AN AUTOMATED-SYSTEM FOR HYDROGEN ISOTOPE ANALYSIS OF WATER

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.