A SIMPLIFIED METHOD FOR DEUTERIUM HYDROGEN ISOTOPE RATIO MEASUREMENTSON WATER SAMPLES OF BIOLOGICAL ORIGIN

Equilibration of hydrogen gas with the water in a variety of biologica l sample materials was carried out in Vacutainers using platinum-on-al umina catalyst physically isolated from the liquid water. The equilibr ation takes 3 days at room temperature-much slower than with catalysts which float on the water surface-but this reduces the short-term temp erature sensitivity of the procedure, and the inexpensive materials us ed allow convenient disposal of biologically contaminated samples afte r analysis. The slow equilibration also allows time for complete excha nge with water contained in a complex sample matrix such as plant stem s or soil without the need for prior isolation of the water sample. Th e method has particular application in studies of human total body wat er where repented studies can be carried out over a short time period without the need to wait for the previous dose to wash out. Water turn over rates from total diurnal energy expenditure studies measured by t his method were not significantly different from those obtained by the zinc reduction method.