An automated inlet system has been developed for deuterium/hydrogen is
otope analysis of water using on-line reduction to hydrogen. A modifie
d HPLC autosampler introduces precise aliquots of water (0.5 to 5 mu l
) into a heated expansion chamber which is connected via a capillary t
o hot uranium where the water is reduced to uranium oxide, and hydroge
n for analysis. The 600 degrees C uranium reduction furnace is kept at
analyzer pressure in the mass spectrometer, which maximizes the lifet
ime of the reductant to handle more than 4000 injections per 0.5 g of
depleted uranium. This is a flow-through system, and unlike zinc or ca
talyst methods, some 'memory' effects are encountered, requiring two i
njections to obtain a delta(D) precision of less than +/-1%, and four
injections far a precision of less than +/-0.5%. Sample preparation is
limited to pipetting water into an autosampler vial. The computer-con
trolled system provides extended unattended operation allowing, for in
stance, large runs of samples that can occupy the instrument over enti
re weekends. (C) 1998 Elsevier Science B.V. All rights reserved.