An automated system for hydrogen isotope analysis of water

An automated inlet system has been developed for deuterium/hydrogen isotope analysis of water using on-line reduction to hydrogen. A modified HPLC autosampler introduces precise aliquots of water (0.5 to 5 mu l) into a heated expansion chamber which is connected via a capillary to hot uranium where the water is reduced to uranium oxide, and hydrogen for analysis. The 600 degrees C uranium reduction furnace is kept at analyzer pressure in the mass spectrometer, which maximizes the lifetime 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 catalyst methods, some 'memory' effects are encountered, requiring two injections 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-controlled system provides extended unattended operation allowing, for instance, large runs of samples that can occupy the instrument over entire weekends. (C) 1998 Elsevier Science B.V. All rights reserved.