Seafood digestion by microwave-induced combustion for total arsenic determination by atomic spectrometry techniques with hydride generation

Abstract

A microwave-induced combustion (MIC) method was proposed for seafood digestion and further total arsenic determination using hydride generation coupled to atomic spectrometry techniques. It was possible to digest up to 500 mg of mussel tissue, fish tissue and whole shrimp. Combustion was carried out in closed quartz vessels with pressurized oxygen. Total arsenic was determined in MIC digests by conventional inductively coupled plasma mass spectrometry (ICP-MS), flow injection hydride generation coupled to atomic absorption spectrometry (FI-HG AAS) and to ICP-MS (FI-HG-ICP-MS). Accuracy was evaluated using certified reference materials of oyster tissue, dogfish muscle, tuna fish tissue and mussel tissue. The use of a reflux step and water or diluted HNO₃ as absorbing solutions was investigated. The agreement to certified values was from 96 to 103% using 0.1 mol l⁻¹ HNO₃ as absorbing solution and 5 min of reflux. The agreement of results for As determination by FI-HG AAS and FI-HG-ICP-MS was better than 98% when compared with results obtained by ICP-MS after digestion. The proposed method by MIC allowed the digestion in less time than other procedures and with low residual carbon content (< 0.5%). With this method up to eight samples could be processed simultaneously in 25 min. Taking into account that concentrated acids were not necessary, the proposed method can be considered in agreement with green chemistry recommendations.