Preparation of Iodine-129 Standard Solutions for Triple Quadrupole ICP-MS

Abstract

Accelerator mass spectrometry (AMS) has been recognized as the most sensitive analytical method for the isotopic ratio 129I/127I, and its limit of detection reaches as low as 129I/127I < 2×10-14. Recently triple quadrupole ICP-MS (ICP-MS/MS) is becoming an alternative analytical method for the rather high isotopic ratio range, 129I/127I > 10-8. Absolute ICP-MS/MS measurements require reliable standard materials for calibration. In this study, 129I standard solutions “tRIC-1” and “tRIC-2” were prepared from a laboratory-stored 129I solution and the 129I radioactivity standard of NIST SRM 4949d, respectively. The isotopic ratios of 129I/127I were determined to be (6.54 ± 0.23) × 10-5 for tRIC-1 and (3.41 ± 0.12) × 10-6 for tRIC-2 from the measurement results of AMS (129I/127I ratio) and ICP-MS/MS (127I concentration). From the 129I and 127I concentrations each calibration line in ICP-MS/MS was used to calculate the 129I/127I isotopic ratios which were (6.51 ± 0.26) × 10-5 for tRIC-1 and (3.34 ± 0.13) × 10-6 for tRIC-2. These isotopic ratios of 129I/127I agree with the value from AMS. It was proved that the two home-made standard solutions could be measured using the latest ICP-MS/MS and reliable isotopic ratios of 129I/127I were obtained.