR 27 8 mussel tissue (Mytilus edulis) and of BCR 422 cod muscle to determin e arsenic by use of FI-HG-AAS. While the microwave system is insuffici ent 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 (B CR 422). A dry ashing procedure is given as a reference digestion, yie lding complete recoveries of arsenic for both materials. The nitrite i nterference arising during measurement can be entirely overcome by usi ng an amino sulfuric acid concentration of about 350 mmol/L in the sol utions for measurement.