Determination of bromine and iodine in shrimp and its parts by ICP-MS after decomposition using microwave-induced combustion

摘要

A digestion method based on microwave-induced combustion (MIC) was developed for bromine and iodine determination in shrimp and its parts (shells and head, and tissue) by inductively coupled plasma mass spectrometry (ICP-MS). Ammonium nitrate solution was used as an igniter for combustion and vessels were pressurized with O2 at 20 bar. Solutions of (NH4)2CO3 (50 or 100 mmol La?’1) and NH4OH (25, 50, 75 or 100 mmol La?’1) were evaluated as absorbing media for Br and I. Better results were obtained for Br and I determination using 50 mmol La?’1 NH4OH as absorbing medium. Using this solution, blanks were always negligible and memory effects were virtually absent. The accuracy of the proposed MIC method was evaluated using a reference material (NIST 8414) with agreement better than 99% for both analytes. The limits of detection by MIC and further ICP-MS determination (Br: 0.12 ??g ga?’1; I: 0.001 ??g ga?’1) were better than those obtained when the extraction procedure was used. Additionally, a microwave-assisted alkaline extraction method was also evaluated using 0.11 mol La?’1 TMAH as extractant solution. However, alkaline extraction was only feasible for shrimp tissue and not for whole shrimp or shells. Decomposition using MIC allowed the determination of Br and I by ICP-MS in shrimp and the respective distribution of these elements in shells and head, and in tissue avoiding the use of concentrated digestion or extraction solutions.