Tyler B. Coplen Lauren V. Tarbox Jennifer M. Lorenz Martha A. Scholl Haiping Qi 2014 <p><span>A new secondary isotopic reference material has been prepared from Puerto Rico precipitation, which was filtered, homogenised, loaded into glass ampoules, sealed with a torch, autoclaved to eliminate biological activity, and calibrated by dual-inlet isotope-ratio mass spectrometry. This isotopic reference material, designated as USGS48, is intended to be one of two isotopic reference waters for daily normalisation of stable hydrogen (δ</span>²<span>H) and stable oxygen (δ</span>¹⁸<span>O) isotopic analysis of water with a mass spectrometer or a laser absorption spectrometer. The δ</span>²<span>H and δ</span>¹⁸<span>O values of this reference water are−2.0±0.4 and−2.224±0.012 ‰, respectively, relative to Vienna Standard Mean Ocean Water on scales normalised such that the δ</span>²<span>H and δ</span>¹⁸<span>O values of Standard Light Antarctic Precipitation reference water are−428 and−55.5 ‰, respectively. Each uncertainty is an estimated expanded uncertainty (</span><i>U</i><span>=2</span><i>u</i>_c<span>) about the reference value that provides an interval that has about a 95&nbsp;% probability of encompassing the true value. This isotopic reference water is available by the case of 144 glass ampoules containing 5&nbsp;mL of water in each ampoule.</span></p> application/pdf 10.1080/10256016.2014.905555 en Taylor & Francis USGS48 Puerto Rico precipitation - A new isotopic reference material for δ²H and δ¹⁸O measurements of water article