Improving hydrogen isotope ratio measurements for on-line chromium reduction systems

Recent advances in on-line metal [U, Mn, Cr] reduction systems for the auto mated analysis of deltaD(VSMOW) in water and organic solvents greatly incre ases sample throughput. However, several sources of uncertainty are inheren t in these systems, including analytical reproducibility, fractionation of reference gas in the inlet system, and memory effects, as well as error int roduced during data normalization that must be quantified. A careful consid eration of these sources of uncertainty suggests that accuracy to <1 parts per thousand may be difficult to achieve due to the combined effects of ana lytical error and uncertainty in the calibration of secondary laboratory st andards. However, for internally consistent data sets, it may be possible t o measure relative differences between samples at the similar to0.5 parts p er thousand level or below. In addition to describing methods for data redu ction, strategies for minimizing and managing uncertainty are presented alo ng with a recipe for greatly increasing reactor life in Cr-reduction system s. Increased reactor life reduces consumable costs by a factor of 10. Copyr ight (C) 2001 John Wiley & Sons, Ltd.