A Novel Approach for the Simultaneous Determination of Iodide, lodate and Organo-Iodide for ~(127)I and ~(129)I in Environmental Samples Using Gas Chromatography-Mass Spectrometry

摘要

In aquatic environments, iodine mainly exists as iodide, iodate, and organic iodine. The high mobility of iodine in aquatic systems has led to ~(129)I contamination problems at sites where nuclear fuel has been reprocessed, such as the F-area of Savannah River Site. In order to assess the distribution of ~(129) and stable ~(127)I in environmental systems, a sensitive and rapid method was developed which enables determination of isotopic ratios of speciated iodine. Iodide concentrations were quantified using gas chromatography-mass spectrometry (GC-MS) after derivatization to 4-iodo-N,N-dimethylaniline. lodate concentrations were quantified by measuring the difference of iodide concentrations in the solution before and after reduction by Na_2S_2O_5. Total iodine, including inorganic and organic iodine, was determined after conversion to iodate by combustion at 900 ℃. Organo-iodine was calculated as the difference between the total iodine and total inorganic iodine (iodide and iodate). The detection limits of iodide-127 and iodate-127 were 0.34 nM and 1.11 nM. respectively, whereas the detection limits for both iodkle-129 and iodate-129 was 0.08 nM (i.e., 2pCi ~(129)I/L). This method was successfully applied to water samples from the contaminated Savannah River Site, South Carolina, and more pristine Galveston Bay, Texas.