Improvement of the detection limit for determination of I-129 in sediments by quadrupole inductively coupled plasma mass spectrometer with collision cell

The previously developed sample introduction device for the hot extraction of iodine from environmental samples (soils or sediments) and on-line introduction of analyte via the gas phase in quadrupole inductively coupled plasma mass spectrometry with hexapole collision cell (ICP-CC-QMS) was equipped with a cooling finger, which allowed intermediate iodine enrichment and improved the detection limits for I-129 down to 0.4 pg g(-1) without any additional sample preparation. A mixture of oxygen and helium as reaction gases in the hexapole collision cell was used for reducing the disturbing background intensity of Xe-129(+). Oxygen was also used as the carrier gas for iodine thermal desorption and transport into the ICP-CC-MS. The developed analytical method was applied for I-129 determination at the ultra-trace level and for isotope ratio measurements of I-129/I-127 down to 10(-7) in contaminated sediments and in SRM 4357 (Ocean Sediment Environment Radioactivity Standard). The measured I-129/I-127 ratio of 5.3x10(-7) corresponded to the expected value of 4.45x10(-7) reported for this sediment in the certificate.