Normalization of stable isotope data is important for meaningful inter-laboratory comparisons of data, especially for waters where there may be large natural variations in isotope ratios of oxygen and hydrogen. As a result, large, systematic errors may arise in continuous dow applications without correction, whereas normalization to the VSMOW/SLAP scale can facilitate inter-laboratory comparison and can be accomplished by a simple procedure in which secondary laboratory standards, carefully calibrated, are analyzed along with unknown samples, Delta values for these standards, as analyzed, are plotted against the calibrated values and a linear regression is performed. The resulting equation is applied to unknown samples to achieve the normalization. The one-sigma [1 sigma] standard deviation fur replicate samples by this normalization method using a Finnigan Gasbenchll should be less than or equal to 0.1 parts per thousand. Because samples are analyzed directly against calibrated laboratory standards, this method also alleviates the requirement to carefully calibrate reference gases, to carefully control absolute temperatures for equilibration methods, or to determine H-3(+) for delta D-VSMOW measurements. Copyright (C) 2000 John Wiley & Sons, Ltd.
