The δ2HVSMOW–SLAP value of total hydrogen of the international measurement standard NBS 22 oil was determined by a new method of sealing water in silver tubes for use in a thermal conversion elemental analysis (TC/EA) reduction unit. The isotopic fractionation of water due to evaporation is virtually non-existent in this silver-tube method. A new value for the δ2HVSMOW–SLAP of NBS 22 oil, calibrated with isotopic reference waters, was determined to be −116.9 ± 0.8‰ (1σ and n = 31). Published in 2010 by John Wiley & Sons, Ltd.