Speciation analysis of iodine and bromine at picogram-per-gram levels in polar ice

Iodine and bromine species participate in key atmospheric reactions including the formation of cloud con- densation nuclei and ozone depletion. We present a novel method coupling a high-performance liquid chromatogra- phy with ion chromatography and inductively coupled plas- ma mass spectrometry, which allows the determination of iodine (I) and bromine (Br) species (IO3−, I−, Br−, BrO3−) at the picogram-per-gram levels presents in Antarctic ice. Chromatographic separation was achieved using an ION- PAC® AS16 Analytical Column with NaOH as eluent. Detection limits for I and Br species were 5 to 9 pg g−1 with an uncertainty of less than 2.5% for all considered species. Inorganic iodine and bromine species have been determined in Antarctic ice core samples, with concentrations close to the detection limits for iodine species, and approximately 150 pg g−1 for Br−. Although iodate (IO3−) is the most abundant iodine species in the atmosphere, only the much rarer iodide (I−) species was present in Antarctic Holocene ice. Bromine was found to be present in Antarctic ice as Br−.