TY - JOUR
T1 - A thermo extraction-UV/Vis spectrophotometric method for total iodine quantification in soils and sediments
AU - Gilfedder, Benjamin
AU - Althoff, Frederik
AU - Petri, Michael
AU - Biester, Harald
PY - 2007
Y1 - 2007
N2 - 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 .
AB - 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 .
UR - http://link.springer.de/link/service/journals/00216/index.htm
U2 - 10.1007/s00216-007-1621-4
DO - 10.1007/s00216-007-1621-4
M3 - Article
SN - 1618-2642
VL - 389
SP - 2323
EP - 2329
JO - Analytical and Bioanalytical Chemistry
JF - Analytical and Bioanalytical Chemistry
IS - 7-8
ER -