EVALUATION OF AN AUTOMATED EQUILIBRATION TECHNIQUE FOR DEUTERIUM HYDROGEN ISOTOPE RATIO MEASUREMENTS WITH RESPECT TO ASSESSING TOTAL-ENERGYEXPENDITURE BY THE DOUBLY LABELED WATER METHOD/

The doubly labelled water (DLW) method for measuring energy expenditur e in free living subjects suffers from inaccuracy and imprecision main ly owing to analytical problems. An automated H/D/O equilibration devi ce was tested for precision, internal validity and matrix effects with particular consideration of DLW studies. The precision was found to b e 05 parts per thousand, and 0.04 parts per thousand for H-2 and O-18, respectively. Dilution series with water standards and mine showed a high linearity and no matrix effects. In addition, the automated prepa ration is less laborious and time consuming and reduces sources of ana lytical imprecisions in studies measuring energy expenditure by the DL W method. (C) 1997 by John Wiley & Sons, Ltd.