A thermo extraction-UV/Vis spectrophotometric method for total iodine quantification in soils and sediments

Benjamin Gilfedder, Frederik Althoff, Michael Petri, Harald Biester

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Iodine in soils and sediments is a difficult element to analyze due to its volatility in acidic conditions. Traditionally it has been quantified using neutron activation analysis techniques, which, unfortunately, requires access to a nuclear reactor. We present here a simple method for solid-phase iodine analysis by thermo extraction at 1000 degrees C and quantification by UV/Vis photometry. Samples are combusted in an oxygen stream and trapped in Milli-Q water. The extracts are then quantified by an As3+ stop-Ce4+ spectrometric method whereby iodide catalyzes the oxidation of As3+ to As5+ and reduction of Ce4+ to Ce3+. Three standard reference materials were analyzed with excellent recoveries (97-113 ) and RSDs (<5 ). Moreover, the detection limit was less than 50 ng absolute iodine with a confidence limit of 95 . When applied to carbonate-rich samples from sediment traps deployed in Lake Constance we found very low iodine levels (0.8-2 mg kg(-1) stop). Despite the low concentrations, the precision of the method was consistently better than 5 RSD. However, the method needed to be slightly modified for organic and iodine-rich sediments (20-30 organic carbon) from a lake in the Black Forest by increasing the oxygen flow rate and decreasing the combustion time. Using the modified method we were able to achieve RSDs lower than 5 .
Original languageEnglish
Pages (from-to)2323 - 2329
Number of pages7
JournalAnalytical and Bioanalytical Chemistry
Issue number7-8
Publication statusPublished - 2007
Externally publishedYes

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