Measurement of I-129 in environmental samples by ICP-CRI-QMS: possibilities and limitations

摘要

129I is preconcentrated from environmental samples and its accessibility is addressed for inductively coupled plasma quadrupole mass spectrometer with collision/reaction interface (ICP-CRI-QMS). By applying oxygen as CRI gas through skimmer cone, the signal of the interfering 129Xe from the impurity of plasma gas can be eliminated while the formation of 127I1H1H+ can be partially removed. The improved ICP-QMS can be employed for investigation of 129I in environmental samples with a 129I/127I ratio down to 10-7. The detection capability was demonstrated by measuring 129I in seaweed samples collected around the nuclear fuel reprocessing plant at La Hague. The abundant 127I in the sample matrix causes a serious problem and degrades the detection capability of the instrument when the concentration of 127I is larger than 105ng/g. Even combined with a sufficient pre-concentration procedure, ICP-QMS is not considered as a suitable technique for the analysis of 129I in uncontaminated environmental samples with 129I/127I ratio of less than 10-7. Results are presented for seaweed samples collected around La Hague. In addition, time dependant I concentrations and ratios are given for colloids and water sampled from Lake Thun