Closed vessel microwave digestion of air filters for measurements of elemental iodine

Abstract

An acid assisted closed vessel microwave digestion procedure was developed for the treatment of fine airborne particulate matter that allows elemental iodine to be solubilised simultaneously with other metallic elements. This procedure is an improvement over existing methods as it allows the iodine to be safely digested from the filter media (polypropylene or cellulose) in less than one hour in up to 70–100% recoveries, without requiring an overnight predigestion step or the addition of reducing agents, with a microwave temperature of 185 °C and the use of 65% HNO₃. A range of filters were investigated to determine the material that has the best properties for microwave digestion that also enabled the deposited iodine present in total suspended particles (TSP) to be rapidly fully digested and quantitatively analyzed using inductively coupled plasma-mass spectrometry (ICP-MS).