Determination of ¹²⁹I in waters associated with coalbed methane using solvent extraction and accelerator mass spectrometry measurement

A method using solvent extraction following a preconcentration of iodine by evaporation was developed for separation of iodine in waters associated with coalbed methane (CBM) for the determination of ¹²⁹I using accelerator mass spectrometry, for exploration of CBM resources. The ¹²⁹I/¹²⁷I ratios in water samples collected in a CBM field have been determined using the developed method to be (1.6–2.4) × 10^–11, which are 2–3 orders of magnitudes lower than that of environmental samples in Xi’an, but 2 orders of magnitude higher than the procedure blank of (1.5–2.1) × 10^–13, confirming no measurable crossover contamination during sample analysis and slightly input of modern water in the CBM water.