Leonard I Wassenaar
Christine Mukwaya
Haiping Qi
Jennifer M. Lorenz
Tyler B. Coplen
2015
<h5>Rationale</h5>
<p>As a result of the need for isotopic reference waters having high <i>δ</i><sup><span>2</span></sup><sub>H<span>VSMOW-SLAP</span></sub> and <i>δ</i><sup><span>18</span></sup><sub>O<span>VSMOW-SLAP</span></sub> values for daily use, especially for tropical and equatorial-zone freshwaters, a new secondary isotopic reference material for international distribution was prepared from water collected from Lake Kyoga, Uganda.</p>
<h5>Methods</h5>
<p>This isotopic reference lakewater was filtered through a membrane with 0.2-µm pore size, homogenized, loaded into glass ampoules that were sealed with a torch and autoclaved to eliminate biological activity, and measured by dual-inlet isotope-ratio mass spectrometry. This reference material is available in a case of 144 glass ampoules each containing 5 mL of water.</p>
<h5>Results</h5>
<p>The <i>δ</i><sup><span>2</span></sup>H and <i>δ</i><sup><span>18</span></sup>O values of this reference material are +32.8 ± 0.4 and +4.95 ± 0.02 mUr (milliurey = 0.001 = 1 ‰), respectively, relative to VSMOW, on scales normalized such that the <i>δ</i><sup>2</sup>H and <i>δ</i><sup>18</sup>O values of SLAP reference water are, respectively, −428 and −55.5 mUr. Each uncertainty is an estimated expanded uncertainty (<i>U</i> = 2<i>u</i><sub><span>c</span></sub>) about the reference value that provides an interval that has about a 95 % probability of encompassing the true value.</p>
<h5>Conclusions</h5>
<p>This isotopic reference material, designated as USGS50, is intended as one of two reference waters for daily normalization of stable hydrogen and oxygen isotopic analysis of water with an isotope-ratio mass spectrometer or a laser absorption spectrometer, of use especially for isotope-hydrology laboratories analyzing freshwater samples from equatorial and tropical regions.</p>
application/pdf
10.1002/rcm.7369
en
Wiley
A new isotopic reference material for stable hydrogen and oxygen isotope-ratio measurements of water—USGS50 Lake Kyoga Water
article