Reporting of stable hydrogen, carbon, and oxygen isotopic abundances

To eliminate possible confusion in the reporting of isotopic abundances on non-corresponding scales, the Commission on Atomic Weights and Isotopic Abundances recommended at the 37 th General Assembly at Lisbon, Portugal that (i) 2 H/ 1 H relative ratios of all substances be expressed relative to VSMOW (Vienna Standard Mean Ocean Water) on a scale such that 2 H/ 1 H of SLAP (Standard Light Antarctic Precipitation) is 0.572 times that of VSMOW, (ii) 13 C/ 12 C relative ratios of all substances be expressed relative to VPDB (Vienna Peedee belemnite) on a scale such that 13 C/ 12 C of NBS 19 carbonate is 1.00195 times that of VPDB, and (iii) 18 O/ 16 O ratios of all substances be expressed relative to either VSMOW or VPDB on scales such that 18 O/ 16 O of SLAP is 0.9445 times that of VSMOW.