An approach for measuring the 129I/127I ratio in fish samples

Abstract The 129 I/ 127 I ratio in marine fish samples was measured employing accelerator mass spectrometry. The measurement was successful because of the low experimental background of 129 I. Pyrohydrolysis was applied to extract iodine from fish samples. The experimental background of pyrohydrolysis was checked carefully and evaluated as 10 4 –10 5  atoms 129 I/combustion. The methodology employed in the present study thus required only 0.05–0.2 g of dried fish samples. The methodology was then applied to obtain the 129 I/ 127 I ratio of marine fish samples collected from the Western Pacific Ocean as (0.63–1.2) × 10 −10 . These values were similar to the ratio for the surface seawater collected at the same station, 0.4 × 10 −10 . The 129 I/ 127 I ratio of IAEA-414, which was a mix of fish from the Irish Sea and the North Sea, was also measured and determined as 1.82 × 10 −7 . Consequently, fish from the Western Pacific Ocean and the North Sea were distinguished by their 129 I/ 127 I ratios. The 129 I/ 127 I ratio is thus a direct indicator of the area of habitat of fish.