Iridium, the new and more recent polluting metal linked to vehicular traffic. its determination in airborne particulate matter, superficial waters, soils/sediments, vegetables, mussels, clams and algae by voltammetry and spectroscopy: critical comparison

Recently, the problem relevant to the increasing presence in the environment of platinum group metals (PGMs) have been a topical subject of great interest, even if the scientific attention has been generally addressed to platinum(II), palladium(II) and rhodium(III), and in few cases to iridium(III), osmium(VIII) and ruthenium(III). This is because the PGMs concentration is significantly growing as a consequence of their increasing use in the production of industrial catalysts, anticancer drugs, jewels, and especially autocatalytic converters. In the case of the last tools, their continuous incorrect use \u201cstop and go\u201d with consequent deterioration implies a considerable release of these metals in the environment. Even if initially the metals used in autocatalytic converters were platinum, palladium and rhodium, in recent years such PGMs were gradually replaced in part, or alloyed with osmium, ruthenium and, especially, iridium. In particular, in the last decade, and always more frequently, iridium is employed as alloying (10-20 % w/w) with platinum, palladium and rhodium in the manufacture of autocatalytic converters in order to withstand high temperature and high wear. Finally, it is also important to highlight that iridium is one of the least abundant elements in the environment, and, probably for this reason, very few data are available. Thus, this work intends to propose voltammetric methods for the determination of ultra-trace iridium in environmental samples: airborne particulate matter, superficial waters, soils/sediments, vegetables, mussels, clams and algae. To better validate the proposed analytical procedures, a critical comparison with spectroscopic measurements \u2014 electro-thermal atomic absorption spectroscopy (ET\u2013AAS) because of its well established and tested robustness \u2014 has been also carried out and discussed here, taking into account all the parameters of interest to set-up an analytical method, such as precision, trueness, limit of detection and quantification, selectivity and, especially, sensitivity